CN102611822B

CN102611822B - Projector and projection image rectifying method thereof

Info

Publication number: CN102611822B
Application number: CN201210066886.0A
Authority: CN
Inventors: 郭大勃; 李磊; 彭伟伦
Original assignee: Hisense Group Co Ltd
Current assignee: Hisense Group Co Ltd
Priority date: 2012-03-14
Filing date: 2012-03-14
Publication date: 2015-07-01
Anticipated expiration: 2032-03-14
Also published as: CN104869377B; CN102611822A; CN104869377A

Abstract

The invention discloses a projector and a projection image rectifying method thereof. The projection image rectifying method includes: taking images of a projection area projected on a display screen by the projector through a taking module and obtaining images; determining corresponding geometric rectifying parameters by a rectifying module according to the projection area in the pictures; computing and converting original images to be projected by utilizing geometric rectifying parameters to obtain rectified images; and projecting the rectified images onto the display screen by the projection module. By analyzing the projection area in the images to perform geometric rectifying process or color rectifying process, so that rectifying operation can be realized without preset images with certain features, and process of rectifying projection images is simplified.

Description

Projector and projected image correction method thereof

Technical Field

The present invention relates to projection technology, and more particularly, to an apparatus and method for correcting a projected image.

Background

A projector is a projection device for enlarging a display image on a screen, and is widely used in presentations and home theaters. For example, for meeting room presentations and for watching movies on a large screen at home by connecting a DVD video player or the like.

If the optical axis of the projector is not perpendicular to the screen surface, i.e. at an oblique angle to the screen surface, distortion of the image displayed on the screen surface may result. In order to correct the distorted image, the tilt angles of the projector in the horizontal and vertical directions may be adjusted by screws under the projector mount to correct the projected image. The manual adjustment makes the projector inconvenient to use.

For this reason, there is provided in the related art a projector having a function of automatically correcting a projected image, as shown in fig. 1, including: correction unit, projection unit, angle sensor unit. An angle sensor unit in the projector automatically calculates the inclination angles of the projected image in the horizontal and vertical directions, and a correction unit corrects the projected image through the projection unit according to the inclination angles in the horizontal and vertical directions calculated by the angle sensor unit. The complexity of this approach is: the angle sensor unit is composed of a distance sensor and an angle calculation unit, the distance sensor needs to acquire the distance from a plurality of measurement points on the surface of the screen to the projector, and therefore the angle calculation unit calculates the inclination angles in the horizontal direction and the vertical direction according to the measured distance. In order to obtain the distances of a plurality of measurement points on the screen surface from the projector, a predetermined image needs to be projected onto the screen. In addition, the method has higher hardware cost because the angle sensor is arranged in the projector.

In addition, another projector provided with a camera in the prior art can use the camera to shoot a projected image to realize the correction of the projected image. However, the automatic correction method of these projectors also requires that some predetermined special images be projected during the correction process. For example, the predetermined special image may be a group of pictures with edge features: the background is black and is uniformly arranged along the edge of the picture by a white spherical dot matrix. After a predetermined image is projected on the screen surface, the camera shoots the projected image, and the distortion is calculated according to the edge characteristics and corrected according to the distortion. Although the method does not need a built-in angle sensor, the hardware cost is reduced, but a preset image still needs to be projected in the correction process, so that the correction process is complicated.

To sum up, in the projector capable of automatically correcting the projected image, some predetermined images need to be projected in the process of correcting the projected image, which makes the correction process more complicated. Also, after the correction is completed, if the projection image is deformed during the normal projection, the projector cannot automatically recognize the deformed projection image because a predetermined image cannot be projected, and cannot automatically perform the correction again unless manual intervention is performed. That is, the projector that automatically corrects the projected image in the related art cannot automatically correct the projected image in real time.

Disclosure of Invention

The embodiment of the invention provides a projector and a projected image correction method thereof, which are used for simplifying a method for automatically correcting a projected image.

According to an aspect of the present invention, there is provided a projection image correction method including: shooting a projection area projected on a display screen by a projector through a camera module to obtain a shot image; after receiving the shot image, the correction module determines corresponding geometric correction parameters according to a projection area in the shot image; and using the geometric correction parameters to perform operation transformation on the original image to be projected to obtain a corrected image; and projecting the corrected image onto a display screen by a projection module.

Preferably, the correction module determines, according to the projection area in the captured image, the corresponding geometric correction parameter as: and the correction module determines corresponding geometric correction parameters according to the position coordinates of the four vertexes of the projection area.

Preferably, the determining the corresponding geometric correction parameter according to the position coordinates of the four vertices of the projection area includes: and calculating geometric correction parameters according to the position coordinates of the four vertexes of the projection area and the position coordinates of the four vertexes of the correction rectangle.

Preferably, the calculating the geometric correction parameter according to the position coordinates of the four vertices of the projection area and the position coordinates of the four vertices of the correction rectangle is specifically according to the following formula:

(formula 1)

Wherein i is [1, 4]]An integer of (x)₁，y₁)、(x₂，y₂)、(x₃，y₃)、(x₄，y₄) Position coordinates of four vertexes of the projection area; (x)₁′，y₁′)、(x₂′，y₂′)、(x₃′，y₃′)、(x₄′y₄') are the position coordinates of the four vertices of the correction rectangle; a. b, c, d, e, f, u and v are calculated geometric correction parameters.

Preferably, the performing operation transformation on the original image to be projected by using the geometric correction parameter to obtain a corrected image includes:

if (x, y) is the position coordinate of a pixel in the original image, according to the following formula:

(formula 2)

The position coordinates (x ', y') of the corresponding pixel in the corrected image are determined.

Wherein the position coordinates of four vertexes of the correction rectangle are predetermined; alternatively, the position coordinates of the four vertices of the correction rectangle are determined from the position coordinates of the four vertices of the projection area in the captured image.

The determination of the position coordinates of the four vertices of the correction rectangle from the position coordinates of the four vertices of the projection area in the captured image includes: determining, for a quadrangle made up of four vertices of a projection area in the captured image, that the position coordinates of the four vertices of the correction rectangle are located within the quadrangle; or, for the quadrangle formed by four vertexes of the projection area in the captured image, determining that the position coordinates of the four vertexes of the correction rectangle are located within the quadrangle, and the aspect ratio of the correction rectangle is the same as that of the original image.

Further, after the image capturing module captures a projection area projected on the display screen by the projector to obtain a captured image, the method further includes: the verification module carries out geometric distortion judgment on the projection area in the shot image and sends a geometric distortion judgment result to the correction module; and after determining the projection area in the shot image, the correction module determines corresponding geometric correction parameters, specifically: and the correction module determines a projection area in the shot image and determines corresponding geometric correction parameters after determining that the geometric distortion judgment result is distortion.

Further, after the image capturing module captures a projection area projected on the display screen by the projector to obtain a captured image, the method further includes: a. the correction module determines the primary colors to be adjusted according to the relative positions of the color coordinates of the background colors of the projection areas in the shot images currently acquired by the camera module in the color coordinate system and the color coordinates of the target colors in the color coordinate system; sending the determined brightness adjustment value of the primary color to be adjusted to the projection module; the brightness adjustment value is predetermined; b. the projection module adjusts the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted; c. the correction module continuously acquires the shot image currently shot by the camera module, and finishes the correction when the relative distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system is determined to be smaller than a set value; otherwise, repeating the steps a, b and c.

Further, after the image capturing module captures a projection area projected on the display screen by the projector to obtain a captured image, the method further includes: the verification module carries out color distortion judgment on the projection area in the shot image and sends a color distortion judgment result to the correction module; and the correction module determines the primary colors to be adjusted according to the relative positions of the color coordinates of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinates of the target color in the color coordinate system, and specifically comprises the following steps: and after the color distortion judgment result is determined to be distortion, the correction module determines the primary color to be adjusted according to the relative position of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system.

Wherein the judging of the color distortion of the projection area in the shot image by the verification module comprises: if the verification module determines that the distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system exceeds a set distance value, determining that the color distortion judgment result is distortion; otherwise, determining that the color distortion judgment result is undistorted.

The correction module determines the primary colors to be adjusted according to the relative positions of the color coordinates of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinates of the target color in the color coordinate system, and comprises the following steps: setting the color coordinates of the three primary color light sources as R, G, B points in the color coordinate system, setting the color coordinates of the target color as W points in the color coordinate system, and setting the color coordinates of the background color of the projection area in the shot image currently acquired by the camera module as T points in the color coordinate system; the straight lines RW, GW and BW are respectively intersected with the straight lines BG, BR and GR at a point P, N, M, and the triangle RGB is divided into small triangles GWM, BWN, GWP, RWN, RWM and BWP; if the T point is located in the small triangle GWM or BWN, determining that the primary color to be adjusted is the R primary color, and the brightness adjustment value of the R primary color is a positive value; if the T point is positioned in the small triangle GWP or RWN, determining that the primary color to be adjusted is the B primary color, and the brightness adjustment value of the B primary color is a positive value; if the point T is located in the small triangle RWM or BWP, determining that the primary color to be adjusted is the primary color G, and the brightness adjustment value of the primary color G is a positive value; if the T point is coincident with the extended line of the BW line segment or is smaller than a set threshold, determining that the primary color to be adjusted is the B primary color, and the brightness adjustment value of the B primary color is a positive value; if the T point is coincident with the extension line of the RW line segment or is smaller than a set threshold, determining that the primary color to be adjusted is the R primary color, and the brightness adjustment value of the R primary color is a positive value; if the T point is coincident with the extension line of the GW line segment or is smaller than a set threshold, the primary color to be adjusted is determined to be the G primary color, and the brightness adjustment value of the G primary color is a positive value.

According to another aspect of the present invention, there is also provided a projector including: the camera module is used for shooting a projection area projected on the display screen by the projector to obtain a shot image; the correction module is used for determining corresponding geometric correction parameters according to the projection area in the shot image; and using the geometric correction parameters to perform operation transformation on the original image to be projected to obtain a corrected image; and the projection module is used for projecting the corrected image onto a display screen.

Preferably, the determining, by the correction module, the corresponding geometric correction parameter according to the projection area in the captured image includes: calculating geometric correction parameters according to the position coordinates of the four vertexes of the projection area and the position coordinates of the four vertexes of the correction rectangle; wherein the position coordinates of the four vertices of the correction rectangle are predetermined; alternatively, the position coordinates of the four vertices of the correction rectangle are determined from the position coordinates of the four vertices of the projection area in the captured image.

The projector further includes: the verification module is used for judging the geometric distortion of the projection area in the shot image and sending the geometric distortion judgment result to the correction module; the correction module is specifically used for determining a projection area in the shot image and determining corresponding geometric correction parameters after determining that the geometric distortion judgment result is distortion; and using the geometric correction parameters to perform operation transformation on the original image to be projected to obtain a corrected image.

Further, the verification module is further configured to perform color distortion judgment on the projection area in the captured image, and send a color distortion judgment result to the correction module.

The correction module is further used for determining a primary color to be adjusted according to the relative position of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system after the color distortion judgment result is determined to be distortion; sending the determined brightness adjustment value of the primary color to be adjusted to the projection module; the brightness adjustment value is predetermined; the projection module is also used for adjusting the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted; the correction module is further used for continuously acquiring a shot image currently shot by the camera module, and continuously determining a primary color to be adjusted according to the relative position between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system when determining that the relative distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system is smaller than a set value; and sending the determined brightness adjustment value of the primary color to be adjusted to the projection module.

Wherein the verification module comprises: the geometric distortion judging unit is used for judging geometric distortion of the projection area in the shot image and sending a geometric distortion judging result to the correcting module; and the color distortion judging unit is used for judging color distortion of the projection area in the shot image and sending the color distortion judging result to the correcting module.

The correction module includes: the geometric correction processing unit is used for receiving the geometric distortion judgment result sent by the geometric distortion judgment unit; if the geometric distortion judgment result is distortion, determining a projection area in the shot image and determining corresponding geometric correction parameters; using the geometric correction parameters to perform operation transformation on the original image to be projected to obtain a corrected image; the color correction processing unit is used for receiving the color distortion judgment result sent by the color distortion judgment unit; if the color distortion judgment result is distortion, then: determining a primary color to be adjusted according to the relative position between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system; sending the determined brightness adjustment value of the primary color to be adjusted to the projection module; after the projection module adjusts the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted, continuously acquiring a shot image currently shot by the camera module, and when it is determined that the relative distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system is smaller than a set value, continuously determining the primary color to be adjusted according to the relative position between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system; and sending the determined brightness adjustment value of the primary color to be adjusted to the projection module.

The projection module includes: the image driving unit is used for projecting according to the corrected image sent by the geometric correction processing unit; and the light source driving unit is used for adjusting the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted, which is sent by the color correction processing unit.

The projector according to the embodiment of the invention analyzes the projection area in the shot image to perform the geometric correction processing or the color correction processing, so that the projector does not need to perform the correction operation by projecting a predetermined image with certain characteristics, thereby simplifying the process of correcting the projected image.

Since the projector according to the embodiment of the present invention does not need to project a predetermined image with a certain feature during the process of performing geometric correction or color correction, the steps S501 to S507 or S801 to S807 described above may not only perform the correction process during the initial period of projection, but also may obtain the captured image in real time through the camera module during the normal projection process, the verification module may perform geometric distortion determination or color distortion determination on the captured image in real time, and the correction module may perform geometric correction processing or color correction processing in real time. Therefore, the projector and the projected image correction method thereof according to the embodiments of the present invention can perform geometric correction or color correction more conveniently.

The projector of the embodiment of the invention can realize color correction, so that the application occasion of the projector is not limited to the occasion that the display screen is white. For other color display screens, such as beige, etc., the projected image effect can be the same as the effect projected on the white display screen through the color correction function, so that the projector is more convenient to use.

Drawings

Fig. 1 is an internal block diagram of a projector having a function of automatically correcting a projected image according to the related art;

FIG. 2 is a schematic illustration of a projected image that is not corrected for geometric distortion in accordance with an embodiment of the present invention;

FIG. 3 is a schematic diagram of an original image being transformed to obtain a corrected image according to an embodiment of the present invention;

fig. 4 and 7 are block diagrams of a projector according to an embodiment of the present invention;

FIG. 5 is a flowchart of a method for geometric correction of a projected image according to an embodiment of the present invention;

FIG. 6 is a diagram illustrating the determination of the vertices of a calibration rectangle according to an embodiment of the present invention;

FIG. 8 is a flowchart of a method for geometric correction and color correction of a projected image according to an embodiment of the present invention;

FIG. 9a is a schematic diagram of color coordinates of a background color of a projection area and color coordinates of a target color in a color coordinate system according to an embodiment of the present invention;

FIG. 9b is a flowchart illustrating a detailed color correction method according to an embodiment of the present invention;

FIG. 10 is a schematic diagram illustrating the adjustment of the coincidence of the T point and the W point according to the embodiment of the present invention;

fig. 11 is a schematic diagram of an internal structure of a projector according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings by way of examples of preferred embodiments. It should be noted, however, that the numerous details set forth in the description are merely for the purpose of providing the reader with a thorough understanding of one or more aspects of the present invention, which may be practiced without these specific details.

As used in this application, the terms "module," "system," and the like are intended to include a computer-related entity, such as but not limited to hardware, firmware, a combination of hardware and software, or software in execution. For example, a module may be, but is not limited to: a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. For example, an application running on a computing device and the computing device may both be a module. One or more modules may reside within a process and/or thread of execution and a module may be localized on one computer and/or distributed between two or more computers. In addition, these modules can execute from various computer readable media having various data structures stored thereon. The modules may communicate by way of local and/or remote processes via signals.

The inventors of the present invention have found that if the optical axis projected by the projector is at an oblique angle to the screen surface, the projected area displayed on the display screen is not a regular rectangle but a distorted quadrangle, i.e., a geometric distortion occurs. If so, the projector needs to project a certain image on the display screen, for example, a certain page of slide in the PPT document needs to be projected on the display screen; or, a certain photo needs to be projected on a display screen; then, since the projected optical axis is at an oblique angle to the screen surface, the projected image displayed in the projection area on the display screen will also be geometrically distorted accordingly. Fig. 2 shows a projected image which is not corrected but geometrically distorted.

Based on the analysis, the idea of the invention is as follows: an original image to be projected by the projector is corrected in advance, for example, as shown in fig. 3, a rectangular original image is subjected to some transformation operation to obtain a corrected image. The corrected image is not a regular rectangle, but an irregular quadrangle after a geometric change. When the projector projects the corrected image, i.e., the trapezoidal image, the distortion of the corrected image is exactly offset by the distortion factor generated by the inclination of the optical axis, so that the projected image displayed in the projection area of the display screen is a regular rectangular image. That is, after the corrected image is projected, the projected image displayed in the projection area is not geometrically distorted with respect to the original image. The parameters for transforming the original image can be obtained by referring to the distortion degree of the projection area. That is, the projection area of the projector on the display screen is shot by the camera, and the distortion condition of the projection area in the shot image is analyzed, so that the parameters of the inverse distortion (or geometric correction parameters) can be calculated. The original image is transformed by using the inverse distortion parameter (or called geometric correction parameter) to obtain a corrected image, so that the projector does not have geometric distortion when projecting the corrected image onto a display screen.

The technical solution of the embodiments of the present invention is described in detail below with reference to the accompanying drawings. As shown in fig. 4, a projector according to an embodiment of the present invention includes: camera module 401, projection module 402, correction module 403.

The projection module 402 projects the light onto the display screen, and a projection area with higher brightness is displayed on the display screen, that is, the brightness of the projection area is higher than that of a non-projection area without projection light. If the projection module 402 also projects an image onto the display screen, a corresponding projected image will be displayed in the projection area. If the optical axis projected by the projection module 402 is at an oblique angle to the screen surface, the high-brightness projection area displayed on the display screen will not be a regular rectangle, but a deformed quadrilateral, i.e. a geometric distortion occurs. Assuming again that the projection module 402 projects an original image without correction processing into the projection area, the projected image will also have corresponding geometric distortion.

The camera module 401 is fixedly disposed on the projector, and preferably, is disposed adjacent to the projection module 402, for example, above the projection module 402, and is configured to capture a projection area projected on the display screen by the projector to obtain a captured image. In practical applications, the camera module 401 can continuously capture the projection area projected on the display screen.

And a correction module 403, configured to determine a corresponding geometric correction parameter according to the projection area in the captured image, and perform geometric correction processing. Specifically, the correction module 403 determines the position coordinates of four vertices of the projection area in the captured image; and calculating geometric correction parameters according to the position coordinates of the four vertexes of the determined projection area, and then performing operation transformation on the original image needing to be projected by using the geometric correction parameters to obtain a corrected image. The correction module 403 transmits the calculated corrected image to the projection module 402.

The projection module 402 projects the corrected image. After the distortion factor of the corrected image is offset with the distortion factor generated by the inclination of the optical axis, a projected image without geometric distortion relative to the original image is displayed on the display screen, so that the correction of the projected image is realized.

Describing the method for geometrically correcting the projected image by the projector according to the embodiment of the present invention in detail, the flow is shown in fig. 5, in step S501, the projection module 402 projects light onto the display screen to display a projection area with higher brightness on the display screen. Of course, when the projection module 402 displays the projection area on the display screen, the image may be projected or may not be projected. If image projection is performed, in the projection areaThe corresponding projection image will be displayed in the field. Next, in step S502, the image capturing module 401 captures a projection area projected on the display screen by the projection module 402 of the projector, and obtains a captured image. Next, the correction module 403 determines a projection area in the captured image (step S503). Specifically, since the captured image is usually stored in a pixel matrix, each pixel includes position information and luminance information of the pixel. The position information is the position coordinates of the pixel in the image, and the brightness information may be the brightness value of the pixel. The image captured by the camera module 401 includes both the projection area with high brightness on the display screen and the partial area without projection on the display screen. Therefore, in the captured image, the luminance value of the projection area is larger than that of the area where no projection is made. Then, the boundary of the projection area can be determined by analyzing the luminance values of the pixels in the captured image. How to determine the boundary of the projection area according to the brightness values of the pixels in the captured image is well known to those skilled in the art and will not be described herein. In step S504, the correction module 403 determines corresponding geometric correction parameters according to the projection area of the captured image. Specifically, after the correction module 403 determines the projection area in the captured image, the degree of geometric distortion caused by the inclination of the optical axis of the projector can be known, and then the inverse distortion parameter, that is, the geometric correction parameter, can be determined. For example, the correction module 403 may obtain position coordinates of four points in the projection area, and learn the degree of geometric distortion caused by the inclination of the optical axis of the projector according to the position coordinates of the four points, so as to determine the inverse distortion parameter. The above transformation theory of removing distortion can be solved by mathematical calculation. Preferably, since the projection area is generally quadrilateral, the degree of geometric distortion caused by the inclination of the optical axis of the projector can be known according to the position coordinates of the four vertices of the projection area in the captured image, and then the inverse distortion parameter, that is, the geometric correction parameter, can be determined. Suppose that, in the xy coordinate system in which both the x-axis and the y-axis are positive, the four vertices of the projection area in the captured image are A, B, C, D points in order clockwise from the upper left corner, and the positions of A, B, C, D four verticesThe coordinates are respectively (x)₁，y₁)、(x₂，y₂)、(x₃，y₃)、(x₄，y₄)。

In fact, the geometric correction parameters may be determined from the position coordinates of the four vertices of the projection area and the position coordinates of the four vertices of a certain correction rectangle. It is assumed here that, in the xy coordinate system in which the x-axis and the y-axis are both positive, the four vertices of the correction rectangle are points a ', B', C ', and D' in order from the upper left corner, and the position coordinates of the points a ', B', C ', and D' are (x), respectively₁′，y₁′)、(x₂′，y₂′)、(x₃′，y₃′)、(x₄′，y₄′)。

The position coordinates of the four vertices of the correction rectangle may be predetermined. For example, a correction rectangle is set as a rectangular area of a set size centered on the captured image, and thus, the position coordinates of the four vertices of the correction rectangle are also set.

Alternatively, the position coordinates of the four vertices of the correction rectangle may be determined from the position coordinates of the four vertices of the projection area in the captured image. Preferably, the correction rectangle may be a rectangle located within a projection area, that is, for a quadrangle constituted by four vertices of a projection area in the captured image, it is determined that the position coordinates of the four vertices of the correction rectangle are located within the quadrangle. Further, in order to ensure that the aspect ratio of the corrected image is consistent with that of the original image, that is, in order to avoid the image from being squashed or stretched, the aspect ratio of the correction rectangle may be made the same as that of the original image, in addition to the position coordinates of the four vertices of the correction rectangle being located within the quadrangle formed by the four vertices of the projection area in the captured image. How to determine a correction rectangle so that the correction rectangle is located within a quadrilateral formed by four vertices of a projection area in a captured image and the aspect ratio of the correction rectangle is the same as that of an original image is well known in the art and will not be described herein.

As shown in fig. 6, equations 1-4 below provide a method of determining the position coordinates of the four vertices of a correction rectangle located within the projection area:

x₁′＝x₄′＝max(x₁，x₄) (ii) a (equation 1)

x₂′＝x₃′＝min(x₂，x₃) (ii) a (equation 2)

y₁′＝y₂′＝min(y₁，y₂) (ii) a (equation 3)

y₃′＝y₄′＝max(y₃，y₄) (ii) a (equation 4)

The max is represented by taking the maximum value of the value in parentheses, and min is represented by taking the minimum value of the value in parentheses.

The correction module 403 calculates geometric correction parameters according to the following formula 1 according to the position coordinates of the four vertices of the projection area in the captured image and the position coordinates of the four vertices of the correction rectangle:

(formula 1)

In the above formula 1, i is an integer between [1, 4 ]; a. b, c, d, e, f, u and v are calculated geometric correction parameters.

Next, in step S505, the correction module 403 performs operation transformation on the original image to be projected by using the geometric correction parameters, so as to obtain a corrected image. Assuming that the position coordinate of a certain pixel in the original image is (x, y), the position coordinate (x ', y') of the corresponding pixel in the corrected image can be calculated according to the following formula 2:

(formula 2)

Obviously, the position coordinates of any pixel in the original image can be substituted into the x, y values in the above formula 2, so as to obtain the position coordinate values x ', y' of the corresponding pixel in the corrected image. And (3) performing operation transformation on all pixels in the original image according to the formula 2 to obtain a corrected image.

Further, since the original image may lose some pixel characteristics after being subjected to the operation transformation, the interpolation operation may be performed on the image obtained after the operation transformation on the original image, so as to obtain the final corrected image. Through interpolation operation, missing pixel points caused by image scaling can be supplemented, a possible mosaic phenomenon is eliminated, the content of a display picture is in smooth transition, and the watching effect is not influenced.

In step S506, the correction module 403 transmits the corrected image to the projection module 402. In step S507, the projection module 402 projects the corrected image onto a display screen. The corrected image obtained after the operation transformation generates certain geometric distortion relative to the original image, and after the distortion factor of the corrected image is offset with the distortion factor generated by the inclination of the optical axis, a projected image without geometric distortion relative to the original image is displayed on the display screen, so that the geometric correction of the projected image is realized.

Preferably, the projector according to the embodiment of the present invention may further include a verification module 404, as shown in fig. 7.

The verification module 404 is disposed between the camera module 401 and the correction module 403, and configured to perform geometric distortion determination on a captured image obtained by the camera module 401, and send a geometric distortion determination result to the correction module 403.

Preferably, the correction module 403 determines whether to perform the geometric correction process according to the geometric distortion determination result sent by the verification module 404:

if the geometric distortion determination result is distortion, the correction module 403 performs operation transformation on the original image according to the method of the above steps S503 to S505 to obtain a corrected image, and sends the corrected image to the projection module 402 for projection display. If the geometric distortion is determined not to be distorted, the correction module 403 directly sends the original image to the projection module 402 for projection display without performing geometric correction processing.

In addition to geometric distortion, the colors of the image may also be distorted during projection, and color distortion may occur. For example, the projected image is orange overall, i.e. a color distortion.

Further, the projector according to the embodiment of the present invention may further perform color correction processing. Specifically, the verification module 404 may further perform color distortion determination on the captured image obtained by the image capturing module 401, and send the result of the color distortion determination to the correction module 403.

The correction module 403 receives the color distortion determination result sent by the verification module 404, and determines whether to perform color correction processing according to the color distortion determination result:

if the color distortion determination result is distortion, the correction module 403 determines the primary color to be adjusted according to the background color of the projection area in the captured image currently acquired by the camera module, and sends the brightness adjustment value of the primary color to be adjusted to the projection module 402; then the projection module 402 adjusts the brightness of the corresponding primary color of the light source according to the received brightness adjustment value of the primary color to be adjusted; the image capturing module 401 continues to capture the projection area projected on the display screen by the projection module 402 of the projector, and obtains a captured image. The correction module 403 continues to acquire the shot image currently shot by the camera module 401, and ends the color correction when it is determined that the relative distance between the color coordinates of the background color of the projection area in the color coordinate system and the color coordinates of the target color in the color coordinate system in the shot image currently acquired by the camera module 401 is smaller than a set value; otherwise, the primary color to be adjusted is determined continuously according to the relative position between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system, and the brightness adjustment value of the primary color to be adjusted is continuously sent to the projection module 402. A specific color correction processing method will be described later. If the color distortion determination result is no distortion, the correction module 403 does not need to perform color correction processing, i.e., does not send the brightness adjustment value of the primary color to be adjusted to the projection module 402. The projection module 402 does not change the primary color brightness of the projection light source.

The projector according to the embodiment of the present invention has a geometric distortion determining and correcting process, and a color distortion determining and correcting process, as shown in fig. 8. In step S801, the projection module 402 projects light onto a display screen, and a projection area with high brightness is displayed on the display screen. Next, in step S802, the image capturing module 401 captures a projection area projected on the display screen by the projection module 402 of the projector, and obtains a captured image. In step S803, the verification module 404 performs geometric distortion determination on the captured image obtained by the image capture module 401, and sends the result of the geometric distortion determination to the correction module 403.

The verification module 404 may perform geometric distortion determination according to a side length ratio of opposite sides of the projection region in the captured image and an included angle between adjacent sides. Specifically, for a quadrangle formed by the projection area:

if the included angle λ between adjacent edges exceeds a set range, it is determined that geometric distortion occurs, for example, the set range is 85 ° to 95 °, and if λ exceeds the set range, it is determined that geometric distortion occurs. Obviously, there are many other ways to determine if λ is outside the set range. In the embodiment of the present invention, the determination is made as follows: if, given a value for σ, λ satisfies the following inequality 1:

(inequality 1)

Judging that the lambda does not exceed the set range; otherwise, judging that the lambda exceeds the set range. The value of sigma can be determined according to the actual situation, if the requirement effect is good, 0.95 can be obtained, and the requirement effect is not high, 0.8 can be obtained.

And if the included angle lambda of the adjacent edges does not exceed the set included angle range, continuously judging whether the side length ratio of the opposite edges of the projection area is in the set range. A quadrilateral of the projected area having two pairs of opposite sides. And respectively judging whether the side length ratio is in a set range or not for the unpaired side. If the side length ratio of a pair of opposite sides exceeds the set range, judging that the geometric distortion occurs. For example, for the projection region with the vertex at A, B, C, D, the AB side and the DC side are opposite sides, the AD side and the BC side are opposite sides, and l_AB、l_DC、l_AD、l_BCThe side lengths of the AB side, the DC side, the AD side and the BC side are respectively. If l is_AB、l_DC、l_AD、l_BCIf one of inequalities 2 and 3 does not satisfy, it is determined that the geometric distortion occurs:

(inequality 2)

(inequality 3)

The skilled person can set the value according to the actual situation. For example, the desired effect may be set to 0.95 if desired, or 0.8 if the desired effect is not as high; in general, the set range may be (0.6. ltoreq. 1).

In step S804, the verification module 404 may further perform color distortion determination on the current captured image captured by the image capture module 401, and transmit the color distortion determination result to the correction module 403.

Specifically, the verification module 404 may determine color coordinates of a background color of the projection region in the captured image in the color coordinate system according to the captured image, and perform the color distortion determination according to the color coordinates of the background color and a distance between the color coordinates of the target color in the color coordinate system. Let the color coordinate of the background color of the projection area be T point in the color coordinate system and the color coordinate of the target color be W point in the color coordinate system (as shown in fig. 9 a). The color coordinates of the target color are preset. The verification module 404 calculates a distance between the point T and the point W, and determines that the color distortion determination result is distortion if the distance exceeds a set distance value; otherwise, determining that the color distortion judgment result is undistorted. For example, the distance between the T point and the W point in the color coordinate system is calculated, if the distance satisfies 0 ≦ γ, the requirement can be considered to be satisfied, and the value range of γ is preset to 0 ≦ γ ≦ 0.03.

One specific method of determining the color coordinates of the background color of the projection area in the captured image may be: after four vertices of the projection area in the captured image are determined, color coordinates of the four vertices are acquired. The average of the color coordinates of the four vertices is taken as the color coordinate of the background color of the projection area in the captured image. For example, assume that the color coordinates of the four vertices of the projection area in the captured image are: (x)_c1，y_c1)、(x_c2，y_c2)、(x_c3，y_c3)、(x_c4，y_c4)。The color coordinate (x) of the background color of the projection area in the photographed image_c，y_c) Determined according to the following equations 5, 6:

x_{c} = \frac{x_{c 1} + x_{c 2} + x_{c 3} + x_{c 4}}{4}

(equation 5)

y_{c} = \frac{y_{c 1} + y_{c 2} + y_{c 3} + y_{c 4}}{4}

(equation 6)

It is possible for those skilled in the art to determine the color coordinates of the background color of the projection area not only by using the color coordinates of the four vertices of the projection area, but also by using the color coordinates of other points within the projection area.

Obviously, steps S803 and S804 may be executed simultaneously, or S803 may be executed first, or S804 may be executed first.

In step S805, if the geometric distortion determination result is distortion, the correction module 403 performs geometric correction processing on the original image to obtain a corrected image, and sends the corrected image to the projection module 402 for projection display. That is, the correction module 403 determines corresponding geometric correction parameters according to the projection area in the captured image, performs geometric correction processing on the original image using the geometric correction parameters to obtain a corrected image, and then sends the corrected image to the projection module 402 for projection display. The method of the geometric correction processing of the correction module 403 has been described in detail in the above steps S503-S505, and is not described herein again.

Next, in step S806, if the geometric distortion is determined not to be distorted, the correction module 403 directly sends the original image to the projection module 402 for projection display without performing geometric correction processing. If the color distortion determination result is distortion, the correction module 403, the image capturing module 401, and the projection module 402 cooperate to perform color correction processing (step S807).

The detailed flow of the color correction process performed by the correction module 403, the camera module 401, and the projection module 402 in cooperation is shown in fig. 9 b. In step S901, the image capturing module 401 captures a projection area projected on the display screen by the projector, and acquires a captured image. The correction module 403 determines the primary color to be adjusted according to the background color of the projection area in the captured image currently acquired by the camera module (step S902). Specifically, the correction module 403 determines the primary colors to be adjusted according to the relative positions of the color coordinates of the background color of the projection area in the captured image currently acquired by the image capturing module 401 in the color coordinate system and the color coordinates of the target color in the color coordinate system.

Specifically, the correction module 403 determines, according to the captured image, color coordinates of the background color of the projection area in the captured image in the color coordinate system, and determines the primary color to be adjusted according to the color coordinates of the background color and the color coordinates of the target color in the color coordinate system, so that after the primary color to be adjusted is adjusted, the background color of the projection area in the captured image that is captured again is close to the target color; that is, after the primary color to be adjusted is adjusted, the color coordinates of the background color of the projection area in the captured image captured again are made to be close to the color coordinates of the target color.

As shown in fig. 10, the color coordinates of the three primary color light sources are R, G, B points in the color coordinate system, the color coordinate of the target color is W point in the color coordinate system, and the color coordinate of the background color of the projection area in the currently captured image is T point in the color coordinate system. R, W points are connected and extended to obtain a straight line RW, G and W points are connected and extended to obtain a straight line GW, and B and W points are connected and extended to obtain a straight line BW.

Firstly, a straight line closest to the point T is determined from among the straight lines RW, GW and BW, and the primary color to be adjusted and the brightness adjustment value of the primary color to be adjusted are determined according to the straight line closest to the point T. The method specifically comprises the following steps: and judging which primary color of the T point is to be adjusted in brightness, and enabling the T point to move to the straight line with the shortest distance, wherein the primary color is the primary color to be adjusted. For example, it is determined that the distance between the T point and the straight line BW is the closest, and in fig. 10, since the T point and the G point are located on the same side of the straight line BW, the T point can be moved to the straight line BW by increasing the luminance of the R primary color of the T point, and thus, it is determined that the primary color to be adjusted is the R primary color; of course, the luminances of the other two colors of the T point may also be reduced, that is, the luminances of the B and G primaries are reduced, so that the T point moves to the straight line BW, and thus, the primaries to be adjusted are determined to be the B and G primaries.

For the case that the distance between the T point and the straight line is smaller than the set threshold or coincides with the set threshold, the method for judging the primary color to be adjusted is as follows: and judging which primary color of the T point is to be adjusted in brightness, and enabling the T point to move towards the W point, wherein the primary color is the primary color to be adjusted. For example, the T point coincides with the straight line BW, and the T point can be moved to W by increasing the luminance of the B primary color of the T point, thereby determining that the primary color to be adjusted is the B primary color; of course, the primary colors to be adjusted can also be determined as the R and G primary colors by reducing the brightness of the other two colors of the T point, i.e., reducing the brightness of the R and G primary colors so that the T point moves toward W. The setting of the threshold value can be set by a person skilled in the art according to the actual situation.

Another preferred method for determining the primary color to be adjusted is as follows: as shown in FIG. 10, straight line RW includes line segments between RW and extensions of RW line segments; the straight line BW comprises line segments between BWs and extension lines of the BW line segments; the straight line GW includes the line segments between GWs and the extensions of the GW line segments. First, the extension line closest to the point T is determined. The method for judging the primary colors to be adjusted comprises the following steps: and judging which primary color of the T point is to be adjusted in brightness, and enabling the T point to move towards the extension line with the shortest distance, so that the primary color is the primary color to be adjusted. The determination method is similar to the above, and is not described herein again.

For the case that the distance between the point T and the nearest extension line is smaller than a set threshold or coincides with the set threshold, the method for determining the primary color to be adjusted is as follows: and judging which primary color of the T point is to be adjusted in brightness, and enabling the T point to move towards the W point, wherein the primary color is the primary color to be adjusted. For example, the T point coincides with the extension line of the BW line segment, and the T point can be moved to W by increasing the brightness of the B primary color at the T point, so that the primary color to be adjusted is determined to be the B primary color.

In this way, the light source can be adjusted by increasing the primary color brightness, rather than decreasing the primary color brightness.

In step S903, the correction module 403 sends the determined brightness adjustment value of the primary color to be adjusted to the projection module 402. After determining the primary color to be adjusted, the correction module 403 may send the brightness adjustment value of the primary color to be adjusted to the projection module 402. For example, in the above example, the T point may be moved to the straight line BW by increasing the luminance of the R primary color at the T point, so as to determine that the primary color to be adjusted is the R primary color. The brightness adjustment value is a predetermined proper step value, the primary color to be adjusted is determined in the subsequent time, and the brightness adjustment value is sent to the projection module 402, so that the T point is finally close to or coincident with the W point.

For another example, in the above example, the luminances of the other two colors at the point T are decreased, that is, the luminances of the B and G primary colors are decreased so that the point T moves to the straight line BW, and thus, the primary colors to be adjusted are determined to be the B and G primary colors.

In step S904, the projection module 402 adjusts the brightness of the corresponding primary color of the light source according to the received brightness adjustment value of the primary color to be adjusted. Specifically, after the projection module 402 receives the brightness adjustment value of the primary color to be adjusted, for example, the brightness adjustment value is the brightness adjustment value of the R primary color, and the brightness adjustment value is positive, the projection module 402 correspondingly increases a certain brightness of the R primary color of the light source. For another example, if the brightness adjustment value is a brightness adjustment value of the primary colors B and G, and the brightness adjustment value is negative, the projection module 402 correspondingly reduces a certain brightness of the primary colors B and G of the light source. The degree to which the projection module 402 increases or decreases the brightness of the primary colors is determined according to the absolute value of the brightness adjustment value. After the projection module 402 adjusts the primary color brightness of the light source, the background color of the image projected onto the display screen will change.

In step S905, the correction module 403 continues to acquire the captured image currently captured by the image capturing module 401, and determines whether the relative distance between the color coordinate of the background color of the projection area and the color coordinate of the target color in the currently acquired captured image is smaller than a set value; if yes, ending the color correction, and executing step S906; otherwise, steps S902-S905 are repeated.

After the projection module 402 adjusts the primary color brightness of the light source, the background color of the projection area in the captured image acquired by the camera module 401 will also change accordingly. The correction module 403 continues to compare the color coordinates of the background color of the changed projection area with the color coordinates of the target color. If the two are close to each other or coincide with each other, the purpose of color correction is achieved, and the color correction process can be finished; otherwise, the color correction is continued. The set value can be determined by the person skilled in the art according to the actual situation, and if the requirement is higher, the set value can be set to be smaller; if the demand is low, the set value can be set to be large. Of course, the setting value may be set to 0, that is, it indicates that the overlap is complete. The set value may be set to be the same as or smaller than the set distance value.

By repeating the steps S902 to S905, the color coordinate T point of the background color of the projection area and the color coordinate W point of the target color are closer to each other until the requirement is met, thereby achieving the purpose of color correction.

Generally, the color coordinate point W of the target color is located within the triangle formed by points R, G, B. The straight lines RW, GW, BW intersect the straight lines BG, BR, GR at point P, N, M, respectively, dividing the triangle RGB into a plurality of small triangles.

The table shown in table 1 lists the method for determining the primary colors to be adjusted when the T points are respectively located in different small triangles. For example, for the case that the point T is located in the small triangle RWM, it is determined that the luminance of the primary color G is increased first, that is, it is determined that the primary color to be adjusted is the primary color G, and the luminance adjustment value of the primary color G is a positive value; the projection module gradually turns the primary color G of the projection light source brighter according to the brightness adjustment value of the primary color G to be adjusted, which is sent by the correction module for multiple times, so that the background color coordinate of the projection area in the shot image shot by the shooting module is closer to the BW straight line (or the extension line of the BW line segment) more and more. When the background color coordinates of the projection area in the shot image shot by the shooting module at present, namely the T point is overlapped with the BW straight line (or the extension line of the BW line segment) or is smaller than a set threshold, determining to increase the brightness of the B primary color, namely determining that the primary color to be adjusted is the B primary color, and the brightness adjustment value of the B primary color is a positive value.

TABLE 1

Is triangular	First step of increasing primary color brightness	Second step of increasing primary color brightness
			GWM	R	B
GWP	B	R
			RWM	G	B
RWN	B	G
			BWP	G	R
BWN	R	G

The manner of determining the primary colors to be adjusted shown in table 1 above is described in detail as follows:

if the T point is located in the small triangle GWM or BWN, determining that the primary color to be adjusted is the R primary color, and the brightness adjustment value of the R primary color is a positive value;

if the T point is positioned in the small triangle GWP or RWN, determining that the primary color to be adjusted is the B primary color, and the brightness adjustment value of the B primary color is a positive value;

if the point T is located in the small triangle RWM or BWP, determining that the primary color to be adjusted is the primary color G, and the brightness adjustment value of the primary color G is a positive value;

if the T point is coincident with the extended line of the BW line segment or is smaller than a set threshold, determining that the primary color to be adjusted is the B primary color, and the brightness adjustment value of the B primary color is a positive value;

if the T point is coincident with the extension line of the RW line segment or is smaller than a set threshold, determining that the primary color to be adjusted is the R primary color, and the brightness adjustment value of the R primary color is a positive value;

if the T point is coincident with the extension line of the GW line segment or is smaller than a set threshold, the primary color to be adjusted is determined to be the G primary color, and the brightness adjustment value of the G primary color is a positive value.

In step S906, this color correction is ended. The correction module 403 no longer sends the brightness adjustment value of the primary color to the projection module 402, and the projection module 402 will maintain the current primary color brightness of the projection light source.

A specific internal structure schematic diagram of a projector according to an embodiment of the present invention, as shown in fig. 11, includes: camera module 401, projection module 402, correction module 403, and verification module 404.

The structural functions of the camera module 401 are the same as those described above, and are not described herein again.

The verification module 404 may specifically include a geometric distortion determination unit 1101 and a color distortion determination unit 1102.

The geometric distortion determination unit 1101 is configured to perform geometric distortion determination on the captured image obtained by the image capture module 401, and send a geometric distortion determination result to the correction module 403. The method for determining the geometric distortion by the geometric distortion determining unit 1101 is the same as that described in step S803, and is not described herein again. The color distortion determination unit 1102 is configured to perform color distortion determination on the captured image obtained by the image capture module 401, and send a color distortion determination result to the correction module 403. The method for determining color distortion by the color distortion determining unit 1102 is the same as that described in step S804, and is not described herein again.

The correction module 403 may include a geometric correction processing unit 1103 and a color correction processing unit 1104. The geometric correction processing unit 1103 is configured to receive the geometric distortion determination result sent by the geometric distortion determination unit 1101, and perform geometric correction processing according to the geometric distortion determination result. Specifically, if the geometric distortion determination result is distortion, the geometric correction processing unit 1103 performs geometric correction processing on the original image to obtain a corrected image, and sends the corrected image to the projection module 402 for projection display; if the geometric distortion determination result is no distortion, the geometric correction processing unit 1103 directly sends the original image to the projection module 402 for projection display without performing geometric correction processing. The method for performing the geometric correction processing on the original image by the geometric correction processing unit 1103 to obtain the corrected image is the same as the method detailed in the previous steps S503-S505, and is not repeated here.

The color correction processing unit 1104 is configured to receive the color distortion determination result sent by the color distortion determination unit 1102; and performing color correction processing according to the color distortion judgment result. Specifically, if the color distortion determination result is distortion, then: determining a primary color to be adjusted according to a color coordinate of a background color of a projection area in a shot image currently acquired by the camera module 401 in a color coordinate system and a relative position between color coordinates of a target color in the color coordinate system; sending the determined brightness adjustment value of the primary color to be adjusted to the projection module 402; after the projection module 402 adjusts the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted, continuously acquiring the shot image currently shot by the camera module 401, and when it is determined that the relative distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system is smaller than a set value, continuously determining the primary color to be adjusted according to the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module 401 in the color coordinate system and the relative position between the color coordinates of the target color in the color coordinate system; and sends the determined brightness adjustment value of the primary color to be adjusted to the projection module 402. If the color distortion determination result is no distortion, the color correction processing unit 1104 does not perform any processing, and the projection module 402 maintains the current primary color brightness of the light source. The method for performing color correction processing by the cooperation of the color correction processing unit 1104 in the correction module 403, the camera module 401, and the light source driving unit 1106 in the projection module 402 is the same as the method for performing color correction processing by the cooperation of the correction module 403, the camera module 401, and the projection module 402 shown in fig. 9b, and the detailed description thereof is omitted here.

The projection module 402 includes an image driving unit 1105 and a light source driving unit 1106. The image driving unit 1105 is configured to perform projection based on the image sent by the geometric correction processing unit 1103. The image sent by the geometric correction processing unit 1103 may be a corrected image or an original image. The light source driving unit 1106 is configured to adjust the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted sent by the color correction processing unit 1104.

Due to the above-described color distortion judgment and color correction processing, geometric distortion judgment and geometric correction processing are not relied upon, that is, the projector can perform only color distortion judgment and correction without performing geometric distortion judgment and correction. Therefore, in practical applications, the verification module of the projector may have only a function of determining color distortion, that is, only the color distortion determination unit 1102. The correction module may also be a function having only color correction processing, i.e., only the color correction processing unit 1104. In the flow steps of the correction process shown in fig. 8, the color distortion determination and the color correction process may be realized solely by the steps S801 to S802, S804, and S807.

The projector according to the embodiment of the present invention performs the geometric correction processing or the color correction processing by analyzing the projection area in the captured image, so that it is not necessary to perform the correction operation by projecting a predetermined image having a certain characteristic, thereby simplifying the process of correcting the projected image.

Those skilled in the art will appreciate that all or part of the steps in the method for implementing the above embodiments may be implemented by relevant hardware instructed by a program, and the program may be stored in a computer readable storage medium, such as: ROM/RAM, magnetic disk, optical disk, etc.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.

Claims

1. A projection image correction method comprising:

shooting a projection area projected on a display screen by a projector through a camera module to obtain a shot image;

carrying out color correction and geometric correction on the shot image;

the color correction includes:

a. the correction module determines the primary colors to be adjusted according to the relative positions of the color coordinates of the background colors of the projection areas in the shot images currently acquired by the camera module in the color coordinate system and the color coordinates of the target colors in the color coordinate system; sending the determined brightness adjustment value of the primary color to be adjusted to a projection module; the brightness adjustment value is predetermined;

b. the projection module adjusts the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted;

c. the correction module continuously acquires the shot image currently shot by the camera module, and when the relative distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system is determined to be smaller than a set value, the color correction is finished; otherwise, repeating the steps a, b and c;

the geometric correction includes:

after receiving the shot image, the correction module determines geometric correction parameters according to the position coordinates of the four vertexes of the projection area in the shot image and the position coordinates of the four vertexes of the correction rectangle; and are

Using the geometric correction parameters to perform operation transformation on the original image to be projected to obtain a corrected image, and sending the calculated corrected image to a projection module;

and projecting the corrected image onto a display screen by a projection module.

2. The method of claim 1, wherein determining geometric correction parameters based on the position coordinates of the four vertices of the projection area and the position coordinates of the four vertices of the correction rectangle comprises calculating geometric correction parameters using the following formula:

(formula 1)

Wherein i is [1, 4]]An integer of (x)₁，y₁)、(x₂，y₂)、(x₃，y₃)、(x₄，y₄) Position coordinates of four vertexes of the projection area; (x)₁'，y₁')、(x₂'，y₂')、(x₃'，y₃')、(x₄'，y₄') are the position coordinates of the four vertices of the correction rectangle; a. b, c, d, e, f, u and v are calculated geometric correction parameters.

3. The method of claim 2, wherein transforming the original image to be projected using the geometric correction parameters to obtain the corrected image comprises determining corrected location coordinates of a pixel in the original image corresponding to the location coordinates of the pixel according to the following equation:

(formula 2)

Where (x, y) is the position coordinate of a pixel in the original image, and (x ', y') is the position coordinate of the pixel after correction.

4. The method of any one of claims 1-3, wherein the coordinates of the positions of the four vertices of the correction rectangle are predetermined; or,

the position coordinates of the four vertices of the correction rectangle are determined from the position coordinates of the four vertices of the projection area in the captured image.

5. The method of claim 4, the position coordinates of the four vertices of the correction rectangle being determined from the position coordinates of the four vertices of the projection area in the captured image comprising:

determining, for a quadrangle made up of four vertices of a projection area in the captured image, that the position coordinates of the four vertices of the correction rectangle are located within the quadrangle;

or, for the quadrangle formed by four vertexes of the projection area in the captured image, determining that the position coordinates of the four vertexes of the correction rectangle are located within the quadrangle, and the aspect ratio of the correction rectangle is the same as that of the original image.

6. The method of claim 5, wherein after the step of determining the geometric correction parameters according to the position coordinates of the four vertices of the projection area and the position coordinates of the four vertices of the correction rectangle in the captured image after the step of receiving the captured image by the correction module, the geometric correction further comprises:

and the verification module judges the geometric distortion of the projection area in the shot image and sends the geometric distortion judgment result to the correction module.

7. The method as claimed in claim 1, further comprising, after the step of capturing the projection area projected on the display screen by the projector by the camera module to obtain the captured image:

the verification module carries out color distortion judgment on the projection area in the shot image and sends a color distortion judgment result to the correction module; and the number of the first and second groups,

the correction module determines the primary colors to be adjusted according to the relative position between the color coordinates of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinates of the target color in the color coordinate system specifically as follows: and after the color distortion judgment result is determined to be distortion, the correction module determines the primary color to be adjusted according to the relative position of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system.

8. The method of claim 7, wherein the verifying module performs a color distortion determination on the projected area in the captured image comprises:

if the verification module determines that the distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system exceeds a set distance value, determining that the color distortion judgment result is distortion; otherwise, determining that the color distortion judgment result is undistorted.

9. The method according to claim 8, wherein the determining, by the correction module, the primary colors to be adjusted according to the relative positions between the color coordinates of the background color of the projection area in the captured image currently acquired by the camera module in the color coordinate system and the color coordinates of the target color in the color coordinate system comprises:

the color coordinates of the three primary color light sources are R, G, B points in the color coordinate system respectively, the color coordinate of the target color is a W point in the color coordinate system, and the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module is a T point in the color coordinate system; the straight lines RW, GW and BW are respectively intersected with the straight lines BG, BR and GR at a point P, N, M, and the triangle RGB is divided into small triangles GWM, BWN, GWP, RWN, RWM and BWP;

10. A projector comprising, a camera module, a correction module, a verification module, and a projection module, wherein:

the camera module is used for shooting a projection area projected on the display screen by the projector to obtain a shot image;

the correction module is used for determining geometric correction parameters according to the position coordinates of the four vertexes of the projection area in the shot image and the position coordinates of the four vertexes of the correction rectangle after determining that the geometric distortion judgment result is distortion; the geometric correction parameters are used for carrying out operation transformation on the original image to be projected to obtain a corrected image, and the calculated corrected image is sent to a projection module;

the verification module is used for judging geometric distortion of a projection area in the shot image and sending a geometric distortion judgment result to the correction module; the correction module is used for judging color distortion of a projection area in the shot image and sending a color distortion judgment result to the correction module;

the correction module is further used for determining a primary color to be adjusted according to the relative position of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system after the color distortion judgment result is determined to be distortion; sending the determined brightness adjustment value of the primary color to be adjusted to the projection module; the brightness adjustment value is predetermined;

the correction module is further used for continuously acquiring a shot image currently shot by the camera module, and continuously determining a primary color to be adjusted according to the relative position between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system when determining that the relative distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system is smaller than a set value; sending the determined brightness adjustment value of the primary color to be adjusted to the projection module; and the number of the first and second groups,

the projection module is used for adjusting the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted; projecting the corrected image onto a display screen.

11. The projector according to claim 10, wherein position coordinates of four vertices of the correction rectangle are predetermined; alternatively, the position coordinates of the four vertices of the correction rectangle are determined from the position coordinates of the four vertices of the projection area in the captured image.

12. The projector as claimed in claim 10, wherein the authentication module comprises:

the geometric distortion judging unit is used for judging geometric distortion of the projection area in the shot image and sending a geometric distortion judging result to the correcting module;

and the color distortion judging unit is used for judging color distortion of the projection area in the shot image and sending the color distortion judging result to the correcting module.

13. The projector as defined in claim 12 wherein the correction module comprises:

the geometric correction processing unit is used for receiving the geometric distortion judgment result sent by the geometric distortion judgment unit; if the geometric distortion judgment result is distortion, determining a projection area in the shot image and determining corresponding geometric correction parameters; using the geometric correction parameters to perform operation transformation on the original image to be projected to obtain a corrected image;

the color correction processing unit is used for receiving the color distortion judgment result sent by the color distortion judgment unit; if the color distortion judgment result is distortion, then: determining a primary color to be adjusted according to the relative position between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system; sending the determined brightness adjustment value of the primary color to be adjusted to the projection module; after the projection module adjusts the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted, continuously acquiring a shot image currently shot by the camera module, and when it is determined that the relative distance between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system is smaller than a set value, continuously determining the primary color to be adjusted according to the relative position between the color coordinate of the background color of the projection area in the shot image currently acquired by the camera module in the color coordinate system and the color coordinate of the target color in the color coordinate system; and sending the determined brightness adjustment value of the primary color to be adjusted to the projection module.

14. The projector as defined in claim 13 wherein the projection module comprises:

the image driving unit is used for projecting according to the corrected image sent by the geometric correction processing unit;

and the light source driving unit is used for adjusting the brightness of the corresponding primary color of the light source according to the brightness adjustment value of the primary color to be adjusted, which is sent by the color correction processing unit.