JP6236764B2 - Image projection apparatus evaluation method, image projection apparatus, image projection apparatus manufacturing method, and image projection apparatus evaluation system - Google Patents

Description

  The present invention relates to an image projection apparatus evaluation method, an image projection apparatus, an image projection apparatus manufacturing method, and an image projection apparatus evaluation system.

Image display devices generally referred to as projectors include CRT projectors, liquid crystal projectors, DMD (Digital Micromirror Device) projectors, and the like, depending on image display elements.
The DMD is a reflective image display element that has a plurality of micromirrors arranged two-dimensionally and changes the tilt angle of each micromirror to turn on / off the reflected light.

In some cases, foreign matter such as dust, dirt, and dirt adheres to the optical elements and components of the illumination system and projection system equipped in the image projection apparatus (projector).
Foreign matter and scratches may affect the projected image, although there are differences depending on the optical parts and location.

There are the following cases for foreign matter to be mixed.
First, it occurs when a member is scraped or the like at a movable part inside the image projection apparatus.
Next, there is a case where fine particles such as dust, pollen and yellow sand in the atmosphere are mixed.
Furthermore, in a projector that uses an ultra-high pressure lamp, a metal halide, or the like as a light source, it is necessary to always cool the inside of the casing of the projector due to the high temperature, and a fan or the like is used. For this reason, air always circulates in the apparatus, and this is a case where foreign matter contained in the air adheres to optical elements / components. In addition, since scratches on the optical elements / parts optically function in the same manner as foreign objects, the scratches are also included here.

  As an influence when a foreign object or a flaw exists in an optical element, the regular light quantity falls because the reflection in a projection surface generate | occur | produces.

Conventionally, there is a method disclosed in Patent Document 1 as a method for dealing with such a problem.
Patent Document 1 discloses a configuration that can acquire unevenness and pattern information of the reflectance of a screen or a wall that is a projection surface and reflect it in the projection of the current image so as to cancel out the information.

With the configuration disclosed in Patent Document 1, it is possible to acquire information on the unevenness and pattern of the reflectance of the screen or wall as the projection surface and reflect it in the projection of the current image so as to cancel it.
However, the target for monitoring the presence of foreign matter on the projection surface is not the foreign matter attached to the inside of the photographing unit, but the outside or the projection surface (projection surface). No problem has been recognized with respect to foreign matters or scratches on the optical elements inside the projector. For this reason, it cannot be dealt with when there is a cause such as adhesion of foreign matter inside the projector, and even if the projection surface (projection surface) is changed, the cause of the reflection cannot be eliminated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image projection apparatus evaluation method capable of evaluating image quality degradation due to reflection of foreign matter or scratches attached to optical elements inside a projector in view of the problems in the conventional image projection method. Is to provide.

In order to achieve this object, the present invention is a first step of imaging a projection surface before an image is projected by an imaging unit, an image obtained by imaging the projection surface before being projected, and a light amount distribution (first light amount). Distribution), a third step of projecting a test projection image by an image projection apparatus having an optical system, a fourth step of capturing a test image with the imaging means, analyzing the captured test image, A light quantity distribution (second light quantity distribution) is obtained, and a fifth step of analyzing a difference between the first light quantity distribution and the second light quantity distribution is executed, and the light quantity distribution of the projection image due to the deposit on the optical system In the image projection apparatus evaluation method, the influence on the image evaluation apparatus is evaluated.

  According to the present invention, in an image projection apparatus, it becomes possible to evaluate the influence of reflection of foreign matter, scratches, etc. in the image projection apparatus.

It is a figure for demonstrating the image projection system used for the image projection method which concerns on embodiment of this invention. It is a figure for demonstrating the modification regarding the structure of the imaging means used for the image projection system shown in FIG. It is a figure for demonstrating another modification regarding the structure of the imaging means used for the image projection system shown in FIG. It is a figure for demonstrating the modification regarding the structure of the analysis means used for the image forming system shown in FIG. It is a flowchart for demonstrating the extraction procedure of the foreign material performed by the analysis means shown in FIG. It is a figure for demonstrating the structure of DMD. It is a figure which shows the reflection contained in the projected test image. FIG. 8 is an enlarged view of the reflection shown in FIG. 7. It is a figure for demonstrating the profile information in the x and y direction which made object the reflection shown in FIG. It is a figure for demonstrating the cancellation procedure used for the analysis of a foreign material from the profile information shown in FIG. It is a figure which shows the alarm state at the time of setting a threshold value in the cancellation procedure shown in FIG. It is a figure which shows the state in which the white reflection has arisen when an all black screen is displayed on a screen. It is a figure which shows the gradation expression regarding the reflection for the all black screen shown in FIG. It is a figure for demonstrating the procedure which cancels white reflection on a black background using gradation expression. It is a figure which shows the case where the reflection by the foreign material inside an image projection apparatus has overlapped with the stain | pollution | contamination, dirt, etc. which were originally on the projection surface. It is a figure for demonstrating the appearance of an image when DMD is used for a spatial light modulation element for all white screen. It is a figure for demonstrating the appearance of an image when DMD is used for a spatial light modulation element for all black screens. It is a figure for demonstrating the behavior of illumination light when black reflection has arisen on the white background. It is a figure for demonstrating the behavior of the illumination light when white reflection has arisen on the black background. It is a figure which shows the optical system of an image projection apparatus. It is a figure which shows the relationship between the foreign material on the folding mirror used for the projection optical system shown in FIG. 20, and the reflection in the image projected on the screen. It is a figure which shows the state in which white reflection appears on a black background in the shape of an arc or a slanted ellipse. It is a figure which shows the case where a pattern, a nonuniformity, dirt, a spot, etc. exist from the screen or a wall originally. It is the figure which showed the mode of the screen or wall (projection surface) before projecting a test image. It is a figure for demonstrating a mode that the test pattern of all white was projected on the projection surface shown in FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
In the following description, the configuration and action required for this procedure will be described together with the procedure for quantifying the appearance of foreign objects, which is a feature of the present invention.

FIG. 1 is a diagram illustrating an example of an image projection system used in an image projection apparatus evaluation method according to an embodiment of the present invention.
In the figure, reference numeral 1 denotes an image projection apparatus (projector), reference numeral 2 denotes an imaging means, reference numeral 3 denotes a screen or wall, reference numeral 4 denotes a projection image, and reference numeral 5 denotes reflection of a foreign object.
In the image projection system, a test image is displayed from the image projection apparatus 1 and is photographed by the imaging means 2.
In FIG. 1, the projection from the image projection apparatus 1 is indicated by a solid line arrow, and the image of the projected image is indicated by a broken line arrow.

As the image pickup means 2, a digital camera, a CCD (Charge-coupled device) camera, or the like is used.
Color is preferable, but when the test image is white or black, a monochrome imaging means may be used. In FIG. 1, an all white screen is projected onto the test image.
The part where the foreign object is reflected shows a dark state.

The imaging unit 2 does not need to be different from the image projection apparatus 1 and may be incorporated in the image projection apparatus 1.
For example, as shown in FIG. 2, it is possible to include a projection lens 22 and an imaging unit 23 incorporated in the image projection device 21. In addition, as shown in FIG. 3, it is possible to provide a plurality of imaging means (indicated by reference numeral 24 in FIG. 3) to be a twin-lens type like a stereo camera.

The evaluation system for the image projection apparatus includes an analysis unit 6 in addition to the imaging unit 2 described above.
The analyzing means 6 is incorporated as a control board provided with an electronic electric circuit inside the image projection apparatus. Therefore, it is hardware-like.

Such analysis means 6 detects unevenness, patterns, spots, dirt, etc. on the screen surface obtained by imaging the screen or wall before irradiating light. The detection target in this case corresponds to the original screen image before image projection.
The analysis means 6 captures the original image on the screen surface before the above-described image projection.
After capture, test image projection according to the magnification ratio of the projection lens, imaging and analysis of the test image, and comparison with the original unevenness, pattern, stain, and dirt, and reflection due to foreign matter inside the image projection device To extract. This can be done by taking the difference between the original image and the test image.

  The analysis unit 6 includes a storage circuit board including a storage unit that can register the original image data described above. The analysis means 6 compares the extracted image with the information of the reflected image stored in advance in the storage circuit board, estimates the adhesion position of the foreign matter, and displays various warnings.

As described above, the analysis unit 6 is not limited to being provided as a hardware element such as a control board.
For example, as shown in FIG. 4, when the image projection apparatus 1 is used by being connected to a personal computer (PC) 7 or the like, it can be used in software as one of analysis programs.
Such a configuration is different from the case of performing analysis processing independently as in the case of a hardware configuration, and is inferior in calculation speed because it follows sequence processing executed by a personal computer (PC). There is an advantage that it is excellent in general purpose and extensibility, such as linking with programs.

FIG. 5 is a flowchart for explaining the contents of the processing executed by the analyzing means 6 shown in FIG.
In FIG. 5, the following process is executed in order to extract the reflection due to the foreign matter inside the image projection apparatus.
[1] Before projecting a test image (in a state where light is not irradiated on the projection surface), an image of a screen or a wall is captured by an imaging unit (first step (indicated by reference sign ST1)).
[2] Next, this image is analyzed to obtain a light amount distribution (first light amount distribution) (second step (indicated by reference ST2)).
[3] A projection image for test is projected (third step (indicated by symbol ST3)).
[4] Photographing is performed by the imaging means (fourth step (indicated by ST4) 4).
[5] The test image is analyzed to obtain a light amount distribution (second light amount distribution), and compared with the original image data (first light amount distribution), analysis for foreign matter extraction in the test image is performed. (Fifth step (indicated by symbol ST5)).

  As shown in FIG. 23, when the screen or the wall originally has a pattern, unevenness, dirt, a stain, or the like, it may be indistinguishable from a reflection due to a foreign substance inside the image projection apparatus. In step 1, before projecting a test image (in a state where light is not irradiated on the projection surface), before projecting a test image for capturing an image of a screen or a wall by the imaging means (light is projected onto the projection surface). An image of the screen or wall is taken by the image pickup means 2 (without irradiation).

In the second step (ST2), analysis of the image obtained in the first step (ST1) (acquisition of light amount distribution) is performed.
In the analysis performed in the second step (ST2), if the projection surface is flat and the illumination of the room light etc. is uniform, if there are spots, dirt, etc., by comparing the amount of light between that part and the surrounding area, The position and degree of the part can be detected.
This is clear from the prior art such as Patent Document 1. Image correction is also possible with the prior art. If the projection surface originally has stains or dirt, information such as the position, size, and amount of decrease in the amount of light is stored in the storage circuit of the projection image apparatus.

In addition, when there are no stains or dirt, the analysis result need not be reflected in the subsequent steps. When there are no spots or stains, the light amount distribution on the projection surface is uniform. When there are stains or stains, the light intensity distribution is darker, and as the number increases, the uniformity of the projection surface is lost.
In the second step, a position (first position information) where the light quantity is higher or lower than a set value (threshold value) is determined from the light quantity distribution. The set value (threshold value) may be set as a set value (threshold value) at a location where the uniformity of the light amount is high. This is a place where there are no stains or dirt.

  In the third step and the fourth step (ST3, 4), the test image is projected and imaged by a known method.

The analysis performed in the fifth step (ST5), variance analysis of light intensity distribution using an imaging picture images is carried out. In particular, in this case, a position (second position information) where the light amount is higher or lower than a set value (threshold value) from the second light amount distribution is used. The set value (threshold value) may be set as a set value (threshold value) at a location where the uniformity of the light amount is high. The second position information in the case of the present embodiment is an area that is not the first position information.
Procedures and methods Extraction of the foreign object with which use imaging field image below and described processing according to the analysis of the results issued collecting.

Spatial light modulation elements used for image formation of an image projection apparatus can be broadly classified as follows.
There are DMDs (Digital Micromirror Devices, Texas Instruments) that move micromirrors, reflective liquid crystal spatial light modulators (LCoS, Liquid Crystal on Silicon), and transmissive liquid crystal spatial light modulators.
The pixels of these spatial light modulation elements have sides of around 10 μm. For example, 1024 × 768 pixels are arranged in a resolution XGA (extended graphic array), and 1280 × 800 pixels are arranged in a WXGA.

In addition, as shown in FIG. 6D, these spatial light modulation elements are provided with a protective cover glass in front of the pixel array.
When foreign matter such as dust, dust, and dirt on the cover glass adheres, it is projected on the screen as reflection of the foreign matter.

The pixel array of the projection lens and the spatial light modulator is in a conjugate relationship, but the cover glass on the front surface (near the projection lens) of about 1 to 2 mm from the pixel array is also in a close conjugate relationship.
Accordingly, the foreign matter adhering to the cover glass is projected onto the screen by the projection lens. However, in this case, since it is so-called defocus, the image is not sharp but is blurred on the screen.

It also depends on the F value and focal length of the projection lens. Further, foreign matters are dust, dust, and the like, and there are various types such as size, shape, transmittance, and reflectance.
However, complete absorbers and reflectors are rare, and most of them are partially absorbed and partially reflected.
Therefore, even if a foreign object absorbs light, it will rarely appear as a complete shadow and appear on the screen. Together with the previous defocus, the center of the reflection will be darker and brighter toward the periphery. It is a reflection. FIG. 7 shows the reflection 5 included in the test image 4 ′ on the projected all-white screen.

In the current spatial light modulation element, gradation is represented by 8 bits (= 2 ⁸ ), that is, 256 levels (0 to 255 gradations). Therefore, to display an all white screen, the gradation is set to 255.
Since it is all white, an image display device composed of the three primary colors of red, green, and blue has red 255 gradation, green 255 gradation, and blue 255 gradation.
In the case of all black, it is 0, red 0, green 0 and blue 0.

An image projection apparatus is often connected to a personal computer (PC) to display an image. Such a gradation setting method is known for setting a color image of a personal computer (PC). However, the brightness on the screen (illuminance, total luminous flux, etc.) is determined by the output of the light source used in the image projection apparatus and the light utilization efficiency of the optical system.
For example, when an ultra-high pressure mercury lamp is used as the light source, the brightness on the screen is brighter when the wattage is larger and when the light use efficiency of the illumination optical system and the projection optical system is higher. Accordingly, when displaying an all-white screen, even if the setting is the same 255 gradations, the brightness on the screen differs if the image projection apparatus is different. In the above example, a digital camera and a CCD camera are used as the imaging unit, but a light meter or the like may be used as the imaging unit.

  Similarly, the imaging means acquires an image with 255 gradations. When an all-white screen is projected, it is preferable to adjust the exposure amount with the aperture and the shutter speed so that all-white corresponds to 255 gradations of the imaging means.

FIG. 24A shows a screen or a wall (projection surface) before the test image is projected. At this point, the image from the projector is not projected and is dark.
At this time, it is assumed that the projection surface is originally dirty. In step 1, the projection plane is imaged by the imaging means. When the image of FIG. 24A imaged by the imaging means is displayed so as to overlap with the pixel array of the imaging element of the imaging means, it is as shown in FIG.
24 (a) and 24 (b) are drawn in the same size, but in practice, (a) is 100 inches diagonal, (b) is 1 / 1.7 inches diagonal, and so on.

Specifically, this is a case where the entire projection surface is imaged using a digital camera. In (b), the pixel size is exaggerated and drawn. Actually, it is several μm.
The position of a certain pixel is represented by coordinates x and y, and the amount of light captured by the pixel (proportional to the gradation) is represented by I, and collectively (x, y, I). When the amount of light on the entire projection surface is uniform, I becomes almost constant regardless of the location (values of x and y).

However, if there is dirt as shown in the figure, I at this position becomes smaller than the surrounding I, and it can be determined that there is dirt at this position. In the above determination, a threshold value may be used to determine how much smaller than I it is determined to be dirty. This analysis is automatically performed by a program. Further, the position and gradation are stored in the storage device.
In FIG. 24, there is only one stain, but there is no problem if there are many stains. Their position and gradation are stored. This is the second step (ST2).

Next, a state in which the test pattern of all white is projected onto the projection surface of FIG. 24 is shown in FIG. 25A (third step (ST3)).
Since the light from the projector is projected onto the projection surface, it becomes brighter. Now, a case is considered in which one dust is attached to the cover glass of the DMD in the used projector and is projected. This is imaged by the imaging means (fourth step (ST4)).
When the image is displayed so as to overlap with the pixel array of the image pickup device of the image pickup means, the content is as shown in FIG.

Similarly to the above, (x, y, I) is examined, and a position where I is smaller than the surroundings is detected and stored.
The position recorded here is compared with the position stored in the second step (ST2), and the part where x and y do not match is newly appearing after the test pattern projection, and is determined to be due to the inside of the projector. it can. The above is the fifth step (ST5) in the present embodiment.
Further, the size or shape of the region can be measured using the information (x, y, I).

  In FIG. 7, the reflection 5 is a foreign matter inside the projector, and is not the original dirt on the projection surface. It is the darkest part (gray) of the reflection 5 and has a gradation of 200. The surrounding area has 255 gradations, and therefore, the foreign substance transmittance is estimated to be 200/255 (= 78.4%) (in the drawing, the dark portion is emphasized).

FIG. 8 is an enlarged view of the reflection 5 in FIG.
In the figure, one square 51 represents one pixel of the imaging means. In order to ensure the spatial resolution, the size of one pixel projected by the spatial light modulator is adjusted so as to be several times as large as one pixel of the imaging means.
The elements used for the adjustment include, for example, the projection magnification (variable magnification) of the projection lens used in the image projection apparatus, the distance between the screen and the apparatus, the photographing magnification of the imaging means, and the focal distance.

Specifically, the pixels of the spatial light modulator are enlarged and projected on the screen by the projection lens. When the size of one side of the square pixel is P0, the size of the image of one pixel on the screen is P1, and the magnification of the projection lens is β, P1 = β · P0. Further, assuming that the size of the image of one pixel actually measured on the screen is P1 ′, the pixel size P0 is known, and the actual magnification β ′ is obtained by P1 / P0.
When a digital camera is used as the image pickup means 2, the size of one side of one pixel of the image pickup device is assumed to be y. The pixel size P1 on the screen is larger than the size y of one pixel of the image pickup means, and the length corresponding to one pixel of the image sensor can be obtained by obtaining P1 / y.

As shown in FIG. 8, when the reflection is acquired as a digital image, the analysis becomes easy. It becomes possible to acquire the position of an arbitrary pixel as (xi, yj) from the captured image. The symbols i and j in this case are integers. It is also possible to obtain the reflection length L and width W.
In this case, if the portion other than the reflection is set to 255 gradations in all whites, for example, when the gradation is 240 gradations, the threshold value is set as the threshold value.
Such a threshold value can be either given in advance to the storage means, or sequentially input.

  Furthermore, as shown in FIG. 9, profile information (position information) can be obtained by taking gradations along the vertical axis in the x-direction and y-direction of reflection. The actual profile is discretized as shown in FIG.

When the detailed information on the reflection of the foreign matter is obtained as shown in FIGS. 8 and 9, the light quantity can be corrected to be increased or decreased based on the difference between the light quantity in the area and the light quantity around the area.
As shown in FIG. 10, the surrounding gradation 255 is lowered to the minimum gradation value 245 in the obtained reflection. This is a trade-off with overall on-screen brightness and on-screen brightness. Therefore, when the minimum value of the reflection is small, correction becomes difficult.
In this case, a threshold value is set in advance as a criterion for determining whether or not there is a problem with the projected image. When the result of reflection analysis falls below this threshold value, as shown in FIG. Is displayed. Such processing corresponds to items indicated by reference numerals ST6 and ST7 in FIG.

  In consideration of the fact that the number of reflections of foreign matter is not limited to one, the analysis means 6 is adapted to match the one with the highest degree of reflection, that is, the one with the lowest gradation.

  In the flowchart of FIG. 5, in step 5, calculation such as obtaining a difference between the test image and the projection surface obtained in step 2, and information such as the shape and size of the foreign matter previously stored in the storage circuit Compare with. As a result, it is determined whether to end or display a warning or the like.

By the way, in the case of an image projection apparatus (projector), not only black reflection on a white background but also white reflection on a black background deteriorates the image quality.
FIG. 12 shows an example in which the all black screen 4 is displayed on the screen 3, and white reflection 5 occurs on the all black screen 4.
The all black screen is when the gradation is 0 (red 0, green 0, blue 0). In the case of white reflection on a black background, the gradation expression is as shown in FIG.

In the case of black reflection on a white background, the cause is that light has been absorbed by a foreign object.
However, in the reflection of white on a black background, light is scattered by foreign matter.
In an image projection apparatus, normally, in the case of an all black screen, the light emitted from the spatial light modulation element is designed not to reach the projection lens. However, when light is scattered by a foreign object, generally, the scattering occurs in all directions, so that light directed toward the projection lens is generated. Such light reaches the screen and causes a white reflection on the black background.

In the present embodiment, the extraction of foreign matters is performed for the all black screen by the following procedure.
When canceling white reflection on a black background, as shown in FIG. 14, the whole is adjusted to the highest gradation portion in the reflection. Therefore, it is a trade-off with black expression. When the degree is large, the so-called black floating is caused and the image quality is lowered.
Therefore, a threshold value is set in advance, and when the result of analysis is greater than or equal to the threshold value, the warning shown in FIG. 11 is displayed.

  In the above analysis procedure, the case of both ends of all white (gradation 255) and all black (gradation 0) is shown, but the test image is not limited to this. Even if it is gray, even if the color is green, blue, red and so on. There are many types of foreign matters, and there are some that absorb and reflect specific colors. In this case, it is preferable to use a test image corresponding to the characteristics.

  Next, with reference to FIG. 15, an analysis will be described with reference to FIG. 15 in the case where the original projection on the projection surface and the reflection due to the foreign matter inside the image projection apparatus overlap.

When the reflection due to the foreign matter inside the image projection apparatus overlaps with the original stain or dirt on the projection surface, the influence of the stain or dirt is subtracted to analyze the reflection due to the foreign matter.
In the case where the original spot and stain overlap on the projection surface, the portion where the light amount is lower than the threshold value set in the first light amount distribution overlaps the portion where the light amount is lower than the threshold value set in the second light amount distribution. This is the case.
In a region 100 with a projection surface, a reflection 102 due to a foreign substance inside the image projection apparatus overlaps with a stain 101 originally on the projection surface.
Therefore, the reflection due to the foreign matter is darker than it actually is (see FIG. 15A).

Assuming that the result of acquiring and analyzing the image is the state shown in FIG. 15B, the gradation is greatly reduced in the portion where the spot 101 and the reflection 102 due to the foreign matter overlap.
At this time, using the a and b portions of the spot portion, a gradation drop curve due to the stain alone is estimated. Next, only this drop is corrected. In this way, it is possible to estimate the amount of reflection due to foreign matter (see FIG. 15C).

By the way, when the above-mentioned DMD is used for the spatial light modulator, double images appear on both the white background and the black background as shown in FIGS.
FIG. 18 is a diagram for explaining the case of black reflection on a white background, and shows a state in which foreign matter adheres to the cover glass.
In the figure, as indicated by reference numeral (1), when illumination light enters a foreign object, absorption occurs. Therefore, the light in this region does not reach the projection lens, and that portion becomes dark.

The light passing through reaches the DMD array, is reflected, and reaches the projection lens. In the figure, as indicated by reference numeral (2), the light irradiated before the foreign matter reaches the DMD array and is reflected, but there is a foreign matter in the optical path and is absorbed.
This light does not reach the projection lens, and that portion becomes dark. On the other hand, the surrounding light reaches the projection lens. Therefore, on the screen, a dark reflection appears on a white background at a close position.

On the other hand, FIG. 19 is a diagram illustrating the case where white is reflected on a black background.
The figure shows a state in which foreign matter is attached to the cover glass.
When the illumination light is incident on the DMD array, if the DMD array is OFF, the illumination system reflected by the array does not reach the projection lens (a state indicated by reference numeral (3) in the figure). Therefore, the front of the screen is black.

However, the illumination light incident on the foreign material is scattered. Of the scattered light, as indicated by reference numeral (1), the light scattered upward reaches the projection lens and produces a white reflection on the screen. The light scattered inside the foreign matter and scattered downward as indicated by reference numeral (2) reaches the DMD array.
If it is normal illumination light, it will be reflected in the direction that does not reach the projection lens, but since it is scattered light, there will be light reflected in the direction that reaches the projection lens. This reaches the screen and produces a white reflection. Therefore, a double white reflection appears on the black background on the screen.

  Therefore, when two images similar to each other appear in the double image, in other words, in the light amount distribution, it is understood that foreign matters are attached to the cover glass of the DMD array used for the image display element. This double image is input in advance to an electrical storage device provided in the image projection apparatus.

When such a double image is detected as a result of projecting a white or black test image, imaging and analyzing it, it can be determined that a foreign substance is attached to the cover glass of the DMD array.
The image projection apparatus includes a cleaner that cleans the cover glass of the DMD array. When it is determined that a foreign substance is attached to the cover glass, the cover glass is cleaned.

Here, the DMD will be described with reference to FIG.
FIG. 6A shows the DMD as viewed from above.
The size of the image display is determined by a diagonal line like the screen size of the television. For example, 0.5 inch, 0.65 inch, and the like.
The ratio of the long side and the short side of the rectangle is taken to express the aspect ratio of the screen as 4: 3, 16:10, or the like. In the image display area, minute mirrors are arranged as pixels (FIG. 6B).

The pixels are square, and the period of the arrangement is referred to as a pixel pitch, which is around 10 μm.
Although details are not shown in the figure, the actual mirror size is slightly smaller than the pixel pitch.
The actual mirror size with respect to the pixel pitch is called the aperture ratio. When the pixel array is viewed from the side, it is as shown in FIG.

A protective cover glass is placed on the upper side of the pixel array. Further, the square pixel rotates with its diagonal line as the rotation axis (FIG. 6C).
The direction of rotation is both clockwise and counterclockwise with respect to the rotation axis. Distinguish between plus and minus. The rotation angle is ± 10 ° to 12 °. The rotation is sometimes referred to as tilt.

The rotated mirror can change the direction of reflected light with respect to incident light between plus and minus (FIG. 6E).
That is, it is a binary value of ON and OFF. The ON light passes through the projection lens and reaches the screen. The OFF light reaches the absorbing member provided at an appropriate position. This light is displayed in black on the screen.

In recent years, an image projection apparatus capable of projecting an image from a close distance (ultra close distance) from a screen or a wall has appeared.
FIG. 20 is a diagram showing an optical system of the image projection apparatus.
In the figure, the image projection apparatus 200 has the following configuration.
White light source (lamp light source) 201 having a reflector, illumination uniformizing element (light tunnel) 202, first and second relay lenses 203, first folding mirror 204, second folding mirror 205, DMD cover glass 206, DMD 207, projection system 208, and dust-proof glass 209.

The first folding mirror 204 is a cylinder mirror. The second folding mirror 205 is a concave spherical surface and has a notch. The projection optical system includes a refractive projection lens 210 using a plurality of lenses, a folding mirror (plane) 211, and a free-form surface mirror 212.
Since the second folding mirror 205 has a notch, the lens barrel on the DMD 207 side of the projection lens 210 is not mechanically overlapped.

The dust-proof glass 209 is for preventing dust and dust from entering the optical system and the DMD 207 from above. Although not shown, there is a color wheel between the lamp light source 201 and the light tunnel 202.
The free-form surface mirror 212 is arranged to achieve projection from a close range. In this illumination system, the exit end of the light tunnel 202 and the DMD 207 surface are conjugate.

The light emitted from the lamp light source 201 passes through the following path.
That is, an illuminance distribution on the DMD 207 is formed through the optical elements of the light tunnel 202, the first and second relay lenses 203, the first folding mirror 204, and the second folding mirror 205. This illuminance distribution is projected onto the screen via a projection optical system.

The light emitted from the projection lens 210 forms an intermediate image on the display surface of the DMD 207 in the vicinity of the flat mirror 211.
The image display surface of the DMD 207 and this intermediate image are conjugate via the projection lens 210.
The free-form surface mirror 212 projects this intermediate image on the screen. Therefore, the intermediate image plane and the screen are conjugate via the free-form mirror 212. However, it is not a strict conjugate relationship.

In the optical system described above, if foreign matter is attached to the first folding mirror 204 or the second folding mirror 205, the image appears on the screen.
When the reflection is black on a white background, it is the same as the reflection of the foreign matter adhering to the cover glass of the DMD 207. However, the image is never doubled.

FIG. 21 is a diagram showing the relationship between the foreign matter on the folding mirror and the reflection in the image projected on the screen.
Therefore, it can be distinguished from the double reflection shown in FIG. If this is stored in a storage circuit built in the image projection apparatus, the position of foreign matter adhesion can be distinguished. The method for canceling the reflection is the same as that shown in FIG. Further, it may be stored in the software of the personal computer PC.

On the other hand, unlike the case shown in FIG. 21, when a foreign object adheres to the folding mirror and this is reflected in white on a black background, an arc shape or an inclined elliptical shape is formed on the screen as shown in FIG. Appears.
First of all, the folding mirror and the screen surface have a close conjugate relationship via the free-form surface mirror.

  Secondly, scattering is caused by the foreign matter, which is projected onto the screen by the free-form surface mirror, but is not regular light, and thus becomes a projection image reflecting the shape of the free-form surface mirror. Since this reflection is characteristic, it is easy to specify the attachment position of the foreign matter. Such reflection information is input to a storage element built in the image projection apparatus. When such a reflection is detected after displaying the test image, acquiring and analyzing the image, correction may be performed.

  Normally, when the DMD array is OFF, light does not reach the projection system, but part of the light reaches the projection system due to stray light or the like. This light may illuminate a foreign object on the free-form surface and cause the reflection as described above.

Since the foreign matter on the cover glass of the DMD and the foreign matter adhering to the folding mirror are both characteristic, they can be reproduced by optical simulation or the like.
By inputting this reflection information into a storage element built in the image projection apparatus at the time of shipment from the factory, it is possible to simplify the comparison of pixel data obtained by the test image projection.

  On the other hand, in this embodiment, when the projection lens is a zoom lens, the reflection changes depending on the zoom position. Accordingly, the above-described imaging, analysis, and correction amounts are obtained at several zoom positions and stored in the storage circuit. An image is displayed using a correction amount in accordance with the actual projected zoom position.

Further, in the present embodiment, the threshold value for reflection by a foreign object, for example, 245/255 or less in gradation expression in the case of black reflection on a white background, and 10/255 or more in advance in the case of white reflection on a black background. It is stored in the memory circuit.
If this threshold is exceeded as a result of analysis, a warning on the screen is issued. This processing procedure is based on the flowchart shown in FIG.

  In the above embodiment, after detecting the original unevenness, pattern, etc. on the projection surface, the reflection due to the foreign matter inside the image projection apparatus is extracted using the test image separately. Then, by comparing with the surroundings and quantifying it, the position and shape of the foreign matter can be specified, and the accuracy of correcting the light quantity change due to the foreign matter or scratches can be improved.

  Further, in the present embodiment, for the purpose of quantification, it is possible to use the transmission of foreign matters by using an all-black image as a test image. Moreover, since the scattering of foreign matter can be used by using an all-white image as a test image, simple processing can be performed without using a special optical element.

  Furthermore, in this embodiment, when extracting a foreign substance by quantification, it can compare with the result of an analysis by inputting a threshold value beforehand into the memory | storage means incorporated in the apparatus.

By executing this comparison, when it is determined that the reflection of foreign matter cannot be eliminated or reduced, a warning that cleaning is necessary can be displayed on the screen.
As a result, it is possible to prevent an erroneous determination from occurring in order to eliminate or reduce the appearance of foreign objects.

In the present embodiment, it is possible to manufacture an image projection apparatus by using light amount correction by setting each step described above.

DESCRIPTION OF SYMBOLS 1 Image projection apparatus 2 Imaging means 3 Screen or wall 6 Analysis means

No. 2008-156050

Claims (12)

  A first step of imaging a projection surface before the image is projected by the imaging means, a second step of analyzing an image obtained by imaging the projection surface before the projection, and acquiring a light amount distribution (first light amount distribution), an optical system A third step of projecting a test projection image by the image projecting apparatus, a fourth step of capturing a test image by the imaging means, and analyzing the captured test image to obtain a light amount distribution (second light amount distribution) And performing a fifth step of analyzing a difference between the first light amount distribution and the second light amount distribution, and evaluating an influence on the light amount distribution of the projection image by the deposit on the optical system. Image projection apparatus evaluation method. Obtaining position information (first position information) at a location where the light quantity is higher or lower than an arbitrary threshold in the first light quantity distribution;
In the second light quantity distribution, position information (second position information) of a place where the light quantity is higher or lower than an arbitrary threshold value is acquired,
The light amount distribution data of an area that is not the first position information in the second position information is acquired, and a difference between the first light amount distribution and the second light amount distribution is analyzed. 2. The image projection apparatus evaluation method according to 1. Obtaining position information (first position information) at a location where the light quantity is higher or lower than an arbitrary threshold in the first light quantity distribution;
In the second light quantity distribution, position information (second position information) of a place where the light quantity is higher or lower than an arbitrary threshold value is acquired,
2. The second light quantity distribution data is corrected using the first light quantity distribution data in an area where the first position information and the second position information coincide with each other. The image projection apparatus evaluation method described in 1. In the image projection device evaluation method according to claim 2 or 3,
A method for evaluating an image projection apparatus, further comprising a storage unit, wherein a warning is projected on a screen when the quantified amount of light in the region exceeds a threshold value preset in the storage unit. In the image projection apparatus evaluation method according to claim 2 or 4,
An image projection apparatus evaluation method, wherein when there are two points that are similar to each other, it is determined that a foreign substance is attached to a cover glass of an image display element of the image projection apparatus. In the image projection device evaluation method according to any one of claims 2 to 5,
An image projection apparatus evaluation method, wherein the size or shape of the region is measured. In the image projection device evaluation method according to any one of claims 1 to 6,
The image projection apparatus evaluation method, wherein the test projection image is an all-white screen. In the image projection device evaluation method according to any one of claims 1 to 6,
The image projection apparatus evaluation method, wherein the test projection image is an all-black screen. In the image projection device evaluation method according to any one of claims 1 to 8,
An image projection apparatus evaluation method for projecting a test image corresponding to a zoom ratio at each zoom ratio of a projection lens. An image projection apparatus comprising: means for cleaning a cover glass of an image display element; and the image projection apparatus using the image projection apparatus evaluation method according to claim 5,
An image projection apparatus characterized by cleaning the cover glass when it is determined that a foreign substance is attached to the cover glass. A method for manufacturing an image projection apparatus, comprising:
A first step of imaging a projection surface before the image is projected by the imaging means, a second step of analyzing an image obtained by imaging the projection surface before the projection, and obtaining a light amount distribution (first light amount distribution), image projection A third step of projecting a test projection image by the apparatus; a fourth step of capturing a test image by the imaging means; and analyzing the captured test image to obtain a light amount distribution (second light amount distribution); A method of manufacturing an image projection apparatus, wherein the fifth step of analyzing a difference between the light amount distribution of the second light amount and the second light amount distribution is executed, and the light amount is corrected for the difference. Imaging means;
An image projection device having an optical system ,
A first step of imaging a projection surface before projecting an image by the imaging means, a second step of analyzing an image obtained by imaging the projection surface before projection, and obtaining a light amount distribution (first light amount distribution), A third step of projecting a test projection image by the image projection device, a fourth step of capturing a test image by the imaging means, analyzing the captured test image, and obtaining a light amount distribution (second light amount distribution); An image projection characterized by executing a fifth step of analyzing a difference between the first light amount distribution and the second light amount distribution, and evaluating an influence on the light amount distribution of the projection image by the deposit on the optical system. Equipment evaluation system.

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