CN103852243A - Method for detecting optical center of wide-angle lens and optical center detecting device - Google Patents

Abstract

A method for detecting the optical center of a wide-angle lens and an optical center detection device. The method for detecting the optical center of a wide-angle lens includes the following steps: attaching a light path changing element to the wide-angle lens; the wide-angle lens receiving light generated by a light source through the light path changing element to generate a detection image; and determining based on the detection image. The optical center. An optical center detection device includes a wide-angle lens, a light path changing element and an image processing unit. The optical path changing element is sleeved on the wide-angle lens. The image processing unit is coupled to the wide-angle lens and used to receive light generated by the light source through the optical path changing element through the wide-angle lens to generate a detection image, and determine an optical center of the wide-angle lens based on the detection image.

Description

Method for detecting optical center of wide-angle lens and optical center detection device

technical field

The invention relates to the detection of the optical center, in particular to a method for detecting the optical center of a wide-angle lens by using an optical path changing element to improve the uniformity of light received, and a related optical center detection device.

Background technique

In the scope of image processing, in order to obtain good imaging quality, it is necessary to accurately determine the optical center of the lens. For wide-angle lenses (such as fisheye lenses), if the position of the optical center can be accurately determined, the effect of image compensation and correction (such as fisheye image correction) can be greatly improved. promote. For example, when a panoramic image (panorama) is generated through image stitching (image stitching), the found optical center position is more accurate, thereby generating a high-quality panoramic image.

One of the methods traditionally used to detect the optical center is to attach the lens flat to the light box (LightBox), and then detect the optical center based on the image formed through the lens. However, in the case of detecting the optical center of the fisheye lens, since the fisheye lens has a convex mirror surface, in the step of attaching the convex fisheye lens to the flat light box, the two cannot be truly flat. Once the angle between the fisheye lens and the light box is offset, the light incident on the fisheye lens will not be uniform enough, resulting in an error in the detected optical center.

Therefore, an innovative method for detecting the optical center is needed to improve the accuracy of detecting the optical center of the wide-angle lens.

Contents of the invention

In view of this, one of the objectives of the present invention is to provide a method for detecting the optical center of a wide-angle lens by using an optical path changing element to improve the uniformity of light received, and its related optical center detection device to solve the above problems.

According to an embodiment of the present invention, a method for detecting an optical center of a wide-angle lens is disclosed. The method comprises the following steps: a light path changing element is sleeved on the wide-angle lens; the wide-angle lens receives light generated by a light source through the light path changing element to generate a detection image; and determining the optical center according to the detection image .

According to an embodiment of the present invention, an optical center detection device is disclosed. The optical center detection device includes a wide-angle lens, an optical path changing element and an image processing unit. The optical path changing element is sleeved on the wide-angle lens. The image processing unit is coupled to the wide-angle lens, and is used to receive light generated by a light source through the optical path changing element through the wide-angle lens to generate a detection image, and determine an optical center of the wide-angle lens according to the detection image. .

Description of drawings

FIG. 1 is a schematic diagram of an embodiment of the optical center detection system of the present invention.

FIG. 2 is a schematic diagram of an embodiment in which the light generated by the light source box shown in FIG. 1 enters the wide-angle lens 130 .

FIG. 3 is a schematic diagram of a detection image generated corresponding to the optical path shown in FIG. 2 .

FIG. 4 is a schematic diagram of determining a binarized image according to the detection image shown in FIG. 3 .

FIG. 5 is a flowchart of an embodiment of a method for detecting an optical center of a wide-angle lens according to the present invention.

FIG. 6 is a schematic diagram of an embodiment of the present invention for detecting pixel values of the binarized image shown in FIG. 4 to determine the geometric center of the image object.

FIG. 7 is a statistical schematic diagram of the detection results of multiple rows shown in FIG. 6 .

FIG. 8 is a schematic diagram of an embodiment in which the optical center detection device shown in FIG. 1 generates a detection image according to ambient light.

FIG. 9 is a schematic diagram of an embodiment of performing a binarization operation and pixel value correction on the detection image shown in FIG. 8 .

FIG. 10 is a flow chart of another embodiment of the method for detecting an optical center of a wide-angle lens according to the present invention.

[Description of main component symbols]

100 Optical center detection system

110 Light box

120 Optical center detection device

130 Wide-angle lens

140 Pipe Sleeve

150 Image processing unit

500, 510, 520, 530, 540, 550, steps

1032, 1036

P_11, P_12, P_1n, P_m1, P_mn pixels

DW_H, DW_V Detection Pane

RB, RB’, RBB’ Image objects

Detailed ways

Please refer to FIG. 1 , which is a schematic diagram of an embodiment of an optical center detection system 100 of the present invention. The optical center detection system 100 includes a light source box 110 and an optical center detection device 120, wherein the optical center detection device 120 includes a wide-angle lens 130, an optical path changing element (optical path changing device) (in this embodiment, it is a tube sleeve (sleeve) (or bushing) 140 ) and an image processing unit 150 . The sleeve 140 is sleeved on the wide-angle lens 130 . The image processing unit 150 is coupled to the wide-angle lens 130 for receiving light generated by the light source box 110 through the wide-angle lens 130 to generate a detection image, and to determine an optical center of the wide-angle lens 130 according to the detection image. In this embodiment, the wide-angle lens 130 is put on the tube cover 140, so that most of the light received by the wide-angle lens comes from the inner wall of the tube cover 140, not only can the wide-angle lens 130 receive light evenly, but also the imaging area in the generated detection image is also approximately is the light-sensing range of the wide-angle lens 130 , therefore, the user can obtain the precise optical center position according to the detection image without preparing a jig for precise alignment and without placing the wide-angle lens 130 close to the light source box 110 . Further explanation follows.

Please refer to Figure 1 and Figure 2 together. FIG. 2 is a schematic diagram of an embodiment in which the light generated by the light source box 110 shown in FIG. 1 enters the wide-angle lens 130 . In this embodiment, the rays received by the wide-angle lens 130 are represented by rays L1-L3, wherein the rays L1 represent the rays generated by the light source box 110 and are directly incident on the wide-angle lens 130, and the rays L2 represent the reflections from the inside of the sleeve 140 The light that is incident on the wide-angle lens 130 later, and the light L3 represents the light that is incident on the wide-angle lens 130 after passing through the sleeve 140 . It can be seen from FIG. 2 that since the inner wall of the sleeve 140 can reflect light to the wide-angle lens 130 and shield part of the light from the light source box 110 outside the sleeve 140, the energy received by the wide-angle lens 130 in a specific range VR1 will be greater than the light-sensitive range VR2 The energy received, wherein the specific range VR1 corresponds to the cross-section of the sleeve 140 . In this embodiment, the sleeve 140 is made of light-permeable material. In another embodiment, the sleeve 140 can also be made of opaque material (the inner wall can reflect light).

It can be known from the above that the sleeve 140 can change the optical path of the light generated by the light source box incident on the wide-angle lens 130 , so that the light received in the photosensitive range VR2 of the wide-angle lens 130 can come from the light reflected/refracted by the sleeve 140 . It is worth noting that the sleeve 140 is used as an optical path changing element only for illustration, and is not used as a limitation of the present invention. Can be used as an optical path changing element.

Please refer to FIG. 3 together with FIG. 2 . FIG. 3 is a schematic diagram of a detection image IMG_D generated corresponding to the optical path shown in FIG. 2 . It can be seen from FIG. 3 that the image range R1 corresponds to the specific range VR1 of the wide-angle lens 130, and the image range R2 corresponds to the photosensitive range VR2 of the wide-angle lens 130, wherein the image boundary of the image range R2 forms a symmetrical geometric shape (that is, a circle) . Therefore, the geometric center (ie, the center of the circle) of the image range R2 can be easily found out, and then the optical center of the wide-angle lens 130 can be determined.

Please refer to FIG. 4 , which is a schematic diagram of determining a binarized image according to the detection image IMG_D shown in FIG. 3 . In this embodiment, the image processing unit 150 shown in FIG. 1 performs a binary-conversion operation (binary-conversion) on the detection image IMG_D to generate a binary image (binary image) IMG_B, so as to To determine the optical center of the wide-angle lens 130 . More specifically, the image processing unit 150 can compare each pixel value (or luminance value) in the detected image IMG_D with a threshold (threshold) to generate the binarized image IMG_B, wherein the threshold can adopt a preset It can also be set according to the pixel value of the detected image obtained each time. In this embodiment, within the visible range of the binarized image IMG_B (corresponding to the bright/white image object RB), the pixel value of each pixel is a first binary value (for example, 1 ), and the pixel values of other pixels outside the visible range (dark/black area) are all a second binary value (for example, 0), wherein the second binary value is different from the first binary value. Next, the image processing unit 150 shown in FIG. 1 determines the optical center of the wide-angle lens 130 by calculating the geometric center of the image object RB.

Please refer to FIG. 5 , which is a flowchart of an embodiment of a method for detecting an optical center of a wide-angle lens according to the present invention. This method can be applied to the optical center detection device 120 shown in Figure 1, and can be simply summarized as follows:

Step 500: start.

Step 510: Connect a sleeve (ie, an optical path changing element) to the wide-angle lens.

Step 520 : Receive light generated by a light source through the sleeve through the wide-angle lens to generate a detection image (eg, a shadow image).

Step 530: Perform a binarization operation on the detected image to generate a binarized image.

Step 540 : Calculate the geometric center (eg, circle center) of the visible range (ie, the white image object) of the binarized image to determine the optical center.

Step 550: end.

In step 530, the binarization operation may be performed by an appropriate threshold to generate the binarized image with a maximum visible range (eg, circles with the same binary value). Since those skilled in the art should be able to easily understand the operation details of steps 510 to 530 shown in FIG. 5 after reading the relevant descriptions in FIGS. 1 to 4 , further descriptions are omitted here. It should be noted that in step 540, the pixel value of the binarized image can be detected to obtain the boundary of the visible range of the binarized image, and then the geometric center of the visible range can be determined. Further explanation follows.

Please refer to FIG. 6 , which is a schematic diagram of an embodiment of the present invention for detecting the pixel values of the binarized image IMG_B shown in FIG. 4 to determine the geometric center of the image object RB. In this embodiment, the binarized image IMG_B has a plurality of pixels P_11 ˜ P_mn (ie, a pixel array of m rows by n columns). First, for each row of pixels in the binarized image IMG_B, move a horizontal detection pane DW_H from left to right and from top to bottom in units of one pixel to detect all pixels in each row and generate corresponding A row of detection results, and then obtain the distribution of the pixel values of each pixel in the row; similarly, for each column (column) pixel in the binarized image IMG_B, from top to bottom and from left to left in units of one pixel Move a vertical detection pane DW_V to the right to detect all pixels in each column and generate a corresponding detection result in a column, and then obtain the distribution of pixel values of each pixel in the column. Finally, the geometric center of the image object RB is determined according to a plurality of row detection results corresponding to m rows of pixels and a plurality of column detection results corresponding to n columns of pixels.

In practice, the horizontal detection pane DW_H can be set as a “1×2” detection pane (that is, two adjacent pixels in the same row can be detected simultaneously). The horizontal detection pane DW_H may first detect the pixels in the first row (ie, the pixels P_11 and P_12 ), detect two pixels at a time, and move to the right in units of one pixel for continuous detection. When the pixels in the horizontal detection pane DW_H have different binary values, it means that the horizontal detection pane DW_H is currently at the boundary of the image object RB. Therefore, the pixel position corresponding to the horizontal detection pane DW_H can be recorded. It is used for subsequent acquisition of the pixel value distribution of the row.

In this embodiment, when the horizontal detection pane DW_H moves to the pixel position A_1P (represented by the horizontal detection pane DW_H (A_1P)), the value of the left pixel in the horizontal detection pane DW_H is binary value "0". , the right pixel value is a binary value "1", which represents that the horizontal detection pane DW_H is scanning from a black area to a white area on the binarized image IMG_B. The image processing unit 150 shown in FIG. 1 will record the pixel position A_1P corresponding to the current horizontal detection pane DW_H. In addition, when the horizontal detection pane DW_H continues to move to the pixel position A_1Q (represented by the horizontal detection pane DW_H (A_1Q)), the left pixel value of the horizontal detection pane DW_H is binary value "1", and the right pixel value is "1". The pixel value is a binary value "0", which represents that the horizontal detection window DW_H is scanning from a white area to a black area on the binarized image IMG_B. Therefore, the image processing unit 150 shown in FIG. The pixel position A_1Q corresponding to the grid DW_H is recorded. After all the pixels in the first row have been detected, the image processing unit 150 shown in FIG. 1 can calculate an average position of the recorded pixel positions (that is, the pixel position A_1P and the pixel position A_1Q) as the row detection The result DR_R1 (that is, the row detection result DR_R1 is the average value of the pixel position A_1P and the pixel position A_1Q). Next, the horizontal detection pane DW_H will continue to detect the pixel values of the pixels in the second row until all the pixels in the m row are detected.

After all the pixels in the m rows are detected, the image processing unit 150 shown in FIG. 1 can count the occurrence times of the average positions corresponding to the detection results DR_R1-DR_Rm of multiple rows to determine the geometric center of the image object RB coordinates in the horizontal direction. Please refer to FIG. 7 , which is a statistical schematic diagram of a plurality of row detection results DR_R1 - DR_Rm shown in FIG. 6 . In this embodiment, the location with the most occurrences is the pixel location A0 , in other words, the coordinates of the geometric center of the image object RB in the horizontal direction (ie, the horizontal coordinate of the center of the circle) is the pixel location A0 .

Similarly, the image processing unit 150 shown in FIG. 1 can also use the vertical detection window DW_V (for example, a “2×1” detection window) to detect each column of pixels in the binarized image IMG_B, record the vertical detection window The pixel positions corresponding to different binary values appearing in the grid DW_V, and an average position of the recorded pixel positions in the row is calculated as the detection result of the row. Finally, the obtained multiple row detection results are counted to determine the coordinates of the geometric center of the image object RB in the vertical direction. Through the above detection steps, the position of the optical center of the wide-angle lens 130 can be detected.

Please note that the horizontal detection pane DW_H with a pane size of “1×2” is used for illustration above, therefore, the horizontal detection pane DW_H moves one pixel at a time. However, the pane size of the horizontal detection pane DW_H is not limited to “1×2”, therefore, the moving distance of the horizontal detection pane DW_H each time can also be adjusted according to the pane size. Similarly, the pane size of the vertical detection pane DW_V is not limited to “2×1”, and the distance of each movement of the vertical detection pane DW_V can also be adjusted according to the pane size. In addition, the moving direction of the horizontal detection pane DW_H may be from right to left, and the moving direction of the vertical detection pane DW_V may also be from bottom to top.

Although the wide-angle lens 130 shown in FIG. 1 is approximately flat on the light source box 110, the optical center detection device and detection method proposed in the present invention are not limited to the relative position between the light source and the wide-angle lens, that is to say, the wide-angle lens can be It is not necessary to be close to the light box, and the incident light of the light box does not have to be parallel to the optical axis of the wide-angle lens (optical axis), and it is even possible to detect the optical center of the wide-angle lens only through roughly uniform ambient light (that is, it does not need light box).

Please refer to FIG. 8 , which is a schematic diagram of an embodiment in which the optical center detection device 120 shown in FIG. 1 generates a detection image IMG_D' according to ambient light. In this embodiment, in addition to the image range R1' (corresponding to the cross-section of the sleeve 140) and the image range R2' (corresponding to the visual range of the wide-angle lens 130), the visible range of the detection image IMG_D' also includes the image range R22', wherein the image range R22' is a reflective image caused by ambient light. In addition, brightness unevenness also appears in the image range R1'.

In order to ensure the accuracy of the detected optical center, the pixel value of the image can be corrected to reduce/eliminate the influence caused by the reflective image or uneven brightness. Please refer to Figure 9 and Figure 10 together. Fig. 9 is a schematic diagram of an embodiment of performing a binarization operation and pixel value correction on the detected image IMG_D' shown in Fig. 8 . FIG. 10 is a flow chart of another embodiment of the method for detecting an optical center of a wide-angle lens according to the present invention, wherein the method shown in FIG. 10 is based on the method shown in FIG. 5 . After the detection image IMG_D' is binarized (as shown in step 530), a binarized image IMG_B' (as shown in the upper part of FIG. 9 ) will be generated, wherein the binarized image IMG_B' contains a white An image object RB' (corresponding to the image range R2') and a white image object RBB' (corresponding to the image range R22'). In this embodiment, the pixel value of each pixel in the image object RB'/image object RBB' is a first binary value (for example, "1"). In addition, the image object RB' surrounds a hole pixel (ie, a black area surrounded by the image object RB') with a second binary value (eg, "0"), wherein the second binary value is different from the first binary value.

In step 1032, the image processing unit 150 shown in FIG. 1 can first determine a maximum object (ie, the image object RB') in the binarized image IMG_B' through the number of pixels of the image objects RB' and RBB'; Next, modify the pixel value of each pixel in objects other than the largest object (ie, the image object RBB') to the second binary value (eg, "0") to set the other objects to A black background (as shown in the middle part of Figure 9). In step 1036, the pixel value of the hole pixels surrounded by the image object RB' can be modified to the first binary value (for example, "1") to remove the unwanted black image (as shown in the middle part of FIG. 9 shown); finally, determine the optical center (as shown in step 540) according to the modified binarized image IMG_B' (as shown in the lower part of Figure 9). For example, Figure 6 and Figure 7 can be used The detection method shown is used to determine the geometric center of the modified binarized image IMG_B' to determine the position of the optical center.

It is worth noting that since the size of the image object RBB' is much smaller than the size of the image object RB', even if the step of setting objects other than the largest object as the background is omitted, the detected optical center of the wide-angle lens 130 is still Pretty accurate. In addition, the black area surrounded by the image object RB' is much smaller than the size of the image object RB', so the step of removing the unwanted black image surrounded by the largest object can also be omitted. In other words, after obtaining the largest object, it is also feasible to directly determine the optical center based on the largest object.

In addition, after the largest object is obtained, only one of the step of setting other objects as the background and the step of removing empty pixels may be performed. In an implementation example, after the image object RBB' is set as the background (as shown in step 1032), step 540 may also be directly executed to determine the optical center. In another implementation example, after the image object RB' is obtained from the binarized image IMG_B', the hollow pixels surrounded by the image object RB' can also be directly removed (as shown in step 1036), and then step 540 is performed to determine the optical center.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (18)

1. a method that detects an optical centre of a wide-angle lens, comprises:

One optical path is changed to element housing and be connected to this wide-angle lens;

This wide-angle lens changes element via this optical path and receives the light being produced by a light source to produce a detected image; And

Decide this optical centre according to this detected image.

2. the method for claim 1, wherein the internal face of this optical path change element is a light reflection surface, this wide-angle lens receives the light that this light source produces and reflect via the light reflection surface of this optical path change element, to produce this detected image.

3. method as claimed in claim 2, wherein this optical path change element is made up of light-permeable material or light tight material.

4. the method for claim 1, wherein decides the step of this optical centre to comprise according to this detected image:

This detected image is carried out to a binaryzation operation to produce a binary image;

In this binary image, along continuous straight runs moves a horizontal detection pane, to detect all pixels of each row in this binary image and to produce multiple row testing results;

In this binary image, move in the vertical direction a vertical detection pane, to detect all pixels of each row in this binary image and to produce multiple row testing results; And

Decide this optical centre according to the plurality of row testing result and the plurality of row testing result.

5. method as claimed in claim 4, if wherein this binary image comprises multiple objects, in each object, the pixel value of each pixel is one first bi-values, judge the maximum object in this binary image according to the pixel quantity of each object, and all pixels that detect each row, column in this maximum object are to produce the plurality of row testing result and the plurality of row testing result.

6. method as claimed in claim 5, it is further revised as one second bi-values by the pixel value of each pixel in other objects except this maximum object, and wherein this second bi-values is different from this first bi-values.

7. method as claimed in claim 5, if wherein this maximum object has surrounded at least one pixel with one second bi-values, is further revised as this first bi-values by the pixel value of this at least one pixel with this second bi-values.

8. the method as described in claim 4 to 7, the step that wherein produces the plurality of row testing result and the plurality of row testing result comprises:

In the time that the corresponding pixel of this horizontal detection pane has different bi-values, record the corresponding location of pixels of this horizontal detection pane;

In the time that the corresponding pixel of this vertical detection pane has different bi-values, record the corresponding location of pixels of this vertical detection pane; And

After the pixel of each row and each row has all completed detection, calculate a mean place of the location of pixels recording in each row and each row, using the row testing result as corresponding and row testing result.

9. method as claimed in claim 8, wherein decides the step of this optical centre to comprise according to the plurality of row testing result and the plurality of row testing result:

Add up respectively the occurrence number of the plurality of row testing result and the corresponding mean place of the plurality of row testing result; And

Decide this optical centre according to the maximum location of pixels of occurrence number in the maximum location of pixels of occurrence number in the plurality of row testing result and the plurality of row testing result.

10. an optical centre pick-up unit, comprises:

One wide-angle lens;

One optical path changes element, is socketed on this wide-angle lens; And

One graphics processing unit, is coupled to this wide-angle lens, receives the light being produced by a light source to produce a detected image, and decide an optical centre of this wide-angle lens according to this detected image in order to see through this wide-angle lens via this optical path change element.

11. optical centre pick-up units as claimed in claim 10, wherein the internal face of this optical path change element is a light reflection surface, this graphics processing unit sees through this wide-angle lens and receives the light that this light source produces and reflect via the light reflection surface of this optical path change element, to produce this detected image.

12. optical centre pick-up units as claimed in claim 11, wherein this optical path change element is made up of light-permeable material or light tight material.

13. optical centre pick-up units as claimed in claim 10, wherein this graphics processing unit carries out a binaryzation operation to produce a binary image to this detected image; In this binary image, along continuous straight runs moves a horizontal detection pane, to detect all pixels of each row in this binary image and to produce multiple row testing results; In this binary image, move in the vertical direction a vertical detection pane, to detect all pixels of each row in this binary image and to produce multiple row testing results; And this graphics processing unit decides this optical centre according to the plurality of row testing result and the plurality of row testing result.

14. optical centre pick-up units as claimed in claim 13, if wherein this binary image comprises multiple objects, in each object, the pixel value of each pixel is one first bi-values, this graphics processing unit is judged the maximum object in this binary image according to the pixel quantity of each object, and all pixels that detect each row, column in this maximum object are to produce the plurality of row testing result and the plurality of row testing result.

15. optical centre pick-up units as claimed in claim 14, wherein this graphics processing unit is separately revised as by the pixel value of each pixel in other objects except this maximum object one second bi-values that is different from this first bi-values.

16. optical centre pick-up units as claimed in claim 14, if wherein this maximum object has surrounded at least one pixel with one second bi-values, this graphics processing unit is separately revised as this first bi-values by the pixel value of this at least one pixel with this second bi-values.

17. optical centre pick-up units as described in claim 13 to 16, when wherein the pixel among this horizontal detection pane has different bi-values, this graphics processing unit records the corresponding location of pixels of this horizontal detection pane; In the time that the corresponding pixel of this vertical detection pane has different bi-values, this graphics processing unit records the corresponding location of pixels of this vertical detection pane; And after the pixel of each row and each row has all completed detection, this graphics processing unit calculates a mean place of the location of pixels recording in each row and each row, using the row testing result as corresponding and row testing result.

18. optical centre pick-up units as claimed in claim 17, wherein this graphics processing unit is added up respectively the occurrence number of the plurality of row testing result and the corresponding mean place of the plurality of row testing result, and decides this optical centre according to the maximum location of pixels of occurrence number in the maximum location of pixels of occurrence number in the plurality of row testing result and the plurality of row testing result.

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