Illumination angle calibration device, method and system
By using transparent substrate and mask structure in computational imaging technology, the illumination angle of the light source is calculated using light shadow images, and the problem of complex and high cost of calibration of the light angle is solved, and accurate calibration of the light angle and imaging quality is achieved.
Patent Information
- Application Number
- CN202210127390.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-02-11
- Publication Date
- 2024-12-24
- Estimated Expiration
- 2042-02-11
AI Technical Summary
In the computational imaging technology of multi-light source and multi-angle illumination, the error of the light angle will reduce the quality of the imaging results, and the existing light angle calibration process is complex and costly.
A transparent substrate is used to parallel the first surface and the second surface, a circular mask is provided on the first surface, and a disk mask is provided on the second surface, and the illumination angle of the light source is calculated by detecting the light shadow image, and the thickness of the transparent substrate is used and The refractive index is accurately determined.
Accurate calibration of lighting angles is achieved, cost reduction, and device and operation are simplified, and imaging quality is improved.
Smart Images
Figure CN114445489B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of information technology, and in particular to a light angle calibration device, method and system. Background Art
[0002] In many computational imaging technologies that rely on multi-light source and multi-angle illumination, such as lensless imaging, Fourier ptychography imaging, coded ptychography, and diffraction tomography imaging, the accuracy of illumination angle information is crucial to the imaging results. The error of illumination angle may reduce the quality of the image reconstructed by computational imaging. At present, the illumination angle is mainly determined by the spatial geometric position of the illumination light source, but the calibration process of illumination angle is complicated and costly. Summary of the invention
[0003] In view of this, an object of the embodiments of the present invention is to provide a device, method and system for calibrating an illumination angle, which has a simple structure and operation, can accurately calibrate the illumination angle and has low cost.
[0004] In a first aspect, an embodiment of the present invention provides a light angle calibration device, comprising a transparent substrate, wherein the transparent substrate comprises a first surface and a second surface parallel to each other, the first surface is provided with a plurality of first masks, the second surface is provided with a plurality of second masks, and the first masks and the second masks at corresponding positions satisfy a concentric relationship; wherein the first masks and the second masks are used for shading.
[0005] Optionally, the thickness of the transparent substrate is much greater than the thickness of the first mask and the second mask.
[0006] Optionally, the first mask is a ring, the second mask is a disk, and the inner diameter of the ring is greater than the diameter of the disk.
[0007] Optionally, the thickness of the transparent substrate ranges from 0.5 mm to 2.5 mm.
[0008] Optionally, the thickness range of the first mask and the second mask is less than 0.1 um.
[0009] In a second aspect, an embodiment of the present invention provides a method for calibrating an illumination angle, which is applied to the above-mentioned device, and includes:
[0010] The device is placed between a light source and an image sensor; the light source is used to generate incident light at a certain angle, and the image sensor is used to capture a light and shadow image generated by the incident light passing through the transparent substrate;
[0011] Detecting shadow position information of a plurality of pairs of the first mask and the second mask having a concentric relationship in the light and shadow image;
[0012] Calculating corresponding displacements according to position information of the first mask and the second mask;
[0013] The illumination angle of the light source is calculated according to the displacement, the thickness of the transparent substrate and the refractive index of the transparent substrate.
[0014] Optionally, the calculation formula of the illumination angle of the light source is as follows:
[0015]
[0016] in, represents the illumination angle, n represents the refractive index of the transparent substrate, h represents the thickness of the transparent substrate, m represents the logarithm of the first mask and the second mask having a concentric relationship, and D i It represents the displacement of the i-th pair of the first mask and the second mask having a concentric relationship.
[0017] Optionally, the method further comprises:
[0018] Calculating an angle according to light and shadow position information of the first mask and the second mask;
[0019] Calculating the component displacements of the light source in two orthogonal planes respectively according to the displacement and the angle;
[0020] The illumination angles of the light source in the two orthogonal planes are calculated respectively according to the component displacements of the light source in the two orthogonal planes, the thickness of the transparent substrate and the refractive index of the transparent substrate.
[0021] Optionally, the calculation formula of the illumination angle of the light source in two orthogonal planes is as follows:
[0022]
[0023]
[0024] in, represents the illumination angle of the first orthogonal plane, represents the illumination angle of the second orthogonal plane, D ix represents the component displacement of the first mask and the second mask having a concentric relationship in the first orthogonal plane, D iyIt represents the component displacement of the i-th pair of the first mask and the second mask having a concentric relationship in the second orthogonal plane.
[0025] In a third aspect, an embodiment of the present invention provides a light angle calibration system, comprising the above-mentioned device, a light source, an image sensor, a detection device and a processor; wherein:
[0026] The light source is used to generate incident light at a certain angle;
[0027] The image sensor is used to capture the light and shadow image generated by the incident light passing through the transparent substrate;
[0028] The detection device is used to detect the shadow position information of a plurality of pairs of the first mask and the second mask having a concentric relationship in the light and shadow image;
[0029] The processor is used to calculate the corresponding displacement according to the position information of the first mask and the second mask, and calculate the illumination angle of the light source according to the displacement, the thickness of the transparent substrate and the refractive index of the transparent substrate.
[0030] The implementation of the embodiments of the present invention includes the following beneficial effects: In the embodiment, the illumination angle calibration device includes a transparent substrate and a first surface and a second surface parallel to each other on the transparent substrate, the first surface is provided with a first mask for shading light, the second surface is provided with a second mask for shading light, the first mask and the second mask are concentric, and incident light forms a light and shadow image after passing through the first mask and the second mask. The illumination angle of the light source is calculated according to the positional relationship of the light and shadow images. The structure and operation of the device are simple, and the illumination angle can be accurately calibrated with low cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 is a structural schematic diagram of a light angle calibration device provided by an embodiment of the present invention;
[0032] Figure 2 It is a schematic diagram of the steps of a method for calibrating an illumination angle provided by an embodiment of the present invention;
[0033] Figure 3 is a structural schematic diagram of a light angle calibration system provided by an embodiment of the present invention;
[0034] Figure 4 is a schematic diagram of a displacement provided by an embodiment of the present invention;
[0035] Figure 5 is a structural schematic diagram of another illumination angle calibration system provided by an embodiment of the present invention;
[0036] Figure 6is a schematic diagram of another displacement provided by an embodiment of the present invention;
[0037] Figure 7 It is a schematic diagram of a process for detecting shadow position information provided by an embodiment of the present invention. DETAILED DESCRIPTION
[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.
[0039] like Figure 1 As shown, Figure 1 (a) is a schematic diagram of the three-dimensional structure of the illumination angle calibration device. Figure 1 (b) is a schematic cross-sectional view of the illumination angle calibration device along a plane perpendicular to the first surface or the second surface, wherein the dotted line indicates the concentric relationship between the ring and the disk. An embodiment of the present invention provides an illumination angle calibration device, comprising a transparent substrate 02, wherein the transparent substrate 02 comprises a first surface 03 and a second surface 05 which are parallel to each other, wherein the first surface 03 is provided with a plurality of first masks 04, wherein the second surface 05 is provided with a plurality of second masks 06, wherein the first masks 04 and the second masks 06 at corresponding positions satisfy a concentric relationship; wherein the first masks 04 and the second masks 06 are used for light shielding.
[0040] Those skilled in the art will appreciate that the specific material of the transparent substrate is determined by the application, such as transparent glass or a stack of two transparent single-sided mask plates of the same material, and this embodiment does not impose any specific limitation.
[0041] It should be noted that the specific material of the first mask or the second mask is determined by the application, such as metal or opaque organic matter, etc., and this embodiment does not impose any specific limitation.
[0042] Optionally, the thickness of the transparent substrate is much greater than the thickness of the first mask and the second mask.
[0043] Optionally, the thickness of the transparent substrate ranges from 0.5 mm to 2.5 mm.
[0044] Optionally, the thickness range of the first mask and the second mask is less than 0.1 um.
[0045] It should be noted that the thickness of the transparent substrate, the thickness of the first mask and the thickness of the second mask are determined according to specific applications, and this embodiment does not impose any specific limitation.
[0046] Optionally, the first mask is a ring, the second mask is a disk, and the inner diameter of the ring is greater than the diameter of the disk.
[0047] The implementation of the embodiments of the present invention includes the following beneficial effects: In the embodiment, the illumination angle calibration device includes a transparent substrate and a first surface and a second surface parallel to each other on the transparent substrate, the first surface is provided with a first mask for shading light, the second surface is provided with a second mask for shading light, the first mask and the second mask are concentric, and incident light forms a light and shadow image after passing through the first mask and the second mask. The illumination angle of the light source is calculated according to the positional relationship of the light and shadow images. The structure and operation of the device are simple, and the illumination angle can be accurately calibrated with low cost.
[0048] See also Figure 2 The embodiment of the present invention provides a method for calibrating an illumination angle, which is applied to the above-mentioned device, and includes:
[0049] S100, placing the device between a light source and an image sensor; the light source is used to generate incident light at a certain angle, and the image sensor is used to capture a light and shadow image generated by the incident light passing through the transparent substrate.
[0050] Specifically, see Figure 3 (a) Place the illumination angle calibration device 01 between the light source 07 and the image sensor 08 so that the circular ring pattern and the circular disk pattern of the illumination angle calibration device 01 are projected onto the target surface of the image sensor to obtain the corresponding shadow image 09. The shadow image 09 is shown in FIG. Figure 3 (b) Figure 3 The illumination angle in (a) is vertical.
[0051] S200: Detect shadow position information of a plurality of pairs of the first mask and the second mask having a concentric relationship in the light and shadow image.
[0052] See also Figure 4 , taking a pair of patterns as an example, when the light source 07 is at an illumination angle When incident from the first surface of the illumination angle calibration device, the circular ring pattern will form a projection on the second mask, and there is a horizontal displacement Z containing the light source illumination information between the projection and the position of the circular ring pattern on the first mask.
[0053] S300: Calculate corresponding displacements according to position information of the first mask and the second mask.
[0054] See also Figure 3 When the light emitted by the light source is incident perpendicularly to the first surface of the illumination angle calibration device, the circular ring pattern and the circular disk pattern form their own shadows on the target surface of the image sensor, and at this time, the shadows of the two patterns are still concentric. Figure 5 , when the light emitted by the light source is incident on the first surface of the illumination angle calibration device at a non-vertical angle, due to the certain thickness of the transparent substrate, the distance from the ring pattern to the image sensor is not the same as the distance from the disk pattern to the image sensor. Therefore, the shadows of the ring pattern and the disk pattern on the image sensor surface are no longer concentric, and the displacement from the shadow center of the ring pattern to the shadow center of the disk pattern is the shadow displacement D, as shown in Figure 4 shown.
[0055] See also Figure 6 According to the principle of light propagation, under the illumination of the light source, the shadow displacement D of the ring pattern and the disk pattern in the shadow image is equal to the displacement Z.
[0056] Specifically, a public circle detection algorithm, such as the circular detection algorithm CHT (Circular Hough Transform) based on the Hough transform principle, is used to retrieve the positions of the ring pattern and the disk pattern in the shadow image, and obtain the position information of m pairs of patterns in the shadow image, thereby calculating the shadow displacement D corresponding to the m pairs of patterns. i (1≤i≤m).
[0057] S400, calculating the illumination angle of the light source according to the displacement, the thickness of the transparent substrate, and the refractive index of the transparent substrate.
[0058] Optionally, the calculation formula of the illumination angle of the light source is as follows:
[0059]
[0060] in, represents the illumination angle, n represents the refractive index of the transparent substrate, h represents the thickness of the transparent substrate, m represents the logarithm of the first mask and the second mask having a concentric relationship, and D i It represents the displacement of the i-th pair of the first mask and the second mask having a concentric relationship, and the value range of i is 1 to m.
[0061] Optionally, the illumination angle calibration method further includes:
[0062] S500, calculating an angle according to light and shadow position information of the first mask and the second mask;
[0063] S600, respectively calculating the component displacements of the light source in two orthogonal planes according to the displacements and the angles;
[0064] S700, calculating the illumination angles of the light source in two orthogonal planes according to the component displacements of the light source in the two orthogonal planes, the thickness of the transparent substrate, and the refractive index of the transparent substrate.
[0065] Optionally, the calculation formula of the illumination angle of the light source in two orthogonal planes is as follows:
[0066]
[0067]
[0068] in, represents the illumination angle of the first orthogonal plane, represents the illumination angle of the second orthogonal plane, D ix represents the component displacement of the first mask and the second mask having a concentric relationship in the first orthogonal plane, D iy It represents the component displacement of the i-th pair of the first mask and the second mask having a concentric relationship in the second orthogonal plane.
[0069] See also Figure 7 ,in, Figure 7 (b) to Figure 7 (d) is a schematic diagram showing the use of the CHT algorithm to locate the ring and disk patterns. The center position information of each pair of pattern shadows can be obtained from the shadow image. A vector is formed by connecting any one center to another center. The direction of this vector is called the first direction. According to the principle of vector orthogonal decomposition, the first direction can be decomposed into two mutually perpendicular directions, namely the second direction x and the third direction y, where the second direction and the first direction form a first angle θ. Therefore, the shadow displacement D i The components about the second direction x and the third direction y can be decomposed into D ix and D iy , respectively D ix =D i *cosθ, D iy =D i *sinθ. According to the above formula, the lighting angle of the light source on two orthogonal planes can be obtained and
[0070] It can be seen that the contents of the above-mentioned device embodiments are all applicable to the present method embodiments, the functions specifically implemented by the present method embodiments are the same as those of the above-mentioned device embodiments, and the beneficial effects achieved are also the same as those achieved by the above-mentioned device embodiments.
[0071] In addition, an embodiment of the present invention provides a light angle calibration system, comprising the above-mentioned device, a light source, an image sensor, a detection device and a processor; wherein:
[0072] The light source is used to generate incident light at a certain angle;
[0073] The image sensor is used to capture the light and shadow image generated by the incident light passing through the transparent substrate;
[0074] The detection device is used to detect the shadow position information of a plurality of pairs of the first mask and the second mask having a concentric relationship in the light and shadow image;
[0075] The processor is used to calculate the corresponding displacement according to the position information of the first mask and the second mask, and calculate the illumination angle of the light source according to the displacement, the thickness of the transparent substrate and the refractive index of the transparent substrate.
[0076] It can be seen that the contents of the above-mentioned device embodiments are all applicable to the present system embodiments, the functions specifically implemented by the present system embodiments are the same as those of the above-mentioned device embodiments, and the beneficial effects achieved are also the same as those achieved by the above-mentioned device embodiments.
[0077] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.
Claims
1. A light angle calibration device, characterized in that: It includes a transparent substrate, which includes a first surface and a second surface parallel to each other, the first surface is provided with a plurality of first masks, the second surface is provided with a plurality of second masks, and the first masks and the second masks at corresponding positions satisfy a concentric relationship; wherein the first masks and the second masks are used for shading.
2. The device according to claim 1, characterized in that The thickness of the transparent substrate is much greater than the thickness of the first mask and the second mask.
3. The device according to claim 1, characterized in that The first mask is a circular ring, the second mask is a circular disk, and the inner diameter of the circular ring is greater than the diameter of the circular disk.
4. The device according to claim 3, characterized in that The thickness of the transparent substrate ranges from 0.5 mm to 2.5 mm.
5. The device according to claim 3, characterized in that The thickness range of the first mask and the second mask is less than 0.1 um.
6. A method for calibrating an illumination angle, characterized in that: The device according to any one of claims 1 to 5 comprises: The device is placed between a light source and an image sensor; the light source is used to generate incident light at a certain angle, and the image sensor is used to capture a light and shadow image generated by the incident light passing through the transparent substrate; Detecting shadow position information of a plurality of pairs of the first mask and the second mask having a concentric relationship in the light and shadow image; Calculating corresponding displacements according to position information of the first mask and the second mask; The illumination angle of the light source is calculated according to the displacement, the thickness of the transparent substrate and the refractive index of the transparent substrate.
7. The method according to claim 6, characterized in that The calculation formula of the illumination angle of the light source is as follows: in, represents the illumination angle, n represents the refractive index of the transparent substrate, h represents the thickness of the transparent substrate, m represents the logarithm of the first mask and the second mask having a concentric relationship, and D i It represents the displacement of the i-th pair of the first mask and the second mask having a concentric relationship.
8. The method according to claim 6, characterized in that The method further comprises: Calculating an angle according to light and shadow position information of the first mask and the second mask; Calculating the component displacements of the light source in two orthogonal planes respectively according to the displacement and the angle; The illumination angles of the light source in the two orthogonal planes are calculated respectively according to the component displacements of the light source in the two orthogonal planes, the thickness of the transparent substrate and the refractive index of the transparent substrate.
9. The method according to claim 8, characterized in that The calculation formula of the illumination angle of the light source in two orthogonal planes is as follows: in, represents the illumination angle of the first orthogonal plane, represents the illumination angle of the second orthogonal plane, D ix represents the component displacement of the first mask and the second mask having a concentric relationship in the first orthogonal plane, D iy It represents the component displacement of the i-th pair of the first mask and the second mask having a concentric relationship in the second orthogonal plane.
10. A light angle calibration system, characterized in that: The method comprises a device, a light source, an image sensor, a detection device and a processor as described in any one of claims 1 to 5; wherein: The light source is used to generate incident light at a certain angle; The image sensor is used to capture the light and shadow image generated by the incident light passing through the transparent substrate; The detection device is used to detect the shadow position information of a plurality of pairs of the first mask and the second mask having a concentric relationship in the light and shadow image; The processor is used to calculate the corresponding displacement according to the position information of the first mask and the second mask, and calculate the illumination angle of the light source according to the displacement, the thickness of the transparent substrate and the refractive index of the transparent substrate.