Photometric stereo-based device and method for rapidly detecting surface features of object

Abstract

Disclosed in the present invention is a photometric stereo-based device for rapidly detecting surface features of an object, capable of rapidly acquiring a plurality of images meeting the requirements of a photometric stereo algorithm. The device comprises a light emitting assembly, an acquisition assembly located above the light emitting assembly, and a data processing module; the acquisition assembly comprises a light path system and a camera group; the light path system comprises: a beam splitting prism group used for splitting reflected light from the surface of an object into a plurality of beams of light and respectively outputting the plurality of beams of light in different preset directions to form images to be processed, and a plurality of bandpass filters correspondingly arranged on the output sides of the plurality of beams of light used for forming said images, wherein the central wavelengths of the bandpass filters are respectively configured to be different wavebands of the reflected light from the surface of the object; the camera group comprises a plurality of cameras which are arranged behind the bandpass filters in a one-to-one correspondence mode and acquire filtered light beams; and the data processing module receives image information sent by the cameras, and performs compensation and photometric stereo reconstruction on the image information, so as to obtain surface features of the object. Further disclosed is a method implemented on the basis of the device.

Description

A rapid detection device and method for object surface features based on photometric stereo. Technical Field

[0001] This invention relates to the field of machine vision inspection technology, and in particular to a rapid detection device and method for object surface features based on photometric stereo. Background Technology

[0002] Currently, photometric stereo technology has been widely used in the detection of surface features of objects, especially in the detection of surface defects in products. Its basic principle is to acquire images of the object surface under different lighting conditions, and use the brightness information in these images to calculate the directional gradient of the object surface, thereby obtaining the three-dimensional shape information of the object surface.

[0003] However, in industrial practice, the application of photometric stereo technology still faces challenges related to image acquisition speed, especially in production line environments. Objects to be inspected typically need to be placed on conveyor belts for sequential lighting and imaging. To acquire multiple images from different angles, the object must be kept stationary for each shot; for example, in a production environment, the conveyor must be stopped, and the object must be lit and photographed from different angles. This inspection method is complex and reduces efficiency to some extent. Therefore, how to quickly acquire multiple images that meet the requirements of photometric stereo algorithms has become an urgent need in the current industrial inspection field. Summary of the Invention

[0004] Therefore, it is necessary to address the above-mentioned shortcomings by providing a rapid detection device and method for object surface features based on photometric stereo. By optimizing the device structure and detection method, it can quickly acquire multiple images that meet the requirements of the photometric stereo algorithm, thereby improving the efficiency of object surface feature detection and providing favorable support for the automation and intelligence of industrial production lines.

[0005] A rapid detection device for object surface features based on photometric stereoscopic imaging includes a light-emitting component for emitting light and illuminating the object surface, a data acquisition component located above the light-emitting component, and a data processing module for processing the image information acquired by the data acquisition component.

[0006] The acquisition component includes an optical path system and a camera group; the optical path system includes a beam splitter prism group for splitting the reflected light from the object surface into multiple beams and outputting each beam in a different preset direction to form an image to be processed, and multiple bandpass filters correspondingly disposed on the output side of each beam used to form the image to be processed, wherein the center wavelength of each bandpass filter is configured to a different band of the reflected light from the object surface; the camera group includes multiple cameras correspondingly disposed after each bandpass filter for acquiring the beams output from the bandpass filters.

[0007] The data processing module is used to receive image information sent by the camera, and to compensate and perform photometric stereo reconstruction on the image information to obtain the surface features of the object.

[0008] In one embodiment, the beam splitter group includes i beam splitters, where i is an integer greater than or equal to 3. The first beam splitter is located coaxially above the light-emitting component and is used to receive reflected light from the surface of the object and split the reflected light from the surface of the object into transmitted light and reflected light, which are output to the first direction and the second direction, respectively. The second beam splitter is located coaxially above or to one side of the first beam splitter and is used to receive the transmitted light or reflected light emitted by the first beam splitter and output to the third direction and the fourth direction, respectively. The remaining beam splitters in the beam splitter group are used to receive the transmitted light and reflected light emitted by the beam splitters in the set positions and output the corresponding transmitted light and reflected light to different preset directions, respectively.

[0009] In one embodiment, a plurality of bandpass filters are respectively disposed on one side of each beam splitter used to output the image to be processed, and are perpendicular to the corresponding extension direction used to form the image to be processed.

[0010] This invention also discloses a rapid detection method for object surface features based on photometric stereo, which is implemented using the aforementioned rapid object surface feature detection device. The rapid object surface feature detection method includes the following steps:

[0011] S1. The light-emitting component works and illuminates the surface of the object; the optical path system of the acquisition component divides the reflected light from the surface of the object into multiple beams, and each beam is output in a different preset direction to form an image to be processed. The image to be processed is filtered, and the camera group of the acquisition component acquires the filtered image.

[0012] S2. Process the images acquired by the camera group using a line compensation algorithm;

[0013] S3. Based on the image processed by the compensation algorithm, the photometric stereo algorithm is used to reconstruct the image in order to detect the surface features of the object.

[0014] In one embodiment, the optical path system includes multiple beam-splitting prisms and multiple bandpass filters; step S1 includes:

[0015] After the object's surface is illuminated, the light reflected from the object's surface enters the optical path system in the acquisition component;

[0016] In the optical path system, multiple beam splitters divide the reflected light from the object's surface into multiple beams, which are then output in different preset directions to form the image to be processed.

[0017] The center wavelengths of the multiple bandpass filters in the optical path system are respectively configured to different bands of the light reflected from the object surface. Each bandpass filter performs filtering processing on the corresponding image to be processed, so as to output multiple beams of light emitted along a preset direction and having different bands to form an image to be acquired.

[0018] The camera group contains multiple cameras that simultaneously acquire images from their respective directions.

[0019] In one embodiment, a plurality of bandpass filters are respectively disposed on one side of each beam splitter used to output the image to be processed, and are perpendicular to the corresponding extension direction used to form the image to be processed.

[0020] The photometric stereo-based rapid detection device and method for object surface features of this invention utilizes an optical path structure composed of a beam-splitting prism group and multiple bandpass filters to split the reflected light from the object surface into multiple beams of light of different wavelengths that do not interfere with each other. Multiple cameras can simultaneously acquire multiple images under different lighting conditions. The images are reconstructed using a compensation algorithm and a photometric stereo algorithm to detect the object surface features. This device and method significantly improve the image acquisition speed, reduce the dwell time of the object to be detected, and realize photometric stereo algorithm-based rapid imaging, greatly improving the detection efficiency. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of a rapid detection device for surface features of an object in one embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of the structure of a rapid detection device for object surface features in one embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of the optical path system structure of a rapid detection device for surface features of an object in one embodiment of the present invention;

[0024] Figure 4 is a flowchart illustrating a rapid detection method for object surface features in one embodiment of the present invention.

[0025] The diagram is labeled as follows: Light-emitting component - 10, Acquisition component - 20, Data processing module - 30, Optical path system - 201, First beam splitter - 2011, Second beam splitter - 2012, Third beam splitter - 2013, First bandpass filter - 2014, Second bandpass filter - 2015, Third bandpass filter - 2016, Fourth bandpass filter - 2017, Camera group - 202, First camera - 2021, Second camera - 2022, Third camera - 2023, Fourth camera - 2024. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] This invention addresses the problems of complex operation and low detection efficiency in current methods for detecting surface features of objects. By splitting and filtering the reflected light from the object's surface, it outputs multiple independent beams of different wavelengths to meet image processing needs, thus reducing the difficulty of detection and improving efficiency. Specifically, referring to Figures 1-3, the photometric stereoscopic rapid detection device for object surface features in this embodiment includes a light-emitting component 10, a data acquisition component 20, and a data processing module 30. The light-emitting component 10 emits light and illuminates the object's surface, providing stable and uniform illumination to ensure effective capture of reflected light. The data acquisition component 20, located above the light-emitting component 10, receives and processes the reflected light from the object's surface. The data processing module 30 processes the image information acquired by the data acquisition component 20.

[0028] In this embodiment, the acquisition component 20 includes an optical path system 201 and a camera group 202. The optical path system 201 includes a beam splitter prism group and multiple bandpass filters. The beam splitter prism group and the multiple bandpass filters work together to split and filter the reflected light from the object surface. Specifically, the beam splitter prism group is used to split the reflected light from the object surface into multiple beams and output each beam in a different preset direction to form an image to be processed. The multiple bandpass filters are correspondingly arranged on the output side of each beam used to form the image to be processed. The center wavelength of each bandpass filter is configured to a different band of the reflected light from the object surface. For example, the center wavelengths of the multiple bandpass filters are respectively configured as λ1, ..., λ2. n ; where λ1, ..., λ n The wavelength refers to different bands of light reflected from the surface of the object. That is, multiple bandpass filters are respectively positioned on one side of each final output direction after beam splitting in the optical path system, with each bandpass filter filtering light within its specific wavelength range. The camera group 202 includes multiple cameras correspondingly positioned after each bandpass filter for acquiring the light beams output from the bandpass filters. In other words, each camera is positioned at a different output end of the optical path system to capture image data processed by the filtered light.

[0029] As a further optimization of the above technical solution, the beam splitter group includes i beam splitters, where i is an integer greater than or equal to 3. The first beam splitter is positioned coaxially above the light-emitting component 10, used to receive reflected light from the object's surface and split it into transmitted light and reflected light, outputting them to the first and second directions respectively. That is, the first beam splitter is positioned coaxially above the light-emitting component, used to receive reflected light from the surface of the object under test and split it into transmitted light and reflected light. The second beam splitter is positioned coaxially above or to one side of the first beam splitter, used to receive the transmitted light or reflected light emitted by the first beam splitter and output it to the third and fourth directions respectively. That is, the second beam splitter is positioned coaxially to the side or above the first beam splitter, used to further process the transmitted light or reflected light from the first beam splitter, further splitting it into transmitted light and reflected light. The remaining beam-splitters in the beam-splitter group receive the transmitted and reflected light emitted by the pre-positioned beam-splitters and output the corresponding transmitted and reflected light to different preset directions. In other words, multiple beam-splitters are strategically arranged in the optical path system to process the transmitted or reflected light from other beam-splitters and further split it into transmitted and reflected light components. Through this cascaded optical path design, the reflected light from the object's surface is ultimately divided into multiple directions for multi-path output. For example, the second beam-splitter is positioned in direction 1 and processes the transmitted light output from the first beam-splitter into transmitted light output in direction 3 and reflected light output in direction 4. The third beam-splitter is positioned in direction 2 and processes the reflected light output from the first beam-splitter into transmitted light output in direction 5 and reflected light output in direction 6, and so on. The light emitted by the remaining beam-splitters (excluding the first and second beam-splitters) is output to directions 5, ..., and N, respectively. In this way, the beam splitters are distributed in a canopy-like pattern, thereby splitting the reflected light from the object's surface into multiple beams for detection.

[0030] In this embodiment, after the reflected light from the object surface is split by multiple beam-splitting prisms, multiple beams of light are finally output along the Lth, ..., Mth directions. Multiple bandpass filters are respectively disposed on one side of each beam-splitting prism used to output light in the Lth, ..., Mth directions, and are perpendicular to the corresponding extension direction used to form the image to be processed. That is, multiple bandpass filters are respectively disposed on one side of each beam-splitting prism used to output light in the Lth, ..., Mth directions, and are perpendicular to the Lth, ..., Mth directions. Multiple cameras in the camera group 202 are disposed after each bandpass filter in the optical path system 201, i.e., in the Lth, ..., Mth directions.

[0031] The data processing module 30 receives image information sent by the camera and performs compensation and photometric stereo reconstruction on the image information to obtain the surface features of the object. Specifically, the data processing module acquires image information sent by multiple cameras, calculates the histograms of the acquired images, performs equalization processing, and then calculates the cumulative probability of the histograms of the multiple equalized images. Taking one equalized image as a reference, the module calculates the difference in cumulative probability between the remaining equalized images and the reference equalized image, creates a mapping relationship using the closest grayscale value, and completes the compensation for the remaining equalized images through histogram matching.

[0032] One of the aforementioned baseline equalized images and the other images processed by the compensation algorithm are input into the photometric stereo algorithm for calculation to obtain the normal vector and reflection coefficient of each pixel. The gradient field is obtained based on the normal vector, and then the depth information of the detected object surface is obtained to obtain the object surface feature parameters.

[0033] Referring to Figures 1-4, this invention also discloses a rapid detection method for object surface features based on photometric stereo, which is implemented using the aforementioned rapid object surface feature detection device. The rapid object surface feature detection method includes the following steps:

[0034] S1. Use a data acquisition component in conjunction with a light-emitting component to acquire images of the object's surface;

[0035] S2. Process the images acquired by camera group 202 using a line compensation algorithm. Specifically, the compensation algorithm is used to process multiple images acquired at the same time to eliminate the effects of wavelength differences caused by the optical path system.

[0036] S3. Based on the image processed by the compensation algorithm, the photometric stereo algorithm is used to reconstruct the image in order to detect the surface features of the object.

[0037] Among them, the use of a data acquisition component in conjunction with a light-emitting component to acquire images of the object surface includes:

[0038] The light-emitting component 10 operates and illuminates the object's surface. Specifically, the light-emitting component 10 is turned on, causing the emitted light to illuminate the object's surface and ensuring that the light evenly and fully covers the entire object's surface.

[0039] The optical path system 201 of the acquisition component 20 splits the reflected light from the object surface into multiple beams, and outputs each beam in a different preset direction to form an image to be processed. The image to be processed is then filtered, and the filtered image is acquired by the camera group 202 of the acquisition component 20. Multiple bandpass filters are respectively disposed on one side of each beam-splitting prism used to output the image to be processed, and are perpendicular to the corresponding extension direction used to form the image. The optical path system 201 includes multiple beam-splitting prisms and multiple bandpass filters. Step S1 includes:

[0040] After the object's surface is illuminated, the light reflected from the object's surface enters the optical path system 201 in the acquisition component 20.

[0041] In the optical path system 201, multiple beam splitters divide the reflected light from the object surface into multiple beams and output them in different preset directions to form an image to be processed. For example, the beams after beam splitting are output along the Lth, ..., Mth directions, respectively.

[0042] The center wavelengths of the multiple bandpass filters in the optical path system 201 are respectively configured to different bands of the light reflected from the object surface. Each bandpass filter performs filtering processing on the corresponding image to be processed, so as to output multiple beams of light emitted along a preset direction and having different bands, forming the image to be acquired. The center wavelengths of the multiple bandpass filters in the optical path system 201 are respectively configured as λ1, ..., λ n ; where λ1, ..., λ n The wavelengths are different bands of light reflected from the object's surface. With this configuration, the optical path system 201 can separate the reflected light from the object's surface into multiple beams of light with different wavelengths, and output them respectively to the Lth, ..., Mth directions. Thus, multiple bandpass filters filter the light in the aforementioned multiple directions, aiming to separate the reflected light from the object's surface into multiple different wavelength bands for output.

[0043] The camera group 202 contains multiple cameras that simultaneously acquire images from their respective directions. Specifically, the multiple cameras can simultaneously acquire multiple images of the object surface illuminated by light of different wavelengths, achieving the effect equivalent to sequentially illuminating and acquiring images from multiple different directions.

[0044] In this embodiment, an acquisition component is used in conjunction with a light-emitting component to acquire images of the object's surface. Multiple acquired images are processed using a compensation algorithm to eliminate the effects of wavelength differences caused by the optical path system. After processing by the compensation algorithm, multiple images are processed using a photometric stereo algorithm to detect the object's surface features.

[0045] The following example illustrates the working process of a rapid detection device for object surface features based on photometric stereo.

[0046] Referring to Figures 1-4, the rapid detection device for object surface features based on photometric stereo in this embodiment includes a light-emitting component 10 and a collection component 20 located above the light-emitting component 10. The collection component 20 includes an optical path system 201 and a camera group 202. The optical path system 201 includes three beam splitters (i.e., the first beam splitter 2011, the second beam splitter 2012, and the third beam splitter 2013) and four bandpass filters (the first bandpass filter 2014, the second bandpass filter 2015, the third bandpass filter 2016, and the fourth bandpass filter 2017). The camera group 202 includes four cameras (the first camera 2021, the second camera 2022, the third camera 2023, and the fourth camera 2024). In the optical path system 201, the first beam splitter 2011 is disposed coaxially above the light-emitting component 10 and is used to receive reflected light from the surface of the object under test and split it into transmitted light and reflected light. The second beam splitter 2012 is disposed coaxially to the side of the first beam splitter 2011 and is used to receive the reflected light from the first beam splitter 2011. The third beam splitter 2013 is disposed coaxially above the first beam splitter 2011 and is used to receive the transmitted light from the first beam splitter 2011.

[0047] The second beam splitter 2012 further splits the reflected light from the first beam splitter 2011 into two parts: transmitted light and reflected light, and outputs them in two different directions. Similarly, the third beam splitter 2013 further splits the transmitted light from the first beam splitter 2011 into two parts: transmitted light and reflected light, and outputs them in two different directions.

[0048] In the optical path system 201, the first bandpass filter 2014 and the second bandpass filter 2015 are respectively positioned in the transmission light output direction and the reflection light output direction of the second beam splitter 2012. The third bandpass filter 2016 and the fourth bandpass filter 2017 are respectively positioned in the transmission light output direction and the reflection light output direction of the third beam splitter 2013. These four bandpass filters have different center wavelengths and bandwidths, selectively filtering light from four different wavelength bands.

[0049] The first camera 2021, the second camera 2022, the third camera 2023 and the fourth camera 2024 in the camera group 202 are respectively positioned after the above four bandpass filters and are used to capture images processed by filtered light.

[0050] For example, the light-emitting component 10 may be a red ring light source;

[0051] The first bandpass filter 2014 can be configured with a center wavelength of 635nm and a bandwidth of 30nm.

[0052] The second bandpass filter 2015 can be configured with a center wavelength of 665nm and a bandwidth of 30nm.

[0053] The third bandpass filter 2016 is available with a center wavelength of 695nm and a bandwidth of 30nm.

[0054] The fourth bandpass filter 2017 is available with a center wavelength of 725nm and a bandwidth of 30nm.

[0055] When the light-emitting component 10 is lit, the optical path system 201 in the acquisition component 20 divides the reflected light from the surface of the object under test into four beams of light with different directions and different wavelengths. The four cameras in the camera group 202 can shoot simultaneously and acquire four images under different lighting conditions at the same time.

[0056] Using one image as a baseline, grayscale and contrast compensation is performed on the other three images using a histogram matching algorithm. Specifically, the histograms of the four images are calculated, and equalization processing is performed. The cumulative probability of the histograms of the four equalized images is calculated. Using one equalized image as a baseline, the difference between its cumulative probability and that of the other three equalized images is calculated. A mapping relationship is created using the closest grayscale values, and compensation for the three equalized images is completed through histogram matching.

[0057] The photometric stereo algorithm is used to reconstruct the features of the object's surface using the four images mentioned above. The reference equalized image and the three images processed by the compensation algorithm are input into the photometric stereo algorithm for calculation to obtain the normal vector and reflection coefficient of each pixel. The gradient field is then obtained based on the normal vector, thereby acquiring the depth information of the detected object's surface.

[0058] The apparatus described in the embodiments above is merely illustrative. The number of beam splitters, bandpass filters, and cameras is not limited to the stated quantities, and the positions of the beam splitters, bandpass filters, and cameras are not limited to the stated arrangements. The light source pattern, light color, number of light sources, and parameters of the bandpass filters can also be adjusted. Where applicable, the above components can be arranged and adjusted according to actual needs. Such changes are not considered deviations from the present invention, but rather reasonable modifications and extensions within the scope of the present invention, and all such modifications are considered to be included within the protection scope of the present invention.

[0059] The photometric stereo-based rapid detection device and method for object surface features of this invention utilizes an optical path structure composed of a beam-splitting prism group and multiple bandpass filters to split the reflected light from the object surface into multiple beams of light of different wavelengths that do not interfere with each other. Multiple cameras can simultaneously acquire multiple images under different lighting conditions. The images are reconstructed using a compensation algorithm and a photometric stereo algorithm to detect the object surface features. This device and method significantly improve the image acquisition speed, reduce the dwell time of the object to be detected, and realize photometric stereo algorithm-based rapid imaging, greatly improving the detection efficiency.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A rapid detection device for object surface features based on photometric stereo, characterized in that, It includes a light-emitting component (10) for emitting light and illuminating the surface of an object, a collection component (20) located above the light-emitting component (10), and a data processing module (30) for processing the image information collected by the collection component (20). The acquisition component (20) includes an optical path system (201) and a camera group (202); the optical path system (201) includes a beam splitter prism group for splitting the reflected light from the object surface into multiple beams and outputting each beam in a different preset direction to form an image to be processed, and multiple bandpass filters correspondingly disposed on the output side of each beam used to form the image to be processed, wherein the center wavelength of each bandpass filter is configured to a different band of the reflected light from the object surface; the camera group (202) includes multiple cameras correspondingly disposed after each bandpass filter and used to acquire the beams output from the bandpass filters. The data processing module (30) is used to receive image information sent by the camera and to compensate and perform photometric stereo reconstruction on the image information in order to obtain the surface features of the object.

2. The rapid detection device for object surface features according to claim 1, characterized in that, The beam splitter group includes i beam splitters, where i is an integer greater than or equal to 3. The first beam splitter is located coaxially above the light-emitting component (10) and is used to receive reflected light from the surface of the object and split the reflected light from the surface of the object into transmitted light and reflected light, which are output to the first direction and the second direction, respectively. The second beam splitter is located coaxially above or to one side of the first beam splitter and is used to receive the transmitted light or reflected light emitted by the first beam splitter and output to the third direction and the fourth direction, respectively. The remaining beam splitters in the beam splitter group are used to receive the transmitted light and reflected light emitted by the beam splitter in the set position and output the corresponding transmitted light and reflected light to different preset directions, respectively.

3. The rapid detection device for object surface features according to claim 1, characterized in that, Multiple bandpass filters are respectively disposed on one side of each beam splitter used to output the image to be processed, and are perpendicular to the corresponding extension direction used to form the image to be processed.

4. A rapid detection method for object surface features based on photometric stereo, implemented using the rapid detection device for object surface features according to any one of claims 1-3, characterized in that, The rapid detection method for object surface features includes the following steps: S1. The light-emitting component (10) works and illuminates the surface of the object; the optical path system (201) of the acquisition component (20) divides the reflected light from the surface of the object into multiple beams of light, and each beam of light is output in a different preset direction to form an image to be processed. The image to be processed is filtered, and the camera group (202) of the acquisition component (20) acquires the filtered image. S2. Process the images acquired by the camera group (202) using a line compensation algorithm; S3. Based on the image processed by the compensation algorithm, the photometric stereo algorithm is used to reconstruct the image in order to detect the surface features of the object.

5. The rapid detection method for object surface features according to claim 4, characterized in that, The optical path system (201) includes multiple beam-splitting prisms and multiple bandpass filters; step S1 includes: After the object surface is illuminated, the light reflected from the object surface enters the optical path system (201) in the acquisition component (20). In the optical path system (201), multiple beam splitters divide the reflected light from the object surface into multiple beams and output them in different preset directions to form an image to be processed. The center wavelengths of the multiple bandpass filters in the optical path system (201) are respectively configured to different bands of the light reflected from the object surface. Each bandpass filter performs filtering processing on the corresponding image to be processed, so as to output multiple beams of light emitted along a preset direction and having different bands to form an image to be acquired. The multiple cameras in the camera group (202) acquire images from their respective directions at the same time.

6. The rapid detection method for object surface features according to claim 4, characterized in that, Multiple bandpass filters are respectively disposed on one side of each beam splitter used to output the image to be processed, and are perpendicular to the corresponding extension direction used to form the image to be processed.

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