Dual-channel imaging and spectral measurement system

Abstract

The invention discloses a dual-channel imaging and spectral measurement system, which is characterized in that an objective lens is connected with a beam splitter prism for splitting light in an imaging light path into transmission light and reflected light, and the direction of a reflected light path is connected with a camera for collecting the reflected light to obtain a target scene image; the spatial light modulator is used for continuously transmitting the target light path backwards, the focusing mirror is used for completely zooming the target surface of the spatial light modulator to the integrating sphere, the integrating sphere is used for improving the uniform illumination of the light beam, and the spectrograph is used for measuring the spectral information of the target position. High-resolution space pictures and hyperspectral data are synchronously obtained through two channels, and the imaging quality is good; the image space telecentric objective lens eliminates measurement errors caused by object distance changes, monitors a target object in real time, does not need scanning imaging, and can detect a moving target. A target occupying a plurality of pixels opens pixels of a plurality of spatial light modulators at the same time, so that the signal-to-noise ratio is greatly improved, and the quality of spectral imaging is further improved; the system has the advantages of low data redundancy, simple structure, compact volume and low cost.

Description

Technical Field

[0001] The invention relates to a spectral imaging device, in particular to a dual-channel imaging and spectral measurement system. Background Art

[0002] Existing research on snapshot spectral imaging technology mainly focuses on the acquisition method and data post-processing of push-scan spectral imaging. CASSI, a snapshot hyperspectral imaging technology based on coding technology and compressed sensing, studied by AAWagadarikar et al., achieves discrete sampling of the target scene by replacing the slit of the traditional push-broom hyperspectral imager with a coding plate, and obtains spectral-spatial compression aliasing data on the detector. Finally, the hyperspectral data is restored through a priori conditions and a spectral reconstruction algorithm based on compressed sensing. CTIS, a snapshot hyperspectral imaging technology based on computational tomography, is studied by M Descour et al. Its optical system projects the spectral information contained in the target image on the detector plane from multiple directions through a two-dimensional grating, and then decodes the hyperspectral data through a spectral reconstruction algorithm. Xue Qingsheng's team from Ocean University of China proposed an optical system with a common objective lens for hyperspectral imaging and array imaging, and uses low-precision POS (Position and Orientation System) data obtained by consumer-grade positioning and inertial navigation devices (GPS / IMU) and auxiliary array cameras to perform geometric correction on push-broom hyperspectral images. First, the push-broom strips are preliminarily corrected using low-precision POS data, and then high-precision relative POS information is extracted from the synchronously acquired inter-frame array images for geometric registration of hyperspectral images. The CASSI method can effectively improve the luminous flux and signal-to-noise ratio, but its spectral reconstruction calculation process requires prior conditions, and due to the compressed sampling of the signal, it is easy to cause reconstruction errors of hyperspectral data. In addition, its reconstruction algorithm is complex and it is difficult to process the original image at a high frame rate, so the effect of hyperspectral video imaging is not good. The CTIS method only obtains the projection of the data cube in a few directions, and there is loss of signal sampling, which will affect the accuracy of spectral reconstruction; in addition, the projection images in several directions need to be collected within the limited detector area, and there are a lot of intervals between projections, the detector utilization rate is not high, and the size of the system field of view is limited. The geometric correction of the push-broom hyperspectral image based on the post-processing of POS data or auxiliary array camera data can partially correct the geometric distortion caused by the misaligned sampling of the drone on the ground, but the data of the missing sampling part is still vacant and still needs to be filled by the interpolation algorithm and cannot be directly obtained. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to obtain spectral data of a target position in a targeted manner, and to provide a dual-channel imaging and spectral measurement system.

[0004] Technical solution: The dual-channel imaging and spectral measurement system described in the present invention includes an objective lens, which is connected to a beam splitter prism that splits the light in the imaging light path into transmitted light and reflected light. The direction of the reflected light path of the beam splitter prism is connected to a camera used to collect reflected light to obtain an image of a target scene; the direction of the transmitted light path of the beam splitter prism is sequentially connected to a spatial light modulator that continues to transmit the target light path backward, a focusing lens used to completely scale the target surface of the spatial light modulator to an integrating sphere, an integrating sphere used to improve the uniform illumination of the light beam, and a spectrometer used to measure the spectral information of the target position.

[0005] Furthermore, the objective lens is an image-space telecentric objective lens, which can eliminate the measurement error caused by the change of object distance and improve the measurement accuracy and imaging quality of the system.

[0006] Furthermore, the beam splitter prism is a 45° beam splitting cubic prism that makes the target scene image obtained by the camera and the image formed by the spatial light modulator symmetrical, and the beam splitting ratio of the transmitted light to the reflected light is 8-9:2-1. Under the premise of satisfying the camera imaging, more light is transmitted backward through the beam splitter prism for spectral measurement, thereby increasing the accuracy of spectral measurement. The camera and the spatial light modulator are symmetrically arranged relative to the beam splitting plane of the beam splitter prism, and have the same resolution and one-to-one correspondence in pixel coordinates. The imaging of the camera and the spatial light modulator is synchronized in real time, and is used to monitor the spectrum of the target object in real time, which is not affected by whether the target moves or not. The tester screens the target of interest through the camera, and according to the pixel coordinates of the target in the camera, opens the pixel corresponding to the pixel coordinate of the spatial light modulator, adjusts the magnification of the focusing mirror so that the light near the target passes through the spatial light modulator and enters the focusing mirror. After multiple reflections and homogenization inside the integrating sphere, the light is transmitted to the fiber optic spectrometer through the optical fiber for spectral measurement to obtain the spectral data of the target of interest. The system does not require scanning imaging, is not affected by platform vibration, can detect moving targets, has no redundancy in spectral data, and is simple and convenient to process.

[0007] Furthermore, the spatial light modulator contains many independent pixels, which are arranged in a two-dimensional array in space. Each pixel can independently receive control of optical or electrical signals, change the amplitude to close or open pixels at different positions, so that the light at the target object continues to be transmitted backward. For targets that occupy multiple pixels, multiple pixels of the spatial light modulator can be turned on at the same time to increase the amount of light passing through for spectral measurement. Compared with single-pixel spectral detection, its signal-to-noise ratio can be greatly improved, thereby ensuring the quality of spectral measurement. Preferably, the resolution of the camera and the spatial light modulator are both 1920×1080, and the pixel size is 10μm, so that the target object can be drawn into multiple pixels as much as possible, and the pixels of multiple spatial light modulators are turned on at the same time for spectral measurement, reducing noise interference and improving the quality of spectral measurement.

[0008] Furthermore, the frame rate of the spatial light modulator is greater than or equal to the frame rate of the camera, preferably the frame rate of the spatial light modulator is greater than or equal to 50 frames / s, and the frame rate of the camera is 24 to 50 frames / s. For the spatial light modulator with higher imaging requirements, the frame rate is set to be larger, and for the camera with lower imaging requirements, the frame rate is set to be smaller.

[0009] Furthermore, the magnification of the focusing mirror is 0.1 to 0.5. The magnification is adjusted according to the distance between the focusing mirror and the spatial light modulator and the integrating sphere, so that the target surface of the spatial light modulator can be completely scaled into the integrating sphere, ensuring that all targets can be spectrally measured, thereby increasing the range of measurable targets.

[0010] Furthermore, the input port and the output port of the integrating sphere are arranged vertically. The inner wall of the integrating sphere is a good spherical surface, coated with a diffuse reflection material with a diffuse reflection coefficient close to 1. The light enters the interior of the integrating sphere from the input port, and after multiple reflections, forms a light with uniform illumination on the inner wall, and enters the spectrometer from the output port, which improves the accuracy of spectral data measurement. The opening size of the integrating sphere is preferably 10mm, and a smaller opening ratio can further improve the accuracy of spectral measurement.

[0011] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The dual-channel setting can simultaneously obtain high spatial resolution images and high spectral data at the target position, and the imaging quality is excellent; 2. The objective lens is an image-side telecentric objective lens, which can eliminate the measurement error caused by the change of object distance, monitor the spectrum of the target object in real time, and is not affected by the movement of the target. The system does not need scanning imaging and is not affected by the vibration of the platform, and can detect moving targets; 3. The resolution is high. For targets occupying multiple pixels, the pixels of multiple spatial light modulators can be opened at the same time to increase the amount of light transmitted. Compared with the spectral detection of a single pixel, the signal-to-noise ratio is greatly improved, and the quality of spectral imaging is further improved; 4. There is less data redundancy and simple processing; 5. The structure is simple, the size is compact, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0014] like Figure 1A dual-channel imaging and spectral measurement system shown includes an objective lens 1, which is connected to a beam splitter prism 2 that splits the light in the imaging light path into transmitted light and reflected light, and the direction of the reflected light path of the beam splitter prism 2 is connected to a camera 3 for collecting reflected light to obtain a target scene image; the direction of the transmitted light path of the beam splitter prism 2 is sequentially connected to a spatial light modulator 4 that continues to transmit the target light path backward, a focusing lens 5 for completely scaling the target surface of the spatial light modulator 4 to an integrating sphere 6, an integrating sphere 6 for improving the uniform illumination of the light beam, and a spectrometer 7 for measuring spectral information of the target position.

[0015] Objective lens 1 is an image-side telecentric objective lens with a focal length of 45 mm and a working distance of 40 mm. Beam splitter prism 2 is a 45° beam splitter cube prism with a side length of 30 mm and is made of fused quartz. The beam splitting ratio of transmitted and reflected light is 8:2 (it can also be set to 9:1 according to requirements, so that more light can be transmitted backward for spectrum measurement while meeting the imaging requirements of camera 3). Camera 3 and spatial light modulator 4 have the same array size and are symmetrically arranged relative to the beam splitting plane of beam splitter prism 2. The distance from beam splitter prism 2 is 5 mm. The frame rate of spatial light modulator 4 is 60 frames / s, and the frame rate of camera 3 is 30 frames / s (the frame rate of spatial light modulator can also be set to be greater than or equal to 50 frames / s and the frame rate of camera to be 24 to 50 frames / s according to the requirements of imaging quality). The focal length of the focusing lens 5 is 30 mm, the distance from the spatial light modulator 4 is 10 mm, the distance from the input port of the integrating sphere 6 is 42 mm, and the other magnification is 0.42 (it can also be adjusted to 0.1 to 0.5 times according to the distance from the spatial light modulator 4 and the integrating sphere 6, so that the target surface of the spatial light modulator 4 is completely scaled into the integrating sphere 6). The inner diameter of the integrating sphere 6 is 50 mm, the aperture of the input port is 10 mm, the output port is an optical fiber output, and the input port and the output port are arranged vertically.

[0016] Acquiring hyperspectral data using the above dual-channel imaging and spectral measurement system mainly includes the following steps:

[0017] 1. Establish the pixel coordinate system of the camera 3 and the pixel coordinate system of the spatial light modulator 4. The camera 3 and the spatial light modulator 4 have the same resolution, that is, the pixel scale and the pixel size of the two are consistent, so that the pixel coordinates of the two correspond one to one;

[0018] 2. Shoot the target scene. The light passes through the objective lens 1 and the beam splitter prism 2. The imaging light is split by the beam splitter prism 2 and reaches the camera 3 and the spatial light modulator 4 at the same time. The target scene image obtained by the camera 3 is symmetrical to the image formed on the spatial light modulator 4.

[0019] 3. Identify the target of interest in the target scene image obtained by camera 3 and perform spectral measurement: According to the pixel coordinates of the target of interest in the image of camera 3, turn on the pixel corresponding to the pixel coordinates of spatial light modulator 4, and all the light near the target enters the focusing mirror 5 through spatial light modulator 4. After multiple reflections and homogenization inside integrating sphere 6, the light is transmitted to fiber optic spectrometer 7 through optical fiber for spectral measurement to obtain the spectral data of the target of interest.

Claims

1. A dual-channel imaging and spectral measurement system, comprising an objective lens (1), It is characterized in that The objective lens (1) is connected to a beam splitter prism (2) for splitting light in an imaging light path into transmitted light and reflected light; the direction of the reflected light path of the beam splitter prism (2) is connected to a camera (3) for collecting reflected light to obtain a target scene image; the direction of the transmitted light path of the beam splitter prism (2) is sequentially connected to a spatial light modulator (4) for further transmitting the target light path backward, a focusing lens (5) for completely scaling the target surface of the spatial light modulator (4) to an integrating sphere (6), an integrating sphere (6) for improving the uniform illumination of the light beam, and a spectrometer (7) for measuring spectral information of the target position.

2. The dual-channel imaging and spectral measurement system according to claim 1, It is characterized in that The objective lens (1) is an image-side telecentric objective lens.

3. The dual-channel imaging and spectral measurement system according to claim 1, It is characterized in that The beam splitting prism (2) is a cubic prism with a beam splitting angle of 45°, which makes the target scene image obtained by the camera (3) and the image formed by the spatial light modulator (4) symmetrical.

4. The dual-channel imaging and spectral measurement system according to claim 3, It is characterized in that The splitting ratio of the transmitted light to the reflected light of the splitting prism (2) is 8-9:2-1.

5. The dual-channel imaging and spectral measurement system according to claim 3, It is characterized in that The camera (3) and the spatial light modulator (4) have the same resolution and pixel coordinates correspond one to one.

6. The dual-channel imaging and spectral measurement system according to claim 5, It is characterized in that The camera (3) and the spatial light modulator (4) are arranged symmetrically with respect to the beam splitting plane of the beam splitting prism (2).

7. The dual-channel imaging and spectral measurement system according to claim 5, It is characterized in that The frame rate of the spatial light modulator (4) is greater than or equal to the frame rate of the camera (3).

8. The dual-channel imaging and spectral measurement system according to claim 7, It is characterized in that The frame rate of the spatial light modulator (4) is greater than or equal to 50 frames / s, and the frame rate of the camera (3) is 24 to 50 frames / s.

9. The dual-channel imaging and spectral measurement system according to claim 1, It is characterized in that The magnification of the focusing lens (5) is 0.1-0.

5.

10. The dual-channel imaging and spectral measurement system according to claim 1, It is characterized in that The input port and the output port of the integrating sphere (6) are arranged vertically.

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