CN107144348A - A kind of polarization differential multispectral imaging device and method for real-time detection - Google Patents

Abstract

The present invention relates to a polarization difference multi-spectral imaging device and method for real-time detection. Imaging objective lens and area array detector; wherein the birefringence filter assembly is composed of N (N=1,2,3...) groups of polarizing elements. The beam emitted or reflected by the detection target passes through the pre-imaging system and enters the birefringent beam splitting prism in the form of parallel light; the incident beam is divided into two beams of orthogonally polarized light by the first birefringent A group of polarizing elements in the refraction filter assembly, the beam is divided into two beams, and the two beams are filtered by different spectrums; finally, after the rear imaging objective lens, two sets of orthogonal polarization states can be obtained on the area array detector at the same time Multispectral images; each group contains 2nth power spectral images. This method can obtain the polarization difference multispectral image of the detection target in real time.

Description

A polarization difference multispectral imaging device and method for real-time detection

technical field

The invention belongs to the technical field of optical imaging detection, in particular to a polarization difference multispectral imaging device and method for real-time detection.

Background technique

At present, optical detection technology is one of the important ways for human beings to obtain target information. Optical detection technology can analyze the physical and chemical properties of the detection target by detecting the image, spectrum, polarization and other information of the target, and provide high-contrast target surface, shape, shadow and other information, thereby significantly improving the ability to identify specific targets in complex background environments . The imaging spectral polarization technology developed from this has formed a cutting-edge optical imaging detection tool with multi-mode detection capabilities by fusing the functions of cameras, spectrometers and polarimeters, which can simultaneously provide spatial, spectral and polarization four-dimensional light information of the target scene . It has important application value in military reconnaissance, agricultural pest detection, pollutant monitoring and other fields.

Polarization difference spectral imaging technology belongs to a class of imaging spectral polarization detection technology. Polarization difference spectral imaging technology can obtain the spectral image of the orthogonal polarization component of the detection target, which can effectively eliminate background noise and improve the contrast of characteristic targets (such as: artificial targets), and has important application value in the fields of biomedicine and military target reconnaissance . For example: in 1999, Backman et al. combined the dispersion grating spectrometer with the polarization difference technology to detect the orthogonal polarization scattering spectrum of early cancer cells and study the mechanism of cancer cell lesions.

As a new type of optical imaging detection technology, the research of differential polarization spectral imaging technology is mainly concentrated in developed countries in Europe and America. According to the different spectral components, they can be roughly divided into three categories:

(1) Differential polarization spectrum imaging technology using acousto-optic tuning filter or liquid crystal tuning filter;

(2) Differential polarization spectroscopy imaging technology using dispersion spectroscopy;

(3) Differential polarization spectral imaging technology using Fourier spectrometer.

However, the above three types of differential polarization spectral imaging technologies all need to push-broom the target to obtain polarization differential spectral images. Therefore, most existing solutions are used to observe static targets, and cannot detect dynamic target scenes in real time.

To sum up, the existing differential polarization spectral imaging technology still lacks an effective solution to the problem of how to detect dynamic target scenes in real time.

Contents of the invention

In order to overcome the problem that the existing differential polarization spectral imaging technology cannot detect dynamic target scenes in real time, the present invention provides a polarization differential multi-spectral imaging device and method for real-time detection. A single exposure can be used to obtain differential polarization multispectral images of the target scene with high spatial resolution.

In order to achieve the above object, the present invention adopts the following technical scheme:

A polarization difference multispectral imaging device for real-time detection, the device comprising:

A front imaging system, a first birefringent beam splitting prism, a birefringence filter assembly, a rear imaging objective lens and an area array detector are sequentially placed along the same optical axis;

The beam emitted or reflected by the detection target passes through the pre-imaging system and enters the first birefringent beam splitting prism in the form of parallel light; the incident beam is divided into two beams of orthogonally polarized light by the first birefringent prism and enters the birefringent filter assembly to form At least two light beams with different frequency spectrums that are 2 to the Nth power; finally pass through the rear imaging objective lens, and simultaneously acquire two sets of multispectral images of orthogonal polarization states on the area array detector.

Further, the front imaging system includes an imaging objective lens, a field diaphragm and a collimating objective lens arranged in sequence along the optical path direction; the image plane position of the imaging objective lens coincides with the front focal plane position of the collimating objective lens, so The field diaphragm is arranged at the coincident position of the image plane of the imaging objective lens and the front focal plane of the collimating objective lens.

Further, the birefringence filter assembly includes at least one set of polarizing elements sequentially arranged along the optical path, and the number of polarizing elements is N, where N=1, 2, 3, . . . .

Further, each group of polarizing elements includes a phase retarder and a second birefringent beam splitting prism arranged in sequence along the optical path.

Further, both the first birefringent beam-splitting prism and the second birefringent beam-splitting prism split the incident beam into two orthogonally polarized beams, and the angles between the two polarized beams and the reference direction are 0° and 90°.

Further, the fast axis directions of the phase retarders in multiple groups of adjacent polarizing elements form an angle of 45° with the reference direction.

In order to overcome the problem that the existing differential polarization spectral imaging technology cannot detect dynamic target scenes in real time, the present invention provides a polarization differential multi-spectral imaging device and method for real-time detection. A single exposure can be used to obtain differential polarization multispectral images of the target scene with high spatial resolution.

In order to achieve the above object, the present invention adopts another kind of technical scheme as follows:

A polarization difference multi-spectral imaging method for real-time detection, the method is based on the system, the light beam emitted or reflected by the detection target passes through the pre-imaging system, and enters the first birefringent beam splitting prism in the form of parallel light; the incident light beam After the first birefringent prism, it is divided into two beams of orthogonally polarized light and enters the birefringent filter assembly to form at least two beams with different spectrums that are 2 to the Nth power beam; finally, after passing through the post-imaging objective lens, it is detected in the area array Two sets of multispectral images of orthogonal polarization states were simultaneously acquired on the detector.

Further, the specific steps for the beam emitted or reflected by the detection target to pass through the front imaging system and enter the first birefringent beam splitting prism in the form of parallel light are:

The incident light beam from the target scene enters the front imaging system, and first passes through the imaging objective lens in the front imaging system to be imaged at its image plane position, and the field diaphragm is used to limit the size of the detection field of view;

Then the target beam passes through the action of the collimating objective lens, enters the first birefringent beam splitting prism in the form of parallel light, and after passing through the first birefringent beam splitting prism, it is divided into a first polarized beam and a second polarized beam;

The vibration direction of the first polarized beam is 0° to the reference direction, the vibration direction of the second polarized beam is 90° to the reference direction, and the first polarized beam and the second polarized beam are separated by a certain angle.

Further, two beams of orthogonally polarized light enter the birefringent filter assembly, and the specific steps for forming at least two beams with different spectrums that are 2 to the Nth power beam are:

The first polarized light beam and the second polarized light beam enter the birefringent filter assembly;

The first group of polarized beams is divided into two beams with different spectra after passing through the first group of polarizing elements, and then divided into four beams with different spectra after passing through the second group of polarizing elements, and after the Nth (N=1,2,3...) group of polarization After the element, the first polarized beam is divided into 2 N-th power beams with different frequency spectrums, and each beam has a different direction angle;

The second group of polarized beams is divided into two beams with different spectra after passing through the first group of polarizing elements; after passing through the second group of polarizing elements, it is divided into four beams with different spectra, and after the Nth (N=1,2,3...) group of polarization After the element, the second polarized beam is also divided into 2 Nth power beams with different spectrums; and the spectral characteristics of each beam are the same as one of the 2 Nth power beams divided by the first polarized beam, But the direction of beam divergence angle is different.

Further, through the post-imaging objective lens, the specific steps for simultaneously acquiring two sets of multispectral image beams with orthogonal polarization states on the area array detector are as follows:

After passing through the first birefringent beam splitting prism and the birefringent filter assembly, the target scene beam is divided into 2(N+1) power beams, and each beam has a different divergence angle;

After the convergence of the imaging objective lens, 2 (N+1) power target images are generated on the target surface of the area array detector at the rear focal plane position, and the polarization difference of the N power spectral segments of the target 2 is recorded image;

Among them, the first polarized light beam generates 2 N multispectral images of the target polarized light at 0° to the reference direction; the second polarized light beam generates spectral images of the target polarized light at 90° to the reference direction, and its spectral band Same spectral band as the multispectral image generated by the first polarized beam.

Compared with prior art, the beneficial effect of the present invention:

(1) A polarization difference multispectral imaging device and method for real-time detection of the present invention can obtain a differential multispectral image of a detection target with a single exposure, and can detect the detection target in real time;

(2) A polarization difference multispectral imaging device and method for real-time detection of the present invention has no slit in the system, and the obtained polarization difference spectrum image has the advantage of high spatial resolution;

(3) A polarization difference multispectral imaging device and method for real-time detection of the present invention, the device before the detector is an all-optical device, and the method is simple and practical without acousto-optic and electro-optic modulation.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application.

Fig. 1 is a structural schematic diagram of a polarization difference multispectral imaging device for real-time detection of the present invention;

Fig. 2 is a schematic diagram of the detection target scene acquired by the detector target surface of the present invention;

Among them: 1-front imaging system: 11-imaging objective lens, 12-field diaphragm, 13-collimating objective lens; 2-first birefringent beam splitting prism; 3-birefringent filter assembly: 31-first group Polarizing element: 311-phase retarder, 312-second birefringent beam splitting prism, 32-second group of polarizing elements: 321-phase retarder, 322-second birefringent beam splitting prism; 4-imaging objective lens; 5- Area detectors.

detailed description:

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1:

As introduced in the background technology, there is a problem that the existing differential polarization spectral imaging technology cannot detect dynamic target scenes in real time, and a polarization differential multispectral imaging device and method for real-time detection is provided. A single exposure can be used to obtain differential polarization multispectral images of the target scene with high spatial resolution.

In a typical implementation of the present application, the following technical solutions are adopted:

A polarization difference multispectral imaging device for real-time detection, as shown in Figure 1, the device includes:

A front imaging system 1, a first birefringent beam splitting prism 2, a birefringent filter assembly 3, a rear imaging objective lens 4 and an area array detector 5 are sequentially placed along the same optical axis;

In this embodiment, the front imaging system 1 includes an imaging objective lens 11, a field diaphragm 12, and a collimating objective lens 13 arranged in sequence along the optical path direction, and the field diaphragm 13 is located at the image plane position of the imaging objective lens 11. It is also the front focal plane position of the collimating objective lens 13.

The birefringence filter assembly 3 is composed of N (N=1, 2, 3, ...) groups of polarizing elements 31, 32 ... arranged sequentially along the optical path, and each group of polarizing elements includes a phase retarder and a second dual Refractive beamsplitter prisms.

In this embodiment, the birefringence filter assembly 3 includes two sets of polarizing elements sequentially arranged along the optical path: a first set of polarizing elements 31 and a second set of polarizing elements 32 . The first group of polarizing elements 31 consists of a phase retarder 311 and a second birefringent beam splitting prism 312 arranged in sequence along the optical path, and the second group of polarizing elements 32 consists of a phase retarder 321 and a second birefringent beam splitting prism arranged in sequence along the optical path. Prism 322 composition.

In this embodiment, the second birefringent beam-splitting prisms 312, 322 in the first refraction beam-splitting prism 2 and the birefringence filter assembly 3 can adopt Wollaston prisms, micro-angular polarization beam-splitting prisms, etc.; It divides the incident beam into two orthogonally polarized beams, the angles between the two polarized beams and the reference direction are 0° and 90°, that is, the vibration direction of the first polarized beam is 0° with the reference direction, and the vibration direction of the second polarized beam is 90° to the reference direction, and the first polarized beam and the second polarized beam are separated by a certain angle.

As shown in FIG. 1 , the fast axis directions of the phase retarders 311 and 321 in the birefringent filter assembly 3 form an angle of 45° with the reference direction.

In order to achieve the above object, the present invention adopts another kind of technical scheme as follows:

A polarization difference multispectral imaging method for real-time detection, the method is based on the system, the light beam emitted or reflected by the detection target passes through the front imaging system 1, and enters the first birefringent beam splitter prism 2 in the form of parallel light; The incident light beam is divided into two beams of orthogonally polarized light by the first birefringent prism 2 and enters the birefringent filter assembly 3 to form 4 beams of light beams with different spectrums; Acquire multispectral images of two sets of orthogonal polarization states.

A polarization difference multispectral imaging method for real-time detection, specifically comprising the following steps:

In the first step, the incident light beam from the target scene enters the front imaging system 1, and is first imaged at the image plane position by the imaging objective lens 11 in the front imaging system 1, and the field diaphragm 12 is used to limit the size of the detection field of view; Then the target beam passes through the effect of the collimating objective lens 13, enters the first birefringent beam splitting prism 2 in the form of parallel light, and after passing through the first birefringent beam splitting prism 2, it is divided into a first polarized beam and a second polarized beam, the first The vibration direction of the polarized beam is 0° to the reference direction, the vibration direction of the second polarized beam is 90° to the reference direction, and the first polarized beam and the second polarized beam are separated by a certain angle;

In the second step, the first polarized beam and the second polarized beam enter the birefringent filter assembly 3; in this embodiment, the birefringent filter assembly 3 includes two groups;

The first group of polarized beams is divided into two beams with different spectra after passing through the first group of polarizing elements 31, and divided into four beams with different spectra after passing through the second group of polarizing elements 32, but the present invention is not limited to two groups of birefringent filter assemblies 3 , and so on, after passing through the Nth (N=1,2,3...) group of polarizing elements, the first polarized beam is divided into 2 N-th power beams with different frequency spectrums, and each beam has a different direction angle ;

The second group of polarized beams is also divided into two beams with different spectra after passing through the first group of polarizing elements 31; after passing through the second group of polarizing elements 32, it is also divided into four beams with different spectra, but the present invention is not limited to two groups of birefringent filters Component 3, and so on, after passing through the Nth (N=1,2,3...) group of polarizing elements, the second polarized beam is also divided into 2 N-th power beams with different spectrums, and the spectral characteristics of each beam It is the same as one beam in the 2n power beams divided by the first polarized beam, but the divergence angle direction of the beam is different.

In the third step, after passing through the first birefringent beam splitting prism 2 and the birefringent filter assembly 3 , the target scene beam is divided into 2 (N+1) power beams, and each beam has a different divergence angle. After the convergence of the imaging objective lens 4, 2 (N+1) power target images are generated on the target surface of the area array detector 5 at the rear focal plane position, and the N power spectral segments of the target 2 are recorded. Polarization difference image; wherein the first polarized beam generates 2 N multispectral images of the target polarized light at 0° to the reference direction; the second polarized beam generates spectral images of the target polarized light at 90° to the reference direction, Its spectral band is the same as that of the multispectral image generated by the first polarized light beam.

As shown in Figure 2, when the birefringent filter assembly 3 in the device of the present invention only includes two groups of polarizing elements 31, 32, 8 slices of differential multispectral images of the target scene are generated on the target surface of the area array detector 5 , divided into four spectral bands.

The simulated target scene is shown in Fig. 2(a); 2(b) is the image acquired by the area detector, the state of the first small image (1) in the image is (λ ₁ , p _// ), the second small image The state of image (8) is (λ ₂ , p _// ), the state of the third small image (8) is (λ ₃ , p _⊥ ), the state of the fourth small image (8) is (λ ₄ , p _⊥ ), the state of the fifth small image (8) is (λ ₄ , p _// ), the state of the sixth small image (8) is (λ ₃ , p _// ), the seventh small image ( 8) is (λ ₂ , p _⊥ ), the state of the eighth small image (8) is (λ ₁ , p _⊥ ) (where λ ₁ , λ ₂ , λ ₃ , λ ₄ represent four spectral bands, p _// Indicates the four spectral images of the target polarized light generated by the first polarized beam at 0° to the reference direction; p _⊥ represents the four spectral images of the target polarized light generated by the second polarized beam at 90° to the reference direction).

Compared with prior art, the beneficial effect of the present invention:

(1) A polarization difference multispectral imaging device and method for real-time detection of the present invention can obtain a differential multispectral image of a detection target with a single exposure, and can detect the detection target in real time;

(2) A polarization difference multispectral imaging device and method for real-time detection of the present invention has no slit in the system, and the obtained polarization difference spectrum image has the advantage of high spatial resolution;

(3) A polarization difference multispectral imaging device and method for real-time detection of the present invention, the device before the detector is an all-optical device, and the method is simple and practical without acousto-optic and electro-optic modulation.

Although the above has described the specific implementation of the present invention in conjunction with the accompanying drawings, the above is only a preferred embodiment of the application, and is not a limitation of the protection scope of the present invention. For those skilled in the art, this application can have Various changes and variations. Those skilled in the art should understand that on the basis of the technical solution of the present invention, various modifications, equivalent replacements or deformations that those skilled in the art can make without creative work are still within the protection scope of the present invention.

Claims (10)

1. A polarization difference multispectral imaging device for real-time detection, characterized in that: the device comprises: A front imaging system, a first birefringent beam splitting prism, a birefringence filter assembly, a rear imaging objective lens and an area array detector are sequentially placed along the same optical axis; The beam emitted or reflected by the detection target passes through the pre-imaging system and enters the first birefringent beam splitting prism in the form of parallel light; the incident beam is divided into two beams of orthogonally polarized light by the first birefringent prism and enters the birefringent filter assembly to form At least two light beams with different frequency spectrums that are 2 to the Nth power; finally pass through the rear imaging objective lens, and simultaneously acquire two sets of multispectral images of orthogonal polarization states on the area array detector. 2. A kind of polarization difference multi-spectral imaging device for real-time detection as claimed in claim 1, characterized in that: the front imaging system includes an imaging objective lens, a field diaphragm and a collimator arranged in sequence along the direction of the optical path. Objective lens; the image plane position of the imaging objective lens coincides with the front focal plane position of the collimating objective lens, and the field stop is arranged at the coincidence of the image plane position of the imaging objective lens and the front focal plane position of the collimating objective lens place. 3. A polarization-difference multispectral imaging device for real-time detection as claimed in claim 1, characterized in that: said birefringence filter assembly includes at least one group of polarization elements arranged sequentially along the optical path, and the number of polarization elements There are N pieces, wherein, N=1, 2, 3,...; each set of polarizing elements includes a phase retarder and a second birefringent beam splitting prism arranged in sequence along the optical path. 4. A polarization-difference multispectral imaging device for real-time detection as claimed in claim 1, wherein the first birefringent beam-splitting prism divides the incident beam into two orthogonally polarized beams, and the two polarized beams The angles between the beam and the reference direction are 0° and 90°. 5. A kind of polarization difference multispectral imaging device for real-time detection as claimed in claim 3, characterized in that: the second birefringent beam splitting prism divides the incident beam into two beams of orthogonally polarized beams, and the two beams of polarized beams The angles between the beam and the reference direction are 0° and 90°. 6. A kind of polarization difference multi-spectral imaging device for real-time detection as claimed in claim 3, characterized in that: the fast axis direction of the phase retarder in multiple groups of adjacent polarizing elements is 45° to the reference direction horn. 7. A polarization difference multispectral imaging method for real-time detection, the method is based on a polarization difference multispectral imaging device for real-time detection as claimed in any one of claims 1-6, characterized in that: the detection target The emitted or reflected beam passes through the pre-imaging system and enters the first birefringent beam splitting prism in the form of parallel light; the incident beam is divided into two beams of orthogonally polarized light by the first birefringent prism and enters the birefringent filter assembly to form at least two Beams that are 2 to the Nth power of beams with different spectra; finally pass through the post-imaging objective lens, and simultaneously acquire two sets of multi-spectral images of orthogonal polarization states on the area array detector. 8. A polarization-difference multispectral imaging method for real-time detection as claimed in claim 7, characterized in that: the light beam emitted or reflected by the detection target passes through the front imaging system and enters the first birefringence in the form of parallel light The specific steps of beam splitting prism are: The incident light beam from the target scene enters the front imaging system, and first passes through the imaging objective lens in the front imaging system to be imaged at its image plane position, and the field diaphragm is used to limit the size of the detection field of view; Then the target beam passes through the action of the collimating objective lens, enters the first birefringent beam splitting prism in the form of parallel light, and after passing through the first birefringent beam splitting prism, it is divided into a first polarized beam and a second polarized beam; The vibration direction of the first polarized beam is 0° to the reference direction, the vibration direction of the second polarized beam is 90° to the reference direction, and the first polarized beam and the second polarized beam are separated by a certain angle. 9. A polarization-difference multispectral imaging method for real-time detection as claimed in claim 7, characterized in that: two beams of orthogonally polarized light enter the birefringence filter assembly to form at least two beams and be N times of 2 The specific steps for square beams with different spectrums are: The first polarized light beam and the second polarized light beam enter the birefringent filter assembly; The first group of polarized beams is divided into two beams with different spectra after passing through the first group of polarizing elements, and then divided into four beams with different spectra after passing through the second group of polarizing elements, and after the Nth (N=1,2,3...) group of polarization After the element, the first polarized beam is divided into 2 N-th power beams with different frequency spectrums, and each beam has a different direction angle; The second group of polarized beams is divided into two beams with different spectra after passing through the first group of polarizing elements; after passing through the second group of polarizing elements, it is divided into four beams with different spectra, and after the Nth (N=1,2,3...) group of polarization After the element, the second polarized beam is also divided into 2 Nth power beams with different spectrums; and the spectral characteristics of each beam are the same as one of the 2 Nth power beams divided by the first polarized beam, But the beam divergence angle direction is different. 10. A kind of polarization difference multi-spectral imaging method for real-time detection as claimed in claim 7, characterized in that: through the rear imaging objective lens, the multi-spectrum of two groups of orthogonal polarization states is simultaneously obtained on the area array detector The specific steps of the image bundle are: After passing through the first birefringent beam splitting prism and the birefringent filter assembly, the target scene beam is divided into 2(N+1) power beams, and each beam has a different divergence angle; After the convergence of the imaging objective lens, 2 (N+1) power target images are generated on the target surface of the area array detector at the rear focal plane position, and the polarization difference of the N power spectral segments of the target 2 is recorded image; Among them, the first polarized light beam generates 2 N multispectral images of the target polarized light at 0° to the reference direction; the second polarized light beam generates spectral images of the target polarized light at 90° to the reference direction, and its spectral band Same spectral band as the multispectral image generated by the first polarized beam.