WO2009109078A1 - A hadamard transform interference spectrum imaging method and device - Google Patents

Abstract

A hadamard transform interference spectrum imaging method comprises the following steps: (1) the light beam is imaged on the surface of the hadamard mask(3); (2) limiting the visual field concerned with hadamard transform encoding and filtrating the stray light; (3) using the lateral shear interferometer(4), shearing the light beam to be two virtual hadamard masks in the direction of perpendicular to the light axis, the two virtual hadamard masks are parallel with the hadamard mask(3) and have the same width direction; (4) appearing interference which is perpendicular to the shearing direction; (5) sending the interference pattern signals tothe computer processing system(8); (6) completing encoding after the light beam is trasnsformed with hadamard mask(3) for n times; (7)the light beam is applied with the Fourier transform and attaining n object spectrum images by encoded with the hadamard mask encoding, decoding the encode and receiving the two-dimensional spatial information and one-dimensional spectral information of the object, and completing the imaging. And a hadamard transform interference spectrum imaging device using the method.

Description

 Hadamard interference interference spectrum imaging method and device

 The invention relates to an interference spectrum imaging method and device, in particular to a method for imaging Hadamard interference interference spectrum and a Hadamard interference interference spectrum imager designed according to the method.

Background technique

 Hadamard Transform spectroscopy is a new spectral modulation technique similar to the Fourier Transform developed in the past forty years. The Hadamard transform is a transformation based on a plane wave function with the advantages of high energy input, multi-channel imaging and high signal-to-noise ratio [M. 0. Harwit, NJA Slone. Hadamard Transform Optics. Academic : New York, 1980], special Suitable for weak spectral signal detection, Hadamard transform spectral imaging technology is one of the international research topics.

 At present, all Hadamard transform spectral imaging techniques replace the entrance slit or the exit slit of the conventional dispersion type (using prism splitting or grating splitting) spectrometer with the Hadamard code template, or simultaneously replace the two for each spectral component. The operation decoding obtains two-dimensional spatial information and one-dimensional spectral information of the detected target.

 The Hadamard transform spectral imaging technique treats the Hadamard template as a wide slit, depending on the spatial symbols involved in the encoding as a whole, but because the Hadamard template has a certain size, and the more the symbols, the wider the size, the more Misalignment and aliasing of spatial information and spectral information; In addition, because the Hadamard spectral imager uses dispersion spectroscopy, the width of the Hadamard template also limits spectral resolution and spatial resolution. The narrower the Hadamard template is, The higher the spectral resolution and spatial resolution, the less light the Hadamard template enters into the spectrometer, and the less the optical energy, the more difficult it is to achieve high spectral resolution and high spatial resolution.

 In order to overcome the above disadvantages, for a large-sized Hadamard template, a cylindrical lens group is usually placed between the template and the spectroscopic device to compress the template and the target image [QS Hanley, PJ Verveer, TM Jovin. Spectral imaging in a programmable array-microscope by Hadamard transform fluorescence spectroscopy. Appl. Spectrosc., 1999, 53 (1): 1~10], increases the complexity of the instrument. Role of cylindrical lens group

- 1 - Confirmation Only the wide-sized Hadamard template is compressed into a narrower Hadamard template. Since the spectral resolution of the dispersive spectrometer and the width of the Hadamard template are mutually constrained, the narrower Hadamard template is beneficial to improve. The spectral resolution of the instrument, but the compressed Hadamard template always has a certain width. Therefore, the misalignment and aliasing of spatial information and spectral information in the Hadamard spectral imaging technology can not be avoided. This misalignment and aliasing can only be It is alleviated by the above method but cannot be completely eliminated.

Summary of the invention

 The object of the present invention is to provide a method and a device for imaging the Hadamard interference interference spectrum, which solves the technical problem that the spatial resolution and the spectral resolution are limited by the size of the Hadamard template and the system structure is complicated in the background art.

 The technical solution of the present invention is:

 A method for imaging Hadamard interference interference spectroscopy, which is characterized in that it comprises the following steps:

(1) a front optical imaging system 1 images a target onto a surface of a Hadamard template 3 having n symbols;

(2) Close to the Adama template 3 Set a stop 2 Limit the field of view of the Hadamard transform code and filter the stray light;

 (3) The target image of the Yadam template 3 is encoded by the transverse shearing interferometer 4, and the Hadamard template 3 is cut into two virtual Adama templates by the transverse shearing interferometer 4 in a direction perpendicular to the optical axis. Parallel to the Adama template 3 and in the same width direction;

 (4) Two imaginary Hadamard templates are subjected to interference by the Fourier mirror 5 and the cylindrical mirror 6, and the interference fringe direction is perpendicular to the shearing direction. The interference optical path difference and the shear amount and the detector are effective. The size is proportional to the focal length of the Fourier mirror 5, the Hadamard template 3 is located on the front focal plane of the Fourier mirror 5, and the detector 7 is located on the back focal plane of the Fourier mirror 5 and the cylindrical mirror 6;

 (5) digitizing the interferogram signal outputted by the detector 7 and sending it to the computer processing system 8;

(6) The Adama template 3 transforms the encoding once, and the detector 7 acquires the interferogram signal once, and the Hadamard template 3 is transformed n times, and the encoding is completed;

 (7) The interferogram signals acquired by n acquisitions are respectively Fourier transformed, and the spectral images of n targets encoded by the Hadamard template are obtained. These images are decoded by the fast Hadamard transform and finally obtain the two-dimensional spatial information of the target. One-dimensional spectral information, complete imaging.

An apparatus for realizing a method for imaging a Hadamard interference interference spectrum, comprising an Adada mode set along an optical path Plate 3, which images the target onto the front optical imaging system 1 on the surface of the Hadamard template 3 with n symbols, and cuts it into two virtual Hadamard templates in the direction perpendicular to the optical axis of the Adama template 3. a transverse shearing interferometer 4, a detector 7 and a computer system 8 connected to the detector 7,

It is special in that it further includes a diaphragm 2 disposed close to the Adama template 3; a Fourier lens 5 and a cylindrical mirror 6 disposed between the transverse shearing interferometer 4 and the detector 7, the Adama The template 3 is located on the front focal plane of the Fourier lens 5, which is located on the back focal plane of the Fourier lens 5 and the cylindrical mirror 6.

 The above-mentioned Hadamard template 3 is in the form of a mobile mechanical template, a liquid crystal spatial light modulator or a digital micro-planar array.

 The above two imaginary Hadamard templates are parallel to the Adama template 3 and have the same width direction.

 The above transverse shearing interferometer is a Sagnac interferometer, a Mach-Zehnder interferometer or a transflective interferometer.

7 as a receiver of the sensing Hadamard transform interference signal, and a linear array detector comprising a detection array ^surface: ₀

 The key to the present invention is the use of a static spatial modulation type interferometric spectrometer to replace the dispersion type (using prism splitting or grating splitting) spectrometer in a conventional Hadamard optical spectroscopy imager.

 The static spatial modulation interference spectrometer is similar in form to the dispersive spectrometer. The dispersive spectrometer is: using dispersive elements (gratings or prisms, etc.) to separate the complex color dispersion at the Hadamard template into sequence lines, and then measuring each with a detector. The intensity of the spectral line element, the spatial modulation interference spectrometer uses the transverse shearing interferometer to simultaneously obtain the interference intensity of all the spectral elements of the complex color at the Hadamard template at different optical path differences, and Fourier transform is performed on the interferogram. The spectrum of the target.

The essential difference between the two is that the width of the Hadamard template in the dispersive spectrometer limits both spectral resolution and spatial resolution and inevitably produces misalignment and aliasing of spatial information and spectral information. The narrower the Hadamard template, the spectral resolution And the higher the spatial resolution, but the narrower the Hadamard template is, the less light energy enters the spectrometer, the less the light energy, the more difficult it is to achieve high spectral resolution and high spatial resolution, so high energy passes through the dispersive spectrometer. The contradiction between the rate, the high spectral resolution and the high spatial resolution is not adjustable; in the static spatial modulation interference spectrometer, the modulation degree of the interferogram is not affected by the shape and size of the Hadamard template, which is a static spatial modulation type. One of the great advantages of interference spectroscopy itself, which means that the spectral resolution is no longer constrained by the width of the Hadamard template. The width of the Hadamard template is only related to the spatial resolution of the spectrometer. The spectral resolution is determined by the number of pixels in the detector, and the optical path difference of all symbols in the Hadamard template is always consistent, without misalignment and aliasing. Therefore, the Hadamard template can be wide or have any shape while maintaining a high spectral resolution, thereby increasing the angle of view (increasing the height of the Adama template) and increasing the radiant energy (increasing the area of the Adama template). With the potential for high throughput, high energy throughput, high spectral resolution and high spatial resolution are easily achieved simultaneously.

 The invention completely eliminates the cylindrical lens assembly which is increased in the traditional Hadamard transform spectral imaging technology in order to improve the spectral resolution, and thus has the advantages of simple structure, small volume and light weight.

 In summary, the present invention has the following advantages:

 1) The optical path difference of all symbols in the Hadamard template is always consistent, so there is no requirement for the spatial coherence of the target, which fundamentally avoids the misalignment and aliasing of spatial information and spectral information.

 2) The degree of modulation of the interferogram is not affected by factors such as the shape and size of the Hadamard template. The spectral resolution is independent of the size of the Hadamard template. High spatial resolution and high spectral resolution imaging are easy to implement.

 3) Since the spectral resolution is independent of the size of the Hadamard template, it allows a larger field of view (increasing the height of the HT template) and a Hadam template of any shape and size to greatly increase the luminous flux.

 4) The width of the Hadamard template is only related to the one-dimensional spatial resolution, regardless of the spectral resolution, thus reducing the design difficulty.

 5) The cylindrical lens compression link in the traditional Hadamard spectral imaging technology is completely eliminated, so that the structure is simple, small, and light.

DRAWINGS

 1 is a schematic structural view of a system of the present invention.

 DESCRIPTION OF REFERENCE NUMERALS 1 - front optical imaging system, 2 - aperture, 3 - Adama template, 4 - transverse shear interferometer, 5 - Fourier lens, 6 - cylindrical mirror, 7 - detector, 8 - Computer processing system.

detailed description

 Referring to Figure 1, the technical method of the present invention is:

 The front optical imaging system 1 images the target on the surface of the Hadamard template with n symbols; the aperture 2 is placed next to the Hadamard template 3, and its role is to limit the field of view and prevention of the Hadamard transform coding. Stray light

The Adama template 3 is located at the front focal plane of the Fourier lens 5, and the target image encoded by the Adama template 3 Entering the transverse shearing interferometer 4, the Hadamard template 3 is cut into two imaginary Hadamard templates in a direction perpendicular to the optical axis, which are parallel to the original Adama template 3 and have the same width direction;

 Two imaginary Hadamard templates are subjected to interference by the Fourier mirror 5 and the cylindrical mirror 6 on the detector 7 located at their back focal plane, the interference fringe direction is perpendicular to the shear direction, the interference optical path difference and the shear amount and detection The effective size of the device is proportional to the focal length of the Fourier mirror 5, and the larger the optical path difference, the higher the spectral resolution;

 The interferogram signal outputted by the detector 7 is digitized and sent to the computer processing system 8; the Hadamard template 3 transforms the encoding once, the detector 7 acquires the interferogram signal once, and the Hadamard template 3 transforms n times, and then completes the encoding;

 The interferogram signals obtained by n acquisitions are respectively Fourier transformed, and the spectral images of n targets encoded by the Hadamard template are obtained. These images are decoded by fast Hadamard transform and finally obtain the two-dimensional spatial information and one-dimensional spectrum of the target. information.

ΠΡ2, 3, ···)次阿达玛编码阵列， 从而 对目标进行 η次阿达玛变换编码， 阿达玛模板可采用移动式机械模板、 液晶空间光 调制器和数字微平面镜阵列等形式。 The front optical imaging system 1 can adopt various forms such as refraction, reflection and reflection, and imaging the target on the surface of the Hadamard template is the main purpose of the front optical imaging system 1. 'The role of the Adama template is to produce η

ΠΡ 2, 3, ···) Sub-Dama code array, which performs η-time Hadamard transform coding on the target. The Hadamard template can be in the form of mobile mechanical template, liquid crystal spatial light modulator and digital micro-planar mirror array.

 The transverse shear interferometer can be a Sagnac interferometer, a Mach-Zehnder interferometer, a polarization birefringence interferometer, or the like. Regardless of the specific structure of the transverse shear detector, its primary function is to separate the Hadamard template perpendicular to the optical path such as the optical axis.

 The detector 7 is a receiver of the Hadamard interference signal, and the linear array detector can obtain the one-dimensional space and the one-dimensional spectrum information of the target; the area array detector can obtain the two-dimensional space and the one-dimensional spectrum information of the target.

Claims

Claim  A method for imaging a Hadamard interference interference spectrum, comprising the steps of:  (1) a front optical imaging system 1 images a target onto a surface of a Hadamard template 3 having n symbols; (2) Close to the Adama template 3 Set a stop 2 Limit the field of view and filter stray light involved in the Hadamard transform code;  (3) The target image encoded by the Adama template 3 enters the transverse shearing interferometer 4, and the Hadamard template 3 is cut into two virtual Adama templates by the transverse shearing interferometer 4 in a direction perpendicular to the optical axis. Parallel to the Adama template 3 and in the same width direction;  (4) Two imaginary Hadamard templates are subjected to interference by the Fourier mirror 5 and the cylindrical mirror 6, and the interference fringe direction is perpendicular to the shearing direction. The interference optical path difference and the shear amount and the detector are effective. The size is proportional to the focal length of the Fourier mirror 5, the Hadamard template 3 is located on the front focal plane of the Fourier mirror 5, and the detector 7 is located on the back focal plane of the Fourier mirror 5 and the cylindrical mirror 6;  (5) digitizing the interferogram signal outputted by the detector 7 and sending it to the computer processing system 8; (6) The Adama template 3 transforms the encoding once, the detector 7 acquires the interferogram signal once, and the Hadamard template 3 transforms n times, and then completes the encoding;  (7) The interferogram signals acquired by n acquisitions are respectively Fourier transformed, and the spectral images of n targets encoded by the Hadamard template are obtained. These images are decoded by the fast Hadamard transform and finally obtain the two-dimensional spatial information of the target. One-dimensional spectral information, complete imaging.  2. Apparatus for implementing the imaging method of claim 1, comprising a Hadamard template 3 disposed along the optical path, imaging the target onto the front optical imaging system 1 on the surface of the Hadamard template 3 having n symbols, at Adama The template 3 is cut perpendicular to the optical axis into a transverse shear interferometer 4 of two virtual Hadamard templates, a detector 7 and a computer system 8 connected to the detector 7, The method further comprises: a diaphragm 2 disposed adjacent to the Adama template 3; a Fourier lens 5 and a cylindrical mirror 6 disposed between the transverse shearing interferometer 4 and the detector 7, the Adama template 3 Located on the front focal plane of the Fourier lens 5, the detector 7 is located on the back focal plane of the Fourier lens 5 and the cylindrical mirror 6.  The image forming apparatus according to claim 2, characterized in that: the Hadamard template 3 is in the form of a mobile mechanical template, a liquid crystal spatial light modulator or a digital micro-planar mirror array. 4. The image forming apparatus according to claim 2, wherein: said two virtual Hadamard templates are The Dharma template 3 is parallel and the width direction is uniform.  The image forming apparatus according to any one of claims 2 to 4, wherein the transverse shearing interferometer is a Sagnac interferometer, a Mach-Zehnder interferometer or a polarization birefringence interferometer.  The imaging apparatus according to claim 5, wherein: said detector 7 is a receiver of a Hadamard interference signal, and includes a line array detector and an area array detector.