Planar grating diffraction efficiency testing device and method

Abstract

The application provides a plane grating diffraction efficiency testing device and method, which comprises a light emitting module, a light splitting module, a plane grating, a light flux receiving module and a diffraction efficiency calculation module; wherein the light splitting module splits the monochromatic light to form first sub-path light and second sub-path light; when the first sub-path light and the second sub-path light directly enter the light flux receiving module respectively, the light flux receiving module obtains the incident light flux of the first sub-path light and the incident light flux of the second sub-path light; when the second sub-path light directly enters the light flux receiving module and the first sub-path light enters the light flux receiving module after being diffracted by the plane grating, the light flux receiving module obtains the diffracted light flux of the first sub-path and the incident light flux of the second sub-path light; and the diffraction efficiency calculation module can obtain the diffraction efficiency of the plane grating. The application improves the accuracy of the diffraction efficiency test of the grating.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of testing diffraction efficiency of a grating, and particularly relates to a device and method for testing diffraction efficiency of a plane grating. BACKGROUND

[0002] At present, the dispersion type spectral imaging system generally uses a prism and a grating as a spectral element. The grating becomes a mainstream spectral element of the spectral imaging system due to its high dispersion and high environmental stability. The diffraction efficiency of the grating, which is an index of the spectral ability of the grating, has a great influence on the overall performance of the instrument. Therefore, the diffraction efficiency testing of the grating is a key in the grating detection. However, the existing diffraction efficiency testing device of the grating has the following problems: (1) a laser is used as a testing light source. The laser as a Gaussian beam is different from a natural light source. The light spot of the laser at the grating is usually small. There is a great difference between the testing light and the working state of the grating. (2) A single light path testing method is used for detection. The influence of the light source fluctuation on the testing result cannot be eliminated. SUMMARY

[0003] In order to solve the above problems, the present application provides a device for testing diffraction efficiency of a plane grating, which comprises a light emission module, a spectral module, a plane grating, a light flux receiving module and a diffraction efficiency calculation module.

[0004] The light emission module emits monochromatic light with a wavelength of λ. The spectral module divides the monochromatic light into at least two sub-path light rays, which are set as a first sub-path light ray and a second sub-path light ray.

[0005] When the first sub-path light ray and the second sub-path light ray are directly incident on the light flux receiving module, the light flux receiving module obtains the incident light flux E0(λ) of the first sub-path light ray and the incident light flux E'0(λ) of the second sub-path light ray.

[0006] When the second sub-path light ray is directly incident on the light flux receiving module and the first sub-path light ray is diffracted by the plane grating and then enters the light flux receiving module, the light flux receiving module obtains the diffracted light flux E0(λ) of the first sub-path and the incident light flux E'0(λ) of the second sub-path light ray. g

[0007] The diffraction efficiency calculation module can obtain the linear relationship between the incident light flux E0(λ) of the first sub-path light ray and the incident light flux E'0(λ) of the second sub-path light ray when the first sub-path light ray and the second sub-path light ray are directly incident on the light flux receiving module. Therefore, when the incident light flux of the second sub-path light ray is E'0(λ), the incident light flux of the first sub-path light ray should be E0(λ)=K×E'0(λ)+b. Then, according to the diffracted light flux E0(λ) of the first sub-path light ray after the diffraction of the plane grating, the diffraction efficiency of the plane grating is obtained. g ​(λ), to obtain the diffraction efficiency η = E of the planar grating g (λ) / E0(λ).

[0008] Preferably, the light flux receiving modules are arranged on the two light paths formed by the first sub-path light and the second sub-path light, respectively, to collect the light flux of the first sub-path light and the light flux of the second sub-path light, respectively.

[0009] Preferably, the light emitting module, the diaphragm, the parabolic mirror and the polarizer are sequentially arranged along the light extending direction.

[0010] Preferably, the light flux collecting module comprises a focusing lens and a detector, the sub-path light is focused by the focusing lens, and the light flux of the focused light is collected and recorded by the detector.

[0011] Preferably, the diaphragm is an aperture diaphragm, which is used to reduce the divergence angle of the light source and has a diameter of 0.1 mm.

[0012] Preferably, the parabolic mirror can collimate the light into parallel light, the aperture of the parabolic mirror is 25.4 mm, the focal length is 25.4 mm, and the off-axis angle is 90°.

[0013] Preferably, the target surface of the detector is 14.4*9.9 mm, and the response wavelength band is 400-1050 nm.

[0014] Preferably, the incident angle of the first sub-path light when entering the planar grating is the same as the incident angle when the planar grating works.

[0015] The application also provides a diffraction efficiency testing method using the planar grating diffraction efficiency testing device.

[0016] S10, the monochromatic light with a wavelength of λ emitted by the light emitting module is split by the light splitting module to form at least two sub-path lights, which are set as a first sub-path light and a second sub-path light;

[0017] S20, the incident light flux E0(λ) of the first sub-path light and the incident light flux E'0(λ) of the second sub-path light are obtained when the monochromatic light with a wavelength of λ at different powers is directly incident on the light flux receiving module.

[0018] Thus, the linear relationship E0(λ) = K × E'0(λ) + b between E0(λ) and E'0(λ) is obtained.

[0019] S30, obtaining the linear relationship between the incident light flux E'(λ) of the second sub-path light and the diffraction light flux E of the first sub-path light, and the incident light flux E'(λ) of the second sub-path light and the diffraction light flux E of the first sub-path light are obtained when the second sub-path light directly enters the light flux receiving module and the first sub-path light enters the light flux receiving module after being diffracted by the plane grating g (λ);

[0020] S40, according to the linear relationship between the incident light flux E0(λ) of the first sub-path light and the incident light flux E'(λ) of the second sub-path light in step S20, it is known that when the incident light flux of the second sub-path light is E'(λ), the incident light flux of the first sub-path light should be E0(λ)=K×E'(λ)+b, and at this time the diffraction light flux of the first sub-path light after the first sub-path light passes through the plane grating is E g (λ), the diffraction efficiency η(λ) of the plane grating is obtained as E g (λ) / E0(λ)=E g (λ) / (K×E'(λ)+b).

[0021] Preferably, after step S40, step S50 is further included, the light emitting module emits monochromatic light of different wavelengths at a preset frequency in a preset spectral range, and the diffraction order of the plane grating is set, so that the diffraction efficiency of the plane grating for monochromatic light of different wavelengths at the preset diffraction order is obtained.

[0022] The beneficial effects of the use of the above technical solution are: the plane grating diffraction efficiency test of the application uses double optical path test, the linear relationship of the two detectors is obtained by calibrating the energy received by the two detectors, and the incident light energy can be calculated by monitoring the energy value received by the detector in the optical path, so as to eliminate the test error caused by the fluctuation of the light source; at the same time, compared with laser, the monochromatic light emitted by the application is a non-Gaussian beam, the illumination area of the parallel light on the grating after the parabolic mirror is larger, which is closer to the normal working state of the grating, and the measured efficiency is more reasonable. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the application, the drawings of the specification of the application will be described and explained below. Obviously, the drawings in the following description only illustrate some aspects of some exemplary embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0024] Figure 1 and Figure 2 It is a schematic diagram of the installation and implementation of the equipment in the test optical path of the plane grating diffraction efficiency test method of the application. DETAILED DESCRIPTION

[0025] Various exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. The present disclosure provides a method for testing diffraction efficiency of a planar grating. Figure 1 And Figure 2 A preferred embodiment of the present application is described in detail below.

[0026] The present application includes a light emitting module, a light splitting module, a planar grating, a light flux receiving module and a diffraction efficiency calculation module. The light emitting module emits monochromatic light. The light splitting module splits the monochromatic light into at least two sub-path light rays, which are set as a first sub-path light ray and a second sub-path light ray. When the first sub-path light ray and the second sub-path light ray directly enter the light flux receiving module, the light flux receiving module obtains the incident light flux of the first sub-path light ray and the incident light flux of the second sub-path light ray. When the second sub-path light ray directly enters the light flux receiving module and the first sub-path light ray enters the light flux receiving module after being diffracted by the planar grating, the light flux receiving module obtains the diffracted light flux of the first sub-path and the incident light flux of the second sub-path light ray. The diffraction efficiency calculation module can obtain the linear relationship between the incident light flux of the first sub-path light ray and the incident light flux of the second sub-path light ray when the first sub-path light ray and the second sub-path light ray directly enter the light flux receiving module, and then obtain the diffraction efficiency of the planar grating according to the diffracted light flux of the first sub-path light ray after being diffracted by the planar grating.

[0027] Specifically, as shown in Figure 1 And Figure 2 It is an embodiment of the installation diagram of the test light path of the method for testing the diffraction efficiency of the planar grating of the present application. The devices needed in the test light path include a monochromator 1, a diaphragm 2, a parabolic mirror 3, a polarizer 4, a beam splitter 5, a planar grating 6, a focusing lens 7, a detector 8 and a control and data processing module 9.

[0028] Specifically, the monochromator 1 is used as a system light source to provide monochromatic light. In this embodiment, a spectrometer with model number HORIBAiHR 320 is used to emit monochromatic light with a preset wavelength at a preset frequency according to the requirements. At the same time, the spectrometer can also adjust the emission power of the light, so that the light flux representing the energy of the light is changed. The light flux refers to the radiation power that can be perceived by the human eye, which is equal to the product of the radiation energy of a certain wave band and the relative visibility of the wave band per unit time. The radiation power refers to the total radiation emitted per unit area of the object surface per unit time.

[0029] The light flux refers to the derived quantity of the radiation flux evaluated according to the standard human eye visual characteristics specified by the international standards, and the unit is lm (lumen). Since the relative visibility of the human eye to light of different wavelengths is different, the light fluxes of light of different wavelengths are not equal when their radiation powers are equal. Therefore, we analyze the efficiency performance of the grating by collecting the light flux of the light.

[0030] The diaphragm refers to an entity that limits the light beam in the optical system. It can be the edge of the lens, frame or a specially set aperture screen. Its function can be divided into two aspects, limiting the light beam or limiting the field of view (imaging range). The diaphragm that limits the light beam most in the optical system is called the aperture diaphragm. The diaphragm 2 used in the present application is an aperture diaphragm, and the aperture thereof is 0.1 mm. The monochromatic light emitted from the monochromator 1 can reduce the divergence angle of the light source, limit the imaging light beam and eliminate the influence of stray light on the image after passing through the diaphragm.

[0031] The parabolic mirror 3 is a mirror with a parabolic reflecting surface. The light beam collected by the diaphragm enters the focal point of the parabolic mirror 3. After being reflected by the parabolic mirror 3, the light beam is parallel to the main axis of the mirror and exits. The parabolic mirror 3 converts the light beam into parallel light. In the embodiment, the aperture of the parabolic mirror 3 is 25.4 mm. The focal length is 25.4 mm, the off-axis angle is 90°, and the reflected wavefront difference is less than λ / 4@633 nm (one-fourth wavelength at 633 nm.

[0032] The polarizer 4 is used to change the parallel light incident after collimation by the parabolic mirror 3 into polarized light. The polarizer is a composite material laminated by a polarizing film, an inner protective film, a pressure-sensitive adhesive layer and an outer protective film. It has the functions of shielding and transmitting incident light, and can select the longitudinal light or the transverse light that can be transmitted. After passing through the polarizer 4, the light becomes polarized light of the same type, such as P-polarized light or S-polarized light.

[0033] The beam splitter is coated with one or more layers of thin film on the surface of optical glass. When a light beam is projected onto the coated glass, the light beam is divided into two or more beams through reflection and refraction. The beam splitter is mainly used to divide the incident light beam into two beams with a certain light intensity ratio. There are fixed beam splitting ratio beam splitters and variable beam splitting ratio beam splitters. The beam splitter 5 used in the present application is a fixed beam splitting ratio beam splitter, and the aperture thereof is 25.4 mm. After the polarized light obtained by the polarizer 4 passes through the beam splitter 5, 50% of the light is transmitted and 50% of the light is reflected, and two sub-path light beams are formed through transmission and reflection.

[0034] The detectors 81 and 82 are used to collect the data of the light flux of the light beams after being split by the beam splitter.

[0035] The steps of the grating test method of the present application are as follows: first, the grating is placed on the optical bench, and the monochromator 1 is used to emit monochromatic light to the grating. Figure 1The test light path is built, and the monochromator 1, the diaphragm 2, the parabolic mirror 3, the polarizer 4 and the beam splitter 5 are placed in sequence according to the light path order. The divergent light beam emitted by the monochromator 1 is collimated into parallel light by the parabolic mirror 3 after passing through the diaphragm 2, and then enters the polarizer 4. After passing through the polarizer 4, the light beam enters the beam splitter 5. After transmission and reflection of the beam splitter 5, two sub-path light rays A and A' are formed, which enter the sub-path A and the sub-path A' respectively, where the focusing lens 71 and the detector 81 are located, and the focusing lens 72 and the detector 82 are located.

[0036] After the focusing lens 71 focuses the sub-path light ray A, the detector 81 can obtain the incident light flux of the sub-path A. After the focusing lens 72 focuses the sub-path light ray A', the detector 82 can obtain the incident light flux of the sub-path A'.

[0037] The wavelength of the monochromatic light emitted by the monochromator is set as λ, the light flux of the sub-path light ray A is E0(λ), and the light flux of the sub-path light ray A' is E'0(λ). The linear relationship between E0(λ) and E'0(λ) is set as E0(λ)=K×E'0(λ)+b. The monochromator 1 is controlled to emit monochromatic light every 5 nm within the range of 400-1050 nm, and the energy values of the light rays received by the two detectors at five different powers are tested. The values of K and b in the linear relationship between E0(λ) and E'0(λ) are calculated, so as to obtain the linear relationship E0(λ)=K×E'0(λ)+b between the light flux E0(λ) of the sub-path light ray A and the light flux E'0(λ) of the sub-path light ray A'.

[0038] In addition, since the values of K and b of the P-polarized light and the S-polarized light are different, the values of K and b under the P-polarized light and the S-polarized light are tested respectively. The linear relationship between the light flux E0(λ) of the sub-path light ray A and the light flux E'0(λ) of the sub-path light ray A' under different wavelengths can be obtained.

[0039] After obtaining the linear relationship between the light flux E0(λ) of the sub-path light ray A and the light flux E'0(λ) of the sub-path light ray A', the data is recorded.

[0040] The test light path is adjusted to Figure 2 As shown in the figure, the sub-path A' remains unchanged, and the detector 82 can obtain the incident light flux E'0(λ) of the sub-path A'.

[0041] Put the plane grating 6 into the sub-path A, rotate the scale of the adjusting frame rotation dimension where the plane grating 6 is located, and rotate 35.8616°, so that the incident light is consistent with the use environment. Make the sub-path light A incident on the plane grating 6 at an incident angle consistent with the use environment. Then move the focusing lens 71 and the detector 81 to a position where the sub-path light A after passing through the plane grating 6 can be received, so that the sub-path light A after passing through the plane grating 6 enters the focusing lens 71 and is focused, and then the detector 81 collects the diffraction light flux E of the sub-path light after diffraction g (λ).

[0042] According to the linear relationship between the light flux E0(λ) of the sub-path light A and the light flux E'0(λ) of the sub-path light A', it is known that when the incident light flux of the second sub-path light is E'0(λ), the incident light flux of the first sub-path should be E0(λ)=K×E'0(λ)+b, and at this time the obtained diffraction light flux of the first sub-path light after passing through the plane grating is E g (λ), and the diffraction efficiency of the plane grating is obtained as the ratio of the first sub-path diffraction light flux obtained by the detector and the calculated incident light flux, that is, η(λ)=E g (λ) / E0(λ)=E g (λ) eight K×E'0(λ)+b).

[0043] Wherein, the aperture of the focusing lens is set to The focal length is 60mm, the target surface of the detector is 14.4*9.9mm, and the response waveband is 400-1050nm. The data processing module 9 is used for the control of the monochromator and the detector and the processing of data.

[0044] The plane grating 6 is a plane blazed grating, the surface of which is coated with a gold reflecting film, and the design parameters are as follows: the effective aperture is 44mm*44mm, the grating period is 53l / mm, the blazed order is +1 order, and the use environment is an incident angle of-35.8616°.

[0045] When the grating is engraved into a sawtooth-shaped line groove section, the light energy of the grating is concentrated in a predetermined direction, that is, a certain spectral order. When detected from this direction, the intensity of the spectrum is maximum, which is called blazed, and this kind of grating is called blazed grating. In such a blazed grating, the groove surface that plays a diffraction role is a smooth plane, which is at an angle with the surface of the grating, called the blazed angle. The wavelength corresponding to the maximum light intensity is called the blazed wavelength. Through the design of the blazed angle, the grating can be adapted to a certain level of spectrum of a certain waveband. The blazed grating design is a specific reflection or projection diffraction grating structure that produces maximum diffraction efficiency at a specific diffraction order. The light power at the designed diffraction order is the majority, and the loss of light power at other levels (especially zero level) is the minimum.

[0046] Therefore, the grating blazed surface profile needs to be considered to concentrate as much light as possible to the selected order, based on the above considerations, the different orders of diffracted light after diffraction by the plane grating 6 are observed in the detector software, the monochromator 1 is controlled to exit monochromatic light every 5 nm in the 400-1050 nm spectral range, the program automatically records the energy values received by the detector in sub-paths A and A', and according to the previously obtained K, b values of the linear relationship between the luminous flux E0(λ) of sub-path light A and the luminous flux E'0(λ) of sub-path light A' at different wavelengths, the diffraction efficiency of the plane grating 6 for different wavelength monochromatic light at the set diffraction order is calculated, and the diffraction efficiency is determined according to the required diffraction order. Part of the results are shown in Table 1.

[0047] Wavelength -3rd order diffraction efficiency 650 0.746 655 0.776 660 0.803 665 0.807 670 0.814 675 0.834 680 0.838

[0048] Table 1

[0049] The description of the exemplary embodiments of the present application is merely illustrative in nature and is in no way intended to limit the disclosure, its application or uses. The disclosure can be implemented in numerous different forms, not limited to the embodiments described herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that: unless otherwise stated, the relative arrangement, numerical expressions and values of components and steps set forth in these embodiments should be interpreted as merely exemplary, not as a limitation.

[0050] The "includes" or "contains" and similar words used in the present disclosure mean that the elements before the word encompass the elements listed after the word, and do not exclude the possibility of also encompassing other elements.

[0051] All terms used in the present disclosure, including technical terms or scientific terms, have the same meaning as understood by those skilled in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in accordance with general dictionaries should be understood to have meanings consistent with their meanings in the context of the relevant art, and should not be interpreted in an idealized or excessively formalized sense, unless explicitly defined herein.

[0052] For components not described in detail in this part, specific models of components, parameters of components, and the relationship between components, and control circuits can be considered as known technology, methods and equipment to those skilled in the art, but in appropriate cases, the technology, methods and equipment should be considered as part of the specification.

[0053] It should be understood that the above-described embodiments are merely intended for explaining the present application, and the protection scope of the present application is not limited thereto, and any person skilled in the art, within the technical scope disclosed by the present application, can make changes, substitutions, combinations of the technical solutions and the inventive concept of the present application, which should be covered within the protection scope of the present application.

Claims

1. A device for testing the diffraction efficiency of a planar grating, characterized in that, The application relates to a light emission module, a light splitting module, a plane grating, a light flux receiving module and a diffraction efficiency calculation module. The light emitting module emits monochromatic light with a wavelength of 405 nm. The light splitting module splits the monochromatic light into at least two sub-path light rays, which are set as a first sub-path light ray and a second sub-path light ray. When the first sub-path light beam and the second sub-path light beam are directly incident on the light flux receiving module, the light flux receiving module obtains the incident light flux of the first sub-path light beam. Incident luminous flux of the second sub-path ray At this point, the diffraction efficiency calculation module can obtain... and linear relationship , When the second sub-path light directly enters the light flux receiving module, and the first sub-path light enters the light flux receiving module after being diffracted by the planar grating, the light flux receiving module obtains the diffracted light flux of the first sub-path light and the incident light flux of the second sub-path light At this time, the diffraction efficiency calculation module can obtain the incident light flux of the first sub-path light when the incident light flux of the second sub-path light is ; and according to the diffracted light flux of the first sub-path light after being diffracted by the planar grating at this time , the diffraction efficiency η = / of the planar grating is obtained . The light flux receiving module includes a focusing lens and a detector, the sub-path light is focused by the focusing lens, and the light flux of the focused light is collected and recorded by the detector. The incidence angle of the first sub-path light entering the plane grating is the same as the incidence angle of the plane grating during operation.

2. The planar grating diffraction efficiency test apparatus according to claim 1, wherein, The diaphragm is an aperture diaphragm, which is used for reducing the divergence angle of the light source and has a diameter of 0.1 mm.

3. The planar grating diffraction efficiency test apparatus according to claim 1, wherein The parabolic mirror can collimate the light into parallel light, the aperture of the parabolic mirror is 25.4 mm, the focal length is 25.4 mm, and the off-axis angle is 90 degrees.

4. The planar grating diffraction efficiency test apparatus according to claim 1, wherein The target surface of the detector is 14.4*9.9 mm, and the response wave band is 400-1050 nm.

5. A method for testing diffraction efficiency using the planar grating diffraction efficiency testing apparatus according to any one of claims 1-4, characterized in that, The application further comprises the following steps: S10, the wavelength emitted by the light emitting module is After the monochromatic light is split by the beam splitting module, it forms at least two sub-path rays, which are designated as the first sub-path ray and the second sub-path ray. S20, obtaining monochromatic light with a wavelength of At different powers, when the first sub-path light and the second sub-path light directly incident on the light flux receiving module, the incident light flux of the first sub-path light and the incident light flux of the second sub-path light ; Thus, the linear relationship between the values of the two variables is With the linear relationship is ; S30, obtaining the incident light flux of the second sub-path light when the second sub-path light directly enters the light flux receiving module and the first sub-path light enters the light flux receiving module after being diffracted by the planar grating and the diffracted light flux of the first sub-path ; S40, the incident light flux of the first sub-path light ray according to step S20 has a linear relationship with the incident light flux of the second sub-path light ray , it can be known that when the incident light flux of the second sub-path light ray is , the incident light flux of the first sub-path should be , and the diffraction light flux of the first sub-path light ray after passing through the plane grating at this time is , and the diffraction efficiency η of the plane grating can be obtained as .​ 6. The diffraction efficiency test method according to claim 5, wherein After step S40, step S50 is further included, the light emission module emits monochromatic light of different wavelengths at a preset frequency in a preset spectral range, a preset diffraction order of the plane grating is set, and the diffraction efficiency of the plane grating for monochromatic light of different wavelengths at the preset diffraction order is obtained.

Images