阅读说明：本技术 基于衍射光栅的玻璃平板折射率均匀性检测装置及检测方法 (Glass plate refractive index uniformity detection device and detection method based on diffraction grating ) 是由 段存丽 惠倩楠 赵鹏程 刘王云 郭荣礼 刘丙才 张玉虹 胡小英 于 2018-07-18 设计创作，主要内容包括：本发明涉及基于衍射光栅的玻璃平板折射率均匀性检测装置及检测方法,该装置包括波长可调光源,沿波长可调光源出射光线光轴方向依次设置扩束镜、针孔光阑、准直镜、可调狭缝和反射式平面衍射光栅,反射式平面衍射光栅6的工作面与所述出射光线光轴之间构成20—45°的入射夹角,在反射式平面衍射光栅的下方竖直依次设光学成像镜头和CCD图像采集系统,CCD图像采集系统连接计算机；在反射式平面衍射光栅和光学成像镜头之间设置待测件。本发明的光路系统实现了大厚度、折射率变化大的光学玻璃的空间折射率均匀性分布的非接触式测量。(The invention relates to a glass plate refractive index uniformity detection device and a detection method based on a diffraction grating, the device comprises a wavelength-adjustable light source, a beam expander, a pinhole diaphragm, a collimating lens, an adjustable slit and a reflective planar diffraction grating are sequentially arranged along the direction of an optical axis of emergent light of the wavelength-adjustable light source, an incident included angle of 20-45 degrees is formed between a working surface of the reflective planar diffraction grating 6 and the optical axis of the emergent light, an optical imaging lens and a CCD image acquisition system are vertically and sequentially arranged below the reflective planar diffraction grating, and the CCD image acquisition system is connected with a computer; and a piece to be measured is arranged between the reflection type plane diffraction grating and the optical imaging lens. The optical path system realizes the non-contact measurement of the spatial refractive index uniformity distribution of the optical glass with large thickness and large refractive index change.)

1. The device for detecting the refractive index uniformity of the glass plate based on the diffraction grating is characterized by comprising a wavelength-adjustable light source (1), wherein a beam expander (2), a pinhole diaphragm (3), a collimating mirror (4), an adjustable slit (5) and a reflective plane diffraction grating (6) are sequentially arranged along the optical axis direction of emergent light of the wavelength-adjustable light source (1), an incident included angle of 20-45 degrees is formed between the working surface of the reflective plane diffraction grating (6) and the optical axis of the emergent light, an optical imaging lens (8) and a CCD image acquisition system (9) are vertically and sequentially arranged below the reflective plane diffraction grating (6), and the CCD image acquisition system (9) is connected with a computer (10); and a to-be-detected piece (7) is arranged between the reflection type plane diffraction grating (6) and the optical imaging lens (8).

2. The apparatus for detecting the uniformity of the refractive index of a glass plate based on a diffraction grating as claimed in claim 1, wherein the focal length of the collimator lens (4) is equal to the distance from the collimator lens (4) to the pinhole diaphragm (3).

3. The apparatus for detecting the uniformity of the refractive index of a glass plate based on a diffraction grating as claimed in claim 1 or 2, wherein the slit width of the adjustable slit (5) is adjustable within a range of 0-10 mm.

4. The method for detecting the uniformity of the refractive index of a glass plate based on a diffraction grating as claimed in claim 1, comprising the steps of:

step 1, adjusting the position of a beam expander to enable light beams emitted by a light source with adjustable wavelength to converge to a point , adding a pinhole diaphragm at the convergence point, filtering stray light, and enabling the emitted light waves to be spherical waves;

step 2, adjusting the position of the collimating mirror to enable incident spherical waves to become planar light waves after passing through;

step 3, adjusting the width of the adjustable slit to enable the planar light waves to pass through the slit and then emit appropriate linear planar light waves;

step 4, adjusting the reflective plane diffraction grating to enable the appropriate linear plane light waves to be incident obliquely, wherein the reflected light waves are diffraction light waves;

step 5, adjusting the reflective plane diffraction grating to enable + 1-order diffraction waves to be converged through the optical imaging lens, obtaining a diffraction pattern A on an image plane of the optical imaging lens, and adjusting the CCD image acquisition system to receive the diffraction pattern A;

step 6, in order to uniformly project + 1-order diffraction waves with the wavelength of 400nm-800nm onto a receiving surface of the CCD, selecting the central wavelength of 600nm of an adjustable light source to calibrate a light beam incident angle, and adjusting the light beam incident angle to enable the diffraction waves with the wavelength of 600nm to vertically incident on the receiving surface of the CCD to serve as a central coordinate received by the CCD;

step 7, adding a to-be-detected piece between the reflective plane diffraction grating and the optical imaging lens, obtaining diffracted light waves B refracted by the to-be-detected piece on an image plane of the optical imaging lens, and adjusting the CCD image acquisition system to receive the diffraction pattern B;

and 8, comparing the diffraction pattern B with the diffraction pattern A by the computer to obtain the spatial distribution information of the refractive index of the to-be-detected piece.

Technical Field

The invention belongs to the field of optical detection, relates to a light diffraction technology, a spectrum analysis technology and a computer image and data processing technology, and particularly relates to a device and a method for detecting the refractive index uniformity of a glass plate based on a diffraction grating.

Background

The optical glass is a main material for manufacturing optical devices such as optical lenses, optical prisms, optical reflectors, spectroscopes, optical fibers, lasers and the like, and the performance of the optical devices is directly influenced by the uniformity of the refractive index of the optical glass. Therefore, the uniformity measurement of optical glass is a research hotspot in the field of optics.

The traditional method for detecting the refractive index of the optical glass mainly comprises the following steps: (1) a needle inserting method; (2) a spectrometer. The incident angle and the refraction angle are mainly measured, and the refractive index of the glass brick is obtained according to the refraction law of glass. The two methods have the advantages of direct measurement, simple measuring instrument and convenient operation. The defects are that contact measurement is carried out, a part to be measured is abraded, the measurement precision is low, and the average refractive index of the optical glass is detected.

The method has the advantages that the space refractive index distribution is measured and detected in a non-contact mode, the measurement precision is high, and the defect is that due to the limitation of interference conditions, the measurement range is small, is suitable for measuring the optical glass material with small thickness and small refractive index change.

There are two main types of optical detection methods based on diffraction gratings: (1) utilizing a transmissive diffraction grating; (2) a reflective diffraction grating is utilized. The two methods mainly utilize the light splitting performance of the diffraction grating to measure the average refractive index of the liquid, the measurement range is large, and the measurement method is simple. The disadvantage is that the measurement is the liquid average refractive index and the measurement accuracy is low.

Disclosure of Invention

The application provides glass flat plate refractive index uniformity detection devices and detection methods based on diffraction grating, and solves the problem that in the prior art, the refractive index detection precision of optical glass with large thickness and large refractive index change is not high.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the glass plate refractive index uniformity detection device based on the diffraction grating comprises a wavelength-adjustable light source, wherein a beam expander, a pinhole diaphragm, a collimating mirror, an adjustable slit and a reflective planar diffraction grating are sequentially arranged along the optical axis direction of emergent light of the wavelength-adjustable light source, an incident included angle of 20-45 degrees is formed between the working surface of the reflective planar diffraction grating 6 and the optical axis of the emergent light, an optical imaging lens and a CCD image acquisition system are vertically and sequentially arranged below the reflective planar diffraction grating, and the CCD image acquisition system is connected with a computer; and a piece to be measured is arranged between the reflection type plane diffraction grating and the optical imaging lens.

And , the focal length of the collimating mirror is equal to the distance from the collimating mirror to the pinhole diaphragm.

And , adjusting the width of the adjustable slit within 0-10 mm.

The glass plate refractive index uniformity detection method based on the diffraction grating comprises the following steps:

step 1, adjusting the position of a beam expander to enable light beams emitted by a light source with adjustable wavelength to converge to a point , adding a pinhole diaphragm at the convergence point, filtering stray light, and enabling the emitted light waves to be spherical waves;

step 2, adjusting the position of the collimating mirror to enable incident spherical waves to become planar light waves after passing through;

step 3, adjusting the width of the adjustable slit to enable the planar light waves to pass through the slit and then emit appropriate linear planar light waves;

step 4, adjusting the reflective plane diffraction grating to enable the appropriate linear plane light waves to be incident obliquely, wherein the reflected light waves are diffraction light waves;

step 5, adjusting the reflective plane diffraction grating to enable + 1-order diffraction waves to be converged through the optical imaging lens, obtaining a diffraction pattern A on an image plane of the optical imaging lens, and adjusting the CCD image acquisition system to receive the diffraction pattern A;

step 6, in order to uniformly project + 1-order diffraction waves with the wavelength of 400nm-800nm onto a receiving surface of the CCD, selecting the central wavelength of 600nm of an adjustable light source to calibrate a light beam incident angle, and adjusting the light beam incident angle to enable the diffraction waves with the wavelength of 600nm to vertically incident on the receiving surface of the CCD to serve as a central coordinate received by the CCD;

step 7, adding a to-be-detected piece between the reflective plane diffraction grating and the optical imaging lens, obtaining diffracted light waves B refracted by the to-be-detected piece on an image plane of the optical imaging lens, and adjusting the CCD image acquisition system to receive the diffraction pattern B;

and 8, comparing the diffraction pattern B with the diffraction pattern A by the computer to obtain the spatial distribution information of the refractive index of the to-be-detected piece.

The invention has the beneficial effects that:

the optical path system of the invention realizes the non-contact measurement of the spatial refractive index uniformity distribution of the optical glass with large thickness and refractive index change, combines the ultrastrong light splitting performance of the reflection type diffraction grating with the data processing technology of a computer, can measure the mean refractive index of the optical glass and the spatial refractive index uniformity, has high measurement precision and measurement range, and is simple to operate.

Drawings

FIG. 1 is a schematic view of the overall structure of the apparatus of the present invention;

FIG. 2 is a schematic view of the measurement path of diffraction pattern A of the present invention;

FIG. 3 is a schematic diagram of the measurement path of diffraction pattern B of the present invention;

in the figure, 1-wavelength adjustable light source, 2-beam expander, 3-pinhole diaphragm, 4-collimating mirror, 5-adjustable slit, 6-reflection type plane diffraction grating, 7-to-be-measured piece, 8-optical imaging lens, 9-CCD image acquisition system, 10-computer, 11-plane monochromatic light wave, 12-normal, 13-0 order diffraction beam, 14- +1 order diffraction beam, 15-600mm +1 order diffraction beam, 16- +1 order diffraction angle, 17-standard glass plate, 18-incidence angle, 19-to-be-measured piece-free light and 20-to-be-measured piece-free light.

Detailed Description

In the following detailed description, the invention is described in conjunction with the accompanying drawings in , where like elements in different embodiments have been given like element numbers associated with them, in which case many details will be described to better understand the present application, however, those skilled in the art will readily appreciate that some of the features may be omitted or replaced with other elements, materials, methods, and in some cases, operations associated with the present application are not shown or described in the specification, which is necessary to avoid overwhelming the core of the present application and to avoid unnecessary detailed description of the associated operations, which will be fully apparent to those skilled in the art based on the description in the specification and general knowledge in the art.

Referring to fig. 1, the device for detecting the refractive index uniformity of a glass plate based on a diffraction grating comprises a wavelength-adjustable light source 1, wherein a beam expander 2, a pinhole diaphragm 3, a collimating lens 4, an adjustable slit 5 and a reflective planar diffraction grating 6 are sequentially arranged along the optical axis direction of emergent light of the wavelength-adjustable light source 1, an incident included angle of 20-45 degrees is formed between the working surface of the reflective planar diffraction grating 6 and the optical axis of the emergent light, an optical imaging lens 8 and a CCD image acquisition system 9 are vertically and sequentially arranged below the reflective planar diffraction grating 6, and the CCD image acquisition system 9 is connected with a computer 10; and a to-be-detected piece 7 is arranged between the reflection type plane diffraction grating 6 and the optical imaging lens 8.

The wavelength-adjustable light source 1 is a xenon lamp light source, and the wavelength adjusting range of the xenon lamp light source is 400nm-800 nm.

The linear logarithm of the reflective planar diffraction grating 6 is 600/mm, and the aperture is 50mm × 50 mm.

The aperture of the pinhole diaphragm 3 is 1.5 mm.

The focal length of the collimator lens 4 is equal to the distance from the collimator lens 4 to the pinhole diaphragm 3.

The adjustable range of the slit width of the adjustable slit 5 is 0-10mm, and the slit length is 30 mm.

The focal length of the optical imaging lens 8 is 25mm, the caliber is 30mm, and the distance between the reflective plane diffraction grating 6 and the optical imaging lens 8 is 100 mm.

The glass plate refractive index uniformity detection method based on the diffraction grating comprises the following steps:

step 1, selecting a xenon lamp light source (400 nm-800 nm) as a wavelength-adjustable light source 1, selecting a certain wavelength of the wavelength-adjustable light source to emit, enabling an emitted light beam to enter a beam expanding lens 2, adjusting the distance of the beam expanding lens 2 along an optical axis, converging the light beam emitted by the wavelength-adjustable light source 1 to a point , adding a small-hole diaphragm 3 (the caliber is 1.5mm) at the converging point, filtering stray light, and enabling the emitted light wave to be a spherical light wave;

step 2, the focal length of the collimating mirror 4 is f, the distance between the collimating mirror 4 and the aperture diaphragm 3 along the optical axis is adjusted to be f, and the incident spherical wave is changed into a planar light wave after passing through the collimating mirror 4;

step 3, adjusting the adjustable slit 5 (the adjustable range is 0-10mm), adjusting the width of the adjustable slit 5 to be 1mm, and adjusting the length of the adjustable slit to be 30mm, so that the planar light wave is emitted out of the ray planar light wave after passing through the slit;

step 4, adjusting the reflective planar diffraction grating 6 to enable the linear planar light wave to be obliquely incident with an incident angle of α (20-45 degrees) and the reflected light wave to be + 1-order diffracted light wave, wherein the linear logarithm of the reflective planar diffraction grating 6 is 600/mm, and the aperture of the reflective planar diffraction grating is 50mm multiplied by 50 mm;

step 5, adjusting the diffracted light wave + 1-order diffracted wave of the reflective planar diffraction grating 6 to converge through the optical imaging lens 8, wherein the focal length of the optical imaging lens 8 is 25mm, the caliber of the optical imaging lens is 30mm, the distance between the reflective planar diffraction grating 6 and the optical imaging lens 8 is 100mm, fixing the image surface behind the optical imaging lens 8 by using an optoelectronic fixing processing system, so that a clear diffraction pattern A is obtained on the image surface behind the optical imaging lens 8, and receiving the diffraction pattern A by using a CCD image acquisition system 9;

and 6, selecting a light source with a wavelength of 600nm for calibration, as shown in figure 2, selecting a light source with a wavelength of 600nm, adjusting the +1 st order diffraction wave of the reflective planar diffraction grating 6 to irradiate the CCD image acquisition system 9 to receive the diffraction pattern M according to the method of step 5, wherein the normal 12 of the reflective planar diffraction grating 6 is defined when the planar monochromatic light wave 11 is incident on the reflective planar diffraction grating 6, the 0 th order diffraction light beam 13 is defined, and the +1 st order diffraction light beam 14 is still a line beam, so that the diffraction pattern M is linear light spot, the position P1 of the linear light spot is recorded, pieces of standard glass plate 17 with the thickness of 10mm and the refractive index of K9 are added, the position P2 of the linear light spot is recorded, the principle is that when the light beam is vertically incident on the standard glass plate 17 at the interface, the refraction angle and the incident angle are both 0 degrees, therefore, the incident angle of the planar light wave obliquely incident on the reflective planar diffraction grating 6 is not separated, the position P1 of the linear light spot is completely coincided with the position P57 of the linear light spot, the standard glass plate, the position where the light beam is determined, the light beam is vertically incident on the standard glass plate 17, the interface, the planar diffraction grating, the planar diffraction pattern M can be calibrated when the optical system, the coordinate of 600nm, the original point is measured, the coordinate of the planar diffraction light beam, and the original.

And 7, adding the to-be-detected piece 7 in front of (without contact with) the reflective plane diffraction grating 6 to obtain a variable diffraction light wave on an image plane of the optical imaging lens 8, and adjusting the CCD image acquisition system 9 to receive the diffraction pattern B.

The test principle is as follows: as shown in fig. 3, for the optical system calibrated in step 6, the line pair number of the diffraction grating is 600/mm, and the equation of the diffraction grating is substituted:

d(sinα±sinθ)＝mλ

wherein α is the incident angle, theta is the diffraction angle,m is the diffraction order, which is the wavelength of the incident light wave.

Selecting a diffraction order m as a +1 order, setting an incidence angle as the incidence angle calibrated in the step 6, substituting the diffraction grating equation when the wavelength of the wavelength-adjustable light source 1 is changed from a visible light range of 400nm-800nm, calculating the +1 order diffraction angle range to be 14-29 degrees and the divergence angle to be 15 degrees, and calculating the position of an image surface and the magnification ratio β of the optical lens according to geometrical optics knowledge if the distance from the selected diffraction grating 6 to the optical lens 9 is 100mm, the focal length of the optical lens is 25mm, and the aperture is 30mm (larger than the size of a projected light spot) like .

As shown in fig. 3, the formula of the law of refraction:

n₁sinθ₁＝n₂sinθ₂

wherein: n is₁Is the refractive index of the incident medium, n₂Is refractive index of the refractive medium, theta₁Is the angle of incidence, θ₂Is the angle of refraction.

It can be known that the refraction angle of the part 7 to be measured is smaller than the angle of the part 7 not to be measured, as shown in fig. 3, the light 19 of the part 7 not to be measured is added, the light 20 of the part 7 to be measured is added, the two light beams have a separation distance d of , the distance d can be collected and calculated by the CCD image collection system 9, if the thickness h and the incident angle theta of the part 7 to be measured are known, the₁Establishing a mathematical model of the refractive index n and related parameters of the to-be-measured piece through a geometric relation formed by a refraction law and a linear propagation law of light beams:

wherein: n is the refractive index of the object 7 to be measured, theta₁The incident angle, h is the thickness of the test object, and d is the distance separating the light 19 without the test object from the light 20 with the test object.

The refractive index variation delta n of the piece to be measured and a related parameter mathematical model are as follows:

wherein: n is the refractive index of the object to be measured, theta₁The incident angle, h, the thickness of the test object, and Δ d, the variation of the distance separating the light 19 of the test object 7 and the light 20 of the test object 7.

Step 8, if the magnification of the CCD front optical lens is β, calculating the distance d 'and the distance variation Δ d' between the light ray 19 without the test piece and the light ray 20 with the test piece from the diffraction pattern B and the diffraction pattern a collected by the CCD image collection system 9, then the actual parameters:

and (4) calculating the average value n and the variable quantity delta n of the refractive index of the to-be-measured piece according to the mathematical model established in the step (7) and the tested parameters d 'and delta d'.

And 9, adjusting the wavelength of the wavelength-adjustable light source 1 to change from the range of 400nm to 800nm, scanning and collecting a plurality of diffraction patterns A without the to-be-detected piece 7 by taking the wavelength difference value 5nm as a step length, respectively storing the plurality of diffraction patterns B with the to-be-detected piece 7, processing by utilizing the established model and the compiled software, and calculating to obtain the spatial refractive index distribution information of the to-be-detected piece.

The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.