CN106370625A - V-prism refractometer based on autocollimation and CCD (Charge Coupled Device) visual technology - Google Patents

Abstract

The V prism refractometer based on self-collimation and CCD vision technology belongs to the field of photoelectric detection technology, including light source, filter assembly, self-collimation collimator, V groove, combined lens group, CCD camera Ⅰ, CCD camera Ⅱ and computer . The invention is a device that adopts self-collimation technology to realize the orthogonality calibration of the V-groove position, adopts a digital imaging system of a CCD camera to measure the deflection angle, has fast measurement and accurate reading, simple structure, low cost and high measurement accuracy High, fast and stable measurement of glass refractive index, ensuring detection accuracy and improving measurement efficiency. The computer program-controlled filter wheel reduces the filter switching time; the structure is simplified, and there is no angle measurement transmission mechanism and servo mechanism in the system, which can avoid the errors introduced by them, shorten the measurement time and improve the measurement efficiency; adopt self-collimation technology Realize V-groove calibration and improve measurement accuracy.

Description

V-prism refractometer based on autocollimation and CCD vision technology

technical field

The invention belongs to the technical field of photoelectric detection, in particular to a V-prism refractometer based on self-collimation and CCD vision technology.

Background technique

With the development of optical and optoelectronic instruments, the requirements for the refractive index of glass are getting higher and higher. The traditional V-prism glass refraction index measuring instrument adopts a complex optical-mechanical alignment and reading mechanism. The human eye is aligned with the telescope, reads the optical dial, and calculates the glass refractive index manually.

With the development of image processing technology and computer control technology, a digital V prism refractometer based on CCD digital image alignment and photoelectric reading has appeared. Although to a certain extent, the detection accuracy and automation of glass refractive index have been improved, but There are still the following deficiencies: 1. Due to the complex structure of the system, there are many error factors, such as the backlash of the transmission mechanism, the angle measurement accuracy of the encoder and the control accuracy of the motor, which will cause measurement errors; 2. Due to the large-angle range scanning alignment , compared with the traditional V-prism refractometer, the test efficiency is greatly reduced; 3. The equipment does not have the V-groove calibration function, which cannot guarantee the orthogonal alignment between the V-groove and the collimator, and it is easy to introduce a glass refractive index system error.

The patent number is 201220371462.0, and the utility model patent titled "Digital V-Prism Refractometer" discloses a digital V-prism refractometer. The device includes a collimator, an object-carrying system and an autocollimating telescope in sequence according to the optical path, and A CCD camera that collects outgoing deflected images. The main feature of this device is that the beam splitter installed inside the autocollimation telescope divides the incident light into two beams, one of which is used for human eyes to observe and adjust the optical path, and the other is used for CCD camera to collect images. . The deflected light is collected by the CCD, and an image with multiple colored horizontal lines is obtained, and the deflection angle is measured according to the position of the spectral lines of different colors. The autocollimating telescope is used to adjust the coaxiality of the optical axis of the collimator and CCD camera. The main defects of this measuring device are: 1. The collimator, the loading system and the self-collimating telescope are fixed on the base through the supporting column, and the two sides of the collimating light tube and the self-collimating telescope can be adjusted through the horizontal adjustment screw and the elevation angle adjustment screw. For the purpose of optical axis coincidence, the adjustment accuracy of this method is low, and the accuracy cannot be quantified. 2. The image formed by the autocollimating telescope on the CCD camera, due to the limitation of the autocollimating telescope, makes the deflection angle measurement range small, which is not suitable for large field of view measurement. 3. The color CCD camera is adopted, the processing speed is slow, and the real-time performance is poor.

Therefore, there is an urgent need for a novel technical solution in the prior art to solve this problem.

Contents of the invention

The technical problem to be solved by the present invention is to provide a V-prism refractometer based on self-collimation and CCD vision technology, which is used to solve the complex structure, large measurement error and low test efficiency of the digital V-prism refractometer in the prior art. Technical problems such as small measurement range.

The V prism refractometer based on self-collimation and CCD vision technology is characterized by: including light source, optical filter assembly, self-collimation collimator, V groove, combined lens group, CCD camera Ⅰ, CCD camera Ⅱ and computer,

The emitted light of the light source is incident on the self-collimating collimator after passing through the filter assembly; the filter assembly is loaded on the filter wheel; , a reticle, a beam splitter, a CCD camera III and a collimator lens group; the frosted glass, a decontamination diaphragm, a reticle, a beam splitter and a collimator lens group are sequentially arranged along the incident direction of the emitted light of the light source; The reticle is located on the focal plane of the self-collimating collimator; the CCD camera III is located on the reflected light path of the beam splitter; the V-groove is located between the self-collimating collimator and the combined lens group; the combined lens group It includes an imaging objective lens and a half mirror; one side of the imaging objective lens is adjacent to the groove, and the other side of the imaging objective lens is adjacent to the half mirror; the CCD camera II is located on the focal plane of the combined lens group; the The CCD camera I and the CCD camera II form a conjugate plane; the computer is respectively connected with the filter wheel, the CCD camera I, the CCD camera II and the CCD camera III.

The optical filter of the optical filter assembly is loaded through the optical filter wheel, and is programmed and selected by the computer according to the measurement requirements.

The reticle is a bright slit structure.

Through the above design scheme, the present invention can bring the following beneficial effects:

The invention is a device that adopts self-collimation technology to realize the orthogonality calibration of the V-groove position, adopts a digital imaging system of a CCD camera to measure the deflection angle, has fast measurement and accurate reading, simple structure, low cost and high measurement accuracy High, fast and stable measurement of glass refractive index, ensuring detection accuracy and improving measurement efficiency.

The invention utilizes the imaging position of the CCD camera to realize the coaxiality calibration of the optical axis of the self-collimating collimator and the measuring CCD; the semi-reflective half lens and the conjugated double CCD camera are used to expand the range of angle measurement, and the deflected light is directly transmitted by the imaging objective lens and the CCD CCD camera reception increases the measurement range of deflection angle, which is suitable for large deflection angle measurement; the autocollimation collimator is used to adjust the orthogonality between the position of the V-shaped groove and the axis of the collimator, and the adjustment accuracy is high.

The invention reduces the filter switching time through the computer program control filter wheel; the structure is simplified, and the angle measurement transmission mechanism and the servo mechanism do not exist in the system, which can avoid the errors introduced by them, shorten the measurement time and improve the measurement efficiency; Collimation technology realizes V-groove calibration and improves measurement accuracy; in addition, when measuring large deflection angles, half mirrors and conjugate dual CCD cameras are used to expand the angle measurement range.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

Fig. 1 is a working principle diagram of the V-prism refractometer based on self-collimation and CCD vision technology of the present invention.

Fig. 2 is a measurement schematic diagram of the V-prism refractometer based on the self-collimation and CCD vision technology of the present invention.

Fig. 3 is a schematic diagram of calculation mathematics of the V-prism refractometer based on self-collimation and CCD vision technology of the present invention.

In the figure 1-light source, 2-filter assembly, 3-autocollimating collimator, 4-V groove, 5-combined lens group, 6-CCD camera Ⅰ, 7-CCD camera Ⅱ, 8-computer, 301 -Frosted glass, 302-Isolation diaphragm, 303-Reticle, 304-Beam splitter, 305-CCD camera III, 306-Collimating lens group, 501-Imaging objective lens, 502-Half mirror.

detailed description

As shown in Figure 1, the V prism refractometer based on self-collimation and CCD vision technology is characterized by: including light source 1, filter assembly 2, self-collimation collimator 3, V groove 4, combined lens group 5 , CCD camera Ⅰ6, CCD camera Ⅱ7 and computer 8,

The emitted light of the light source 1 is incident on the self-collimating collimator 3 after passing through the filter assembly 2; the filter assembly 2 is loaded on the filter wheel; the self-collimating collimator 3 includes frosted glass 301, decontamination diaphragm 302, reticle 303, beam splitter 304, CCD camera III 305 and collimating lens group 306; The group 306 is arranged sequentially along the incident direction of the emitted light of the light source 1; the reticle 303 is located on the focal plane of the self-collimating collimator 3; the CCD camera III 305 is located on the reflected light path of the beam splitter 304; the V groove 4 is located between the self-collimating collimator 3 and the composite lens group 5; the composite lens group 5 includes an imaging objective lens 501 and a half mirror 502; one side of the imaging objective lens 501 is adjacent to the V-groove 4, imaging The other side of the objective lens 501 is adjacent to the half mirror 502; the CCD camera II7 is positioned on the focal plane of the combined lens group 5; the CCD camera I6 and the CCD camera II7 form a conjugate plane; the computer 8 is connected to the CCD camera II7 respectively The filter wheel, CCD camera I6, CCD camera II7 and CCD camera III305 are connected.

The filter assembly 2 is loaded with several filters on the filter wheel, and the rotation of the filter wheel is controlled by the computer 8. According to different light sources, the corresponding filter is selected by program control to realize the automatic replacement of the filter.

A stray stop 302 is used in front of the reticle 303 in the self-collimating collimator 3 to shield the influence of external stray light.

The reticle 303 in the self-collimating collimator 3 adopts a thin bright slit structure, and the traditional reticle uses dark lines in the bright slits for deviation angle comparison, and the reticle 303 is replaced by a thin bright slit structure. The slit, the thin bright slit is very thin, which is equivalent to the dark line in the original bright slit, and is placed on the focal plane of the self-collimating collimator 3 to form a bright slit image as an alignment target. In this way, according to the image sub-pixel subdivision technology, the sub-pixel subdivision alignment line can be obtained to improve the measurement accuracy.

A CCD camera III 305 and a beam splitter 304 are added to the self-collimating collimator 3 to realize the photoelectric self-collimation function, and achieve the orthogonal calibration of the optical axes of the V-groove 4 and the self-collimating collimator 3 .

The digital imaging system is composed of CCD camera I6, CCD camera II7 and imaging objective lens 501. The slit collimated light beam emitted from the V-groove 4 forms a slit image on the CCD camera I6 or CCD camera II7, and the deflection is obtained by processing the image. angle.

CCD camera I6 and CCD camera II7 are used as detectors to indirectly measure the deflection angle of the slit collimated beam exiting V-groove 4 .

In order to realize large-scale measurement, a conjugated dual CCD camera is used to expand the field of view. After passing through the imaging objective lens 501, the light is simultaneously reflected and transmitted through the half mirror 502. The CCD camera Ⅰ6 and the CCD camera Ⅱ7 are located on the conjugate plane to realize double-field stitching and increase the measurement angle range.

The measurement principle of the present invention is shown in Figure 2, where d is the displacement of the bright slit image received by the CCD camera I6 or CCD camera II7, and f' is the focal length of the combined lens group. The light is deflected after passing through the V groove 4, and the deflection angle is θ. Through the imaging objective lens 501, the half mirror 502 forms a slit image on the camera. By measuring its imaging height d, as shown in Figure 3, it is obtained by the formula, The deflection angle of light after passing through the V-groove 4 can be obtained. by the basic formula Find the refractive index n, where n ₀ is the refractive index of the V prism, θ is the deflection angle when the light exits the V prism, and n is the refractive index of the glass to be measured.

The effect of the V-prism refractometer based on self-collimation and CCD vision technology involved in the present invention is: through computer 8 program-controlled filter wheels, the time for switching filters is reduced; the structure is simplified, and there is no angle measuring transmission mechanism and servo in the system. mechanism, which can avoid the errors introduced by them, shorten the measurement time, and improve the measurement efficiency; the self-collimation technology is used to realize the calibration of the V groove 4, and the measurement accuracy is improved; in addition, when the large deflection angle is measured, the semi-reflective half-mirror 502 and the Conjugate double CCD camera namely CCD camera Ⅰ 6, CCD camera Ⅱ 7 CCD extended angle measuring range.

The refractometer involved in the present invention needs to calibrate the newly replaced V-groove 4 before measuring the refractive index of the glass. The specific principle is as follows: the light emitted by the spectral light source 1 is filtered by the filter assembly 2, after the frosted glass 301 is homogenized, the stray light is eliminated by the stray stop 302, and then the single slit bright line is formed by the reticle 303 After passing through the beam splitter 304, the light is collimated by the collimator lens group 306, and is incident on the polished surface of the V-groove 4. The reflected light generated on this surface passes through the collimator lens group 306, is reflected by the beam splitter 304 and reaches the CCD camera III 305, the CCD camera III 305 is connected with the computer 8, and the computer 8 processes the image collected by the CCD camera III 305, and displays the image position and the reference position on the monitor, and the operator can adjust the orthogonality of the V groove 4 according to the position deviation , until the two positions overlap, at this time, it means that the V-groove 4 is perpendicular to the optical axis of the self-collimating collimator 3 , and finally the base of the V-groove 4 is fixed to realize the calibration of the V-groove 4 .

After V-groove 4 is calibrated, the glass refractive index is measured. The specific working principle is as follows: when the light emitted by spectral light source 1 passes through the filter assembly 2, the computer 8 controls the rotation of the filter wheel in the assembly to select the corresponding filter for filtering. Light, the monochromatic light required for measurement is obtained, the light is homogenized by the frosted glass 301, the stray light is eliminated by the stray stop 302, the reticle 303 forms a single slit bright line, and the light is realized by the collimator lens group 306 after passing through the beam splitter 304 Collimation, through the V-groove 4 and deflection of the light emitted by the sample, after the imaging objective lens 501 and the half-mirror 502 split the light, the bright line of the single slit is imaged on the CCD camera I6 and the CCD camera II7. Among them, CCD camera Ⅰ6 and CCD camera Ⅱ7 are in the conjugate position, and the field of view stitching is realized by image processing software to increase the measurement field of view. Into the formula Calculate the refractive index n of the glass, where n ₀ is the refractive index of the V prism, θ is the deflection angle when the light exits the V prism, and n is the refractive index of the glass to be measured.

Claims (3)

1. The V prism refractometer based on self-collimation and CCD vision technology is characterized in that it includes light source (1), filter assembly (2), self-collimation collimator (3), V groove (4), Combined lens group (5), CCD camera I (6), CCD camera II (7) and computer (8), The emitted light of the light source (1) is incident on the self-collimating collimator (3) after the filter assembly (2); the filter assembly (2) is loaded on the filter wheel; the self-collimation The collimator (3) includes a ground glass (301), a stray stop (302), a reticle (303), a beam splitter (304), a CCD camera III (305) and a collimator lens group (306); The frosted glass (301), the decontamination diaphragm (302), the reticle (303), the beam splitter (304) and the collimating lens group (306) are sequentially arranged along the incident direction of the emitted light of the light source (1); The reticle (303) is located on the focal plane of the self-collimating collimator (3); the CCD camera III (305) is located on the reflected light path of the beam splitter (304); the V-groove (4) is located on the self-collimating Between the straight collimator (3) and the composite lens group (5); the composite lens group (5) includes an imaging objective lens (501) and a half mirror (502); one side of the imaging objective lens (501) Adjacent to the groove (4), the other side of the imaging objective lens (501) is adjacent to the half mirror (502); the CCD camera II (7) is positioned on the focal plane of the combined lens group (5); the The CCD camera I (6) forms a conjugate plane with the CCD camera II (7); )connect. 2. The V-prism refractometer based on self-collimation and CCD vision technology according to claim 1, characterized in that: the filter of the filter assembly (2) is loaded by the filter wheel, according to the measurement requirements Select by computer (8) program control. 3. The V-prism refractometer based on self-collimation and CCD vision technology according to claim 1, characterized in that: the reticle (303) is a bright slit structure.