Method and system for measuring the stability of eyeglass frames

Abstract

The present invention relates to the technical field of optical instrument evaluation, and discloses a method and system for measuring the stability of a frame to ensure the reliability and convenience of the measurement. The method comprises: loading a first reflector on the frame to be measured, and deploying the first reflector in a column of optical paths of an interference observation system; collecting interference fringe images, and determining the coordinates of a reference point for observing the light and dark changes of interference fringes; collecting interference fringe images periodically and extracting pixel information of the reference point; fitting a pixel information change curve of the reference point over time according to the extracted pixel information; and calculating the stability index of the frame to be measured according to the distribution periodicity of crests and troughs in the pixel information change curve and the wavelength of the light source corresponding to the interference fringes, as well as the geometric space information between the first reflector and the interference fringe image acquisition device.

Description

Technical Field

[0001] The present invention relates to the technical field of optical instrument evaluation, and in particular to a method and system for measuring the stability of a spectacle frame. Background Art

[0002] Due to the stress inside the machine or the influence of its use environment, the mechanical parts will have a certain instability. Especially in optical experiments, the collimation and stability of the optical path are very important for optical experiments, and the stability of the frame is closely related to the collimation and stability of the optical path. The better the stability of the frame, the better the stability of the optical path. Therefore, the stability of the frame is crucial to the stability of the optical path. Summary of the invention

[0003] The present invention aims to disclose a method and a system for measuring the stability of a spectacle frame, so as to ensure the reliability and convenience of the measurement.

[0004] To achieve the above object, the present invention discloses a method for measuring the stability of a frame, comprising:

[0005] Mounting a first reflector on a mirror frame to be tested, and disposing the first reflector in a light path of an interference observation system;

[0006] Collect interference fringe images and determine the coordinates of a reference point for observing light and dark changes in interference fringes;

[0007] Periodically collecting interference fringe images and extracting pixel information of the reference points;

[0008] Fitting a curve of pixel information variation of the reference point over time according to the extracted pixel information;

[0009] The stability index of the frame to be tested is calculated according to the distribution periodicity of the peaks and troughs in the pixel information change curve, the wavelength of the light source corresponding to the interference fringes, and the geometric space information between the first reflector and the interference fringes image acquisition device.

[0010] Preferably, the interference observation system is a Michelson interference experimental device, and the corresponding optical path relationship specifically includes:

[0011] The laser light generated by the laser passes through a polarizer to convert the laser light into linear polarized light, and the linear polarized light passes through a polarization beam splitter cube to be split into two beams of light, one of which passes through the first reflector mounted on the mirror frame to be measured, and the other passes through the second reflector. The two laser beams respectively reflected by the first reflector and the second reflector are then combined by the polarization beam splitter cube to form interference fringes and imaged on the CCD;

[0012] Wherein, the laser, polarizer, beam splitter cube and second reflector are all fixed.

[0013] Preferably, determining the coordinates of a reference point for observing the light and dark changes of the interference fringes specifically includes:

[0014] The grayscale value information of the interference fringe image is read, and the read grayscale value is normalized and smoothed, and then the column with the most obvious image fringe contrast is screened out from the interference fringe image, and then the coordinates corresponding to the pixel point with the largest grayscale value are selected from the screened column as the reference point, wherein the direction of the column of the interference fringe image is consistent with the direction of change of the light and dark interval of the interference fringe.

[0015] Preferably, the method for calculating the stability index of the frame to be tested is specifically:

[0016] Δ=k·λ

[0017] Wherein, Δ represents the optical path difference, k represents the order of change of bright fringes, and λ represents the wavelength of light. The movement of the mirror frame to be measured causes an optical path difference between the two columns of light, so that when the laser wavelength is determined, the changed optical path difference is proportional to the order of change of fringes.

[0018] Calculate the rotation arc of the mirror frame to be tested;

[0019]

[0020] Wherein, Q is the rotation arc of the lens frame to be tested, and D is the distance between the lens frame to be tested and the CCD; or

[0021]

[0022] Where m is the number of peak / valley values ​​that characterize the light-dark change cycle.

[0023] To achieve the above-mentioned purpose, the present invention further discloses a system for measuring the stability of a mirror frame, wherein a first reflector is mounted on the mirror frame to be measured, and the first reflector is deployed in a column of optical paths of an interference observation system; the interference observation system comprises an industrial computer connected to an interference fringe image acquisition device, the industrial computer comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the following steps when executing the computer program:

[0024] Instructing the interference fringe image acquisition device to acquire the interference fringe image and determine the coordinates of a reference point for observing the light and dark changes of the interference fringe;

[0025] Continue to instruct the interference fringe image acquisition device to periodically acquire interference fringe images and extract pixel information of the reference point; then fit the pixel information change curve of the reference point over time according to the extracted pixel information; finally, calculate the stability index of the frame to be tested according to the distribution periodicity of the peaks and troughs in the pixel information change curve and the wavelength of the light source corresponding to the interference fringes, as well as the geometric space information between the first reflector and the interference fringe image acquisition device.

[0026] Preferably, the industrial computer is also used to read the grayscale value information of the interference fringe image, and normalize and smooth the read grayscale values, and then filter out the columns with the most obvious image fringe contrast from the interference fringe image, and then select the coordinates corresponding to the pixel point with the largest grayscale value from the filtered columns as the reference points, wherein the direction of the columns of the interference fringe image is consistent with the direction of change of the light and dark intervals of the interference fringes.

[0027] Similarly, the preferred method for the industrial computer to calculate the stability index of the tested mirror frame can be specifically as follows:

[0028] Δ=k·λ

[0029] Wherein, Δ represents the optical path difference, k represents the order of change of bright fringes, and λ represents the wavelength of light. The movement of the mirror frame to be measured causes an optical path difference between the two columns of light, so that when the laser wavelength is determined, the changed optical path difference is proportional to the order of change of fringes.

[0030] Calculate the rotation arc of the mirror frame to be tested;

[0031]

[0032] Wherein, Q is the rotation arc of the lens frame to be tested, and D is the distance between the lens frame to be tested and the CCD; or

[0033]

[0034] Where m is the number of peak / valley values ​​that characterize the light-dark change cycle.

[0035] The present invention has the following beneficial effects:

[0036] Since the interference system can measure small changes, the measurement experimental device of this method is an interference light path; in the interference light path, some small changes in the light path are judged by observing the changes in the interference fringes. By fixing the other frames in the light path, the frame to be tested becomes the only variable in the interference light path. Therefore, the change in the interference fringes is caused by the instability of the frame to be tested. The stability indicators such as the rotation arc of the frame to be tested are judged by calculating the change period of the interference fringes. The reliability of the instability results of the frame to be tested and the convenience of implementation are ensured.

[0037] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0039] Figure 1 It is a block diagram of a system for measuring the stability of a mirror frame disclosed in an embodiment of the present invention.

[0040] Figure 2 It is a schematic diagram of a pixel and intensity curve disclosed in an embodiment of the present invention; wherein the horizontal axis is the image column coordinate position, and the vertical axis is the contrast.

[0041] Figure 3 The figure is a schematic diagram of a curve showing a change in grayscale value over time according to an embodiment of the present invention; wherein the horizontal axis is time and the vertical axis is grayscale value.

[0042] Figure 4 This is a curve showing the change of the rotation arc of the frame to be measured versus the measurement time disclosed in an embodiment of the present invention; wherein the horizontal axis is time and the vertical axis is the rotation arc. DETAILED DESCRIPTION

[0043] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0044] Example 1

[0045] The embodiment of the present invention discloses a method for measuring the stability of a spectacle frame, comprising:

[0046] Step S1, loading a first reflector on the frame to be tested, and deploying the first reflector in a column of optical paths of the interferometric observation system. It is worth noting that the "loading" described in this step is not equivalent to "fixing". Usually, the expected effect of loading is that the first reflector can move accordingly with the adjustment parts such as knobs of the frame, but will not be disturbed by external factors such as environmental wind and produce shaking.

[0047] Preferably, the interference observation system is a Michelson interference experimental device, and the corresponding optical path relationship can be as follows: Figure 1As shown, it specifically includes: a laser 1, a polarizer 2, a polarization beam splitter cube 3, a device CCD4 for collecting interference fringe images, a second reflector 5 and a first reflector 6. The laser light generated by the laser passes through a polarizer to convert the laser light into linearly polarized light, and the linearly polarized light passes through the polarization beam splitter cube to be divided into two beams of light, one of which passes through the first reflector mounted on the mirror frame to be measured, and the other passes through the second reflector. The two laser beams reflected by the first reflector and the second reflector are then combined by the polarization beam splitter cube to form interference fringes and imaged on the CCD; wherein the laser, polarizer, beam splitter cube and second reflector are all fixed.

[0048] As an alternative, when the above-mentioned polarizing plate is omitted, the above-mentioned "polarizing beam splitter cube" is replaced by a "non-polarizing beam splitter cube".

[0049] Step S2: collect interference fringe images and determine the coordinates of a reference point for observing light and dark changes of the interference fringes.

[0050] Preferably, determining the coordinates of a reference point for observing the light and dark changes of the interference fringes specifically includes:

[0051] The gray value information of the interference fringe image is read, and the gray value after reading is normalized and smoothed, and then the column with the most obvious image fringe contrast is screened out from the interference fringe image, and then the coordinates corresponding to the pixel point with the largest gray value are selected from the screened column as the reference point, wherein the direction of the column of the interference fringe image is consistent with the direction of the change of the light and dark interval of the interference fringe. Generally, the contrast calculation formula is:

[0052] Contrast ratio = (maximum light intensity - minimum light intensity) / (maximum light intensity + minimum light intensity).

[0053] Step S3, periodically collecting interference fringe images and extracting pixel information of the reference points.

[0054] Step S4: fitting a curve of pixel information variation of the reference point over time according to the extracted pixel information.

[0055] In this step, preferably, the specific form of the pixel information may be grayscale value, brightness, etc.

[0056] Step S5, calculating the stability index of the frame to be tested according to the distribution periodicity of the peaks and troughs in the pixel information change curve, the wavelength of the light source corresponding to the interference fringes, and the geometric space information between the first reflector and the interference fringes image acquisition device. The geometric space information includes the distance between the first reflector and the interference fringes image acquisition device, etc.

[0057] In this step, it is assumed that the displacement of the frame to be tested is adjusted by a mechanical structure such as a knob. Preferably, the stability index of the frame to be tested can be calculated by calculating the rotation arc generated by the knob adjustment member due to interference from factors such as stress or vibration. The specific formula includes:

[0058] Δ=k·λ

[0059] Among them, Δ represents the optical path difference, k represents the order of change of the bright stripes, and λ represents the wavelength of light. The movement of the mirror frame to be measured causes an optical path difference between the two columns of light, so that when the laser wavelength is determined, the changed optical path difference is proportional to the order of change of the stripes.

[0060] The offset distance and the distance between the first reflector and the interference fringe image acquisition device are used as two right-angled sides of the right triangle to calculate the rotation arc of the test frame. The rotation arc is the angle offset caused by the influence of self-stress / environmental jitter, etc.

[0061]

[0062] Wherein, Q is the rotation arc of the lens frame to be tested, and D is the distance between the lens frame to be tested and the CCD; or

[0063]

[0064] Where m is the number of peak / valley values ​​that characterize the light-dark change cycle.

[0065] In a specific set of experiments conducted by the applicant's laboratory, the interferometric observation system was used Figure 1 The architecture shown uses CCD for data acquisition, with a sampling interval of 30s, a total time of >8h, and more than 1000 images. The size of a single pixel of CCD is 2.2um×2.2um.

[0066] Use Matlab to process the collected interference patterns. First, take the gray value information of the first image, normalize and smooth the gray value after reading, and select the column with the most obvious stripe contrast in the image to make the following Figure 2 The pixel and intensity curve shown in the figure is then selected. The peak position is the first peak position. After that, the gray value information of all the images collected by the CCD at this position is taken out in turn and subjected to the same normalization and smoothing processing, and then the following is done: Figure 3 The gray value changes over time as shown in Figure 3 Find the peak / valley position in the image. For each change in the light and dark cycle, the test mirror frame will rotate a certain angle, from which the number of peaks and troughs m can be obtained. The distance between the test mirror frame and the CCD is 0.18m. Finally, calculate the rotation arc of the test mirror frame according to the above calculation formula and draw it as shown below. Figure 4The curve of the rotation arc of the frame to be tested changing with the measuring time is shown. After analyzing the measurement results of a large number of frames, it is known that the stability of the frame is good when the rotation arc is within 10urad.

[0067] Example 2

[0068] This embodiment discloses a system for measuring the stability of a mirror frame. A first reflector is mounted on the mirror frame to be measured, and the first reflector is deployed in a light path of an interference observation system. The interference observation system includes an industrial computer connected to an interference fringe image acquisition device. The industrial computer includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the following steps are implemented:

[0069] Step S10, instructing the interference fringe image acquisition device to acquire the interference fringe image, and determining the coordinates of a reference point for observing the light and dark changes of the interference fringes.

[0070] Step S20, continue to instruct the interference fringe image acquisition device to periodically acquire interference fringe images and extract pixel information of the reference point; then fit the pixel information change curve of the reference point over time according to the extracted pixel information; finally, calculate the stability index of the frame to be tested according to the distribution periodicity of the peaks and troughs in the pixel information change curve and the wavelength of the light source corresponding to the interference fringes, as well as the geometric space information between the first reflector and the interference fringe image acquisition device.

[0071] Preferably, the industrial computer is also used to read the grayscale value information of the interference fringe image, and normalize and smooth the read grayscale values, and then filter out the columns with the most obvious image fringe contrast from the interference fringe image, and then select the coordinates corresponding to the pixel point with the largest grayscale value from the filtered columns as the reference points, wherein the direction of the columns of the interference fringe image is consistent with the direction of change of the light and dark intervals of the interference fringes.

[0072] Similarly, the preferred method for the industrial computer to calculate the stability index of the tested mirror frame can be specifically as follows:

[0073] Δ=k·λ

[0074] Wherein, Δ represents the optical path difference, k represents the order of change of bright fringes, and λ represents the wavelength of light. The movement of the mirror frame to be measured causes an optical path difference between the two columns of light, so that when the laser wavelength is determined, the changed optical path difference is proportional to the order of change of fringes.

[0075] Calculate the rotation arc of the mirror frame to be tested;

[0076]

[0077] Wherein, Q is the rotation arc of the lens frame to be tested, and D is the distance between the lens frame to be tested and the CCD; or

[0078]

[0079] Where m is the number of peak / valley values ​​that characterize the light-dark change cycle.

[0080] In summary, the method and system for measuring the stability of a spectacle frame disclosed in the above two embodiments of the present invention respectively have the following beneficial effects:

[0081] Since the interference system can measure small changes, the measurement experimental device of this method is an interference light path; in the interference light path, some small changes in the light path are judged by observing the changes in the interference fringes. By fixing the other frames in the light path, the frame to be tested becomes the only variable in the interference light path. Therefore, the change in the interference fringes is caused by the instability of the frame to be tested. The stability indicators such as the rotation arc of the frame to be tested are judged by calculating the change period of the interference fringes. The reliability of the instability results of the frame to be tested and the convenience of implementation are ensured.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the stability of a frame, characterized in that: include: Mounting a first reflector on a mirror frame to be tested, and disposing the first reflector in a light path of an interference observation system; Collect interference fringe images and determine the coordinates of a reference point for observing light and dark changes in interference fringes; Periodically collecting interference fringe images and extracting pixel information of the reference points; Fitting a curve of pixel information variation of the reference point over time according to the extracted pixel information; Calculating the stability index of the frame to be tested according to the distribution periodicity of the peaks and troughs in the pixel information change curve, the wavelength of the light source corresponding to the interference fringes, and the geometric space information between the first reflector and the interference fringes image acquisition device; The method for calculating the stability index of the frame to be tested is specifically as follows: Δ=k·λ Wherein, Δ represents the optical path difference, k represents the order of change of bright fringes, and λ represents the wavelength of light. The movement of the mirror frame to be measured causes an optical path difference between the two columns of light, so that when the laser wavelength is determined, the changed optical path difference is proportional to the order of change of fringes. Calculate the rotation arc of the mirror frame to be tested; Wherein, Q is the rotation arc of the lens frame to be tested, and D is the distance between the lens frame to be tested and the CCD; or Where m is the number of peak / valley values ​​that characterize the light-dark change cycle.

2. The method according to claim 1, characterized in that The interference observation system is a Michelson interference experimental device, and the corresponding optical path relationship specifically includes: The laser light generated by the laser passes through a polarizer to convert the laser light into linear polarized light, and the linear polarized light passes through a polarization beam splitter cube to be split into two beams of light, one of which passes through the first reflector mounted on the mirror frame to be measured, and the other passes through the second reflector. The two laser beams respectively reflected by the first reflector and the second reflector are then combined by the polarization beam splitter cube to form interference fringes and imaged on the CCD; Wherein, the laser, polarizer, beam splitter cube and second reflector are all fixed.

3. The method according to claim 1 or 2, characterized in that: The step of determining the coordinates of a reference point for observing the light and dark changes of interference fringes specifically includes: The grayscale value information of the interference fringe image is read, and the read grayscale value is normalized and smoothed, and then the column with the most obvious image fringe contrast is screened out from the interference fringe image, and then the coordinates corresponding to the pixel point with the largest grayscale value are selected from the screened column as the reference point, wherein the direction of the column of the interference fringe image is consistent with the direction of change of the light and dark interval of the interference fringe.

4. A system based on the method for measuring the stability of a frame according to any one of claims 1 to 3, characterized in that: A first reflector is mounted on a mirror frame to be tested, and the first reflector is deployed in a light path of an interference observation system; the interference observation system includes an industrial computer connected to an interference fringe image acquisition device, the industrial computer includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the following steps when executing the computer program: Instructing the interference fringe image acquisition device to acquire the interference fringe image and determine the coordinates of a reference point for observing the light and dark changes of the interference fringe; Continue to instruct the interference fringe image acquisition device to periodically acquire interference fringe images and extract pixel information of the reference point; Then, a pixel information variation curve of the reference point over time is fitted according to the extracted pixel information; finally, the stability index of the frame to be tested is calculated according to the distribution periodicity of the peaks and troughs in the pixel information variation curve, the wavelength of the light source corresponding to the interference fringes, and the geometric space information between the first reflector and the interference fringe image acquisition device.

5. The system according to claim 4, characterized in that The industrial computer is also used to read the gray value information of the interference fringe image, and normalize and smooth the read gray value, then filter out the column with the most obvious image fringe contrast from the interference fringe image, and then select the coordinates corresponding to the pixel point with the largest gray value from the filtered column as the reference point, wherein the direction of the column of the interference fringe image is consistent with the direction of change of the light and dark interval of the interference fringe.

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