CN110095262B - Device for detecting optical crosstalk transmittance between optical fibers in optical fiber image transmission element - Google Patents
Device for detecting optical crosstalk transmittance between optical fibers in optical fiber image transmission element Download PDFInfo
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- CN110095262B CN110095262B CN201910347893.XA CN201910347893A CN110095262B CN 110095262 B CN110095262 B CN 110095262B CN 201910347893 A CN201910347893 A CN 201910347893A CN 110095262 B CN110095262 B CN 110095262B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/0257—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0285—Testing optical properties by measuring material or chromatic transmission properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
- G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
Abstract
The invention relates to a device for detecting the optical crosstalk transmittance between optical fibers in an optical fiber image transmission element, which comprises: a detection system and a control system; the detection system comprises: the cabinet body is used for preventing external light from entering the detection system and providing a light-shading environment for detection; a light source for providing light required for detection; a measurement template providing a standard pattern for detection; the image acquisition mechanism is used for acquiring an image formed by the standard pattern on the optical fiber image transmission element to be detected; the control system includes: an image data processing unit and a control unit. The device adopts the measuring template with the standard pattern, so that the standard pattern forms an image after being transmitted by the optical fiber image transmission element to be measured, and the image data is analyzed to obtain the transmittance value for representing the stray light crosstalk performance between the optical fibers. The device can improve the reliability and accuracy of the detection result, and reduce the detection cost and the dependence of the detection result on external conditions.
Description
Technical Field
The invention relates to an automatic detection device, in particular to a device for detecting the optical crosstalk transmittance between optical fibers in an optical fiber image transmission element.
Background
Currently, the super-second generation and third generation low-light night vision technology develops to the 4G technology, and the spectral response wavelength extends to the long wave direction and the short wave direction, the imaging quality factor exceeds 1800 and is higher than the imaging resolution of 57lp/mm and higher imaging resolution is required. The stray light crosstalk between optical fibers is a main factor for deteriorating the image definition and reducing the contrast. How to characterize the stray light crosstalk performance in the optical fiber image transmission element becomes an important problem.
The current characterization method related to the optical crosstalk performance evaluation is a knife edge response value, and the brightness of light transmitted through a knife edge by an optical fiber image transmitting material is measured. The method is still the index for representing the optical crosstalk performance commonly adopted by the manufacturers of the domestic optical fiber image transmission elements at present. For the representation of the parasitic light crosstalk performance, no unified standard exists at home and abroad. Characterization of optical crosstalk performance by knife-edge response values has three significant drawbacks from a detection point of view: firstly, the measured value is inaccurate, and the testing condition is inconsistent with the actual service environment, and system appearance is complicated and system appearance influences the measuring result great to lead to the stability of testing result or reliability to have the problem, often the edge of a knife response value of a sample detects the result of volume many times and has great difference, and the maximum deviation can exceed 50%. Secondly, the method has no universality. The optical fiber image transmission element has range requirements on the testing thickness, and products with a thickness higher than a certain thickness cannot be directly detected. Therefore, the optical fiber straight plate, the optical fiber image inverter and the optical fiber light cone product are indirect testing representations, only a partial area of the tested product can be tested, and the slicing position cannot usually represent the whole optical crosstalk performance of the whole tested product. Thirdly, the existing knife edge response measuring equipment is only one in China, the measuring precision is seriously reduced along with the aging of the equipment, and the knife edge response measuring equipment also has the tendency of being gradually eliminated. Therefore, it is very urgent and necessary to invent a new method for characterizing the crosstalk performance of stray light.
Disclosure of Invention
The invention mainly aims to provide a device for detecting the optical crosstalk transmittance between optical fibers in an optical fiber image transmission element, which is used for representing the optical crosstalk performance based on the light transmittance of gray value normalization, improving the reliability and accuracy of a detection result and obviously improving the detection efficiency, thereby reducing the detection cost and the dependency of the detection result on external conditions.
The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. The invention provides a device for detecting the optical crosstalk transmittance among optical fibers in an optical fiber image transmission element, which comprises: a detection system and a control system, wherein,
the detection system comprises:
the cabinet body is used for preventing external light from entering the detection system and providing a light-shading environment for detection;
a light source for providing light required for detection;
the measuring template is used for providing a standard pattern for detection, and consists of a first area and a second area, wherein the transmittance of the first area is less than that of the second area, and the difference between the transmittances of the first area and the second area is greater than 90%;
when the optical fiber image transmission element is used, a first surface of the optical fiber image transmission element to be detected is attached to the measuring template, light rays emitted by the light source sequentially pass through the measuring template and the optical fiber image transmission element to be detected, and then a first image and a second image are formed on a second surface, opposite to the first surface, of the optical fiber image transmission element to be detected, wherein the first image corresponds to the first area, and the second image corresponds to the second area; and
the image acquisition mechanism is used for acquiring an image formed by the standard pattern on the optical fiber image transmission element to be detected;
the light source, the measuring template and the image acquisition mechanism are sequentially arranged in the cabinet body;
the light source and the image acquisition mechanism are coaxially arranged, and the measuring template is perpendicular to the axis of the light source;
the control system includes:
the image data processing unit is connected with the image acquisition mechanism and used for processing the image acquired by the image acquisition mechanism to obtain a light transmittance value; and
and the control unit is connected to the detection system and the image data processing unit and is used for controlling the detection system and the image data processing unit to operate.
The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.
Preferably, the apparatus for detecting optical crosstalk transmittance between optical fibers in the optical fiber image transmitting element further comprises: the black cover covers the light source and the measuring template, and one surface of the black cover close to the measuring template is provided with an opening for placing an optical fiber image transmission element to be measured.
Preferably, the device for detecting optical crosstalk transmittance between optical fibers in the optical fiber image transmission element is provided, wherein an optical filter is arranged between the light source and the measuring template.
Preferably, the device for detecting optical crosstalk transmittance between optical fibers in the optical fiber image transmission element is provided, wherein a diffusion glass is arranged between the optical filter and the measuring template.
Preferably, in the apparatus for detecting optical crosstalk transmittance between optical fibers in the optical fiber image sensor, the transmittance of the first region is less than 2%, and the transmittance of the second region is greater than 95%.
Preferably, the image capturing mechanism includes a camera and a corresponding lens.
Preferably, the camera is a CCD or CMOS photosensitive device, and the device for detecting optical crosstalk transmittance between optical fibers in the optical fiber image sensor is described above.
Preferably, the lens is a microscope lens, and has a zoom lens, and the optical magnification adjustment range can reach 2 to 100 times.
Preferably, the apparatus for detecting optical crosstalk transmittance between optical fibers in the optical fiber image transmitting element further comprises: and the detection table is formed by combining granite and a three-dimensional precision mechanical transmission assembly and is used for placing the light source and the measurement template.
Preferably, the apparatus for detecting optical crosstalk transmittance between optical fibers in the optical fiber image transmitting element further comprises: and the frame is used for fixing the detection table and the image acquisition mechanism.
By the technical scheme, the device for detecting the optical crosstalk transmittance among the optical fibers in the optical fiber image transmission element at least has the following advantages:
1. the device of the invention is provided with a measuring template with a standard pattern; the method comprises the steps of enabling patterns on a measuring template to form images after being transmitted by an optical fiber image transmission element to be measured, conducting gray scale analysis on image data to obtain gray values of different pixel points, conducting normalization processing on the gray values of different positions to obtain normalized transmittance values, and representing stray light crosstalk performance between optical fibers in the optical fiber image transmission element by utilizing the normalized transmittance values. The device can improve the reliability, accuracy and repeatability of the detection result, can also obviously improve the detection efficiency, and reduces the detection cost and the dependence of the detection result on external conditions.
The method can realize direct measurement of the product, the obtained result directly reflects the stray light crosstalk performance of the tested product, a new method is provided for the progress of the automatic detection technology of the optical fiber image transmission element product, and related detection equipment can be developed based on the method. The method can effectively improve the reliability, accuracy and repeatability of the detection result, and can also obviously improve the detection efficiency, thereby reducing the detection cost and the dependency of the detection result on external conditions.
2. The device can realize automatic detection and calculation of the light transmittance by arranging the detection system control unit and the data processing unit, the obtained result directly reflects the stray light crosstalk performance of a detected product, the test efficiency is high, the external influence factors are small, the dependence on operators and sample preparation is small, and the measurement precision is superior to 5%.
3. The device has the advantages of good repeatability of the transmittance test result, simple operation, high automation degree and intuitive test result, is more suitable for batch production, can accurately represent the slight difference of different optical crosstalk performances of the optical fiber image transmission element, and has good consistency of the obtained transmittance and the modulation function (MTF) of the optical fiber image transmission element after the management.
4. The device can measure the light transmittance of the light passing through the optical fiber image transmission element to be measured, and the light transmittance can be used for representing the optical crosstalk performance among the optical fibers in the optical fiber image transmission element to be measured. The device can measure the optical crosstalk transmittance between the optical fibers at any position point on the optical fiber image transmission element, and realizes the comprehensive characterization of the optical crosstalk performance between the optical fibers of the optical fiber image transmission element.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
FIG. 1 is a schematic view of a transmittance testing apparatus of an optical fiber image sensor according to an embodiment of the present invention;
FIG. 2 is a schematic view of a transmittance testing apparatus of an optical fiber image sensor according to another embodiment of the present invention;
FIG. 3 is a schematic diagram of a measurement template according to one embodiment of the present invention;
FIG. 4 is a schematic diagram of selecting a gray value measurement range according to one embodiment of the invention;
FIG. 5 is a schematic diagram of selecting a gray value measurement range according to another embodiment of the present invention;
FIG. 6 is a graph showing the variation trend of the normalized transmittance measured in example 1 of the present invention;
FIG. 7 is a graph showing the variation trend of the normalized transmittance value measured for the first time in example 2 of the present invention;
FIG. 8 is a graph showing the variation trend of the normalized transmittance value measured for the second time in example 2 of the present invention.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be given to the embodiments, structures, features and effects of an apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image sensor according to the present invention with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
As shown in fig. 1-3, an embodiment of the present invention provides an apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image sensor, comprising: a detection system and a control system, wherein,
the detection system comprises:
the cabinet body 111 is used for preventing external light from entering the detection system and providing a light-shading environment for detection;
a light source 3 for providing light required for detection;
the measuring template 1 is used for providing a standard pattern for detection, the measuring template 1 is composed of a first area 11 and a second area 12, the transmittance of the first area 11 is smaller than that of the second area 12, and the difference between the transmittances of the first area 11 and the second area 12 is larger than 90%;
when the optical fiber image transmission element is used, a first surface of the optical fiber image transmission element to be detected is attached to the measuring template, light rays emitted by the light source sequentially pass through the measuring template and the optical fiber image transmission element to be detected, and then a first image and a second image are formed on a second surface, opposite to the first surface, of the optical fiber image transmission element to be detected, wherein the first image corresponds to the first area, and the second image corresponds to the second area; and
the image acquisition mechanism is used for acquiring an image formed by the standard pattern on the optical fiber image transmission element 2 to be detected;
the light source 3, the measuring template 1 and the image acquisition mechanism are sequentially arranged in the cabinet body 111; the light source 2 and the image acquisition mechanism are coaxially arranged, and the measuring template 1 is perpendicular to the axis of the light source 2.
In order to prevent the influence of external light on the detection result to obtain an accurate image gray value, the detection system of the embodiment of the invention must perform detection in a light-shielding environment. The cabinet body is not particularly limited, such as a darkroom or a darkbox, and preferably is an integrated sealable control cabinet body, one side of which is provided with an openable and closable operation door for putting in or taking out the optical fiber image transmitting element to be detected. The cabinet body is made of metal, and the inner surface of the cabinet body is coated with a light-absorbable coating.
The embodiment of the invention does not specifically limit the light source, and can adopt a coaxial light source and also can adopt a point light source. The white coaxial LED cold light source is adopted, so that the uniformity and the brightness of the light source can be effectively ensured, and the long service life is obtained. Required uniformity (gray level difference): less than 1.0; light source life: 100000 hours. The invention can also select a white point light source, and an emulsified diffusion glass needs to be additionally arranged in actual use to enable the point light source to become diffused light so as to meet the light source requirement required by the instrument. The brightness of the light source is controllable, the brightness of the light source required by each optical fiber image transmission element sample to be detected is adjusted according to the requirement, but the transmittance of each optical fiber image transmission element sample to be detected is detected by using the light source with the same brightness.
The standard pattern is provided by the detection of the measuring template, and the transmittance of the light passing through the optical fiber image transmission element to be detected is mainly detected, so that the transmittances of the first area and the second area on the measuring template are uniform, and an obvious boundary line is formed between the first area and the second area on the measuring template, so that the change of the light on the boundary line can be reflected. The first region and the second region have a difference in transmittance, and the greater the difference, the higher the detection accuracy. The larger the difference in the transmittances of the first region and the second region, the better, the first region is ensured to have a sufficiently low transmittance, the second region is ensured to have a sufficiently high transmittance, and the difference in the transmittances of the first region and the second region is preferably greater than 93%, more preferably greater than 98%. The shape of the measuring template is not particularly limited in the present invention, and a circular shape or a square shape is preferable. The area of the measuring template is larger than the maximum cross-sectional area of the optical fiber image transmission element to be measured, the size and the shape of the first region and the second region can be the same or different, and the shape of the first region and the second region is preferably square. The first area and the second area are a first square area and a second square area which are connected, and one side of the first square area is overlapped with one side of the second square area.
In addition, in the embodiment of the present invention, the first region and the second region of the measurement template are used to distinguish the transmittance of the two regions from each other, the transmittance of the first region is a transmittance from the incident surface of the first region to the emergent surface of the first region, the transmittance of the second region is a transmittance from the incident surface of the second region to the emergent surface of the second region, the incident surface of the first region and the incident surface of the second region face the light source, the emergent surface of the first region and the emergent surface of the second region face the optical fiber image transmission element to be measured, and the two incident surfaces and the two emergent surfaces of the first region and the second region are located on the same plane and are parallel to the first surface of the optical fiber image transmission element to be measured.
In a preferred embodiment, the transmittance of the first region 11 is < 2%, and the transmittance of the second region 12 is > 95%.
The measuring template can be directly purchased or self-made on the market, and the self-making step comprises the following steps: a glass plate (e.g., a piece of abrasion-resistant quartz glass) having a transmittance of greater than 95% is selected and a light-absorbing or light-reflecting coating is applied to the glass plate to provide a transmittance of less than 2%. The measurement template can directly adopt the American standard USAF1951 of the international standard to distinguish the test target or an equivalent resolution test target. When in actual use, the surface of the measuring template can be repeatedly used after being cleaned as long as the surface of the measuring template is not scratched.
The embodiment of the invention requires that an image acquisition mechanism meets the following requirements: the higher the pixel value, the smaller the pixel, the stronger the detail resolution, and the greater the bit depth. A high-resolution and low-noise digital camera is preferably selected, a high-bit-depth and high-resolution photosensitive element ccd or cmos is adopted for the digital camera, a microscope lens is adopted for a lens of the digital camera, the lens requires the resolution less than 3 mu m and the imaging distortion rate superior to 0.5 percent, the continuous zoom lens is provided, and the magnification adjusting range can reach 2-100 times.
The embodiment of the invention utilizes a high-resolution and low-noise digital camera to acquire a real-time image of an optical signal passing through an optical fiber image transmission material, and measures the imaging gray value of a pixel point. The dynamic range should be higher than 60dB, the pixel pitch is not lower than 6 μm, the output noise: not higher than 5e- @60Hz, and the image bit depth is not lower than 8 bit. The measured data of the camera can be developed and utilized secondarily. And obtaining the gray value of each pixel point by secondary development of the camera data. Therefore, the camera is required to have a high pixel value, a small pixel, a strong detail resolution capability, and a large bit depth.
The control system 6 includes:
the image data processing unit is connected to the image acquisition mechanism and used for processing the image acquired by the image acquisition mechanism to obtain a light transmittance value; and
and the control unit is connected to the detection system and the image data processing unit and is used for controlling the detection system and the image data processing unit to operate.
The image data processing unit comprises a data processing module, wherein the data processing module is connected with an image acquisition control module, processes images acquired by an image acquisition mechanism, selects a proper range and a measurement position according to the requirement of the measurement point after acquiring the gray value of each point of an imaging picture, obtains a light transmittance value by normalizing the images acquired by the image acquisition mechanism, and represents the stray light crosstalk performance of an optical fiber image transmission element by using the obtained normalized transmittance value.
The embodiment of the invention carries out data processing on the acquired image through software suitable for testing and analyzing the imaging gray value of the optical fiber image transmission element, such as carrying out data analysis on the image by utilizing an MATLAB simulation software system. The camera imaging system is connected with a computer through a serial port communication wire, collects CCD/CMOS data, performs normalization processing on the data, and converts the gray value on the pixel point into a light transmittance value. Finally, the detection result is displayed on a display, and analysis and judgment can be carried out.
The control unit of the embodiment of the invention comprises: the light source control module is used for controlling the opening and closing of the light source; the image acquisition control module is used for controlling the image acquisition mechanism to work, and the data processing control module is used for controlling the data processing unit to work. The control system controls the whole device to work, realizes automatic detection and calculation of the light transmittance, obtains results which directly reflect the stray light crosstalk performance of a tested product, has high test efficiency and small external influence factors, particularly has small dependence on operators and sample preparation, and has the measurement precision superior to 5 percent.
As a preferred embodiment, the detection system further comprises: and the black cover 112 covers the light source 3 and the measuring template 1, and an opening is formed in one surface, close to the measuring template 1, of the black cover 112 and is used for placing the optical fiber image transmission element 2 to be measured.
In order to avoid the influence of unnecessary light on the accuracy of measurement and stray light on the measurement of gray scale values, a black mask is required to be additionally arranged, the optical fiber image transmission element in the black mask is not required to exceed 1/3 of the total height of the element, and the imaging surface of the optical fiber image transmission element to be measured is not in the black mask so as to acquire the image of the imaging surface of the optical fiber image transmission element to be measured.
The material of the black cover can be the same as or different from that of the cabinet body, the embodiment of the invention does not specifically limit the material of the black cover, and the black cover has the function of preventing stray light from influencing the measurement accuracy of the gray value. In a preferred embodiment, a filter 7 is arranged between the light source 3 and the measuring template 2.
In order to simulate the actually used incident light source of the optical fiber image transmission element to be tested, an optical filter can be added between the incident end face of the product and the parallel white light source to filter the light emitted by the light source, for example, the optical fiber image transmission element used in the night vision technology, the filter adopts a VG9 optical filter or an equivalent green optical filter, and the actually used light source is simulated by adding the green optical filter.
In a preferred embodiment, a diffusing glass 8 is arranged between the filter 7 and the measuring template 1.
When a white point light source is selected, an emulsified diffusion glass (ground glass) is required to be added between the incident end of a product and the optical filter in actual use for light diffusion so as to meet the light source requirement required by the optical fiber image transmission element.
As a preferred embodiment, the image acquisition mechanism comprises a camera 5 and a corresponding lens 4.
The image acquisition mechanism is used for acquiring an image formed by the standard pattern on the optical fiber image transmission element to be detected.
In a preferred embodiment, the camera 5 employs a CCD or CMOS light sensing element.
The digital camera adopts a CCD or CMOS photosensitive element with high bit depth and high resolution to collect real-time images of optical signals passing through the optical fiber image transmission element to be detected.
In a preferred embodiment, the lens 4 is a microscope lens with a zoom lens, and the optical magnification can be adjusted in a range of 2-100 times.
The lens of the digital camera adopts a microscope lens, the lens requires a resolution less than 3 μm and an imaging distortion rate superior to 0.5%, and has a zoom lens, and the optical magnification adjusting range can reach 2-100 times.
As a preferred embodiment, the detection system further comprises: and the detection table is formed by combining granite and a three-dimensional precision mechanical transmission assembly and is used for placing the light source and the measurement template.
The detection platform is formed by combining 00-grade granite and a three-dimensional precision mechanical transmission assembly, can realize that the mobile positioning precision is better than 3.0 mu m, the repeated positioning precision is better than 2.0 mu m, and meets the high-precision detection requirement. The mechanical transmission assembly of the detection table can transmit the detection template, or the light source, or the optical fiber image transmission element, so that the measurement point on the optical fiber image transmission element is positioned on the boundary line of the first area and the second area, and the measurement point is positioned on the axial line of the light source and the image acquisition mechanism.
As a preferred embodiment, the detection system further comprises: and the frame is used for fixing the detection table and the image acquisition mechanism.
The frame adopts an integrated stainless steel material component.
The invention discloses a detection principle of a device for detecting the optical crosstalk transmittance between optical fibers in an optical fiber image transmission element, which comprises the following steps: the optical fiber placed on the intersection line of a USAF test target or a corresponding resolution target is imaged by using a digital imaging device (a high-precision CMOS/CCD camera and a high-resolution microscope lens) (an illumination light source is a transmission light source and covers diffusion glass and a VG9 green color filter), and the gray value of an imaging picture (no less than 8bit digital image) is analyzed and processed by a computer to obtain the light transmittance test result between optical fibers of the optical fiber. The device for detecting the optical crosstalk transmittance between the optical fibers in the optical fiber image transmission element can be used for representing the optical crosstalk performance between the optical fibers in the optical fiber image transmission element.
As shown in fig. 1 to 4, an embodiment of the present invention further provides a method for characterizing the stray light crosstalk performance of an optical fiber image transmission element by using the aforementioned apparatus for detecting the optical crosstalk transmittance between optical fibers in the optical fiber image transmission element, which specifically includes the following steps:
s1, respectively arranging a light source 3 and an optical fiber image transmission element 2 to be detected on two sides of the measuring template 1, and enabling a first surface 2B of the optical fiber image transmission element 2 to be detected to be tightly attached to 1A of the measuring template 1;
the measuring template 1 consists of a first area 11 and a second area 12; the transmittance of the first region 11 is less than that of the second region 12, and the difference between the two transmittances is more than 90%;
further preferably, the optical fiber 21 in the optical fiber image transmission element 2 to be measured is perpendicular to the measuring template 1.
The embodiment of the invention does not specifically limit the optical fiber image transmission element to be detected, the optical fiber image transmission element can be straight, conical or bent, and a single optical fiber in the optical fiber image transmission element can be straight, twisted or conical, so long as the image of the template can be transmitted to the second surface, and the optical crosstalk performance of any optical fiber image transmission element can be represented by the method.
In order to make the first surface of the optical fiber image transmission element to be measured tightly fit with the measuring template, firstly injecting a proper amount of coupling oil on the measuring template, and then fitting with the optical fiber image transmission element to be measured. The tight fit ensures that no pore exists between the optical fiber image transmission element to be measured and the measuring template, and the optical fiber image transmission element and the measuring template are completely fitted together.
S2, in a light-shielding environment 111, after the light 31 emitted from the light source 3 sequentially passes through the measurement template 1 and the optical fiber image transmitting element 2 to be detected, the first region 11 and the second region 12 of the measurement template 1, which are overlapped with the optical fiber image transmitting element to be detected, form an image 1' on the second surface 2A of the optical fiber image transmitting element 2 to be detected; the second surface 2A is a surface of the optical fiber image transmitting element 2 to be tested, which is opposite to the first surface 2B;
it should be noted that, in the embodiment of the present invention, the first surface and the second surface of the optical fiber image transmitting element to be tested are two surfaces that are disposed opposite to each other, where the first surface and the second surface are only used to distinguish two different surfaces, and are not limited to them.
As a preferred embodiment, as shown in fig. 4 and 5, in step S2, the forming an image 1' of the first region 11 and the second region 12 on the measurement template 1 on the second surface 2A of the optical fiber image transmitting element 2 to be measured includes: selecting any point on the second surface 2A of the optical fiber image transmission element 2 to be measured as a measurement point, moving the optical fiber image transmission element 2 to be measured or the measurement template 1 to make the measurement point located on the boundary line LG between the first area 11 and the second area 12, and obtaining a corresponding first image 11 'and a second image 12' on the second surface 2A of the optical fiber image transmission element 2 to be measured, wherein the first image 11 'corresponds to the first area 11, and the second image 12' corresponds to the second area 12.
It is further preferred that the measurement point is located at a midpoint O of a boundary line LG between the first region 11 and the second region 12.
It should be noted that the area covered by the optical fiber image transmitting element to be measured is not larger than the first area and the second area, that is, the measuring template is larger than the optical fiber image transmitting element to be measured, and the measuring point on the optical fiber image transmitting element to be measured needs to be located on the boundary line LG between the first area and the second area, so the first image and the second image are not necessarily the full image of the first area and the second area, and only the first area and the second area which are overlapped with the optical fiber image transmitting element to be measured can be imaged on the second surface.
S3, collecting the image 1 ', processing the image 1 ' to obtain the gray value of each pixel point on the image 1 ';
in the embodiment of the invention, the digital camera is used for collecting the image of the second surface of the optical fiber image transmission element to be detected.
S4, carrying out normalization processing on the gray value to obtain a normalized transmittance value of any position point, and representing the stray light crosstalk performance of any position point on the optical fiber image transmission element by using the obtained normalized transmittance value.
As a preferred embodiment, in step S4, the normalization process includes:
selecting a measurement range containing the measurement points, calculating an average gray value in the measurement range in the direction parallel to the boundary line, selecting the maximum average gray value and the minimum average gray value, and performing normalization calculation to obtain a normalized transmittance value of any position point in the measurement range; the measurement range includes the first image 11 'and the second image 12', and the measurement point is located on a boundary line between the first image 11 'and the second image 12'.
The image normalization method adopts linear function conversion, and the expression is as follows:
y＝(x-MinValue)/(MaxValue-MinValue)
description of the drawings: x and y are values before and after conversion respectively, and MaxValue and MinValue are maximum values and minimum values of the samples respectively.
In the embodiment of the present invention, x is a gray value obtained from an image, y is a value obtained by performing a normalization calculation on the gray value, that is, a normalized transmittance value, MaxValue is a maximum average gray value in a parallel direction with the boundary line in the measurement range, and MinValue is a minimum average gray value in a parallel direction with the boundary line in the measurement range.
Calculating the normalized transmittance value and the change trend thereof: after the gray values of all points of the imaging picture are obtained, a proper measuring range and a proper measuring position are selected according to the requirements of the measuring points, and meanwhile, the gray values of all pixel points in the range are obtained. Therefore, the camera is required to have a high pixel value, a small pixel, a strong detail resolution capability, and a large bit depth. The average gray value of the selected range is obtained through computer calculation, and then the change trend graph is made on the average value to obtain the change trend graph of the gray, as shown in fig. 6, 7 and 8.
As a preferred embodiment, as shown in fig. 4 and 5, the measuring range is a circle 91 with the measuring point as the center; alternatively, the measurement range is a square 92 with the boundary LG as the center line.
In the embodiment of the invention, the determination of the measurement range can select a square area or a circular area, and the shape and the area of the first area are completely the same as those of the second area. The first area is square, and the second area is square; or, the first area is circular and the second area is circular. The measuring range is symmetrical by taking the boundary line as a central line, the shape and the size of the two sides are the same, and the measuring range can enable the representation result to be more accurate and enable the image to be more visual during actual calculation and drawing.
In a preferred embodiment, the measuring point coincides with a midpoint O of a boundary line LG between the first region 11 and the second region 12 on the measuring template 1.
The change of the gray value represents the change trend of the light transmittance: the key of the method is how to describe the change trend of the gray value by using a universal index. The maximum value and the minimum value of the average gray values in the measurement range are selected, the average gray values in the measurement range are all normalized to be numerical values from 0 to 1, the numerical values are called normalized transmittance values, a change trend graph is made according to the numerical values, and the normalized transmittance value of any position in the measurement range is further obtained. Therefore, the normalized transmittance value at a certain position can be selected as an index for evaluating the stray light crosstalk performance between the optical fibers in the optical fiber image transmission element according to the individual requirements of the use performance of the device. When the position to be measured is in the first region with low transmittance, the larger the normalized transmittance value in the region is, the stronger the optical crosstalk performance between the optical fibers in the optical fiber image transmission element is, and the weaker the optical crosstalk performance between the optical fibers in the optical fiber image transmission element is. When the position to be measured is located in the second region with high transmittance, the smaller the normalized transmittance value in the region is, the stronger the optical crosstalk performance between the optical fibers in the optical fiber image transmission element is, and the weaker the optical crosstalk performance between the optical fibers in the optical fiber image transmission element is.
In the embodiment of the invention, the pixel offset depends on the size of the pixel point of the camera, and the minimum offset displacement of each pixel is taken as the pixel number x the size of the pixel.
In a preferred embodiment, the light 31 emitted by the light source 3 is filtered before it impinges on the 1B of the measuring template 1.
In order to simulate the actually used incident light source of the optical fiber image transmission element to be tested, an optical filter can be added between the incident end face of the product and the parallel white light source to filter the light emitted by the light source, for example, the optical fiber image transmission element used in the night vision technology, the filter adopts a VG9 optical filter or an equivalent green optical filter, and the actually used light source is simulated by adding the green optical filter.
In a preferred embodiment, the light beam impinging on 1B of the measuring template 1 is diffuse light.
When the second point light source is selected, an emulsified diffusion glass (ground glass) is required to be added between the incident end of the product and the optical filter in actual use for light diffusion so as to meet the light source requirement required by the optical fiber image transmission element.
The embodiment of the invention shields the incident light source, and except the light incident to the optical fiber image transmission element, other light is shielded to prevent stray light from influencing the gray value measurement.
The test principle of the method of the embodiment of the invention is as follows: based on an image formed by transmitting a standard image through an optical fiber image transmission element, gray levels of different pixel points are obtained by analyzing gray levels of image data, the gray levels at different positions are normalized to obtain normalized transmittance values, and the normalized transmittance values are utilized to represent stray light crosstalk performance among optical fibers in the optical fiber image transmission element.
The invention realizes automatic detection and calculation, has high test efficiency, small external influence factor and small dependence on operators and sample preparation, can realize direct measurement on products, directly reflects the stray light crosstalk performance of the tested products as a result, and effectively improves the accuracy and the repeatability of the detection result.
The invention aims to invent a device and a method for directly representing the stray light crosstalk performance between optical fibers in an optical fiber image transmission element, which are stable, reliable, simple and easy to operate, and hope to establish corresponding specifications and standards and corresponding standard detection equipment based on the method. At present, no relevant patent or literature is known for calculating the normalized transmittance value of different position points based on the measurement of the gray value of an image and representing the imaging definition by the value.
The present invention will be further described with reference to the following specific examples, which should not be construed as limiting the scope of the invention, but rather as providing those skilled in the art with certain insubstantial modifications and adaptations of the invention based on the teachings of the invention set forth herein.
Example 1
A method for detecting the optical crosstalk transmittance among optical fibers in an optical fiber image transmission element by using the device specifically comprises the following steps: 1) starting control software of the optical fiber image transmission element contrast test system;
2) injecting a proper amount of coupling oil on a USAF test target, and putting an optical fiber image transmission element to enable the optical fiber to be tightly attached to the test target;
3) opening the operation door of the camera bellows, and placing the jointed test target and the optical fiber image transmission element on the optical working platform; the test target and the optical fiber image transmission element are relatively positioned by the clamp, and the clamp is only required to be arranged on a positioning pin on the workbench;
4) closing the dark box operation door to enable the optical workbench and the whole test system to be in a closed dark operation environment, and filtering interference influence of external natural light;
5) clicking a start button on control software, firstly obtaining an image of a light source in a closed state, then turning on a transmission bottom light source by a system, taking the middle point of a boundary line of a pattern on a test target as a central position, obtaining an image of a measuring point at the central position, respectively transmitting the obtained image data to a computer at any position of 5.25mm and 8.125mm away from the central position, and obtaining a gray value of each pixel point in the image data; determining a measuring range, calculating the average gray value in the measuring range in the direction parallel to the boundary line, then selecting the maximum and minimum average gray values to perform normalization processing to obtain a normalized transmittance value of 0-1, and obtaining the normalized transmittance of the optical fiber image transmission element at different positions through the calculation of built-in software; finally, test results are obtained, and a part of representative results are listed in table 1, wherein in table 1, 0.000mm refers to the center position; 5.250mm refers to any position point 5.25mm away from the center; 8.125mm means any position point 8.125mm from the center position, and the normalized transmittance-position curve is obtained by plotting the data in Table 1, as shown in FIG. 6, a represents the normalized transmittance-position curve at the center position of 0.000mm, b represents the normalized transmittance-position curve at 5.25mm from the center position, and c represents the normalized transmittance-position curve at 8.125mm from the center position;
6) and recovering the zero position of the machine, turning off the power supply, taking out the optical fiber image transmission element, cleaning the resolution test target and completing the test work.
TABLE 1 Gray values of pixels and normalized transmittance values within the measurement range
It can be seen from table 1 and fig. 6 that the gray value of any point of the optical fiber image transmission element and its normalized transmittance value can be obtained by the method of the present invention. The area with high gray value is a white area, the area with low gray value is a black area, the size of the white area light string to the black area at the black-white boundary can be represented by obtaining the change trend of the light transmittance when passing through the black area and the white area, namely the light crosstalk performance between the optical fibers, when the normalized transmittance value of the black area is larger, the light crosstalk performance is stronger, and otherwise, the light crosstalk performance is weaker. Therefore, the crosstalk performance of light among the optical fibers is from weak to strong in sequence as follows: curve a, curve b and curve c.
Example 2
A method for detecting the optical crosstalk transmittance between optical fibers in an optical fiber image transmission element verifies the accuracy of a detection result, and specifically comprises the following steps:
1) starting control software of the optical fiber image transmission element contrast test system;
2) injecting a proper amount of coupling oil on a USAF test target, and putting an optical fiber image transmission element to enable the optical fiber to be tightly attached to the test target;
3) opening the operation door of the camera bellows, and placing the jointed test target and the optical fiber image transmission element on the optical working platform; the test target and the optical fiber image transmission element are relatively positioned by the clamp, and the clamp is only required to be arranged on a positioning pin on the workbench;
4) closing the dark box operation door to enable the optical workbench and the whole test system to be in a closed dark operation environment, and filtering interference influence of external natural light;
5) clicking a start button on control software, firstly obtaining an image under a light source closed state, then, turning on a transmission bottom light source by a system to obtain an image at a central position, transmitting all gray data corresponding to the obtained image to a computer, selecting a square area of 2.2 multiplied by 2.2mm with the central position as a central point as a measurement range, averaging gray values in a parallel black-white boundary line direction, carrying out normalization processing on the maximum and minimum average gray values in the square area of 2.2 multiplied by 2.2mm to obtain a normalized transmittance value of 0-1, and obtaining a position coordinate through pixel offset in built-in software so as to obtain the normalized transmittance of the optical fiber image transfer element on different displacements; finally, a first test result is obtained, the average gray value and the normalized transmittance of the pixel points within the square range of 2.2 × 2.2mm are listed in table 2, and the corresponding normalized transmittance-position curve is shown in fig. 7, where d in fig. 7 represents the normalized transmittance-position curve at the central position of 0.000mm of the first measurement. If the normalized transmittance at the position offset of 0.1mm is selected as an index for representing the optical crosstalk performance, the optical crosstalk transmittance at the center position of the first measurement is 0.0084;
6) and recovering the zero position of the machine and turning off the power supply. Clicking a starting button on the control software again, firstly obtaining an image under the light source closing state, then turning on the transmission bottom light source by the system, obtaining an image at the central position, transmitting data at the central position to a computer, selecting a gray value in the same range as that in the step 5), calculating an average gray value in the direction parallel to the black-white boundary line, and then selecting the maximum and minimum average gray values for normalization calculation; the normalized transmittance of the optical fiber image transmission element at different displacements is obtained through the calculation of the built-in software; finally, a second test result is obtained, the average gray value and the normalized transmittance of the pixel points in the measurement range are listed in table 2, and the corresponding normalized transmittance-position curve is shown in fig. 8, where in fig. 8, e represents the normalized transmittance-position curve at the central position of 0.000mm in the second measurement. If the normalized transmittance at a position shifted by 0.2991mm is selected as an index for characterizing the optical crosstalk performance, the optical crosstalk transmittance at the center position of the second measurement is 0.0082. Compared with 0.0083 of the optical crosstalk transmittance at the same position at the last time, the error is 1.22%.
7) And recovering the zero position of the machine, turning off the power supply, taking out the optical fiber image transmission element, cleaning the resolution test target and completing the test work.
TABLE 22.2 X2.2mm square range pixel mean gray scale value and normalized transmittance
As can be seen from table 2, fig. 7 and fig. 8, the accuracy of the optical crosstalk transmittance value measured by the apparatus is high, and the repeatability is good.
The device can realize automatic detection and calculation of the light transmittance by arranging the detection system control unit and the data processing unit, the obtained result directly reflects the stray light crosstalk performance of a detected product, the test efficiency is high, the external influence factors are small, the dependence on operators and sample preparation is small, and the measurement precision is superior to 5%.
In the description of the present invention, it should be noted that the terms "upper", "lower", "horizontal", "vertical", and the like indicate orientations or positional relationships based on methods or positional relationships shown in the drawings, and are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
In addition, in the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
It will be appreciated that the relevant features of the devices described above may be referred to one another. In addition, "first", "second", and the like in the above embodiments are for distinguishing the embodiments, and do not represent merits of the embodiments.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.
Claims (10)
1. An apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image transmitting element, comprising: a detection system and a control system, characterized in that,
the detection system comprises:
the cabinet body is used for preventing external light from entering the detection system and providing a light-shading environment for detection;
a light source for providing light required for detection;
the measuring template is used for providing a standard pattern for detection, and consists of a first area and a second area, wherein the transmittance of the first area is less than that of the second area, and the difference between the transmittances of the first area and the second area is greater than 90%;
when the optical fiber image transmission element is used, a first surface of the optical fiber image transmission element to be detected is attached to the measuring template, light rays emitted by the light source sequentially pass through the measuring template and the optical fiber image transmission element to be detected, and then a first image and a second image are formed on a second surface, opposite to the first surface, of the optical fiber image transmission element to be detected, wherein the first image corresponds to the first area, and the second image corresponds to the second area; and
the image acquisition mechanism is used for acquiring an image formed by the standard pattern on the optical fiber image transmission element to be detected;
the light source, the measuring template and the image acquisition mechanism are sequentially arranged in the cabinet body;
the light source and the image acquisition mechanism are coaxially arranged, and the measuring template is perpendicular to the axis of the light source;
the control system includes:
the image data processing unit is connected with the image acquisition mechanism and used for processing the image acquired by the image acquisition mechanism to obtain a light transmittance value; and
and the control unit is connected to the detection system and the image data processing unit and is used for controlling the detection system and the image data processing unit to operate.
2. The apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image transmitting element according to claim 1, wherein the detection system further comprises:
the black cover covers the light source and the measuring template, and one surface of the black cover close to the measuring template is provided with an opening for placing an optical fiber image transmission element to be measured.
3. The apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image transmission element according to claim 1, wherein an optical filter is disposed between the light source and the measurement template.
4. The apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image transmission element according to claim 3, wherein a diffusion glass is disposed between the optical filter and the measurement template.
5. The apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image transmission element according to claim 1, wherein the transmittance of the first region is < 2% and the transmittance of the second region is > 95%.
6. The apparatus for detecting optical crosstalk transmittance between optical fibers of an optical fiber image transmission element according to claim 1, wherein the image capturing mechanism comprises a camera and a corresponding lens.
7. The apparatus for detecting the optical crosstalk transmittance between optical fibers in an optical fiber image transmission element according to claim 6, wherein the camera employs a CCD or CMOS photosensitive element.
8. The apparatus for detecting the optical crosstalk transmittance between optical fibers in an optical fiber image transmission element according to claim 6 or 7, wherein the lens is a microscope lens with a zoom lens, and the adjustment range of the optical magnification can reach 2-100 times.
9. The apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image transmitting element according to claim 1, wherein the detection system further comprises:
and the detection table is formed by combining granite and a three-dimensional precision mechanical transmission assembly and is used for placing the light source and the measurement template.
10. The apparatus for detecting optical crosstalk transmittance between optical fibers in an optical fiber image transmitting element according to claim 9, wherein the detection system further comprises:
and the frame is used for fixing the detection table and the image acquisition mechanism.
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