CN107843213B - Confocal auto-collimation center deviation and curvature radius measuring method and device - Google Patents
Confocal auto-collimation center deviation and curvature radius measuring method and device Download PDFInfo
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Abstract
The invention belongs to the technical field of optical precision machining detection, and relates to a confocal auto-collimation center deviation and curvature radius measuring method and device. The method comprises the steps of utilizing a confocal chromatography focusing method to focus the sphere center and the vertex of a measured lens, measuring the position of the focus by a position detection system, calculating to obtain the curvature radius of the measured lens, utilizing an auto-collimation method to detect the path of reflected light on a detection surface in the rotation process of the measured lens so as to obtain the eccentricity of the measured lens, and then integrating the eccentricity and the curvature radius to calculate to obtain the eccentricity. The invention firstly applies the confocal chromatography focusing principle to the field of center deviation measurement, improves the traditional auto-collimation center deviation measurement method, invents the confocal auto-collimation center deviation and curvature radius measurement device, and the measurement result shows that the method has the advantages of high measurement precision, large measuring range, high efficiency and no need of repeated clamping, and can be used for the precise processing detection of the center deviation and the curvature radius of the optical element.
Description
Technical Field
The invention belongs to the technical field of optical precision machining detection, combines a confocal chromatography focusing technology with an auto-collimation center deviation measurement technology, relates to a method and a device for measuring the confocal auto-collimation center deviation and curvature radius, and can be used for measuring the center deviation and curvature radius of a spherical lens and a spherical reflector and detecting the center deviation of a lens group and fitting an optimal optical axis.
Technical Field
The eccentricity of the optical element is an error which has a great influence on the quality of the whole optical assembly and is difficult to control in the manufacturing error of an optical instrument. The presence of decentration destroys the centration of the optical system, resulting in astigmatism and distortion asymmetry of the image. Therefore, the method has important significance for accurate measurement and correction of the decentration. Existing methods for measuring the center deviation are classified into two types, namely a contact method and a non-contact method. The contact method is only suitable for the lens processing stage, and comprises a spherical contact centering method and an aspheric contact centering method. The spherical contact type centering method is characterized in that a coaxial chuck is used for clamping two spherical surfaces by means of spring force, and then a spherical lens is rotated for centering processing, so that automatic centering can be realized, the centering precision is low, and eccentric data cannot be measured; the aspheric surface contact type centering method introduces a point detection probe to measure the axial position of the lens and a piezoelectric displacement sensor to measure the transverse position of the lens, the centering precision can reach 0.5', and accurate eccentric data can not be obtained. The non-contact method can measure the processed lens, and the method utilizes the optical characteristics of the lens to detect, and comprises the methods of laser centering measurement, interference eccentricity measurement, autocollimation eccentricity measurement and the like.
The laser centering measurement method is a method for measuring eccentricity by hitting a laser beam on the surface of a lens and obtaining the surface appearance of the lens by means of reflection of the surface of the lens, and comprises a point scanning centering measurement method, a line scanning centering measurement method, a structured light centering measurement method and the like. The point scanning centering measurement method scans the surface of a lens point by utilizing thin beams, records the height information of each scanning point after the beams are reflected by the surface of the lens, and then reconstructs the surface appearance of the lens by integrating the height information of all the scanning points so as to measure the eccentricity of the lens, and the method can measure the eccentricity of a spherical lens and an aspherical lens, but has long scanning time and low measurement efficiency and can only measure the eccentricity of a single surface; the line scanning centering measurement method utilizes line laser to scan the surface of a lens, and then reconstructs the surface appearance to obtain the eccentricity of the lens, and the method improves the scanning efficiency, but can only measure the eccentricity of a single surface; the structured light centering measurement method is characterized in that structured light is projected on the surface of a lens, meanwhile, the height information of each point on the surface is obtained, then the height information of each point is synthesized to reconstruct the surface appearance, and the eccentricity is measured.
The interference eccentricity measurement method comprises an equal-thickness fringe eccentricity measurement method, a tuning optical angular momentum eccentricity measurement method, a circular light path interference center eccentricity measurement method and the like. The equal-thickness fringe eccentricity measurement method obtains an interference pattern through equal-thickness interference between a lens to be measured and a standard mirror, obtains the eccentricity of the lens to be measured through the change of fringes in the interference pattern, and further obtains a central deflection angle, the measurement precision of the method can reach 0.12', but the method has high requirements on measurement environment, and when the environment is interfered, the fringes can generate obvious distortion, so that the method cannot be applied to complex processing and assembling environments; the method for tuning the light angular momentum eccentricity uses linear polarization laser to generate spiral light beams through a spiral phase plate, a diffraction pattern is generated after the light beams penetrate through a lens to be measured, the angular momentum is resolved through secondary diffraction fringes in the diffraction pattern, the central deviation of the lens is obtained through the deflection of the angular momentum, the measuring precision can reach 0.1', the method simplifies a measuring light path, and a strict laboratory environment is still needed; the circular light path interference center deviation measuring method utilizes a circular light path, a measured lens is placed in a measuring arm of the interference light path, measuring light can be incident to a measured lens in the positive and negative directions to generate interference respectively by means of a spectroscope, the center deviation of the measured lens is obtained through the separation condition of the centers of two interference fringes, the measuring precision can reach 0.1', the method improves the light energy utilization rate of the interference light path, and the method cannot be separated from a strict laboratory environment.
The autocollimation central deviation measuring method is a method for measuring the eccentricity by means of the change of the focus imaging of a full-aperture light beam, and comprises a reflection type autocollimation central deviation measuring method, a collimation polarization central deviation measuring method and the like. The method can measure the eccentricity of a single lens, can position other lenses in a lens group and measure the eccentricity of the lens group, but can calculate the center offset only by needing optical parameters such as curvature radius, thickness, interval and the like of all lenses in the lens group, and the measurement precision can reach 0.2'; the collimation polarization central deviation measurement method is characterized in that a measured lens is placed between two linear deflectors and a lambda/2 wave plate, white light penetrates through the measured lens after passing through the linear deflectors, enters a detection surface after passing through the lambda/2 wave plate and the other linear deflector, a polarization diagram is obtained on the detection surface, and the central deviation is obtained through the stripes and the color change of the polarization diagram, the measurement precision of the method can reach 0.14', the measured lens does not need to be rotated, but the method can only measure the central deviation of a single lens and cannot obtain the central deviation of a lens group.
Compared with other measuring methods, the auto-collimation center deviation measuring method has the advantages of high measuring efficiency and strong anti-interference capability, and becomes the mainstream center deviation measuring method. However, the auto-collimation decentration method still has the following problems:
1) before the measurement center is deviated, the curvature radius of the lens needs to be measured by other methods, and measurement errors are introduced by repeatedly installing the card;
2) the axial positioning precision is poor, the lens cannot be accurately positioned at the spherical center of the lens, and a measurement error is introduced due to centering offset;
3) the chromatographic positioning cannot be realized, when the center deviation of the lens group is measured, the spherical center position of the next lens is positioned, optical parameters of all the previous lenses need to be obtained in advance, the calculation is complex, the positioned position is a theoretical position, and the positioning is inaccurate.
Aiming at the problems of an auto-collimation center deviation measuring method, a confocal auto-collimation center deviation and curvature measuring method and a confocal auto-collimation center deviation and curvature measuring device are provided, the method utilizes the chromatographic focusing advantage of the confocal method to improve the axial positioning precision, and particularly can accurately position a lens group consisting of a plurality of lenses and the spherical center of an additional lens; the curvature radius measurement and the center deviation measurement can be simultaneously completed, the repeated clamping of the measured lens is avoided, the measurement process is simplified, and the measurement precision is improved.
Disclosure of Invention
The invention aims to solve the problem of high-precision processing and detection of center deviation of spherical lenses and spherical reflectors, and provides a confocal auto-collimation center deviation and curvature radius measuring method and device.
The method has the core idea that the sphere center and the vertex of the measured lens are focused by a confocal chromatography focusing method, the position of the focus is measured by a position detection system, the curvature radius of the measured lens is obtained by calculation, the path of reflected light on a detection surface in the rotation process of the measured lens is detected by an auto-collimation method so as to obtain the eccentricity of the measured lens, and then the eccentricity and the curvature radius are synthesized to obtain the eccentricity. The high-precision and high-efficiency processing detection of the center deviation of the lens and the spherical reflector is realized.
The purpose of the invention is realized by the following technical scheme.
The invention provides a confocal auto-collimation center deviation and curvature radius measuring method, wherein a high-axial positioning capability confocal detection system focuses the axial position of a measured mirror at a focusing light spot, a high-precision air floatation rotation system drives the measured mirror to rotate, and after the measured mirror rotates for a circle, the auto-collimation centering detection system records the radial position of the focusing light spot reflected by the measured mirror to obtain the eccentricity; the high-precision distance measuring system records the position of a focusing light spot when the focusing light spot is focused on the vertex and the spherical center of a measured mirror to obtain a curvature radius, then integrates the curvature radius and the eccentricity, and calculates to obtain the center deviation, and comprises the following steps:
the method comprises the following steps that firstly, a point light source generating system emits light beams, the light beams penetrate through a first spectroscope and are reflected by a second spectroscope, then the light beams penetrate through a collimating objective lens and are changed into parallel light, and the parallel light is focused at a front focal point of a focusing objective lens through the focusing objective lens to form a measuring light cone;
moving the measuring light cone along the measuring optical axis to focus the light cone on the spherical center of the measured lens, scanning the light cone near the spherical center, reflecting the light beam by the measured lens, entering a confocal detector to measure a confocal intensity response curve, focusing by means of the characteristic that an extreme point of the confocal curve accurately corresponds to a focusing point, and recording the position of a focusing light spot as z1；
Starting the air-floatation rotating shaft to drive the detected mirror to rotate, focusing the light beam on the detection surfaces of the confocal detector and the first detector after the light beam is reflected by the detected mirror, enabling the path of the reflected light beam on the detection surface of the first detector to be approximately a circle after the light beam rotates for a circle, and taking n points A on the path1，A2…AnPerforming circle fitting, and recording the radius of a fitting circle as a;
moving the measuring light cone along the measuring optical axis to focus the light cone on the vertex of the measured lens, scanning the light cone near the vertex, focusing by means of the characteristic that the extreme point of the confocal curve corresponds to the focusing point accurately, and focusing the light coneThe position of the time-focused spot is noted as z2Twice focal point z1And z2The distance r between the two is the curvature radius of the measured mirror, and r is equal to z1-z2；
Step five, according to the curvature radius r of the measured lens, the radius a of the fitting circle and the magnification β of the focusing objective lens1Magnification β of the second microscope objective2β, the eccentricity is calculated to be
Center deflection
The invention provides a confocal auto-collimation decentration and curvature radius measuring device, which is characterized in that: the device comprises a point light source generating system, a first spectroscope arranged along the emergent direction of a light beam, a second spectroscope arranged along the transmission direction of the first spectroscope, a collimating objective arranged along the reflection direction of the second spectroscope, a focusing objective positioned in front of the collimating objective, a first detector positioned at the rear focal point of the collimating objective in the reflection direction of the second spectroscope, and a confocal detector positioned in the reflection direction of the first spectroscope; the device comprises a one-dimensional translation system for driving a measuring host to translate along a measuring optical axis, a position recording system for recording the position of the measuring host, an air floatation rotating shaft for driving a measured mirror to rotate, and a platform for placing the air floatation rotating shaft and the one-dimensional translation system.
The invention provides a confocal auto-collimation decentration and curvature radius measuring device, which is characterized in that: the confocal detector consists of a second microscope objective and a second detector, the second detector is positioned at the focal position of the second microscope objective, and three pixels at the center of a light spot on a detection surface are taken as the detection area of the confocal detector.
The invention provides a confocal auto-collimation decentration and curvature radius measuring device, which is characterized in that: the point light source generating system can be composed of a pulse laser, a first microscope objective lens positioned in the emitting direction of the laser, a pinhole positioned at the focus position of the first microscope objective lens and a reticle positioned in front of the pinhole.
The invention provides a confocal auto-collimation decentration and curvature radius measuring device, which is characterized in that: the position recording system can be composed of a length measuring interferometer and a total reflection prism arranged on a measuring host.
The invention provides a confocal auto-collimation decentration and curvature radius measuring device, which is characterized in that: the one-dimensional translation system can be composed of an air-floating guide rail, a sliding block for installing the measuring host and a driving lead screw for driving the sliding block to translate on the air-floating guide rail.
The confocal auto-collimation center deviation and curvature radius measuring method and device provided by the invention combine curvature radius measurement into a center deviation measuring process, can simultaneously measure the curvature radius and the center deviation of the measured lens, improve the measuring efficiency, avoid the measuring error caused by repeated clamping, and improve the measuring precision.
Advantageous effects
Compared with the prior art, the invention has the following innovation points:
1. the confocal chromatography focusing method is applied to the field of central deviation measurement for the first time, the characteristic that an extreme point of a confocal curve accurately corresponds to a focus point is used for focusing, the centering precision is improved, and the measurement error caused by defocusing is avoided;
2. the curvature radius measuring process is integrated into the center deviation measuring process, so that the measuring process is simplified, the measuring efficiency is improved, and meanwhile, the measuring error caused by repeated clamping is avoided;
3. the system objective and the microscope objective amplify the area to be measured twice, so that the reading error introduced by a single pixel is reduced, and the measurement error introduced by axial shaking is reduced by using the air-floating rotating shaft with stable rotation, thereby improving the measurement precision.
Compared with the prior art, the invention has the following advantages:
1. measurement errors caused by defocusing and repeated clamping are avoided, the measurement errors caused by pixel reading and axial shaking are reduced, and the measurement precision of center deviation is improved;
2. in the center deviation measurement method, the curvature radius measurement process required in center deviation measurement is integrated, so that the measurement efficiency is improved;
3. the measuring main machine is arranged on the air floatation guide rail, and an air floatation rotating shaft with a large turning radius is adopted, so that the measuring range is expanded, the volume of the measuring main machine is reduced, and the overall dimension is only 100 multiplied by 200 multiplied by 500 mm;
4. by means of the characteristic that the extreme point of the confocal curve corresponds to the focus point accurately, accurate positioning is achieved, the chromatographic positioning advantage is obvious in the center deviation measurement of the lens group, complex theoretical calculation is avoided, and meanwhile centering accuracy is improved.
Drawings
FIG. 1 is a schematic diagram of the confocal auto-collimation decentration and curvature radius measurement principle;
FIG. 2 is a schematic view of a confocal auto-collimation radius of curvature measurement light cone being focused at the vertex of a concave lens;
FIG. 3 is a schematic diagram of a confocal auto-collimation decentration and radius of curvature measurement device;
FIG. 4 is a schematic diagram of a confocal auto-collimation decentration and curvature radius measuring device for convex lens measurement;
FIG. 5 is a schematic diagram of a confocal auto-collimation decentration and curvature radius measuring device for lens group measurement;
wherein: 1-pulse laser, 2-first microscope objective, 3-pinhole, 4-reticle, 5-first spectroscope, 6-second spectroscope, 7-collimation objective, 8-focusing objective, 9-measured lens, 10-air-floating rotating shaft, 11-second microscope objective, 12-second detector, 13-first detector, 14-measuring host, 15-one-dimensional translation system, 16-position recording system, 17-point light source generating system, 18-confocal detector, 19-length measuring interferometer, 20-total reflection prism, 21-air-floating guide rail, 22-air-floating slide block, 23-driving screw rod, 24-base, 25-main control computer and 26-measuring optical axis.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
The basic idea of the invention is to use the confocal chromatography focusing method to focus the sphere center and the vertex of the measured lens, measure the position of the focus by means of the position detection system, calculate the curvature radius of the measured lens, use the auto-collimation method to detect the path of the reflected light on the detection surface in the rotation process of the measured lens so as to obtain the eccentricity of the measured lens, and then calculate the eccentricity by integrating the eccentricity and the curvature radius. The high-precision and high-efficiency processing detection of the center deviation of the lens and the spherical reflector is realized.
Example 1
As shown in fig. 1, fig. 2 and fig. 3, the confocal auto-collimation decentration and curvature radius measuring method comprises the following measuring steps:
before measurement, firstly, the measurement optical axis 26 is adjusted to coincide with the axis of the air-floatation rotating shaft 10, the measurement optical axis 26 is parallel to the air-floatation guide rail 21, and the optical axis of the length measurement interferometer 19 coincides with the measurement optical axis 26. During detection, a plane mirror is used as a detected mirror 9 and placed in the center of the air-floating rotating shaft 10, and the driving screw 23 is started to drive the sliding block 22 to enable a measuring light cone emitted by the measuring host 14 to be focused on the surface of the plane mirror; and starting the air floatation rotating shaft 10 to drive the plane mirror to rotate, observing the running path of the light spots on the first detector 13 and the confocal detector 18, and adjusting the axial surface of the air floatation rotating shaft 10 so that the light spots are always positioned in the same pixel in the rotating process.
During measurement, measurement software in the main control computer 25 is started to complete hardware communication with the pulse laser 1, the first detector 13, the second detector 12, the length measuring interferometer 19, the air floatation rotating shaft 10 and the driving lead screw 23. Parallel light emitted by the 533nm light source is converged to a first pinhole 3 of a front focus of the objective lens to form a point light source after passing through the first microscope objective lens 2, is changed into a cross light beam after passing through the reticle 4, is changed into parallel light after being transmitted by the first spectroscope 5 and reflected by the second spectroscope 6, and is changed into a measuring light cone through the collimating objective lens 7 for measurement.
The driving screw 23 drives the slide block 22 to move along the optical axis 26 to measure the light cone, so that the light cone is focused at the spherical center of the measured lens 9, the light cone scans near the spherical center, after being reflected by the measured lens 9, the light cone is converged at the front focal point of the focusing objective lens 8, and enters the measuring host 14 again, one path of light is transmitted by the second beam splitter 6 to enter the first detector 13, the other path of light is reflected by the second beam splitter 6 and the first beam splitter 5 to enter the confocal detector 18, and the light intensity response curve is measured by the second detector 12 and the position recording system 16, so as to accord with the Gaussian distributionThe length measuring interferometer 19 records the extreme point z of the response curve2I.e. the position of the spherical center of the test mirror 9; starting the air-float rotating shaft 10 to drive the tested mirror 9 to rotate, wherein the path of the reflected light beam on the confocal detector 18 is approximate to a circle during the rotation process, and taking a point A on the path1，A2…AiPerforming circle fitting by using a least square method, wherein the center of the fitting circle is (x)OyO), radius a, magnification β of the focusing objective 71Magnification β of second microscope objective 112β, the eccentricity χ is:
χ＝a/(2β)
the driving lead screw 23 pushes the slide block 22 to slide along the guide rail 21, so that the light cone is focused at the vertex position of the measured mirror 9, the light cone scans near the vertex, after being reflected by the measured mirror 9, the light cone enters the first detector 13 and the confocal detector 18, the light intensity response curve is measured by the second detector 12 and the position recording system 16 and accords with Gaussian distribution, and the length measuring interferometer 19 records the extreme point z of the response curve1I.e. the position of the vertex of the test mirror 9. Master control computer 28 synthetic vertex z1And the center of sphere z2The radius of curvature r is calculated as:
r＝|z1-z2|
calculating the center deviation by integrating the curvature radius r and the eccentricity chi
Comprises the following steps:
example 2
As shown in fig. 4, the confocal auto-collimation decentration and curvature radius measuring method can also measure the curvature radius and decentration of the convex lens, and the measuring steps are the same as those in embodiment 1:
firstly, the axial line of an air-floating rotating shaft 10 is adjusted and coincided with an optical axis 26 of a measuring host 14, a measured mirror 9 is a convex lens and is arranged at the center of the air-floating rotating shaft 10, the measuring host 14 is moved along the direction of the measuring optical axis 26, so that measuring light cones are respectively focused at the vertex and the spherical center of the measured mirror 9, and a recording vertex of a length measuring interferometer 19 recordsPoint z1And the center of sphere z2Calculating the radius of curvature r ═ z1-z2(ii) a At the center of sphere z2Starting the air-float rotating shaft 10 to drive the measured lens 9 to rotate, and if the radius of the fitting circle on the confocal detector 18 is a, the center of the measured convex lens deviates to
Example 3
As shown in fig. 5, the confocal auto-collimation decentration and curvature radius measuring method can also measure the curvature radius and decentration of the lens group and obtain the best fit optical axis, and the measuring steps are as follows:
step one, a lens group is used as a measured lens 9 and placed in the center of an air-floating rotating shaft 10, the bottom surface of the lens group is superposed with the axial surface of the air-floating rotating shaft 10, a lead screw 23 drives a sliding block 22 to move along a guide rail 21, a measuring light cone is focused on the spherical center of a first lens, and eccentricity chi existing in the first lens is detected1＝a1/(2β)；
Step two, moving the measuring host 14, measuring the focus of the light cone to the spherical center of the second lens, detecting the eccentricity between the second lens and the axis of the lens group, and compensating the measured eccentricity result by considering the eccentricity of the first lens and the magnification introduced by the interval during calculation
m21The magnification ratio of the first lens to the second lens;
and thirdly, by analogy, arranging the eccentric residual errors of all the lenses, and fitting an optimal optical axis when the sum of the residual errors is minimum by using a least square method.
The embodiment realizes the precision processing detection of the center deviation and the curvature radius of the spherical lens and the concave reflector by a series of measures, completes the method and the device for measuring the center deviation and the curvature radius of the confocal auto-collimation, and has the advantages of high measurement precision, large measurement range, no need of repeated clamping, high measurement efficiency and the like.
While the invention has been described in connection with specific embodiments thereof, it will be understood that these should not be construed as limiting the scope of the invention, which is defined in the following claims, and any variations which fall within the scope of the claims are intended to be embraced thereby.
Claims (6)
1. The confocal auto-collimation decentration and curvature radius measuring method is characterized in that: the axial position of a focusing light spot of a confocal detection system with high axial positioning capacity focuses on a measured mirror (9), after a high-precision air floatation rotation system drives the measured mirror (9) to rotate for a circle, a self-alignment centering detection system records the radial position of the focusing light spot reflected by the measured mirror (9) to obtain the eccentricity; the high-precision distance measurement system records the position of a focusing light spot when the focusing light spot is focused on the vertex and the spherical center of a measured mirror to obtain a curvature radius, then integrates the curvature radius and an eccentric amount, and calculates to obtain the center deviation, and the method comprises the following steps:
the method comprises the following steps that firstly, a point light source generating system (17) emits light beams, the light beams penetrate through a first spectroscope (5) arranged along the light beam emitting direction, are reflected by a second spectroscope (6) arranged along the transmission direction of the first spectroscope (5), and then are changed into parallel light through a collimating objective lens (7) arranged along the reflection direction of the second spectroscope (6), and the parallel light is focused at the front focal point of the focusing objective lens (8) through a focusing objective lens (8) positioned in front of the collimating objective lens (7), so that a measuring light cone is formed;
the one-dimensional translation system (15) drives the measuring host (14) to translate along the measuring optical axis (26), the position recording system (16) is used for recording the position of the measuring host (14), and the air floatation rotating shaft (10) and the one-dimensional translation system (15) are placed on the platform (24);
moving the measuring light cone along the measuring optical axis (26) to focus the light cone on the spherical center of the measured mirror (9), scanning the light cone near the spherical center, reflecting the light beam by the measured mirror (9), entering a confocal detector (18), measuring a confocal intensity response curve, performing focusing by means of the characteristic that an extreme point of the confocal curve accurately corresponds to a focus point, and recording the position of a focus light spot at the moment as z1；
Step three, focusing the measuring light cone on the spherical center of the measured mirror (9), starting the air-floating rotating shaft (10), driving the measured mirror (9) to rotate at a constant speed, and rotating the measured mirrorThe path focusing light spot is deflected after being reflected by the measured mirror (9), an eccentric circle is generated at the spherical center position of the measured mirror (9), the reflected light beam is respectively focused on the detection surfaces of the confocal detector (18) and the first detector (13), the light spot path of the reflected light beam on the detection surface of the first detector (13) is approximate to a circle, and n points A on the path are taken1，A2…AnPerforming circle fitting, and recording the radius of a fitting circle as a;
wherein the first detector (13) is positioned at the back focal point of the collimating objective lens (7) in the reflection direction of the second beam splitter (6); the confocal detector (18) is positioned in the reflection direction of the first spectroscope (5) and consists of a second microscope objective (11) and a second detector (12), the second detector (12) is positioned at the focal position of the second microscope objective (11), and three pixels at the center of a light spot on a detection surface are taken as the detection area of the confocal detector;
moving the measuring light cone along the measuring optical axis (26) to focus the light cone on the vertex of the measured mirror (9), scanning the light cone near the vertex, performing focusing by means of the characteristic that an extreme point of a confocal curve accurately corresponds to a focusing point, and recording the position of a focusing light spot as z2Twice focal point z1And z2The distance r between the two is the curvature radius r ═ z of the measured mirror (9)1-z2|；
Step five, according to the curvature radius r of the measured lens (9), the radius a of the fitting circle and the magnification β of the focusing objective lens (8)1Magnification β of the second microscope objective (11)2β, the eccentricity is calculated to be
Center deflection
2. The confocal auto-collimation decentration and curvature radius measurement method according to claim 1, wherein the position of the spherical center can be determined during the process of focusing the spherical center of the measured lens (9), characterized in that:
measuring lightThe cone is focused on the spherical center of the measured lens (9), the reflected light beam enters a confocal detector (18) after being reflected by a first spectroscope (5) and a second spectroscope (6) in a collimation light path, and is focused on a detection surface of a second detector (12) in the confocal detector (18) after being amplified by a second microscope objective (11), a light intensity response signal acquired by the second detector (12) conforms to Gaussian distribution, an extreme point of a Gaussian curve of the response signal accurately corresponds to the spherical center of the measured lens (9) and is recorded as z1I.e. the position of the centre of the sphere.
3. The confocal auto-collimation decentration and curvature radius measurement method according to claim 1, wherein the position of the surface vertex can be determined during the process of focusing the surface vertex of the measured lens (8), characterized in that:
the measuring light cone is focused on the surface vertex position of the measured mirror (9), the reflected light beam enters a confocal detector (18) after being reflected by a first spectroscope (5) and a second spectroscope (6) in a collimation light path, and is focused on the detection surface of a second detector (12) in the confocal detector (18) after being amplified by a second microscope objective (11), the light intensity response signal acquired by the second detector (12) conforms to Gaussian distribution, the extreme point of a Gaussian curve of the response signal accurately corresponds to the surface vertex of the measured mirror (9) and is recorded as z2I.e. the position of the surface vertex.
4. The confocal auto-collimation decentration and curvature radius measurement method according to claim 1, characterized in that: the point light source generating system (17) is composed of a pulse laser (1), a first microscope objective (2) positioned in the emitting direction of the laser, a pinhole (3) positioned at the focal point of the first microscope objective (2) and a reticle (4) positioned in front of the pinhole (3).
5. The confocal auto-collimation decentration and curvature radius measurement method according to claim 1, characterized in that: the position recording system (16) is composed of a length measuring interferometer (19) and a total reflection prism (20) arranged on the measuring host (14).
6. The confocal auto-collimation decentration and curvature radius measurement method according to claim 1, characterized in that: the one-dimensional translation system (15) is composed of an air-floating guide rail (21), a slide block (22) for installing the measuring host (14) and a driving lead screw (23) for driving the slide block (22) to translate on the air-floating guide rail (21).
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