CN105157606A - Non-contact type high-precision three-dimensional measurement method and measurement device for complex optical surface shapes - Google Patents

Abstract

The invention discloses a non-contact type high-precision three-dimensional measurement method and a measurement device for complex optical surface shapes and relates to the technical field of optical surface shape detection, which solves the problems in the prior art that existing measurement methods for the surface shapes of optical elements are high in measurement cost and low in precision and cannot realize the three-dimensional measurement on the surface shapes of optical elements. According to the technical scheme of the invention, the two-dimensional distribution of the height information of an optical surface is acquired through the non-contact three-dimensional coordinate position scanning process, and then the surface shape or the profile information of the optical surface can be measured. A three-dimensional translation platform conducts the translational motion in the x-y direction to realize the point-by-point scanning process of the optical surface, so that the height h variation of the optical surface over all scanning points can be measured. During the scanning process, along with the height h variation of the optical surface, the three-dimensional translation platform is moved in the z direction, so that a spectrum confocal sensor is enabled to always focus the surface of a to-be-measured optical element. A micro three-beam interferometer is aligned with a standard planar mirror. The distance between the surface of the to-be-measured optical element and the standard planar mirror is measured in real time, so that the surface shape information of the to-be-measured optical element can be obtained. The measurement device is low in cost and easy in operation.

Description

Non-contact complex optical surface shape high-precision three-dimensional measurement method and measurement device

technical field

The invention relates to the technical field of optical surface shape detection, in particular to a non-contact high-precision three-dimensional measuring device and method for complex optical surface shape.

Background technique

Driven by urgent needs and technological progress, more and more optical components with complex surface shapes are used in optical systems. Complex surface optical elements have more degrees of freedom, which can effectively correct various advanced aberrations, simplify the structure of the optical system, and improve the performance of the optical system. Complex surface optical components are of great significance to the development of modern optical systems, and are widely used in various types of optical imaging, optical detection, and photoelectric countermeasure systems.

Optical surface shape measurement methods are divided into interferometry and profile scanning measurement. Compensation mirrors and computational holograms are generally used to measure complex optical surfaces by interferometry; compensation mirror interferometry needs to design and process specific compensation mirrors for the specific surface shape to be measured, and the measurement cost is extremely high; The measurement range and accuracy of the measured surface shape are limited by the manufacturing accuracy and size of the hologram, and the larger the size, the lower the accuracy. The contour scanning measurement method is divided into contact type and non-contact type; the contact type surface shape scanning measurement device mainly includes a three-coordinate measuring machine and a probe type profiler. The optical surface finish and film layer are not suitable for the measurement of optical surfaces; the non-contact profile scanning measurement method mainly includes a long-range profiler, which is a f-θ lens system, and measures the deviation of the measurement beam from the standard beam by an optical probe to measure the optical surface. The slope of the surface can be used to measure its surface profile, but only one-dimensional scanning surface shape can be obtained, and three-dimensional surface shape cannot be obtained.

Contents of the invention

In order to solve the problems of high measurement cost, low precision and inability to realize three-dimensional measurement of the surface shape of the optical element in the existing method for measuring the surface shape of the optical element, the present invention provides a non-contact complex optical surface shape high-precision three-dimensional measurement method and measuring device.

A non-contact complex optical surface shape high-precision three-dimensional measurement method, the method is realized by the following steps:

Step 1, using an autocollimator to adjust the pointing of the spectral confocal sensor, the miniature three-beam interferometer and the standard plane mirror, so that the spectral confocal sensor, the miniature three-beam interferometer and the standard plane mirror are coaxial;

Step 2, install the optical element to be tested on the measurement platform, determine the number of scanning points and the scanning distance of the surface shape of the optical element to be measured; scan the scanning points of the surface shape of the optical element to be measured in sequence, measure and record each The three-dimensional profile information of the scanning points; polynomial fitting is performed on the three-dimensional profile information of all scanning points to obtain the three-dimensional surface diagram of the surface shape of the optical element to be measured;

The specific measurement process is:

First, move the three-dimensional translation platform in the X-Y direction to the initial scanning point of the surface shape of the optical element to be measured, and move the three-dimensional translation platform in the Z direction to make the spectral confocal sensor focus on the initial scanning point, and the spectral confocal The distance between the sensor and the initial scanning point is d, and the miniature three-beam interferometer measures the distance to the standard flat mirror to obtain the three-dimensional profile information of the initial scanning point on the optical element to be tested;

Then, move the three-dimensional translation stage to the next scanning point of the surface shape of the optical element to be measured in the X-Y direction, and move the three-dimensional translation stage in the Z direction to make the spectral confocal sensor focus on the corresponding scanning point, and keep the spectral confocal sensor The distance from the corresponding scanning point is d; the micro three-beam interferometer measures the distance from the micro three-beam interferometer to the standard plane mirror in real time, and obtains the three-dimensional profile information of the scanning point until the three-dimensional profile information of all scanning points is completed. Measurement;

Finally, polynomial fitting is performed on the three-dimensional profile information of all scanning points to obtain a three-dimensional surface diagram of the surface shape of the optical element to be measured.

Non-contact complex optical surface shape high-precision three-dimensional measurement, the device includes a measurement platform, a spectral confocal sensor, a three-dimensional translation stage, a miniature three-beam interferometer and a standard flat mirror; the spectral confocal sensor and a miniature three-beam interferometer It is fixed on the three-dimensional translation platform; the three-dimensional translation platform and the standard plane mirror are fixed on the measurement platform.

Beneficial effects of the present invention: The device of the present invention obtains the two-dimensional distribution of the height information of the optical surface (distribution of height h with x, y) based on non-contact three-dimensional coordinate position scanning, thereby measuring its surface shape or contour information. The optical surface is scanned point by point by the translation of the three-dimensional translation stage in the x-y direction, and the change of the height h of the optical surface profile at each point is measured (Z direction); during the scanning process, as the height of the optical surface changes, the three-dimensional The translation stage makes the spectral confocal sensor always focus on the surface of the optical element to be tested, that is, the distance between the spectral confocal sensor and each measurement point remains unchanged, and acts as a "zero position monitor";

The miniature three-beam interferometer is aimed at the standard plane mirror, and the change of the distance between the two is measured in real time. The change is the relative height change h of different scanning points on the optical surface; the (x, y, h) information of different scanning points is recorded , the surface shape information of the optical surface can be obtained; the best approximate surface can be obtained by using multi-degree polynomial fitting, which can be used to describe the surface shape of the optical surface. The measuring platform adopts stainless steel air floating platform, which can eliminate the influence of external vibration;

The non-contact surface shape scanning measurement device of the present invention can measure the 3D surface shape of complex optical surfaces with high precision without damaging the optical surface, and has the advantages of low cost, easy operation and the like.

Description of drawings

Fig. 1 is a schematic structural diagram of a non-contact complex optical surface shape high-precision three-dimensional measuring device according to the present invention.

In the figure: 1. Test platform, 2. Three-dimensional translation stage, 3. Spectral confocal sensor, 4. Miniature three-beam interferometer, 5. Standard flat mirror, 6. Optical components to be tested.

Detailed ways

Specific Embodiments 1. A non-contact complex optical surface shape high-precision three-dimensional measurement method, which is implemented by the following steps:

1. Use the autocollimation theodolite to aim at the spectral confocal sensor 3, the miniature three-beam interferometer 4, and the standard flat mirror 5, respectively, and adjust the attitude of the three so that they point in the same direction;

2. Install the optical element 6 to be tested on the test platform, use a level to assist in adjusting the attitude of the sample, and eliminate errors such as tilt; according to the measurement requirements and the size of the optical element to be tested, determine the scanning parameters such as the number of scanning measurement points N and the spacing d; Set the three-dimensional translation stage 2 to move to the scanning starting point (x ₀ , y ₀ ) in the horizontal direction X and the vertical direction Y, and move in the front and rear direction z to make the spectral confocal sensor 3 focus on this point; the micro three-dimensional The beam interferometer 4 measures the distance h _(0,0) to the standard flat reflector 5;

3. The three-dimensional translation stage 2 moves to the next scanning point (x ₁ , y ₀ ) in the XY direction, and moves in the Z direction to make the spectral confocal sensor 3 focus on this point, that is, to keep the probe of the spectral confocal sensor during the scanning process The distance with the 6 measuring points of the optical element to be measured is constant; the miniature three-beam interferometer 4 measures the distance h _(1,0) to the standard plane reflector 5;

4. Repeat the above process to obtain the height distribution information (x _i , y _j , h _{(i, j)} ) of all scanning points;

5. Perform polynomial fitting on the height distribution information (x _i , y _j , h _{(i, j)} ) of all scanning points to obtain a three-dimensional surface diagram of the surface shape of the optical element to be measured.

The spectral confocal sensor 3 described in this embodiment has an accuracy of "zero position monitoring" of the surface shape of the optical element to be measured at 20nm; the distance measurement accuracy of the miniature three-beam interferometer 4 to the standard plane mirror 5 is 1nm; the three-dimensional translation stage X-Y The movement range in the direction is 400mm, the position repeatability is better than 3μm, the movement range in the Z direction is 50mm, and the position repeatability is better than 50nm; the standard plane mirror 5 has a diameter of 300mm, the surface shape accuracy is λ/8, and the surface is coated with aluminum film.

Specific Embodiment 2. This embodiment is described in conjunction with FIG. 1. This embodiment is a measuring device for the non-contact complex optical surface shape high-precision three-dimensional measurement method described in Specific Embodiment 1. The device includes a measurement platform 1, a spectral confocal Sensor 3, three-dimensional translation platform 2, miniature three-beam interferometer 4 and standard plane reflector 5; The spectral confocal sensor 3 and miniature three-beam interferometer 4 are fixed on the three-dimensional translation platform 2; the three-dimensional translation platform 2 and The standard flat mirror 5 is fixed on the measurement platform 2 .

The measuring platform 1 described in this embodiment adopts a stainless steel air-floating platform, and the surface of the standard plane mirror 5 is coated with an aluminum film.

Claims (7)

1. contactless complicated optical surface profile high precision three-dimensional measurement method, it is characterized in that, the method is realized by following steps:

Step one, use autocollimator adjustment Spectral Confocal sensor (3), miniature Three-beam Interfere instrument (4) and standard flat catoptron (5) point to, and make described Spectral Confocal sensor (3), miniature Three-beam Interfere instrument (4) and standard flat catoptron (5) coaxial;

Step 2, optical element to be measured to be arranged on measuring table (1), to determine analyzing spot quantity and the sweep span of optical component surface shape to be measured (6); The analyzing spot of described optical component surface shape to be measured (6) is scanned successively, measures and record the three-D profile information of each analyzing spot; Fitting of a polynomial is carried out to the three-D profile information of all analyzing spots, obtains the 3 d shape figure of optical component surface shape to be measured (6);

Concrete measuring process is:

First, in X-Y direction moving three dimension translation stage (2) to the initial sweep point of optical component surface shape to be measured (6), at Z-direction moving three dimension translation stage (2), Spectral Confocal sensor (3) is made to focus in described initial sweep point, described Spectral Confocal sensor (3) is d with the distance of initial sweep point, miniature Three-beam Interfere instrument (4) measures the distance to standard flat catoptron (5), obtains the three-D profile information of initial sweep point on optical element to be measured;

Then, in the x-y directions D translation platform (2) is moved to the next analyzing spot of optical component surface shape to be measured (6), at Z-direction moving three dimension translation stage (2), make Spectral Confocal sensor (3) focus analyzing spot in correspondence, the distance of the confocal sensor of spectral preservation (3) analyzing spot corresponding to this is d; Miniature Three-beam Interfere instrument (4) measures the distance of described miniature Three-beam Interfere instrument (4) to standard flat catoptron (5) in real time, obtain the three-D profile information of this analyzing spot, until complete the measurement of all analyzing spot three-D profile information;

Finally, fitting of a polynomial is carried out to the three-D profile information of all analyzing spots, obtain the 3 d shape figure of optical component surface shape to be measured.

2. contactless complicated optical surface profile high precision three-dimensional measurement method according to claim 1, it is characterized in that, Spectral Confocal sensor is as zero-bit monitor, and measuring accuracy is 20nm.

3. device according to claim 1, is characterized in that, the surface of described standard flat catoptron is coated with aluminium film.

4. the device of contactless complicated optical surface profile high precision three-dimensional measurement method according to claim 1, it is characterized in that, this device comprises measuring table (1), Spectral Confocal sensor (3), D translation platform (2), miniature Three-beam Interfere instrument (4) and standard flat catoptron (5); Described Spectral Confocal sensor (3) and miniature Three-beam Interfere instrument (4) are fixed on D translation platform (2); Described D translation platform (2) and standard flat catoptron (5) are fixed on measuring table (1).

5. device according to claim 4, is characterized in that, described measuring table (1) adopts stainless steel air floating platform.

6. device according to claim 5, is characterized in that, the surface of described standard flat catoptron (5) is coated with aluminium film.

7. device according to claim 5, is characterized in that, described Spectral Confocal sensor is as zero-bit monitor, and measuring accuracy is 20nm.