CN101672628A - Aspheric optical element surface shape detection device - Google Patents

Abstract

The invention discloses an aspheric optical element surface shape detection device. Based on prior interference method surface shape detection devices, the aspheric optical element surface shape detection device realizes the measurement of the light intensities of detection light waves and reference light waves by additionally arranging two controllable optical stops and can acquire phase shift interference fringes by additionally arranging piezoelectric ceramics. An aspheric surface shape measurement software package can conveniently acquire a phase offset between the surface shape and an ideal surface shape of an aspheric optical element to be detected by computing the phase offset between the surface shape to be detected and a standard surface shape of the aspheric optical element to bedetected and the phase offset between the ideal surface shape and the standard surface shape of the aspheric optical element to be detected. Therefore, the aspheric optical element surface shape detection device can effectively solve the surface shape detection problem of aspheric optical elements with large offset without a practical processing computed hologram, thereby reducing detection cost,shortening detection cycle and improving detection accuracy.

Description

Aspheric optical element surface shape detection device

Technical field

The present invention relates to technical field of optical precision measurement, particularly a kind of aspheric optical element surface shape detection device that can detect big aspherical degree.

Background technology

Up at present the detection by quantitative of aspheric optical element surface shape being remained a challenge in the optical metrology detection range.Main cause is not have corresponding standard aspheric surface model to be used for standard detection, thereby causes in interfere detecting interference fringe overstocked, and can not satisfy sampling thheorem.The solution that adopts has sub-aperture stitching method and penalty method at present.The mechanical motion of sub-aperture stitching method utilization precision detects the different subregions of aspherical optical element, and then each testing result is spliced into the face shape testing result of whole aspherical optical element.Penalty method utilizes compensating glass or computed hologram to compensate detecting light path, makes that the interference fringe that is write down can normally be sampled.In the calculation holographic detection method of existing aspherical optical element, all must the actual computed hologram that processes, and in detecting light path, debug.To increase detection cost, the lengthening sense cycle of aspherical optical element like this, simultaneously since the restriction of computed hologram machining precision can not the face shape of the excessive aspherical optical element of aspherical degree and face shape steepness be detected.

Summary of the invention

The objective of the invention is, overcome existing with calculating the deficiency that holographic technique detects computed hologram processing in the aspheric optical element surface shape, debugs difficulty, provide a kind of aspheric optical element surface shape detection device, to realize high Precision Detection to the aspheric optical element surface shape of big aspherical degree and big face shape steepness based on two step phase-shifting technique, calculation holographic technology and digital hologram interference techniques.

The present invention realizes above-mentioned purpose by the following technical solutions.

Aspheric optical element surface shape detection device comprises helium-neon laser, microcobjective, pinhole filter, spectroscope, aplanat, the first controlled diaphragm, standard flat catoptron, piezoelectric ceramics, the second controlled diaphragm, ccd detector and computing machine, the standard flat catoptron places on the piezoelectric ceramics, first, second controlled diaphragm and piezoelectric ceramics all are subjected to the control of computing machine, and the rear focus of microcobjective, the focus in object space of aplanat and pinhole filter all are positioned at the equivalent centre of sphere place of the optimum matching sphere of aspherical optical element to be checked; During detection, the laser beam that described helium-neon laser sends forms the standard spherical light wave through the pin hole place that described microcobjective converges to described pinhole filter, this standard spherical light wave is divided into two bundles by described spectroscope: shine directly into to be measured of described aspherical optical element to be checked by the light wave of spectroscope reflection through the described second controlled diaphragm and go up and be reflected and promptly be defined as the detection light wave, light-wave irradiation by the spectroscope refraction forms plane light wave to described aplanat, shine on the standard flat catoptron again and be reflected through the first controlled diaphragm then and promptly be defined as reference light wave, described detection light wave and described reference light wave are respectively on the target surface through shining described ccd detector after spectroscope transmission and the reflection and send into after opto-electronic conversion in the described computing machine; When described first, second controlled diaphragm was opened simultaneously, what described ccd detector detected was interference fringe, and when the first controlled diaphragm or the second controlled diaphragm were opened, what ccd detector detected was the light intensity of described reference light wave or described detection light wave.

Computing machine is equipped with A/D converter, storer and aspheric surface measurement software package, storer is stored known parameter required in the aspheric surface measurement software package operational process in advance, the aspheric surface measurement software package contains control module, memory module, data acquisition module, data input module, desirable interference fringe parameter calculating module, phase difference calculating module, phase place separates parcel module and surface form deviation computing module, the function of control module is the phase shift that control piezoelectric ceramics 8 produces pi/2, controls the opening and closing of first, second controlled diaphragm; Process data in the memory module storage data processing and the correlation parameter of in program operation process, storing in invoked procedure data and the storer; The function of data acquisition module is to gather piezoelectric ceramics by A/D converter to detect when the zero-bit on original position interference fringe that light wave and reference light wave form and this position and detect the light intensity of light wave and the light intensity of reference light wave, detect the phase shift interference striped that light wave and reference light wave form when gathering piezoelectric ceramics phase shift pi/2, and image data sent in the storer store by A/D converter; Data input module receives the desirable face shape equation and the caliber size thereof of the artificial aspherical optical element of importing to be checked by keyboard and sends in the memory module; Desirable interference fringe parameter calculating module simulates desirable original position interference fringe and desirable phase shift interference striped according to Ray-tracing Method and principle of interference, calculate and desirablely to detect the light intensity of light wave and the light intensity of desired reference light wave, and will simulate to send in the storer and store with computational data; The phase difference calculating module calculates to be measured shape of aspherical optical element to be checked and simulate ideal face shape according to the simulate ideal face shape of phase deviation between to be measured shape of measuring aspherical optical element to be checked and the standard sphere and analog computation aspherical optical element to be checked and the phase deviation between the standard sphere and is wrapped in phase deviation between 0 to 2 π; Phase place is separated the parcel module and is calculated one group of continually varying phase difference value according to digital baseband input signal; The result of calculation that the surface form deviation computing module utilizes phase place to separate the parcel module solves the deviation between to be measured shape and the simulate ideal face shape and is exported.

Beneficial effect of the present invention is embodied in the following aspects.

(1) the present invention is based upon on the basis of existing interferometric method surface shape detection apparatus, has realized detecting the luminous intensity measurement of light wave and reference light wave by setting up two controlled diaphragms, has realized collection to the phase shift interference striped by setting up piezoelectric ceramics; The aspheric surface measurement software package by calculating optical element to be checked to be measured shape and phase deviation and the desirable face shape of aspherical optical element to be checked and the phase deviation between the standard sphere between the standard sphere, can obtain the face shape of aspherical optical element to be checked and the phase deviation between its desirable face shape easily.Compare with traditional calculation holographic detection method, the present invention does not need the actual processing of computed hologram and follow-up light path to debug, thereby has reduced the detection cost, shortened sense cycle and improved accuracy of detection.

(2) the present invention combines two step phase-shifting techniques, calculation holographic technology and digital hologram interference technique, make between the face shape of aspherical optical element to be checked and its desirable face shape and compare, thereby reduced the departure in the testing process, and then can detect the face shape of big aspherical degree with the aspherical optical element of big face shape steepness.

(3) aspheric optical element surface shape detection device that adopts aspheric optical element surface shape detection method of the present invention to set up can detect the face shape of big aspherical degree with the aspherical optical element of big face shape steepness, need not actual processing computed hologram, can reduce and detect cost, shortening sense cycle, and improve accuracy of detection.

Description of drawings

Fig. 1 is the principle schematic of aspheric optical element surface shape detection device of the present invention.

Fig. 2 is the workflow diagram of aspheric surface measurement software package in the device shown in Figure 1.

Embodiment

The present invention is described in further detail below in conjunction with accompanying drawing and preferred embodiment.

According to shown in Figure 1, aspheric optical element surface shape detection device of the present invention comprises helium-neon laser 1, microcobjective 2, pinhole filter 3, spectroscope 4, aplanat 5, the first controlled diaphragm 6, standard flat catoptron 7, piezoelectric ceramics 8, the second controlled diaphragm 9, ccd detector 11, computing machine 12.The operation wavelength of helium-neon laser 1 is 632.8nm, the magnification of microcobjective 2 is 100, the diameter of pinhole filter 3 is 5 μ m, spectroscope 4 is semi-transparent semi-reflecting 45 ° of right-angle prisms, the splitting ratio of its light splitting surface is 1: 1, the surface figure accuracy of standard flat catoptron 7 is better than λ/20 and places on the piezoelectric ceramics 8, and piezoelectric ceramics 8 is subjected to the control of computing machine 12 and does translation with respect to the reference beam center with standard flat catoptron 7, and its bearing accuracy is better than 10nm.Ccd detector 11 is selected area array CCD for use.Pinhole filter 3 is in the equivalent centre of sphere place of the optimum matching sphere of aspherical optical element 10 to be checked, and the rear focus of microcobjective 2 and the focus in object space of aplanat 5 also are on this position simultaneously.During test, the laser beam that helium-neon laser 1 sends converges to the pin hole place of pinhole filter 3 through microcobjective 2, formation standard spherical light wave, this standard spherical light wave is divided into two bundles by spectroscope 4: its reflecting light shines directly into to be measured of aspherical optical element 10 to be checked through the second controlled diaphragm 9 and goes up and be reflected, its refraction light wave shines on the aplanat 5 and forms plane light wave, shine on the standard flat catoptron 7 again through the first controlled diaphragm 6 then and be reflected, owing to include aspheric shape information to be checked in the light wave of aspherical optical element 10 reflections to be checked, thereby can be with it as the detection light wave in the test, then as the reference light wave in the test, detect light wave and reference light wave respectively on the target surface through shining ccd detector 11 after spectroscope 4 transmissions and the reflection and after opto-electronic conversion, send in the computing machine 12 by the light wave after standard flat catoptron 7 reflection.First, second controlled diaphragm 6,9 difference and corresponding to the switch with reference to light wave and detection light wave, both opening and closing all are subjected to computing machine 12 controls.When first, second controlled diaphragm 6,9 was opened simultaneously, what ccd detector 11 was surveyed was interference fringe, and when the first controlled diaphragm 6 (or second controlled diaphragm 9) when opening, what ccd detector 11 was surveyed is the light intensity of reference light wave (or detecting light wave).

A/D converter, storer and aspheric surface measurement software package are housed in the computing machine 12.Storer is stored known parameter required in the aspheric surface measurement software package operational process in advance, these known parameters comprise between used Wavelength of Laser λ, pinhole filter 3 and the spectroscope 4 apart from d, the pixel count M * N of area array CCD detector 11 and Pixel Dimensions Δ x * Δ y.The aspheric surface measurement software package contains control module, memory module, data acquisition module, data input module, desirable interference fringe parameter calculating module, phase difference calculating module, phase place separates parcel module and surface form deviation computing module, and its workflow is seen Fig. 2.

The function of control module is the phase shift that control piezoelectric ceramics 8 produces pi/2, controls the opening and closing of first, second controlled diaphragm 6,9.The function of memory module be storage in the data processing process data and in program operation process, call correlation parameter in these process datas and the storer.The function of data acquisition module is to gather piezoelectric ceramics by A/D converter to detect the light intensity that detects light wave on original position interference fringe that light wave and reference light wave form and this position when the zero-bit | O ₁| ²Light intensity with reference light wave | R ₁| ²Detect the phase shift interference striped that light wave and reference light wave form when gathering piezoelectric ceramics phase shift pi/2, and four data will gathering are sent in the storer and are stored by A/D converter.The function of data input module is to receive the desirable face shape equation and the caliber size D thereof of the aspherical optical element to be checked of artificial input by keyboard, and sends in the memory module; The function of desirable interference fringe parameter calculating module be utilize between desirable face shape equation, caliber size D and the pinhole filter 3 and the spectroscope 4 of aspherical optical element to be checked of input apart from d, adopt method and the principle of interference simulate ideal original position interference fringe and the desirable phase shift interference striped of ray tracing, calculate the desirable light intensity that detects light wave | O ₂| ²Light intensity with the desired reference light wave | R ₂| ², and will simulate and computational data is sent in the storer and stored.The phase difference calculating module is wrapped in phase deviation Δ φ between 0 to 2 π according to the desirable face shape of phase deviation between to be measured shape of measuring aspherical optical element to be checked and the standard sphere and analog computation aspherical optical element to be checked and to be measured shape that the phase deviation between the standard sphere calculates aspherical optical element to be checked and its simulate ideal face shape _w:

In the formula of (1)～(3), I ₁Be the light intensity of original position interference fringe, I ₂Be the light intensity of phase shift interference striped, O ₁For detecting the complex amplitude of light wave at ccd detector 11 target surface places, R ₁Be the complex amplitude of reference light wave at ccd detector 11 target surface places,

Be complex amplitude O ₁Phase place,

Be complex amplitude R ₁Phase place, above-mentioned parameter all can obtain from measurement parameter; In the formula of (4)～(6), I ₃Be the light intensity of desirable original position interference fringe, I ₄Be the light intensity of desirable phase shift interference striped, O ₂Be the complex amplitude that the simulate ideal face shape reflected light of aspherical optical element to be checked is located on the record plane, R ₂Be the complex amplitude of analog references light wave at place, record plane,

Be complex amplitude O ₂Phase place,

Be complex amplitude R ₂Phase place, above-mentioned parameter obtains by desirable interference fringe parameter calculating module; (7) in the formula

For reflecting the deviation phase of to be measured shape of aspherical optical element to be checked and its simulate ideal face shape,

Be the normal phase differential between actual acquisition and the analog computation, it does not influence the detection to aspheric optical element surface shape to be checked, can be by with all Δ φ _wWith selected reference point (as Δ φ _W1) subtract each other and eliminate.The function that phase place is separated the parcel module is the digital baseband input signal Δ φ that will be wrapped between 0 to 2 π _wResolving is one group of continually varying phase difference value Δ φ; The function of surface form deviation computing module is to utilize formula (8) to calculate to be measured shape of aspherical optical element to be checked and the surface form deviation between its simulate ideal face shape and result of calculation is exported:

$z=\frac{\mathrm{\Δ\φ}}{4\mathrm{\π}}\mathrm{\λ}---\left(8\right)$

(8) z is the surface form deviation of to be measured of aspherical optical element to be checked in the formula.

Claims (1)

1. aspheric optical element surface shape detection device, comprise helium-neon laser [1], microcobjective [2], pinhole filter [3], spectroscope [4], aplanat [5], standard flat catoptron [7], ccd detector [11] and computing machine [12], it is characterized in that: also comprise the first controlled diaphragm [6], the second controlled diaphragm [9] and piezoelectric ceramics [8], described standard flat catoptron [7] places on the described piezoelectric ceramics [8], described first, the second controlled diaphragm [6,9] and piezoelectric ceramics [8] all be subjected to the control of described computing machine [12], the rear focus of described microcobjective [2], the focus in object space of described aplanat [5] and described pinhole filter [3] all are positioned at the equivalent centre of sphere place of the optimum matching sphere of aspherical optical element to be checked [10]; During detection, the laser beam that described helium-neon laser [1] sends forms the standard spherical light wave through the pin hole place that described microcobjective [2] converges to described pinhole filter [3], this standard spherical light wave is divided into two bundles by described spectroscope [4]: shone directly on the aspheric surface to be checked of described aspherical optical element [10] by the light wave of spectroscope [4] reflection through the described second controlled diaphragm [9] and be reflected and promptly be defined as the detection light wave, light-wave irradiation by spectroscope [4] refraction upward forms plane light wave to described aplanat [5], shine standard flat catoptron [7] again through the first controlled diaphragm [6] then and go up and be reflected and promptly be defined as reference light wave, described detection light wave and described reference light wave are respectively on the target surface through shining described ccd detector [11] after spectroscope [4] transmission and the reflection and send into after opto-electronic conversion in the described computing machine [12]; When described first, second controlled diaphragm [6,9] when opening simultaneously, what described ccd detector [11] detected is interference fringe, when the first controlled diaphragm [6] or the second controlled diaphragm [9] when opening, what ccd detector [11] detected is the light intensity of described reference light wave or described detection light wave; Computing machine is equipped with A/D converter, storer and aspheric surface measurement software package, storer is stored known parameter required in the aspheric surface measurement software package operational process in advance, the aspheric surface measurement software package contains control module, memory module, data acquisition module, data input module, desirable interference fringe parameter calculating module, phase difference calculating module, phase place separates parcel module and surface form deviation computing module, the function of control module is the phase shift that control piezoelectric ceramics 8 produces pi/2, controls the opening and closing of first, second controlled diaphragm; Process data in the memory module storage data processing and the correlation parameter of in program operation process, storing in invoked procedure data and the storer; The function of data acquisition module is to gather piezoelectric ceramics by A/D converter to detect when the zero-bit on original position interference fringe that light wave and reference light wave form and this position and detect the light intensity of light wave and the light intensity of reference light wave, detect the phase shift interference striped that light wave and reference light wave form when gathering piezoelectric ceramics phase shift pi/2, and image data sent in the storer store by A/D converter; Data input module receives the desirable face shape equation and the caliber size thereof of the artificial aspherical optical element of importing to be checked by keyboard and sends in the memory module; Desirable interference fringe parameter calculating module simulates desirable original position interference fringe and desirable phase shift interference striped according to Ray-tracing Method and principle of interference, calculate and desirablely to detect the light intensity of light wave and the light intensity of desired reference light wave, and will simulate to send in the storer and store with computational data; The phase difference calculating module calculates to be measured shape of aspherical optical element to be checked and simulate ideal face shape according to the simulate ideal face shape of phase deviation between to be measured shape of measuring aspherical optical element to be checked and the standard sphere and analog computation aspherical optical element to be checked and the phase deviation between the standard sphere and is wrapped in phase deviation between 0 to 2 π; Phase place is separated the parcel module and is calculated one group of continually varying phase difference value according to digital baseband input signal; The result of calculation that the surface form deviation computing module utilizes phase place to separate the parcel module solves the deviation between to be measured shape and the simulate ideal face shape and is exported.

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