CN106768890A - For the gray scale cosine distribution optical target analogue means of modulation transfer function detection - Google Patents
For the gray scale cosine distribution optical target analogue means of modulation transfer function detection Download PDFInfo
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
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Abstract
The present invention relates to a kind of gray scale cosine distribution optical target analogue means for modulation transfer function detection, belong to optical system picture element assessment technique field, the device includes lighting source, narrow band pass filter, flat field microcobjective, pin hole graticle, the first optical alignment system, polarizing beam splitter mirror, tunable optical density board, the first standard flat speculum, the second standard flat speculum, beam splitter, calibration for cameras, coupling object lens, the second optical alignment system, high precision displacement adjustment platform and controller.The gray scale cosine distribution target that can be matched with optical system to be measured with accurate simulation spatial frequency and modulation degree for the gray scale cosine distribution optical target analogue means of modulation transfer function detection proposed by the invention, the MTF detections of optical system to be measured are realized as input using the gray scale cosine distribution target, not only conform with the original definition of MTF, and can direct measurement go out the MTF of optical system to be measured, without follow-up data processing, so as to improve the precision and efficiency of MTF detections.
Description
Technical field
It is more particularly to a kind of for modulation transfer function detection the present invention relates to optical system picture element assessment technique field
Gray scale cosine distribution optical target analogue means.
Background technology
At present, space optical camera uses time delay integration charge-coupled image sensor (Time Delayed mostly
Integration CCD, TDICC) coordinate the optical telescope of front end to obtain ground scene information, wherein TDICCD linear array sides
To corresponding to space optical camera visual field direction, normal thereto is to wear rail direction, and scene image is by TDICCD with time integral
Obtain.Space optical camera uses modulation transfer function (Modulation Transfer during ground test
Function, MTF) as standard, the image quality of quantitative assessment space optical camera.The method of testing of current MTF is more, right
In using TDICCD as sensor space optical camera, due to its be limited by during ground test be difficult obtain perpendicular to
The image of TDICCD linear arrays direction dimension, therefore the optical target of square-wave profile is pressed as input frequently with gray scale, according to space
The half-tone information of optical camera output image and its distribution, measure the system-level contrast that space optical camera is all imaged link
Transmission function (Contrast Transfer Function, CTF), then closed according to the Taylor series expansion between CTF and MTF
System, and after ignoring high order component, approximate calculation obtains the system-level modulation transfer function of space optical camera, and also referred to as system is quiet
State modulation transfer function.But it is this that system-level modulation transmission is obtained as input by the optical target of square-wave profile using gray scale
There is following defect in the method for function：
(1) the black and white strip optical target or black and white strip optical target of gray scale square-wave profile are used as input, side
The spatial frequency of ripple needs (i.e. parallel with optical alignment system according to the focal length of telescope, detection in space optical camera to be measured
Light pipe) focal length, TDICCD pixel dimensions, and calculate corresponding system cut-off frequency and each rank frequency dividing according to Nyquist laws,
And the measurement error of above-mentioned each focal length value has considerable influence to the computational accuracy of the optical target spatial frequency of gray scale square-wave profile；
In addition the optical target of gray scale square-wave profile uses the manufacture of photoetching technique, and its accuracy of manufacture is general in micron dimension,
The examining system cutoff spatial frequency (generally non-integer) for being difficult to be obtained with theoretical calculation is matched completely.Therefore in synthesis
State every error, it will the testing result to the system-level modulation transfer function of space optical camera introduces larger not knowing
Degree.
(2) limited by sampling thheorem, the optical target of the gray scale square-wave profile of input and the initial alignment of TDICCD alignments
Precision has considerable influence to CTF measurement results, can even cause CTF measurement results vibration occur when position deviation is larger originally.
There is vibration to avoid CTF, current solution is typically to enter according to gray value in all of output streak line is to image
Row universe is searched for, according to the maximum Search Results of adjacent stripes grey-scale contrast as output image Contrast Detection result,
But this solution will cause CTF testing results to there is larger contingency, and then influence MTF computational accuracies.
(3) because the definition of transmission function is that linear system is responded for the output of cosine distribution function, it is therefore desirable to right
The CTF results for measuring carry out further Mathematical treatment, when the conversion of the mathematics between CTF and MTF is carried out, should lead in theory
Cross repeatedly measurement and obtain the CTF values of correspondence high-order frequency dividing, then carry it into taylor series expansion respectively, be calculated MTF.When
When system space cut-off frequency is relatively low, the mathematical processing methods that high-order frequency dividing item is ignored in the prior art will not measure essence to MTF
Degree produces considerable influence, this to ignore the Mathematical treatment side that high-order divides item however as the continuous improvement of TDICCD resolution ratio
Method will produce significant impact to the final calculation result of MTF.
Additionally, optical fiber image transmission beam is introduced into conventional electrophotographic system, light path can be made to possess " flexibility ", and significantly improve
The combination property of photoelectric instrument, but the image quality of all imaging links is tested and assessed using existing IMAGE QUALITY EVALUATION FOR, then
There is larger difficulty.For the photo electric imaging system containing optical fiber image transmission beam, due to there is face battle array optical fiber image transmission beam pixel and face
Coupling sampling effect between battle array CCD pixels so that imaging system has coupling discrete sampling characteristic.Currently used for area array CCD
As the technology that the MTF of the photo electric imaging system of detector is detected, mainly include angled slots or cutting edge as analytical technology, point source
Target image analytical technology etc., but the picture matter of photo electric imaging system that these technologies are difficult to meet above-mentioned introducing optical fiber image transmission beam
Evaluation demand, main reason is that：
(1) image analysis technology according to angled slots, inclination cutting edge, Point Target is all based on Fast Fourier Transform (FFT)
Is multiplied with cascade theoretical and realizes, but for two-stage couples discrete sampling imaging system, there is pixel coupling error in it,
This will cause to be vibrated with the quantity of contained coupling pixel in system based on the theoretical MTF result of calculations of Fast Fourier Transform (FFT) receives
Hold back, i.e., only after contained coupling pixel reaches certain amount in system, the MTF of system can just converge to fixed value.
(2) though inclining cutting edge, angled slots image analytical method can take into account the discrete sampling characteristic of area array CCD, sampling is improved
Spatial frequency and MTF accuracy of detection, but limited by pixel coupling error, it carries out inverse Fourier transform to solve in cutting edge function
A large amount of random noises can be introduced during calculating line spread function, the measurement result to MTF produces considerable influence.
The content of the invention
Gray scale square-wave profile optical target of the prior art is prepared on the glass substrate by photoetching technique,
Cause the spatial frequency and contrast of gray scale square-wave profile optical target to be unable to arbitrary continuation to adjust, can only be by manufacturing multigroup
Line dividing plate is manually changed and realizes to the space optical camera with different photoelectric parameters and possess coupling and discrete adopt again
The MTF detections of the photo electric imaging system of sample characteristic so that the detection efficiency of MTF is relatively low, and causes with gray scale square-wave profile light
Target is learned as input detection space optical camera and the precision of the MTF of the photo electric imaging system for possessing coupling discrete sampling characteristic
It is not high.Based on this, it is necessary to in the prior art to space optical camera with possess coupling discrete sampling characteristic photoelectricity into
As the problem that MTF detection efficiencies are relatively low, accuracy of detection is not high of system, there is provided a kind of gray scale for modulation transfer function detection
Cosine distribution optical target analogue means.
To solve the above problems, the present invention takes following technical scheme：
A kind of gray scale cosine distribution optical target analogue means for modulation transfer function detection, described device includes shining
Mingguang City source, narrow band pass filter, flat field microcobjective, pin hole graticle, the first optical alignment system, polarizing beam splitter mirror, tunable optical
Density board, the first standard flat speculum, the second standard flat speculum, beam splitter, calibration for cameras, coupling object lens, the second light
Colimated light system, high precision displacement adjustment platform and controller are learned,
The collimation collimated light beam that the lighting source sends generates collimated monochromatic light after being filtered through the narrow band pass filter, institute
State collimated monochromatic light and be irradiated into the flat field microcobjective, the pin hole graticle and the first optical alignment system successively
System, and the flat field microcobjective is identical with the relative aperture of first optical alignment system, the pin hole graticle is located at
The object space focal plane of the flat field microcobjective；
The collimation collimated light beam of the first optical alignment system outgoing exposes to the polarizing beam splitter mirror, the polarization point
After Shu Jing carries out reflection of polarization and polarization refraction to the collimation collimated light beam, the first orthogonal polarized monochromatic of polarization direction is obtained
Light beam and the second polarized monochromatic beamlets；First polarized monochromatic beamlets by described first after the tunable optical density board by being marked
Directrix plane speculum reflexes to the polarization angle rotation of first polarized monochromatic beamlets after the polarizing beam splitter mirror, and reflection
90 °, the optical axis of the axial direction of the tunable optical density board and the first standard flat speculum with the collimation collimated light beam
Optical axis it is vertical；Second polarized monochromatic beamlets reflex to the polarizing beam splitter mirror by the second standard flat speculum,
And the polarization angle of second polarized monochromatic beamlets after reflection is rotated by 90 °, the optical axis of the second standard flat speculum
Optical axis with the collimation collimated light beam is parallel；The light beam that the polarizing beam splitter mirror is reflected the first standard flat speculum
After the light beam reflected with the second standard flat speculum is reflected and reflected respectively, obtain and the collimation collimated light beam
The vertical interfering beam of optical axis；
The interfering beam exposes to the beam splitter, and the beam splitter is reflected and reflected to the interfering beam
Afterwards, obtain demarcating interfering beam and target interfering beam；It is described to demarcate the imaging thing that interfering beam exposes to the calibration for cameras
Mirror；It is described coupling object lens object plane be infinity, and it is described coupling object lens focal length and relative aperture respectively with the demarcation phase
The focal length and relative aperture of the image-forming objective lens of machine are directly proportional, and the target interfering beam exposes to the coupling object lens, the coupling
Be imaged the target interfering beam to the image space focal plane of the coupling object lens by compound mirror, the coupling object lens and described the
The linear field of two optical alignment system parfocalizations and the coupling object lens is identical with the linear field of second optical alignment system, institute
State the second optical alignment system and export the gray scale cosine distribution optical target detected for modulation transfer function；
The spatial frequency of the demarcation light beam that the controller is obtained according to pre-set space frequency and the calibration for cameras
The high precision displacement adjustment platform is driven to finely tune, the high precision displacement adjustment platform drives the second standard flat speculum edge
The optical axis direction trace movement of the second standard flat speculum, until the demarcation light beam of calibration for cameras acquisition
Spatial frequency is identical with the pre-set space frequency；The institute that the controller is obtained according to default modulation degree and the calibration for cameras
The rotary axis gyration of the modulation degree driving tunable optical density board for demarcating light beam is stated, until the calibration for cameras is obtained
The demarcation light beam modulation degree it is identical with the default modulation degree.
The above-mentioned gray scale cosine distribution optical target analogue means for modulation transfer function detection can be empty with accurate simulation
Between the gray scale cosine distribution target that is matched with the testing requirement of optical system to be measured of frequency and modulation degree, with the gray scale cosine point
Cloth target realizes the MTF direct detections of optical system to be measured as input, not only conforms with the original definition of MTF, and can be direct
The MTF of optical system to be measured is measured, without follow-up data processing, so as to effectively improve the precision and efficiency of MTF detections.Together
When, the above-mentioned gray scale cosine distribution optical target analogue means for modulation transfer function detection also has following technique effect：
(1) present invention is double by building for the gray scale cosine distribution optical target analogue means of modulation transfer function detection
The common optical interference circuit of light beam, and by the side interfere arm in dual-beam altogether optical interference circuit and there is high-resolution high precision position transposition
Whole connection, drives high precision displacement adjustment platform to drive the second standard flat speculum to be carried out along optical axis direction micro- by controller
Amount motion, so as to change the length of the common optical interference circuit interference cavity of dual-beam, realizes the tuning of interference fringe spacing, and then realize ash
Spend cosine distribution optical target spatial frequency can continuously, hair-breadth tuning；It is simultaneously another in dual-beam altogether optical interference circuit
Tunable optical density board is set in the interfere arm of side, and the tunable optical density board carries out rotary axis under the driving effect of controller and returns
The ratio between transhipment is dynamic, so that change the luminous intensity of the first polarized monochromatic beamlets and the second polarized monochromatic beamlets, and then change interference light
The gray modulation degree of the interference fringe of beam, finally realizes the continuously-tuning of the modulation degree of gray scale cosine distribution optical target.Cause
This, the gray scale that the gray scale cosine distribution optical target analogue means for modulation transfer function detection proposed by the present invention is simulated
Cosine distribution optical target can realize quantitative, the continuous adjustment of spatial frequency and fringe gray level modulation degree, disclosure satisfy that tool
Have different photoelectric parameters optical system to be measured (such as space optical camera and possess coupling discrete sampling characteristic photoelectronic imaging system
System etc.) system-level MTF high precision test.
(2) after high-resolution optical fiber image transmission bundle being added into conventional electrophotographic system, light path can be made to possess " flexibility ", is had
Beneficial to the optical property for improving photo electric imaging system and the volume and weight of photo electric imaging system is reduced, therefore this possessed
The new ideas photo electric imaging system of " flexibility " light path in all great application potential in the fields such as astronomy, national defence, medical science, biology, but by
In the coupling sampling nature that it is limited by discrete picture elements, therefore traditional MTF detection methods can cause measurement result to vibrate, it is difficult to
Efficiently, the image quality of this kind of photo electric imaging system with coupling discrete sampling characteristic, but this hair accurately, are quantitatively evaluated
Bright the proposed gray scale cosine distribution optical target analogue means for modulation transfer function detection, can not receive discrete picture elements
The influence of coupling sampling nature and directly simulate generation gray scale cosine distribution optical target, if using the optical target as to be measured
The input of optical system and the definition based on MTF, it becomes possible to which the output according to optical system to be measured for being input into optical target rings
Answer characteristic and accurately measure the MTF for being all imaged link, realize to the photo electric imaging system with coupling discrete sampling characteristic
High accuracy MTF is detected.
(3) the gray scale cosine distribution optical target analogue means profit for modulation transfer function detection proposed by the invention
With speckle in narrow band pass filter and space filtering light path realization removal interference fringe, the optics mesh of simulation generation can be effectively improved
Mark quality, while after the second optical alignment system in invention is replaced by into objective with variable focal length, present invention can apply to all
Such as the first-class production of digital camera, cell-phone camera and the quick pixel soil loss of production line in detection workshop.Due to photoelectronic imaging system
Unite and meet the original physical definition of MTF for the output response of cosine optical target, therefore apply gray scale cosine distribution optics mesh
Mark carries out the picture quality detection of photo electric imaging system without follow-up complicated image procossing and mathematical algorithm, to test environment disturbance
Sensitiveness is greatly reduced, and without the various errors introduced by test link are filtered with treatment, therefore the present invention is applied
Detection efficiency and reduces cost can be effectively improved in the MTF quick detections of optical workshop.
Brief description of the drawings
Fig. 1 is the present invention former for the light path of the gray scale cosine distribution optical target analogue means of modulation transfer function detection
Reason schematic diagram；
Fig. 2 is the structural representation of the gray scale cosine distribution optical target analogue means for modulation transfer function detection.
Specific embodiment
Technical scheme is described in detail below in conjunction with accompanying drawing and preferred embodiment.
Because the spatial gradation information theory of equal inclination fringe is according to cosine distribution therefore of the invention for modulating
The gray scale cosine distribution optical target analogue means of transmission function detection is also based on principle of interference structure.A reality wherein
Apply in example, as depicted in figs. 1 and 2, the gray scale cosine distribution optical target analogue means for modulation transfer function detection includes
Lighting source 1, narrow band pass filter 2, flat field microcobjective 3, pin hole graticle 4, the first optical alignment system 5, polarizing beam splitter mirror
6th, tunable optical density board 7, the first standard flat speculum 8, the second standard flat speculum 9, beam splitter 10, calibration for cameras 11,
Coupling object lens 12, the second optical alignment system 13, high precision displacement adjustment platform 14 and controller.
Specifically, in the present embodiment, lighting source 1 is used to provide the collimation directional light for illuminating for analogue means
Beam.Used as a kind of specific embodiment, the lighting source 1 in the present invention can use the wide spectrum comprising 632.8nm spectral coverages
Xenon lamp, so as to eliminate due to causing the speckle phenomena often occurred in interference fringe using usual LASER Light Source.
The collimation collimated light beam that lighting source 1 sends generates collimated monochromatic light after narrow band pass filter 2 is filtered, wherein narrow
The coherence length of collimation collimated light beam can be shortened with optical filter 2, so that filtered collimated monochromatic light meets interference fringe
The condition of generation.As a kind of specific embodiment, the narrow band pass filter 2 in the present invention be centre wavelength for 632.8nm and
Narrow band pass filter with a width of 0.1nm, after the collimation collimated light beam sent by lighting source 1 is by narrow band pass filter 2, turns into
Centre wavelength is 632.8nm, the collimated monochromatic light with a width of 0.1nm.
As shown in Fig. 2 flat field microcobjective 3, pin hole graticle 4, focal length for adjusting flat field microcobjective 3 it is micro-
Object lens focus adjusting mechanism 15 and for adjust pin hole graticle 4 translational motion pin hole two-dimension translational adjustment platform 16 collectively form
Illuminator, illuminator focusing platform 17 can be realized to the overall focusing along optical axis direction of the illuminator.Here can be with
Whether the shape of the interference fringe obtained by calibration for cameras 11 and distribution are accurate relative to the first optics to judge illuminator
Direct line 5 defocus of system, specific method is：If interference fringe is concentric circles distribution or striped bending facing one direction, show to shine
There is defocus relative to the first optical alignment system 5 in bright system；If interference fringe is vertical and equidistantly distributed, show illumination system
System does not exist defocus relative to the first optical alignment system 5.Therefore, according to the above-mentioned interference fringe obtained to calibration for cameras 11
Shape and the determination methods of distribution, it is possible to achieve close the position of focal plane between collimation collimated light beam and the first optical alignment system 5
The calibration of system.Collimated monochromatic light is irradiated into flat field microcobjective 3, the optical alignment system 5 of pin hole graticle 4 and first successively,
Wherein flat field microcobjective 3 is identical with the relative aperture of the first optical alignment system 5, and pin hole graticle 4 is located at the micro- thing of flat field
The object space focal plane of mirror 3.Collimated monochromatic light is converged after being irradiated into the flat field microcobjective 3 of image space telecentricity, forms relative aperture
It is the convergence sphere glistening light of waves beam of F, pin hole graticle 4 and its multidimensional adjustment machine is placed in the object space plane of flat field microcobjective 3
The diameter in the asterism hole of structure, wherein pin hole graticle 4 can be according to actual needs optical target light intensity and set, example
Such as the diameter in the asterism hole of pin hole graticle 4 can be set as 0.005mm；Pin hole graticle 4 is arranged on the micro- thing of flat field
The object plane of mirror 3, is irradiated into what flat field microcobjective 3 was formed using the multi-dimensional adjusting mechanism of pin hole graticle by collimated monochromatic light
The geometric center of focal beam spot overlaps with the geometric center in the asterism hole of pin hole graticle 4.This kind of light path arrangement method will enter one
Step improves the quality of outgoing beam, improves the uniformity of light distribution, and is formed close to preferable spherical wave.The convergence sphere glistening light of waves
Beam is irradiated into the first optical alignment system 5, wherein the bore of the first optical alignment system 5 is larger and with subsequent intervention light path
Bore is equal, while the relative aperture of the first optical alignment system 5 is identical with the relative aperture of flat field microcobjective 3, converges ball
Face glistening light of waves beam through the first optical alignment system 5 collimate after turn into collimation collimated light beam, centered on the collimation collimated light beam wavelength with
The centre wavelength of narrow band pass filter 2 is identical and possesses the directional light of go-no-go.Alternatively, the bore of the first optical alignment system
It is 50mm, focal length is 150mm, and relative aperture is 10.
During the object space focal plane that pin hole graticle 4 is arranged at into flat field microcobjective 3, can use with lower section
Method determines whether pin hole graticle 4 has been located in the object space focal plane of flat field microcobjective 3：Using microcobjective focus adjusting mechanism 15
Flat field microcobjective 3 is carried out along the adjustment of optical axis direction, interference fringe in the interference image according to formed by calibration for cameras 11
Resolution ratio come determine pin hole graticle 4 whether be located at flat field microcobjective 3 object space focal plane on, meanwhile, control pin hole graduation
The pin hole two-dimension translational adjustment platform 16 of plate 4 enters to pin hole graticle 4 along the both direction vertical with the optical axis of collimation collimated light beam
Row two-dimension translational is adjusted, and the gray value of the interference fringe image obtained until calibration for cameras 11 meets the threshold value of setting.
The collimation collimated light beam of the outgoing of the first optical alignment system 5 exposes to inclined on the optical axis of collimation collimated light beam
Shake beam splitter 6, after the collimation collimated light beam of polarizing beam splitter mirror 6 is reflected and reflected, obtains two orthogonal light of polarization direction
Beam, respectively the first polarized monochromatic beamlets and the second polarized monochromatic beamlets, the first polarized monochromatic beamlets and the second polarized monochromatic light
Beam is irradiated into the both sides interfere arm of common optical interference circuit respectively, and wherein both sides interfere arm is by standard flat speculum and its tune
Whole mechanism composition, side interfere arm possesses along the high-resolution displacement mechanism of optical axis direction, such as using piezoelectric ceramics as actuating
The micro-displacement mechanism (piezoelectric ceramics micrometric displacement translational platform) of device, the micro-displacement mechanism can be realized being transported along the translation of optical axis direction
It is dynamic, and connected standard flat speculum is driven, standard flat speculum thereon is also translated along optical axis direction
Motion, is provided with tunable optical density board in opposite side interfere arm, and process can be changed by adjusting the tunable optical density board
The light intensity of light beam.
After first polarized monochromatic beamlets and the second polarized monochromatic beamlets reflect through standard flat speculum respectively, irradiate again
Into polarizing beam splitter mirror 6, it is concerned with after the refraction of beam-splitting surface polarization and reflection of polarization of polarizing beam splitter mirror 6 respectively, forms interference bar
Line, that is, the first polarized monochromatic beamlets reflect by being reflected by the first standard flat speculum 8 after tunable optical density board 7
The polarization angle of the first polarized monochromatic beamlets be rotated by 90 ° and expose to polarizing beam splitter mirror after again passing by tunable optical density board 7
6, the optical axis of the axial direction of tunable optical density board 7 therein and the first standard flat speculum 8 with the optical axis of collimation collimated light beam
Vertically；Second polarized monochromatic beamlets reflex to polarizing beam splitter mirror 6 by the second standard flat speculum 9, and second inclined after reflection
The polarization angle of homogeneous beam of shaking also is rotated by 90 °, optical axis and the collimation collimated light beam of the second standard flat speculum 9 therein
Optical axis is parallel；The light beam and the second standard flat speculum 9 of 6 pairs of reflections of the first standard flat speculum 8 of polarizing beam splitter mirror reflect
Light beam reflected respectively and reflected after, two light beams form intensity interferometry after meeting coherent condition, obtain and collimate directional light
The vertical interfering beam of the optical axis of beam.
Interfering beam exposes to beam splitter 10, and interfering beam is divided into two light beams by beam splitter 10 by reflection and refraction,
Interfering beam and target interfering beam are respectively demarcated, wherein the image-forming objective lens that interfering beam exposes to calibration for cameras 11 are demarcated,
It is imaged to its focal plane CCD, the enlargement ratio and CCD pictures of the image-forming objective lens of the calibration for cameras 11 through the image-forming objective lens of calibration for cameras 11
Elemental size can be demarcated in advance, and the enlargement ratio and CCD pixel dimensions according to the advance image-forming objective lens demarcated can be precalculated and obtained
The parameters such as the measurement dimension and its corresponding amplification coefficient of calibration for cameras 11, and the parameter of calibration for cameras 11 is stored to control
Device；Target interfering beam exposes to the coupling object lens 12 that object plane is infinity, wherein the focal length and relative aperture of coupling object lens 12
It is directly proportional to the focal length and relative aperture of the image-forming objective lens of calibration for cameras 11 respectively, and the coupling optical alignment of object lens 12 and second
The parfocalization of system 13, that is, the image space focal plane for coupling object lens 12 is overlapped with the focal plane of the second optical alignment system 13, and guarantee is filled
Full its available field of view, meanwhile, the linear field for coupling object lens 12 is identical with the linear field of the second optical alignment system 13, specifically can be with
Change the focal length of coupling object lens 12 using object lens focus adjusting mechanism 18 is coupled, so as to change the size of its linear field, and then change
Be imaged target interfering beam to coupling object lens by the size of the gray scale cosine distribution optical target simulated, coupling object lens 12
In 12 image space focal plane, the second optical alignment system 13 is converted to the interference fringe in the image space focal plane for coupling object lens 12
Far field interference fringe, obtains the gray scale cosine distribution optical target for modulation transfer function detection.It is with optical system to be measured
As a example by space optical camera, because the front end of space optical camera is the telescope optical system that object plane is located at infinity, therefore this
The analogue means of invention needs the gray scale cosine distribution optical target that will be simulated using the second optical alignment system 13 to be converted to
After far-field optics target, system-level MTF detections are used further to.When optical system to be measured for object plane is located at the photographic lens for having range line
When, analogue means of the invention will directly couple the thing of object lens 12 then without setting the second optical alignment system 13 in the optical path
Face is adjusted to the object plane parfocalization with the optical imaging system of optical system front end to be measured.
The gray scale cosine distribution optical target analogue means for modulation transfer function detection in the present embodiment also includes
Controller (in Fig. 1 and Fig. 2 and be not drawn into), the controller constitutes measurement-fortune with high precision displacement adjustment platform 14, calibration for cameras 11
Dynamic control closed loop, meanwhile, the controller constitutes another measurement-motion control closed loop with tunable optical density board 7, calibration for cameras 11.
The concrete methods of realizing of the above two measurement-motion control closed loop that controller is constituted with other optics can be using existing
The servo closed control method for having technology is realized.
Specifically, the spatial frequency of the demarcation light beam that controller is obtained according to pre-set space frequency and calibration for cameras 11 is real-time
The actuator of control high precision displacement adjustment platform 14 is exerted oneself, and drives high precision displacement adjustment platform 14 to finely tune, while high precision displacement
Adjustment platform 14 drives the second standard flat speculum thereon along the optical axis direction trace movement of the second standard flat speculum, from
And the fine setting of interference cavity length is realized, the relative distance between two interfere arms is changed, and then realize the gray scale to being simulated
The continuous tuning of the spatial frequency of cosine distribution optical target, until the demarcation light beam that pre-set space frequency is obtained with calibration for cameras
Spatial frequency it is identical after, controller stop to high precision displacement adjust platform 14 drive control.
Preferably, high precision displacement adjusts platform 14 for piezoelectric ceramics micrometric displacement translational platform, and piezoelectric ceramics displacement platform
Motion Resolution rate is less than or equal to 200nm, to ensure the gray scale cosine distribution optical target that analogue means of the present invention is generated
The continuously adjustable of spatial frequency, to gray scale cosine distribution optical target when meeting different optical system detection MFT to be measured
The different requirements of spatial frequency.
Additionally, the modulation degree driving tunable optical of the demarcation light beam that controller is obtained according to default modulation degree and calibration for cameras 11
The rotary axis gyration of density board 7, the continuous light strength ratio for changing two coherent beams, so as to realize analogue means of the present invention
The continuous tuning of the modulation degree of the gray scale cosine distribution optical target simulated, until default modulation degree is obtained with calibration for cameras 11
Demarcation light beam modulation degree it is identical after, the station keeping of controller control tunable optical density board 7.
The gray scale cosine distribution optical target analogue means for modulation transfer function detection proposed by the invention can be with
The gray scale cosine distribution target that accurate simulation spatial frequency and modulation degree are matched with optical system to be measured, with the gray scale cosine point
Cloth target realizes that the MTF of optical system to be measured is detected as input, not only conforms with the original definition of MTF, and can direct measurement
Go out the MTF of optical system to be measured, without follow-up data processing, so as to effectively improve the precision and efficiency of MTF detections.Meanwhile,
The above-mentioned gray scale cosine distribution optical target analogue means for modulation transfer function detection also has following technique effect：
(1) present invention is double by building for the gray scale cosine distribution optical target analogue means of modulation transfer function detection
The common optical interference circuit of light beam, and by the side interfere arm in dual-beam altogether optical interference circuit and there is high-resolution high precision position transposition
Whole connection, drives high precision displacement adjustment platform to drive the second standard flat speculum to be carried out along optical axis direction micro- by controller
Amount motion, so as to change the length of the common optical interference circuit interference cavity of dual-beam, realizes the tuning of interference fringe spacing, and then realize ash
Spend cosine distribution optical target spatial frequency can continuously, hair-breadth tuning；It is simultaneously another in dual-beam altogether optical interference circuit
Tunable optical density board is set in the interfere arm of side, and the tunable optical density board carries out rotary axis under the driving effect of controller and returns
The ratio between transhipment is dynamic, so that change the luminous intensity of the first polarized monochromatic beamlets and the second polarized monochromatic beamlets, and then change interference light
The gray modulation degree of the interference fringe of beam, finally realizes the continuously-tuning of the modulation degree of gray scale cosine distribution optical target.Cause
This, the gray scale that the gray scale cosine distribution optical target analogue means for modulation transfer function detection proposed by the present invention is simulated
Cosine distribution optical target can realize quantitative, the continuous adjustment of spatial frequency and fringe gray level modulation degree, disclosure satisfy that tool
Have different photoelectric parameters optical system to be measured (such as space optical camera and possess coupling discrete sampling characteristic photoelectronic imaging system
System etc.) system-level MTF high precision test.
(2) after high-resolution optical fiber image transmission bundle being added into conventional electrophotographic system, light path can be made to possess " flexibility ", is had
Beneficial to the optical property for improving photo electric imaging system and the volume and weight of photo electric imaging system is reduced, therefore this possessed
The new ideas photo electric imaging system of " flexibility " light path in all great application potential in the fields such as astronomy, national defence, medical science, biology, but by
In the coupling sampling nature that it is limited by discrete picture elements, therefore traditional MTF detection methods can cause measurement result to dissipate, it is difficult to
Efficiently, the image quality of this kind of photo electric imaging system with coupling discrete sampling characteristic, but this hair accurately, are quantitatively evaluated
Bright the proposed gray scale cosine distribution optical target analogue means for modulation transfer function detection, can not receive discrete picture elements
The influence of coupling sampling nature and directly simulate generation gray scale cosine distribution optical target, if using the optical target as to be measured
The input of optical system and the definition based on MTF, it becomes possible to which the output according to optical system to be measured for being input into optical target rings
Answer characteristic and accurately measure the MTF for being all imaged link, realize to the photo electric imaging system with coupling discrete sampling characteristic
High accuracy MTF is detected.
(3) the gray scale cosine distribution optical target analogue means profit for modulation transfer function detection proposed by the invention
With speckle in narrow band pass filter and space filtering light path realization removal interference fringe, the optics mesh of simulation generation can be effectively improved
Mark quality, while after the second optical alignment system in invention is replaced by into objective with variable focal length, present invention can apply to all
Such as the first-class production of digital camera, cell-phone camera and the quick pixel soil loss of production line in detection workshop.Due to photoelectronic imaging system
Unite and meet the original physical definition of MTF for the output response of cosine optical target, therefore apply gray scale cosine distribution optics mesh
Mark carries out the picture quality detection of photo electric imaging system without follow-up complicated image procossing and mathematical algorithm, to test environment disturbance
Sensitiveness is greatly reduced, and without the various errors introduced by test link are filtered with treatment, therefore the present invention is applied
Detection efficiency and reduces cost can be effectively improved in the MTF quick detections of optical workshop.
Gray scale cosine distribution optical target analogue means for modulation transfer function detection proposed by the invention is not
Using usual LASER Light Source as optical interference circuit lighting source, but use xenon source coordinate narrow band pass filter, flat field
Microcobjective and pin hole dividing plate produce high-quality coherent illumination beam, because the light intensity of laser beam is Gaussian Profile
, and there are pattern effects, there is speckle, ghost image phenomenon etc. with being difficult to avoid that in the interference fringe produced by laser lighting,
And these phenomenons have considerable influence for the quality of interference fringe, it is difficult to meet the high-acruracy survey demand of MTF；Secondly, it is safe
The usual optical interference circuit structure such as graceful-Green, Feisuo, lateral shear is extremely sensitive to environmental perturbation, the ring such as vibration, air-flow
Border disturbance is likely to bring more random error, spatial frequency and its stability, percentage modulation the striped arrow to interference fringe
Amount direction etc. can produce more adverse effect, and the common optical interference circuit of dual-beam proposed by the invention can then eliminate above-mentioned
Environmental perturbation, and the requirement for taking into account that interference fringe spatial frequency is adjustable, modulation degree is adjustable etc. to light path arrangement；Finally, this hair
Bright analogue means adds calibration for cameras in the optical path, and it mainly has two aspect effects：First can be the ash to being simulated
Spending the spatial frequency of cosine distribution optical target, modulation of fringes carries out real-time calibration, it is ensured that institute's analog gray scale cosine distribution light
Learn the stabilization of target items optical parametric, can reconcile controllable, second is that can be used for debuging for the whole analogue means light path of itself
And self calibration, due to the alignment precision and whole illuminator and the first optical alignment of pin hole graticle and flat field microcobjective
The parfocalization degree of system focal plane all can produce considerable influence to optical target analog-quality, therefore by setting demarcation in the optical path
Camera, and the proper calibration camera measurement parameter, it is possible to achieve for the gray scale cosine distribution light of modulation transfer function detection
The self calibration and self-calibration of target simulator are learned, so as to be surveyed for optical system to be measured provides high-quality optical target, is improved
The accuracy of detection of system-level MTF.
Each technical characteristic of embodiment described above can be combined arbitrarily, to make description succinct, not to above-mentioned reality
Apply all possible combination of each technical characteristic in example to be all described, as long as however, the combination of these technical characteristics is not deposited
In contradiction, the scope of this specification record is all considered to be.
Embodiment described above only expresses several embodiments of the invention, and its description is more specific and detailed, but simultaneously
Can not therefore be construed as limiting the scope of the patent.It should be pointed out that coming for one of ordinary skill in the art
Say, without departing from the inventive concept of the premise, various modifications and improvements can be made, these belong to protection of the invention
Scope.Therefore, the protection domain of patent of the present invention should be determined by the appended claims.
Claims (5)
1. it is a kind of for modulation transfer function detection gray scale cosine distribution optical target analogue means, it is characterised in that including
Lighting source (1), narrow band pass filter (2), flat field microcobjective (3), pin hole graticle (4), the first optical alignment system (5),
Polarizing beam splitter mirror (6), tunable optical density board (7), the first standard flat speculum (8), the second standard flat speculum (9), point
Shu Jing (10), calibration for cameras (11), coupling object lens (12), the second optical alignment system (13), high precision displacement adjust platform (14)
And controller,
The collimation collimated light beam that the lighting source (1) sends generates collimated monochromatic light after being filtered through the narrow band pass filter (2),
The collimated monochromatic light is irradiated into the flat field microcobjective (3), the pin hole graticle (4) and first optics successively
Colimated light system (5), and the flat field microcobjective (3) is identical with the relative aperture of first optical alignment system (5), it is described
Object space focal plane of the pin hole graticle (4) positioned at the flat field microcobjective (3)；
The collimation collimated light beam of first optical alignment system (5) outgoing exposes to the polarizing beam splitter mirror (6), the polarization
After beam splitter (6) carries out reflection of polarization and polarization refraction to the collimation collimated light beam, orthogonal first inclined in polarization direction is obtained
Shake homogeneous beam and the second polarized monochromatic beamlets；First polarized monochromatic beamlets are by quilt after the tunable optical density board (7)
The first standard flat speculum (8) reflexes to the first polarized monochromatic light after the polarizing beam splitter mirror (6), and reflection
The polarization angle of beam is rotated by 90 °, the light of the axial direction of the tunable optical density board (7) and the first standard flat speculum (8)
Optical axis of the axle with the collimation collimated light beam is vertical；Second polarized monochromatic beamlets are by the second standard flat speculum
(9) polarization angle for reflexing to second polarized monochromatic beamlets after the polarizing beam splitter mirror (6), and reflection is rotated by 90 °, institute
The optical axis for stating the second standard flat speculum (9) is parallel with the optical axis of the collimation collimated light beam；The polarizing beam splitter mirror (6) is right
The light beam of the first standard flat speculum (8) reflection and the light beam difference of the second standard flat speculum (9) reflection
After being reflected and being reflected, the interfering beam vertical with the optical axis of the collimation collimated light beam is obtained；
The interfering beam exposes to the beam splitter (10), and the beam splitter (10) is reflected and rolled over to the interfering beam
After penetrating, obtain demarcating interfering beam and target interfering beam；The demarcation interfering beam exposes to the calibration for cameras (11)
Image-forming objective lens；The object plane of coupling object lens (12) is infinity, and coupling object lens (12) focal length and relative aperture point
It is not directly proportional to the focal length and relative aperture of the image-forming objective lens of the calibration for cameras (11), the target interfering beam exposes to institute
Coupling object lens (12) is stated, be imaged for the target interfering beam to the image space of coupling object lens (12) by coupling object lens (12)
It is described to couple object lens (12) and the second optical alignment system (13) parfocalization and the line for coupling object lens (12) on focal plane
Visual field is identical with the linear field of second optical alignment system (13), and second optical alignment system (13) is exported for adjusting
The gray scale cosine distribution optical target of modulation trnasfer function detection；
The spatial frequency of the demarcation light beam that the controller is obtained according to pre-set space frequency and the calibration for cameras (11)
Drive the high precision displacement to adjust platform (14) to finely tune, the high precision displacement adjusts platform (14) and drives second standard flat
Speculum (9) along the second standard flat speculum (9) optical axis direction trace movement, until the calibration for cameras obtain
The spatial frequency for demarcating light beam is identical with the pre-set space frequency；The controller is according to default modulation degree and the mark
The modulation degree for determining the demarcation light beam of camera (11) acquisition drives the rotary axis revolution fortune of the tunable optical density board (7)
It is dynamic, until the modulation degree of the demarcation light beam of the calibration for cameras (11) acquisition is identical with the default modulation degree.
2. it is according to claim 1 for modulation transfer function detection gray scale cosine distribution optical target analogue means,
Characterized in that,
The lighting source (1) includes the wide spectrum xenon lamp of 632.8nm for spectral coverage.
3. the gray scale cosine distribution optical target for modulation transfer function detection according to claim 1 and 2 simulates dress
Put, it is characterised in that
The centre wavelength of the narrow band pass filter (2) is 632.8nm, with a width of 0.1nm.
4. the gray scale cosine distribution optical target for modulation transfer function detection according to claim 1 and 2 simulates dress
Put, it is characterised in that
The bore of first optical alignment system (5) is 50mm, and focal length is 150mm, and relative aperture is 10.
5. the gray scale cosine distribution optical target for modulation transfer function detection according to claim 1 and 2 simulates dress
Put, it is characterised in that
It is piezoelectric ceramics micrometric displacement translational platform that the high precision displacement adjusts platform (14), the motion of the piezoelectric ceramics displacement platform
Resolution ratio is less than or equal to 200nm.
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| CN112099227A (en) * | 2020-09-16 | 2020-12-18 | 吉林大学 | Angle tolerance distribution method for high polarization-maintaining orthogonal reflector group with vibrating mirror |
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