Background technology
In recent years; The superiority of freeform optics surface causes scientific and technical personnel's extensive concern; And attempt using free form surface and improve Performance of Optical System; Generally believe that freeform optics surface will produce revolutionary impact to the quality of optical system, miniaturization etc., but be that cost of manufacture or machining precision all far can not be compared with traditional aspheric surface that it is the bottleneck technology of restriction free form surface technical development that the precision of face shape detects.
The processing of freeform optics surface is divided into milling, grinding, polishing three phases, according to the difference of each stage precision prescribed, adopts the different detection means respectively.Generally; Phase one and subordinate phase use three coordinate machine and face shape contourgraph to detect respectively; The phase III accuracy requirement is the highest, makes traditional contact type measurement can't reach requirement through the freeform optics surface after the polishing for superhigh precision requirement of measuring and the contradiction that in testing process, must take into account between measuring accuracy and the measurement range.At present, the freeform optics surface detection technique has been proposed diverse ways both at home and abroad, but all existed problem: measuring method is slow, and is flexible not enough.People such as Petz M are at " Reflection grating method for 3D measurement of reflecting surfaces " (SPIE; V4399; 2001) propose the reflection grating photogrammetry in, precision can reach micron dimension, but needs to use numerous and diverse iterative algorithm.People such as Zhang Xin are at " detection method of freeform optics surface " (" Chinese optics and applied optics " the 1st volume; The 1st phase, 2008) use CGH in and detect non-rotational symmetric three phase boards, utilize computed hologram to remove the detection optical free form surface as zero compensation machine as zero compensation machine; Saved complicated iterative algorithm; But there are one-to-one relationship in zero-bit CGH and freeform optics surface, and cost is very high, and when seized slope is excessive; The mismachining tolerance of CGH increases, precise decreasing.People such as Jan Liesener are at " Interferometer with Dynamic Reference " (SPIE; V5252,2004) an a kind of technical scheme of middle proposition based on Thailand's graceful Green's type interference system and many inclinations of the vertical axle distribution of pointolite array generation corrugated interference.This scheme can detect the symmetrical aspheric surface of rotation; Also can detect the symmetrical aspheric surface of non-rotation, have the application prospect that detects free form surface, but safe graceful Green's pattern of interference system application enhancements; In interferometer reference arm, introduce many optical elements; Light path is complicated, and error source is more, is unfavorable for improving accuracy of detection.
Summary of the invention
The object of the present invention is to provide a kind of check that is suitable for optical aspherical surface and freeform optics surface, cover more tested object, the striking rope type freeform optics surface interference checking device that precision height and cost are low.
The technical solution that realizes the object of the invention is: a kind of freeform optics surface interference checking device comprises laser instrument, beam-expanding system, controlled lenticule point source array, Amici prism, standard sphere lens combination, phase shifter, aperture, imaging len, charge coupled device ccd, monitor and computing machine; Laser instrument is placed beam-expanding system at the back; Place controlled lenticule point source array behind the beam-expanding system, controlled lenticule point source array is placed Amici prism at the back, and light channel structure is divided into two-way behind Amici prism; One the tunnel is to place standard sphere lens combination behind the Amici prism; The phase shifter driving standard sphere lens combination that is connected with standard sphere lens combination moves laterally, and aperture is placed in the catoptrical direction of Amici prism in another road, and aperture is placed imaging len at the back; Place charge coupled device ccd behind the imaging len, charge coupled device ccd is connected with computing machine with monitor.
The present invention compared with prior art; Its remarkable advantage: (1) interference system of the present invention adopts striking rope type; Use controlled lenticule point source array to produce many visual fields interferogram reconstruction free form surface face shape in the light path; Produce the bright scheme of controlled point source array point according to the tested surface characteristic, device can cover than polymorphic type tested object (comprising aspheric surface).Existing free form surface detection method unicity and expensive shortcoming have been overcome.(2) with reference to corrugated and inclination corrugated, many visual fields through much at one optical element, and system adopts striking rope type, overcome the big defective of being brought by non-light path altogether in the existing detection method of error.(3) interference system need not motion assemblies such as precision micro-displacement platform, has overcome the sub-aperture method defective high to the displacement accuracy requirement.
Embodiment
Freeform optics surface interference checking device of the present invention comprises laser instrument 1, beam-expanding system 2, controlled lenticule point source array 3, Amici prism 4, standard sphere lens combination 5, phase shifter 6, aperture 8, imaging len 9, charge coupled device ccd 1, monitor 11 and computing machine 12; Controlled lenticule point source array 3 comprises that microlens array 3-1, array of orifices 3-2 and light source select mask plate 3-3, and controlled lenticule point source array 3 is positioned on the emitting light path of laser instrument, be used to produce the pointolite that will select.Microlens array 3-1 places array of orifices 3-2 thereafter, and array of orifices 3-2 places the back light source again and selects mask plate 3-3; The number of arrays of said microlens array 3-1, the number of arrays of array of orifices 3-2 and light source select number of arrays three's number of mask plate 3-3 identical.
Beam-expanding system 2 is placed in laser instrument 1 back; Controlled lenticule point source array 3 is placed in beam-expanding system 2 backs, and Amici prism 4 is placed in controlled lenticule point source array 3 back, and light channel structure is divided into two-way behind Amici prism 4; One the tunnel is Amici prism 4 back placement standard sphere lens combination 5; The phase shifter 6 driving standard sphere lens combination 5 that is connected with standard sphere lens combination 5 moves laterally, and apertures 8 are placed in Amici prism 4 catoptrical directions in another road, and imaging len 9 is placed in aperture 8 back; Charge coupled device ccd 1 is placed in imaging len 9 backs, and charge coupled device ccd 1 is connected with computing machine 12 with monitor 11.
Freeform optics surface interference checking device of the present invention; Beam-expanding system 2 is the keplerian telescope structure; By the first lens 2-1, the second aperture 2-2; The second lens 2-3 forms, and the first lens 2-1 overlaps with the focus of the second lens 2-3, and the second aperture 2-2 is placed on the focus of the first lens 2-1 and the second lens 2-3.
Freeform optics surface interference checking device of the present invention; Said light source select mask plate 3-3 by with microlens array 3-1 in the same number of mask baffle plate of lenticule form; Computing machine is through the open and close of circuit program control mask baffle plate, and when the mask baffle plate blocked array of orifices 3-2 and goes up the aperture corresponding with it, the pointolite that corresponding lenticule produces among the microlens array 3-1 i.e. quilt was blocked; When the mask baffle plate was opened, the pointolite that corresponding lenticule produces among the microlens array 3-1 was promptly lighted.
The invention is characterized in the design of pointolite array and optical interference circuit; Let light source select mask plate to make the aperture that is positioned on the optical axis open light as a reference all the time; Thereby make reference light and test light light path altogether; See through optical element much at one, have striking rope type optical interference circuit characteristic, error is little.The present invention adopts the many visual fields interferogram reconstruction free form surface face shape error that is produced by controlled lenticule point source array.Utilize microlens array and light source to select mask plate to produce inclination corrugated, many visual fields, the tested free form surface that throws light on, interference system adopt striking rope type, and many visual fields interferogram restores by the movable phase interfere technology and obtains subregion corrugated data set; Demarcate the position relation between CCD pixel and the many visual fields interferogram with the standard sphere as measurand, when measuring free form surface, will squint in interferogram position, many visual fields, obtain wave tilt information by side-play amount; According to inclination information and subregion corrugated, many visual fields data set reconstruct tested surface face shape information.Produce the bright scheme of controlled point source array point according to the tested surface characteristic, device can cover more tested object.Concrete principle of work is: the light beam by the He-Ne laser instrument sends, behind beam-expanding system, produce the uniform parallel beam incident of illumination microlens array, and produce pointolite.The light source aperture that wherein is positioned on the optical axis is in open mode all the time; Light as a reference; The light beam that pointolite sends on the axle is assembled by the standard spherical lens behind Amici prism; Convergent point overlaps with last sphere centre of sphere of standard spherical lens, and a part of light beam sees through the tested free form surface of last sphere incident of standard spherical lens, and a part of light beam is directly by last spheric reflection of standard spherical lens light beam as a reference that goes back.If tested free form surface is reduced to idol time aspheric surface, then only on the chosen axis pointolite just can accomplish detection.
Below in conjunction with accompanying drawing, the present invention is described in further detail.
Referring to Fig. 1 and Fig. 2; The light beam that sends by He-Ne laser instrument 1;, beam-expanding system 2 forms the controlled lenticule point source array 3 of the uniform parallel beam incident of illumination after being made up of lens 2-1, aperture 2-2, lens 2-3; Controlled lenticule point source array 3 selects mask plate 3-3 to form by microlens array 3-1, array of orifices 3-2 and light source; Light source is selected mask plate 3-3 to make to be positioned among the array of orifices 3-2 aperture on the optical axis to open all the time a last pointolite is provided, and by 5 convergences of standard sphere lens combination, convergent point overlaps with the centre of sphere of last sphere in the standard sphere lens combination 5 light beam that pointolite sends on the axle behind Amici prism 4; Part light beam sees through the tested free form surface 7 of standard sphere lens combination 5 incidents, and another part light beam is directly by the light beam as a reference that goes back of last spheric reflection in the standard sphere lens combination 5.If tested free form surface 7 is reduced to idol time aspheric surface, then only on the chosen axis pointolite just can detect.If 7 shape complicacies of tested free form surface; Then by the selection scheme of its face shape characteristics determined off-axis point light source igniting; After the light beam that the off-axis point light source sends is assembled by standard sphere lens combination 5; Central ray is along the tested free form surface 7 of normal direction incident of tested free form surface 7, through test beams that tested free form surface 7 returns with by axle on the reference beam that last spheric reflection is returned in standard sphere lens combination 5 that sends of pointolite form interference.Pointolite is lighted the reference beam and the test beams that form with the off-axis point light source igniting and is all got into the interference image acquisition system that is formed by aperture 8, imaging len 9, CCD1 by Amici prism 4 reflections at last on the axle, monitors interferogram when monitor 11 is used for the device adjustment in real time.5 phase shifts of phase shifter 6 control criterion spherical lens groups produce phase-shift interference, and the phase-shift interference of 12 pairs of collections of computing machine is handled the face shape of calculating tested free form surface.
When detecting free form surface face shape, adopt the standard sphere to demarcate the detection of free form surface.Identical pointolite is selected scheme for use when in the freeform optics surface pick-up unit, adopting with the detection free form surface; With the standard sphere as measured piece 7; Obtain identical with the free form surface incident beam; Reflex to one group of pixel reference position on the CCD1 target surface by the standard sphere, promptly chief ray reference position data on the CCD1 target surface in many visual fields supply the reconstruct of free form surface face shape to use.
On the basis of test, for face shape, need elder generation by 7 shape characteristics of tested free form surface through the tested free form surface 7 of interferometry reconstruct, through three-dimensional reverse optical path-tracing, obtain the pointolite of measuring this tested free form surface 7 and select scheme for use.By the reverse optical path-tracing model that tested free form surface 7 sets out, the application with two aspects: 1 face shape characteristic by tested free form surface 7, confirm off-axis point light source optimal selection scheme, this moment by tested free form surface 7 traces to microlens array 3-2 plane; 2 confirm to put on the tested free form surface 7 corresponding relation between the location of pixels on position and the CCD1 target surface, and the gained result is used for the follow-up standard sphere demarcation and the three-dimensional reconstruction of free form surface face shape.Light the microlens array pointolite successively by computing machine 12 controls, and control phase shifter 6 generation phase-shift interferences, by movable phase interfere art corrugated restoration model, obtain each visual field face graphic data group; Use standard sphere displacement measured piece; Carry out identical test process, obtain the reference position of each visual field on the CCD1 target surface, utilize two secondary data result; Find out each corrugated, visual field data and corrugated barycentre offset, by going parcel and seed mediated growth method reconstruct free form surface face shape.