DE19853302A1 - Sensor for measuring distance or surface profiles of workpieces; includes optical branches monitoring two static characteristics to provide focusing corrections - Google Patents

Sensor for measuring distance or surface profiles of workpieces; includes optical branches monitoring two static characteristics to provide focusing corrections

Info

Publication number
DE19853302A1
DE19853302A1 DE1998153302 DE19853302A DE19853302A1 DE 19853302 A1 DE19853302 A1 DE 19853302A1 DE 1998153302 DE1998153302 DE 1998153302 DE 19853302 A DE19853302 A DE 19853302A DE 19853302 A1 DE19853302 A1 DE 19853302A1
Authority
DE
Germany
Prior art keywords
distance sensor
sensor according
lens
characterized
objective lens
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
DE1998153302
Other languages
German (de)
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BREITMEIER, ULRICH, 76133 KARLSRUHE, DE
Original Assignee
Waelde Juergen
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Waelde Juergen filed Critical Waelde Juergen
Priority to DE1998153302 priority Critical patent/DE19853302A1/en
Publication of DE19853302A1 publication Critical patent/DE19853302A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00Measuring arrangements characterised by the use of optical means
    • G01B11/02Measuring arrangements characterised by the use of optical means for measuring length, width or thickness
    • G01B11/026Measuring arrangements characterised by the use of optical means for measuring length, width or thickness by measuring distance between sensor and object

Abstract

The sensor (10) objective lens (18) can be focused by solenoid. Its position is monitored by a measurement system. Laser diode (11) is a light source. Two optical branches (30, 31) each having cylindrical lens (34, 35) with different depths of focus monitor two static characteristics with different slopes and lengths. Their associated control systems enable focusing corrections to be made.

Description

The invention relates to a for spacing and / or surfaces Profile measurement determined optical distance sensor with a laser diode as a light source, a package arranged in the beam path of the laser diode Mator lens for beam collimation, at least one beam splitter for the beam division and beam deflection, a movable, the beam splitter nachge switched objective lens with an actuator, and with one on the object Measuring lens attached as a position transmitter, as well as with a photo Detector and a control loop for tracking the objective lens in depend ability of a focus error voltage supplied by the photodetector.

Sensors of this type are already known. This is primarily around sensors for scanning CD disks.

So in the from the Institute for Process Measurement and Sensor Technology Techni University of Ilmenau published specialist publication "Optical fiber coupled laser interferometer with non-contact optical probing of test specimen surfaces "is already a process and one of the processes performing sensor system described. With this sensorsy stem enters a laser beam, its divergence angle using a collimator tik is minimized as a largely parallel light in a beam splitter and is partially directed onto a CD surface via focusing optics. The laser beam reflected from the surface of the test object is reflected by a Lin projected onto a quadrant photodiode. Depending on whether the The specimen surface is in the focus point or not, the optics cause that is designed astigmatic, different intensity distributions of the La  radiation. From the intensity distribution of the reflec on the photodetector a focus error signal can be obtained.

In contrast, the invention is intended to provide an optical distance sensor Measurement of workpieces are created, in particular for Distance and surface profile measurement is suitable and determined.

This object is achieved in that in the upper Concept of claim 1 specified sensor for focus detection two optical branches each with a cylindrical lens and a photodetector are seen and that the two cylindrical lenses have different focal lengths have.

Useful developments of the invention are in the subordinate patent claims 2 to 20 specified.

In contrast to the read heads used in CD record players stands for distance sensors of the aforementioned type and purpose Demand for a comparatively large working distance, high Dy namik, low drift, a large measuring range and high resolution. This one The distance sensor according to the invention meets requirements.

Based on the accompanying drawings, Ausführungsfor men of the distance sensor according to the invention and what can be achieved therewith Measuring methods are explained. Schematic views show:

Fig. 1 shows the basic structure of the distance sensor,

Fig. 2 shows details of the distance sensor,

Fig. 3 using a graph, the courses of the focus error voltage over the defocus and

Fig. 4 in a view as in Fig. 1 shows an alternative embodiment of a distance sensor.

The schematically illustrated in Fig. 1 in its entirety distance sensor 10 has a light source, a laser diode 11 and a beam path in which Strah arranged collimator lens 12 to minimize the Divergenzwin kels the laser beam. A beam splitter 13 with a plate prism 14 is arranged behind the collimator lens 12 in the beam direction. On the side of the free surface of the plate prism 14 , a mirror 15 is attached, which can either be covered electronically (for example via an electronically controllable LCD surface) or can be tilted.

A filter 17 is located between the beam splitter 13 of the collimator lens 12 , which, however, is of no further interest here. Between a send to vermes object surface 16 and the beam splitter 13 is a respect to their From prior trackable from the object surface 16 objective lens 18 disposed. The distance between the object surface 16 and the objective lens 18 is equal to the lens focal length and is designated by 19 . Furthermore, the sensor 10 comprises, on the side of the beam splitter 13 facing away from the object surface 16, a confocal detector branch 20 , which consists of a collecting lens 21 , an aperture 22 and a photodiode 23 arranged in the beam path of the reflected light.

Finally, a second beam splitter 25 with a splitter prism 26 is arranged between the diaphragm-side converging lens 21 of the confocal detector branch 20 and the beam splitter 13 in the beam path of the light reflected from the object surface 16 , in order to pass part of the reflected light via a further collecting lens 27 onto a CCD camera 28 deflect at right angles.

A filter 29 is in turn switched into the beam path between the converging lens 27 and the beam splitter 25 .

In addition, the distance sensor 10 comprises two detection branches 30 , 31 , each with a photodetector 32 , 33 and a cylindrical lens 34 , 35 in the beam path of the respective photodetector 32 , 33rd The detection branch 30 is also equipped with a converging lens 36 . The beam path of the photodetector 32 is coupled via a beam splitter 38 with a splitter prism 39 between the Kol limatorlinse 12 and the laser diode 11 in its beam path, as is the beam path of the photodetector 33 via a beam path of the photodetector 32 between the latter and the beam splitter 38 another beam splitter 40 with plate prism 41 .

In the embodiment shown in FIG. 2, the objective lens 18 is held in a ring magnet 44 and fastened via a carrier tube 45 to a spring parallelogram 40 , which has two spaced apart springs 48 with one end clamped in a holder 47 , 49 owns. By means of a coil 50 concentrically around the ring magnet 40 , the carrier tube 45 and thus the objective lens 18 can be displaced according to the double arrow 51 , that is to say the distance of the objective lens 18 from the object surface 16 can be changed when current flows through the coil 50 .

An inductive measuring system 54 is also attached to the carrier tube 45 for measuring the position of the objective lens 18 as a secondary measuring system. The inductive measuring system 54 comprises a ferrite core 56 fastened to the carrier tube 41 by means of a holder 55 and a plunger coil 57 into which the ferrite core 56 is immersed.

Instead of the inductive measuring system 54 , an optical measuring system could also serve, for example a light barrier.

Further, Fig. 2 shows a operatively connected to the moving coil 57 of the inductive measuring system 54 Measurement display 60, and a control circuit 61 for tracking of the objective lens 18. The control circuit 61 is followed by an amplifier 62 which is operatively connected to the coil 50 concentrically surrounding the ring magnet 44 . The control circuit 61 is controlled by a photodetector 63 via an amplifier 64 .

Finally, for scanning the object surface 16 to be optically measured, the objective lens 18 is optionally assigned a stylus 66 , which is detachably received on a stylus needle holder, which is held on the ring magnet 44 and is designed as a ferromagnetic metal ring 67 .

In order to achieve the largest possible measuring range when the level sensor 10 according to the invention is used as intended with a constant size of the light spot to be scanned, the objective lens 18 must always be tracked during the measurement such that the focal point of the light beam coincides with the object surface 16 . In the embodiment of the invention illustrated in the drawing, this is done in such a way that the outer coil 15 pushes the carrier tube 45 via the ring magnet 44 , in which the objective lens 18 is received, when current flows through, depending on the determined focus error voltages.

The secondary measuring system 54 , which is designed as an inductive measuring system, is used for the respective position measurement of the objective lens 18 . If the moving coil 57 of the measuring system 54 is subjected to a constant carrier frequency of, for example, 10 kHz, a displacement of the ferrite core 56 modulates this carrier frequency in accordance with the immersion depth of the ferrite core 56 in the moving coil 57 .

It makes sense to operate the distance sensor 10 such that the measuring light spot is always focused on the object surface 16 . The actuating signal for this is provided by the photodetectors 30 , 31 . In the optimal position of the objective lens 18, these emit a certain error voltage, which is generally zero volts. If the distance between the object surface 16 and the objective lens 18 changes, the error voltage also changes. About egg NEN this is given as a control variable to an electronic control circuit, which moves the objective lens 18 via the coil actuator until the control voltage has become zero again.

The measurement value accessible to the user is output via the secondary measuring system 54 . The underlying measurement philosophy can be defined as follows:
The focal length of the objective lens 18 is constant and thus serves as a "sensor" for the object distance; when the distance between the object surface 16 and the objective lens 18 changes , the lens is tracked until the object distance again corresponds to the focal length of the objective lens. The then valid position of the objective lens 18 is displayed via the secondary measuring system 54 and is a measure of the object distance, correct calibration naturally being a prerequisite.

In the focus detection method according to the astigmatism method, the light point on the object side is only formed as a circular disk on the photodetector if the object distance corresponds to the focal length of the objective lens 18 . The sum output voltage formed, for example, from the four quadrants of the detector is then zero. In all other lens positions, the image point is a more or less pronounced ellipse depending on the degree of focusing, the main axis of which is rotated by 90 °, depending on whether the object distance is larger or smaller than the lens focal length.

The measuring sensitivity and the static measuring range, that is, the length of the characteristic curve, depend mainly on the numerical aperture of the objective lens 18 , but also on the optical design of the detector branch 30 equipped with the cylindrical lens 34 . The physical properties of the objective lens 18 are determined when the sensor 10 is designed . A high numerical aperture provides high sensitivity, but also a short characteristic. This is disadvantageous in practice, because the shorter the characteristic curve, the faster the control loop must correct the focus. For this, the control signal must be low-noise. If the object surface to be scanned has an abrupt discontinuity, for example a step that is higher than the characteristic curve long, the controller loses the surface, ie the control loop disengages and the measured value is lost.

In contrast to distance sensors according to the prior art, the distance sensor 10 according to the invention has two detection branches 30 , 31 with two cylindrical lenses 34 , 35 and possibly different imaging scales. As shown in FIG. 3, this results in two characteristic curves 70 , 71 . The characteristic curve 70 has a large slope with a small length and thus has a high sensitivity, while the characteristic curve 71 has a lower slope with a greater length and accordingly indicates a lower sensitivity. This is achieved in that the converging lens 36 and the cylindrical lens 34 are arranged under the image point F, the position of which results when the objective lens 18 is positioned so that the focus error voltage is zero. A control loop is assigned to each of the detectors 30 , 31 . These control loops have different control characteristics corresponding to the steepness of the respective characteristic curve 70 , 71 . In view of this design, even with larger surface jumps, the control loop assigned to the detector branch with the long characteristic curve remains engaged and, via a suitable electronic circuit or programming, immediate retraction of the other - more sensitive - control loop is unproblematically possible.

An enlargement of the "catch area" also results from an enlargement Enhancement of the photosensitive surfaces of the detector. This increases everything dings the capacity and the cutoff frequency decreases. You can now take advantage fortunately in one detector branch a geometrically rather small detector and a larger quadrant photodetector in the other detector branch install. This achieves a high cutoff frequency during the latched measuring process over the first-mentioned detector and uses the off output voltage of the second detector for monitoring the lens position and if necessary for rough adjustment of the same.

A filter element can thus be realized by means of the electronics and the two detector branches 30 , 31 . Small defocusing is measured quickly and possibly corrected via the characteristic curve of the first detector, while larger defocusing is practically achieved by means of the characteristic curve of the second detector, as it were in a low-pass behavior.

Another advantageous extension of the spacing according to the invention sors can be implemented by implementing a CCD chip with the Section of the object surface can be displayed on a monitor. You can see at any time where there is something to be measured on the surface Workpiece the measuring light beam is located. This measuring light beam can be used moderately weakened by a filter in front of the CCD chip the.  

A particular problem is the adjustment of the sensor components to one another. In order to simplify such an adjustment, a confocal detection branch 20 can be provided. If the divider prisms are optimally adjusted and the objective lens 18 is not tilted, the photodiode receives maximum intensity if a mirror is placed instead of the surface.

Within the scope of the invention, the distance sensor 10 can also be operated in a confocal modex. The confocal branch consists of a Sam lens 21 , an aperture 22 and a photodiode 23rd Optinonally, the objective lens 18 is attached to a branch of a tuning fork. If this is set in vibration by an oscillator, the photodiode receives maximum light intensity when the object distance corresponds to the cutting distance of the objective lens. The measured value can be read out via a secondary measuring system. In order to produce the mass symmetry of the two vibrating fork branches, a lens can also be attached to the other branch, in which case both lenses together represent the sensor objective. According to Fig. 4 15 of the confocal detection arm can be replaced by a branch interferomatischen by addition of a converging lens 21 and a photo diode array 72 at fix mounted mirror.

It is desirable that the zero crossings of the characteristic curves 70 , 71 , of the two detection branches 30 , 31 equipped with the cylindrical lenses 34 , 35 coincide. This has the advantage that there is no measurement offset when switching from one detection branch to the other. This can be achieved by a mirror 15 being attached to the side of the free surface of the plate prism 14 . This can either be electronically concealed, for example, via an electronically controllable LCD surface or can be tipped over. During measurement breaks, the mirror 15 is swiveled in or released electronically. The beam guidance in the receiving beam path then corresponds to the focused state and the voltage emitted by the two detectors 30 , 31 must be zero. In the event of a deviation, a correction voltage is added so that the total voltage is zero.

Visually measured profiles on surface discontinuities can suffer from artefacts and also only deliver non-standardized measured values. In this respect, it may be desirable to check the surface profiles measured with the optical distance sensor 10 according to the invention by scanning the workpiece with a stylus 66 . In this respect, an iron ring 67 is provided as a stylus holder, which is arranged coaxially with the ring magnet 44 receiving the objective lens 18 and held on it. To take off the stylus 66 , the holder 67 could have a small coil which, when disassembled, a counter magnetic field flows through it, so that the stylus 66 falls off. This is not further illustrated in the drawing.

Alternatively, the stylus 66 can, however, also be rigidly mounted on the lens holder, namely set back in the axial direction of the objective lens 18 by a measure corresponding to half the measuring range. In tactile sensor operation, the coil, which normally contains the readjustment voltage according to the focus error signal, is supplied with a preset current via an electronic switch, whereby the carrier tube 45 is deflected and the stylus 66 touches the surface 16 of the object with constant force.

Instead of the usual distance or profile measurement with a light spot, the profile can also advantageously be measured by means of two measurement light spots 76 , 77 projected onto the object surface, as shown in FIG. 4. If the measuring light points are close to each other (distance a few micrometers), one can subtract the distance measured values of the assigned measuring spots from each other and thereby gain insensitivity to vibrations of the measuring object. To generate two adjacent measuring light points, a polarizing beam splitter 73 is inserted, which has two mirror surfaces 73 , 75 , one of which ( 75 ) is tilted by a very small angle against the axis of the incident light beam. The incident light beam is divided by the beam splitter 73 and the partial emitters reflected by the mirror surfaces generate two light points on the object surface 16 . These are imaged in the rear beam path in such a way that the image of one falls on the detector 32 and the image of the other on the detector 33 . Each detector provides the distance measurement associated with a light spot. These can then be offset against one another as required.

Reference list

10th

Distance sensor

11

Laser diode

12th

Collimator lens

13

Beam splitter

14

Disc prism

15

mirror

16

Object area

17th

filter

18th

Objective lens

19th

Working distance

20th

Detector branch

21

Converging lens

22

cover

23

Photodiode

24th

Converging lens

25th

Beam splitter

26

Divider prism

27

Converging lens

28

CCD camera

29

filter

30th

Detector branch

31

Detector branch

32

Photodetector

33

Photodetector

34

Cylindrical lens

35

Cylindrical lens

36

Converging lens

38

Beam splitter

39

Divider prism

40

Beam splitter

41

Divider prism

44

Ring magnet

45

Carrier tube

46

parallelogram

47

bracket

48

Leaf fields

49

Leaf spring

50

Kitchen sink

51

Displacement

54

inductive measuring system

55

bracket

56

Ferrite core

57

Plunger

60

Measured value display

61

Control loop

62

amplifier

63

Photodetector

64

amplifier

66

Stylus

67

Iron ring (bracket)

70

curve

71

curve

72

Photo diode line

73

Divider prism

74

mirror

75

mirror

76

Measuring light spot

77

Measuring light spot

Claims (20)

1. For distance and surface profile measurement of certain optical position sensors with a laser diode as a light source, a collimator lens arranged in the beam path of the laser diode for beam collimation, we at least a beam splitter for beam splitting and beam deflection, a displaceable, downstream in the beam splitter objective lens with an actuator, and with one measuring system attached to the objective lens as a position transmitter, and with a photodetector and a control circuit for tracking the objective lens as a function of a focus error voltage supplied by the photodetector, characterized in that two optical branches ( 30 , 31 ), each with a cylindrical lens ( 34 , 35 ) and a photodetector ( 32 , 33 ) are provided and that the cylindrical lenses ( 34 , 35 ) have different focal lengths.
2. Distance sensor according to claim 1, characterized in that the Fo todetector is a four quadrant photodiode.
3. Distance sensor according to claim 2, characterized in that photo detectors of different geometric dimensions in the two optical branches are used for photo detection.
4. Distance sensor according to claim 2 or 3, characterized in that the photodetector has a photosensitive dead zone.  
5. Distance sensor according to claim 1, characterized in that the Fo todetector contains multiple individual elements.
6. Distance sensor according to claim 5, characterized in that the Fo is designed as a CCD chip.
7. Distance sensor according to one of claims 1 to 6, characterized records that the cylinder lens towards one of the two detector branches ter the pixel generated by the collimator lens is arranged.
8. Distance sensor according to claim 7, characterized in that at egg the cylindrical lens and another Sam lens behind the pixel generated by the collimator lens are not.
9. Distance sensor according to one of claims 1 to 8, characterized records that each of the two detector branches has its own control loop is assigned to track the objective lens.
10. Distance sensor according to claim 9, characterized in that the Re gel circles of the two detector branches have different structures.
11. Distance sensor according to one of claims 1 to 10, characterized records that in a divider prism of the beam splitter in front of the objective lens a shadable or tiltable mirror surface behind the free surface is appropriate.
12. Distance sensor according to one of claims 1 to 11, characterized records that the objective lens is attached to a spring parallelogram is brought.  
13. Distance sensor according to one of claims 1 to 12, characterized records that the actuator is designed as a magnet / coil system.
14. Distance sensor according to one of claims 1 to 13, characterized records that the objective lens is attached to a branch of a tuning fork is brought.
15. Distance sensor according to claim 14, characterized in that at egg Another lens is attached to the second branch of the tuning fork which is a collecting lens or a diverging lens.
16. Distance sensor according to one of claims 1 to 15, characterized records that the object field via a further beam splitter and a Optics can be mapped to a CCD camera.
17. Distance sensor according to one of claims 1 to 16, characterized records that this one from a collective lens of an aperture, and one Photodiode or an existing confocal branch of a photodiode array owns.
18. Distance sensor according to one of claims 1 to 17, characterized records that a holder of the objective lens, if necessary detachable stylus is attached.
19. Distance sensor according to one of claims 1 to 18, characterized records that the actuator of the objective lens two degrees of freedom de has, namely perpendicular and parallel to the object surface, and that the control loops for tracking the objective lens accordingly are laid.  
20. Distance sensor according to one of claims 1 to 19, characterized in that the illumination beam path behind the laser diode ( 11 ) has a further converging lens ( 24 ) and a further polarizing beam splitter ( 73 ), the surface ( 74 ) of which is mirrored and on the sen second usable surface a tilted or tiltable mirror surface ( 75 ) is arranged.
DE1998153302 1998-11-19 1998-11-19 Sensor for measuring distance or surface profiles of workpieces; includes optical branches monitoring two static characteristics to provide focusing corrections Withdrawn DE19853302A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE1998153302 DE19853302A1 (en) 1998-11-19 1998-11-19 Sensor for measuring distance or surface profiles of workpieces; includes optical branches monitoring two static characteristics to provide focusing corrections

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1998153302 DE19853302A1 (en) 1998-11-19 1998-11-19 Sensor for measuring distance or surface profiles of workpieces; includes optical branches monitoring two static characteristics to provide focusing corrections

Publications (1)

Publication Number Publication Date
DE19853302A1 true DE19853302A1 (en) 2000-05-25

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10014627A1 (en) * 2000-03-24 2001-09-27 Sick Ag Method and device for imaging objects
EP1225443A2 (en) * 2001-01-22 2002-07-24 Balluff GmbH Sensor device for flashes
DE10232131C1 (en) * 2002-07-11 2003-11-20 Balluff Gmbh Workpiece bore or edge checking device compares signals from distance sensor scanning workpiece and distance sensor scanning reference object
US6879404B2 (en) 2001-01-22 2005-04-12 Balluff Gmbh Device and method for checking bores in or edges on an object of measurement
US7243553B2 (en) 2004-02-09 2007-07-17 Balluff Gmbh Sensor device for the examination of surfaces
DE10220824B4 (en) * 2001-05-14 2010-08-05 Robert Bosch Gmbh Optical measuring device
DE202011001808U1 (en) * 2011-01-22 2012-04-27 Sick Ag Optoelectronic sensor
EP2482111A1 (en) * 2011-01-31 2012-08-01 Mitutoyo Corporation Autofocus device with rotation unit
DE102012200344A1 (en) * 2012-01-11 2013-07-11 Carl Zeiss Microscopy Gmbh Microscope system and method for 3-D high-resolution microscopy
DE10312682B4 (en) * 2002-03-22 2015-07-16 Carl Zeiss Meditec Ag Microscope arrangement with autofocus and astigmatic-shaped analysis light beam
CN110686617A (en) * 2019-11-22 2020-01-14 北京理工大学 Aspheric parameter error interferometry method and system based on astigmatism positioning

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10014627A1 (en) * 2000-03-24 2001-09-27 Sick Ag Method and device for imaging objects
US7023564B2 (en) 2001-01-22 2006-04-04 Balluff Gmbh Sensor device for burr examination
EP1225443A2 (en) * 2001-01-22 2002-07-24 Balluff GmbH Sensor device for flashes
EP1225443A3 (en) * 2001-01-22 2002-12-04 Balluff GmbH Sensor device for flashes
US6879404B2 (en) 2001-01-22 2005-04-12 Balluff Gmbh Device and method for checking bores in or edges on an object of measurement
DE10220824B4 (en) * 2001-05-14 2010-08-05 Robert Bosch Gmbh Optical measuring device
DE10312682B4 (en) * 2002-03-22 2015-07-16 Carl Zeiss Meditec Ag Microscope arrangement with autofocus and astigmatic-shaped analysis light beam
DE10232131C1 (en) * 2002-07-11 2003-11-20 Balluff Gmbh Workpiece bore or edge checking device compares signals from distance sensor scanning workpiece and distance sensor scanning reference object
US7243553B2 (en) 2004-02-09 2007-07-17 Balluff Gmbh Sensor device for the examination of surfaces
DE202011001808U1 (en) * 2011-01-22 2012-04-27 Sick Ag Optoelectronic sensor
EP2482111A1 (en) * 2011-01-31 2012-08-01 Mitutoyo Corporation Autofocus device with rotation unit
US8772688B2 (en) 2011-01-31 2014-07-08 Mitutoyo Corporation Autofocus device including line image forming unit and rotation unit that rotates line image
DE102012200344A1 (en) * 2012-01-11 2013-07-11 Carl Zeiss Microscopy Gmbh Microscope system and method for 3-D high-resolution microscopy
US10459208B2 (en) 2012-01-11 2019-10-29 Carl Zeiss Microscopy Gmbh Microscope and method for high-resolution 3-D fluorescence microscopy
CN110686617A (en) * 2019-11-22 2020-01-14 北京理工大学 Aspheric parameter error interferometry method and system based on astigmatism positioning

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