JPS58176505A - Non-contact displacement detector - Google Patents

Abstract

PURPOSE:To measure displacement with high accuracy by providing a light source and an objective lens which irradiates the light from the light source as a micro spot to the surface of an object to be measured of displacement and detecting the reflected luminous flux from the surface of said object. CONSTITUTION:The laser light emitted from a laser light source 1 is collimated to parallel light by a collimator lens 2. The parallel light passes through a polarization prims 3 having a polarization fiom, a 1/4 wavelength plate 4 and an objective lens 5, and the light reflected from the surface of a measuring object 6 is made incident through the lens 5 and the plate 4 to the prism 3 as parallel light. The light which is made incident to the prism 3 is deflected in the direction perpendicular to the plane of the figure by the plate 4; therefore, the above- mentioned incident light is reflected by the prism 3 and is made incident to a photodetector 7. The displacement is thus measured with high accuracy by detecting the luminous flux reflected from the surface of the object to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-contact displacement detection device for detecting displacement of an object in a non-contact state using optical means, and relates to means for improving displacement measurement performance.

Most conventional non-contact displacement measurement devices of this type simply use a general-purpose proximity sensor as a displacement detector. When the linearity measurement range is expanded, the resolution tends to decrease.For example, if the resolution is set to about 1.3m, the linearity measurement range will be 89-degrees, and if the linearity measurement range is expanded to 2
When expanded to -11 degrees, the resolution drops to about 50 degrees. 〇9th, the displacement of the minute point of 1-2-11 degrees is 1-2-
Even though there was a desire to be able to measure within a certain degree of accuracy measurement range, there was no non-contact displacement measuring device that could meet this requirement. Among the conventional non-contact proximity sensors, Uzuden IIILrIJ1-1! ! Sensors have the disadvantage that they can only be used when the object is a conductive material, and optical sensors have the disadvantage of being susceptible to rounding and measurement errors that are affected by factors such as the surface reflectance of the object. The purpose of the invention is to measure the displacement of minute points with a diameter of about 1 to 2 cars.
To provide a non-contact displacement measuring device capable of measuring 1 to 2-s degrees of linearity with a constant range concavity of 4111, and capable of stably defining highly accurate displacement regardless of the material or reflectance of the object to be measured. It is.

Embodiments of the present invention will be described below with reference to the drawings. The first factor is a diagram showing the configuration of an embodiment of the present invention. Reference numeral 1 is a Rade light source, and the Rade light emitted from the Rade light source 1 is made into parallel light by a collimator lens 1, and then polarized by a polarizing film. 60 objects to be measured via prism, 9% 1/4 wavelength plate 4, and objective lens 5! Nis/y) diameter l~
The light is focused as a minute spot of 2#+1 and reflected on the surface of the object 60 through the objective lens 5.1/
4i1 The light enters the polarizing grism 3 as parallel light through the long plate 4, but since the light incident on the polarizing grism 3 is polarized by the 1/4 wavelength plate 4 in a direction perpendicular to the plane of the paper,
The above incident light is polarized! It is reflected at rhythm 1 and enters photodetector 7.

The photodetector 1 is tilted at an angle θ with respect to the optical axis and is placed in a far field sufficiently far away from the focal point of the objective lens 5 in good condition. The photodetector 7 is shown in FIG. 1 as well as its projected plan view.
It has two light-receiving areas, FB, in which the 0-incidence plane is divided into two by a plane that includes an optical axis and is perpendicular to the above-mentioned incident plane and the paper plane. Each light receiving area 7A of the photodetector 1sy.

Each of the lights incident on 71 is converted into an electric signal and input to the differential amplifier 1. The differential amplifier 1 obtains the differential output of the signals from the two light receiving areas 7B, and supplies this output to the amplifier. Sir? Anguk amplifies the difference output to make it a sir I output, which is then supplied to the objective lens drive mechanism 10. The objective lens drive mechanism 10 includes a support tube 1
A pair of leaf springs 111, 1:111. A magnetic body is attached to a part of the lens holder 13 and is wound with a drive coil 14, and the lens 5 is movable in the optical axis direction. 15 is inserted into the gear f section G of the magnet device 16 identified in the support tube 1 so as to be able to move in the same direction as the moving direction of the lens 5. Therefore, the drive coil 14 of this lens drive mechanism 10 has a
? When the Ang output is supplied, the magnetic body J5 and the magnet device 1
Due to the electromagnetic force acting between the lens holder 13, the magnetic body 15, and the lens 5, the linear motion of the lens holder 13, the magnetic body 15, and the lens 5 is integrally controlled by a predetermined amount in the direction of the optical axis of the lens 5.

By the way, on the holding frame 17 that supports the periphery of the lens 5 at the top of the lens holder 13 in the lens drive mechanism 10, an arm 1s for indicating nine displacements is attached, which is made by bending a piece of metal into an L shape. For example, an eddy current proximity sensor 1 is installed near the arm 18 to detect the displacement of the arm 1# that moves with the movement of the lens 5.
9 has been installed. The detection output of this proximity sensor 19 is transmitted to a displacement indicator 10 including, for example, an indicator or a recorder.
It is used to display the amount of displacement, etc.

It is assumed that the sensor 19 has a relatively large beam linearity measurement range of, for example, 2 gm and 5 degrees.Next, the operation of the apparatus configured as described above will be explained. Now, when the object 6 is displaced in the direction approaching the objective lens 5, that is, in the direction of arrow a, the incident light on the photodetector 1 has an incident angle smaller than θ in the light receiving area FA, and on the contrary, in the light receiving area IB. The angle of incidence is larger than θ. Object 6
When is displaced in the direction away from the objective lens 5, that is, in the b direction, the incident light on the photodetector 1 has an incident angle that is much larger in the light receiving area IA, and an incident angle of 0 in the light receiving area IB.
Yo, it will be 0% smaller.

In general, the relationship between the sensitivity of a photodetector and the angle of incidence shows a tendency for the relative sensitivity to decrease as the angle of incidence increases, as shown in Figure 2. The sensitivity of one person in the light receiving area and the sensitivity of the light receiving area IB have a relationship as shown in FIG. That is, when the object 6 is displaced in the direction a, the sensitivity of the light receiving area 7A becomes greater than the sensitivity of the light receiving area IB, as shown by the solid line, and when the object 6 is displaced in the direction b, the opposite characteristic 1 is exhibited as shown by the broken line. - In the focused state, the sensitivity of one person in the light receiving area and the sensitivity of the light receiving area 7B are equal.

Thus, the output of the differential amplifier 8, which is the difference output between the output of one light-receiving region and the output of the light-receiving region IB, becomes as shown in FIG. It becomes a positive polarity output signal whose size corresponds to the amount of displacement,
When shifted in one direction, a negative polarity output signal of magnitude 9 is generated depending on the amount of displacement. The differential amplifier I outputs a force and a sing error signal indicating the direction and magnitude of the focus shift of the objective lens 5, that is, the direction and magnitude of the displacement of the object 6. The output of is sir? It is converted into an output and supplied to the drive coil 14 in the lens drive mechanism 10. Then, the magnetic body 15 receives a driving force commensurate with the differential output shown in FIG.
is driven to a position where it is in focus. In this way, the distance between the lens 5 and the object 6 is controlled to always be constant. In this case, sir? The gain of the system is set to have an open loop gain of 60 dB or more when the object σOtS dynamic frequency is 0 Ha or less, so the displacement with an amplitude of 2- is ±2. Tracking is possible within an error range of amli degrees.

The movement of the lens 5 operating with such follow-up characteristics is detected by the near II dragon sensor 1g which detects the movement of the arm 1M that operates integrally with the lens 5. Then, the detected displacement of the lens 5 is displayed by the displacement display @go.The sensor 1# is the arm 1
Since the detection is performed in a non-contact state with sensor 1, there is no possibility that the operation of objective lens IS will be hindered by sensor 1 -0 is used, so measurement II
On the other hand, since the direct detection target of this sensor 1g is the arm 18 rather than the minute spot I, there is no problem in terms of resolution. Since the diameter of the groove is approximately 1 to 2 μm, the displacement of minute portions can be defined with high resolution.

By the way, the depth of focus of the objective lens 50 is relatively shallow, and it is easy to focus only on the surface of the object 6.Furthermore, the focus control system controls changes in the focusing position of the reflected light beam within the light receiving area 1 of the light receiver r.

It is detected as a change in the angle of incidence with respect to IB,
There is no direct relationship with the amount of reflected light flux, etc. Therefore, even if the displacement measurement object 6 is a transparent object made by Garasugo,
Furthermore, there is no problem even with non-metallic objects such as black glass, glue, etc., and high-precision positioning is possible for almost all objects.6. Note that the present invention is not limited to the embodiments described above. For example, in the above embodiment, an eddy current reduction proximity sensor is used as the displacement detecting means, but an optical sensor, a magnetic sensor, or an electrostatic sensor may also be used. A sensor or the like may be used for the type O-type that contacts the arm 11 on the condition that the movement is not seriously obstructed.In addition, in the above embodiment, a photodetector is used to detect changes in the convergence position of the reflected light. Although the detection is shown as a change in the angle, it is also possible to detect a change in the focal position of the reflected light beam as a change in the shape of the light beam incident on the photodetector. Various modifications can be made within the same range.

As explained above, according to the present invention #4, the light from the light source passes through the objective lens and hits the surface of the displacement measurement object 0,
), and a split-type photodetector detects changes in the focusing position of the reflected light beam to obtain a focus error signal, and based on the signal, the objective lens is constantly focused on one side of the object by means of a sensor. In addition to this, the movement of the objective lens is detected by the displacement detection means, so that the displacement of a minute point with a diameter of 1 to 2 mm can be measured within the linearity measurement range of 1 to 2-S degrees. Since displacement can be detected regardless of the amount of reflected light, it is possible to provide a non-contact displacement measuring device that can maintain highly accurate displacement regardless of the reflectance in the material of the object to be measured.

[Brief explanation of drawings]

1 to 4 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a configuration diagram, and FIGS. 2 to II4 are characteristic diagrams for explaining the operation of the focus control system. 1... Laser light source, 2... Collimator lens, I.
...Polarizing prism, 4...1/4 wavelength plate, 5...Objective lens, 6...Displacement measurement mat, 1...Two-split photodetector, 8...Differential amplifier, 9... Circular angle, 10... Objective lens drive mechanism, 18... Arm for displacement indication, 19... Proximity sensor, 20... Displacement indication. l.゛ Applicant's agent Patent attorney - Jiang Wu Liao Commissioner of the Patent Office Haruki Shimada 1. Indication of the case Patent application No. 57-59020 No. 2, name of the invention Non-contact displacement detection device 3, supplementary IF person Relationship with the case Patent applicant (037) t I) Nnosu Kogaku Kogyo Co., Ltd. 4, Agent Person Address: 17 Mori Building, 1-chome, Toranomon, Minato-ku, Tokyo, Part No. 5, 105 Telephone: 03 (502) 3181 (Main Representative) Commissioner of the Japan Patent Office Kazuo Wakasugi, 1, Indication of the case, especially No. 57-59020 2, Name of the invention Non-contact displacement detection device 3, Relationship with the person making the amendment Patent applicant (037) Olympus Optical Industry Co., Ltd. 4, Agent 5, Spontaneous armrest 7, Contents of amendment + 11 Specification Iris 9N No. 16 Insert the following sentence next to "It is possible." in the line. Next, other embodiments of the present invention will be described. FIG. 5 shows an embodiment using a critical angle type focus control system. In Fig. wJ5, 21 is a detection prism to which the output surface of the polarizing prism 3 is joined, and its reflection 1t122 is set so as to be at a critical angle I or slightly smaller than the critical angle I with respect to the incident ray in the focused state. , N. le. 23Fi
The above detection prism JO output iI. This is a two-split photodetector arranged opposite to each other. Fi other than above
It has the same configuration as the previous embodiment. In this embodiment configured in this way, the objective lens 5 is directed toward the object g! cm When in self-focusing state, the light is reflected by the deflection prism 3! 1 is totally reflected in the reflection direction of the detection prism 21. In fact, since the state of the reflection direction is not perfect, some light is transmitted in the n direction. The totally reflected light beam as described above is transmitted to the two light receiving areas 23 of the photodetector 23.
Since the amount of light that enters and is received by the 23BV is evenly distributed, differential amplification is achieved! ! The sizes of the mountain numbers input to 8 are the same. Therefore, the output of the sir & amplifier 9 is zero, and the output of the objective lens 5
Fi remains stationary. When the object 6 is in focus a
When displaced in the direction, the light beam reflected by the polarizing prism 3 is reflected by the detection prism 21 at 1k122V, and the incident light of the outer medulla -all, ml! The incident angle is as shown in '. That is, the reflection direction 2217
Of the light beams incident on one person, half of the light beams (in the figure) are all glans, and the angle of incidence of the incident light beams is all 4 smaller than the critical angle. Therefore, there is a light beam transmitted through the lower half of the luminous flux KFi.
A bundle of rays containing J to n is transmitted. Therefore, the intensity of the reflected light flux (from arl to center light ht) is half of the above (above) by the amount of the transmitted light! i#i gets erect. Reflective surface 2
From the central light of the light flux incident on 2, the light flux in the upper half of the figure has a12 as the glans, and the angle of incidence of the incident light is all n.
It will be thicker than the corner. Therefore, there is no transmitted light in the upper half of the luminous flux, and all of the incident luminous flux is reflected. Therefore, the reflected light beam in the upper half (from ar2 to the center ray) is not intensified ytt2s. As a result, when the object 6 is displaced in the direction a, the amount of light received in the light receiving area 23A of the two-split light detection tjZS decreases. A focus lens error signal indicating the magnitude of displacement in one direction is output from the amplifier 8, and the objective lens 5 follows the same movement as in the previous embodiment. This movement is detected by the proximity sensor 19, and the displacement is displayed. Vessel 2
Displayed at 0. On the other hand, when the object 6 is displaced in the n direction, the light beam reflected by the polarizing prism 3 is reflected by the incident light l1IIlbi1. b
The light enters with an inclination as represented by 12. That is, in this case, the relationship of the magnitude of the incident light beam incident on the reflection direction 22 is opposite to that in the case of displacement in the a-direction described above. Therefore, the relationship between the amount of light received in each of the light receiving areas 23 and 23B (D) of the bisecting 111ji detector 23 is also reversed. In this case, the reflected light and the transmitted light in the reflection direction 22rc are denoted by the symbols brl, br2 and btz, respectively.Thus, At this time, focus song error No. 48 indicating the magnitude of the displacement in the n direction is output from the @1 differential amplifier 8, and the objective lens 5 follows the same way as in the previous embodiment, and this movement is detected by the proximity sensor. Detected by 19, displacement table Fuki 2
0). In this embodiment, the same effects as those of the previous embodiment can be achieved, and when the VC is out of focus, the luminous flux on one side is totally reflected as the boundary is at the center edge, and the luminous flux on the other side is reflected at the extreme Kldi. Since the amount of light is small, the difference in the amount of light in the light receiving area PC becomes more pronounced, which has the advantage of allowing highly accurate detection of the spiritual position. (2) ``Glaze characteristic diagram'' of Mukai 11 x 11 ¥ 4 set 8 strokes is one characteristic diagram, and Fig. 5 is a diagram showing the configuration of another embodiment of the present invention. ” he stopped. (3) Circular No. 1] Your line 14, “...displacement indicator,” [...displacement indicator, 2)...detection prism,
22... Reflection (3), 23... Two-split photodetector,
I am corrected. (4) Add Bessho Ward 1iii as “Figure 5”.

Claims (1)

[Claims] A light source, an objective lens that irradiates the light from the light source as a minute spot on the surface of the object to be displaced, and receives the reflected light beam coming from *m of the object through the 2" object lens and calculates the amount of the reflected light beam. A split-type photodetector that detects changes in the focusing position and converts it into an electrical signal, and a 04
a signal processing means for outputting a focus error signal by processing the signal s; A therme means that controls the surface so that it is always in focus, and a two-hand method.
A non-contact displacement detection device comprising: displacement detection means for detecting displacement of the object from movement of the objective lens.