JP3261332B2 - Optical displacement measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement measuring device. Specifically, the present invention relates to an optical displacement measurement device including an objective lens that projects light on a measurement surface, and a displacement sensor that outputs a signal corresponding to a shift amount from a focal position of the objective lens to the measurement surface. It can be used for non-contact type shape measuring machines.

[0002]

2. Description of the Related Art As a displacement measuring device, an optical displacement measuring device including an objective lens for projecting light onto a measuring surface and a displacement sensor for outputting a signal corresponding to the amount of displacement from the focal position of the objective lens to the measuring surface. Devices are known. For example, Japanese Patent Application Laid-Open No. 4-366711 discloses an objective lens that focuses a laser beam on a surface to be measured, and a focal point at a distance between the objective lens and the surface to be measured by reflected light reflected from the surface to be measured. A detection optical system that detects the amount of deviation from the distance, and an actuator that moves the objective lens in the optical axis direction based on the output of the detection optical system so that the distance between the objective lens and the surface to be measured becomes the focal length A displacement detection device including a linear scale mounted integrally with the actuator and disposed coaxially with the optical axis of the objective lens is shown.

[0003]

However, the above-described displacement detecting device has a structure in which a detecting optical system, a linear scale, and an actuator are sequentially arranged along the optical axis of an objective lens. It is arranged near. Usually, since the actuator is composed of the coil and the magnet, the linear scale is easily affected by the heat generated by the coil, and as a result, there is a problem that high-accuracy measurement cannot be expected.

An object of the present invention is to solve such a conventional problem and to provide an optical displacement measuring device capable of preventing a thermal influence on an optical scale and capable of performing high-accuracy measurement.

[0005]

SUMMARY OF THE INVENTION An optical measuring apparatus according to the present invention includes an objective lens for projecting light on a measurement surface, and outputs a signal corresponding to a shift amount from a focal position of the objective lens to the measurement surface. A displacement sensor; driving means for moving the objective lens to follow the measurement surface such that the measurement surface coincides with the focal position of the objective lens based on an output signal from the displacement sensor; and the objective lens by the driving means. An optical displacement measuring device provided with a displacement detecting means for detecting a moving amount of the objective lens , wherein the driving means holds the objective lens
Holder and this holder on the sensor body of the displacement sensor
A pair that supports the objective lens so that it can be displaced in the optical axis direction.
Parallel leaf spring and an actuator consisting of a coil and a magnet.
And a tutor, and the holder is:
A first plate holding the coil, and the objective lens
And a second plate holding the optical scale,
A connection shaft for holding the plate at a predetermined distance.
The displacement detecting means is configured to include an optical scale, and the optical scale is arranged near the objective lens and at a position away from the actuator.

According to such a configuration, even if heat is generated from the coil constituting the actuator, the optical scale constituting the displacement detecting means is disposed at a position distant from the actuator comprising the coil and the magnet. The influence on heat generation from the coil can be reduced. Moreover, since the optical scale is arranged near the objective lens, the displacement of the objective lens can be measured with high accuracy.

[0007]

Further, a first plate which holds the coil,
Since the objective lens and the second plate holding the optical scale are held at a predetermined interval by the connecting shaft, the objective lens and the optical scale can be separated from the coil with a simple structure.

Preferably, a magnetic fluid is filled between the coil and the magnet. With this configuration, heat from the coil can be released to the sensor body to which the magnet is attached through the magnetic fluid and the magnet, so that the thermal effect on the optical scale can be further reduced.

Further, it is desirable that a stopper accommodating the holder is provided in the case housing the displacement sensor, the driving means and the displacement detecting means. With this configuration, first, the holder is displaced and brought into contact with the stopper, and in this state, the value of the displacement detection means is set to a predetermined value, that is, when the leaf spring returns to the neutral position, the displacement detection means Is set to be 0, the origin of the displacement detecting means can be set at an intermediate position in the measurement range.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of the optical displacement measuring device of the present embodiment. The optical displacement measuring device is
It comprises a box-shaped case 1 and an optical unit 5 housed and arranged in the case 1. The main body case 1
A through hole 2 is formed in the bottom wall, and a stopper 3 made of a hard sphere is provided in the vicinity of the through hole 2.

The optical unit 5 includes an objective lens 19 for projecting light on the measurement surface of the object to be measured, and a displacement sensor 10 for outputting a signal corresponding to a shift amount from the focal position of the objective lens 19 to the measurement surface. A driving means 30 for moving the objective lens 19 on the measurement surface so that the measurement surface coincides with the focal position of the objective lens 19 based on the output signal from the displacement sensor 10; 19 and an incremental displacement detecting means 50 for detecting the movement amount of the moving object.

As shown in FIG. 2, the displacement sensor 10 includes a semiconductor laser 11, a collimator lens 12 for converting light emitted from the semiconductor laser 11 into parallel rays,
Beam splitters 13 and 1 disposed between them
A quarter-wave plate 14, a half mirror 15 for reflecting the light beam collimated by the collimating lens 12 at right angles, and a light beam whose traveling direction has been changed by the half mirror 15 is reflected toward the measurement surface 32. A mirror 16 to form a light spot by condensing the reflected light from the mirror 16 on the measurement surface 18 of the device 17 to be measured, and further divide the light split by the beam splitter 13 into two. An edge mirror 20 for splitting, two split light receiving elements 21 and 22 for detecting each light split by the edge mirror 20 as an electric signal, and two split light receiving elements 2
And a detection circuit 23 that outputs a signal corresponding to the amount of displacement from the focal position of the objective lens 19 to the measurement surface 18 based on the output signals from the first and second 22. The components except for the detection circuit 23 are attached to the sensor main body 24 (see FIG. 1).

As shown in FIGS. 3 and 4, the driving means 30 includes a holder 31 holding the objective lens 19.
And the holder 31 is attached to the projection 24A of the sensor body 24.
A pair of parallel leaf springs 36 and 37 that are supported to be displaceable in the vertical direction (the optical axis direction of the objective lens 19), an actuator 38 that displaces the holder 31 based on an output signal from the detection circuit 23, It is composed of
The holder 31 includes a first plate 32, a second plate 33 that holds the objective lens 19, and a lower surface of which can contact the stopper 3, and a plurality of holders that hold the two plates 32, 33 at predetermined intervals. (Three) connecting shafts 34. In the center of the second plate 33, a through hole 35 for allowing light from the mirror 16 to enter the objective lens 19 is formed. The plates 32 and 33 and the connecting shaft 34 are formed of a lightweight metal such as aluminum. The actuator 3
8 includes a coil 39 provided on the lower surface of the first plate 32, magnets 40 arranged on both sides of the coil 39, and a magnet holder 41 for fixing the magnet 40 to the sensor main body 24. I have. The space between the coil 39 and the magnet 40 is filled with a magnetic fluid 42 mixed with magnetic powder.

The displacement detecting means 50 is located near the objective lens 19 and away from the actuator 38, here, an optical scale 51 fixed to the second plate 33, and fixed to the sensor body 24. This is an incremental structure including a detection head (not shown) for reading the scale of the optical scale 51 and a counter (not shown) for processing a signal from the detection head and counting the displacement of the objective lens 19.

Next, the operation of the present embodiment will be described. In measurement, first, the origin of the displacement detecting means 50 is set. To this end, the coil 39 of the actuator 38 is energized, and the holder 31 is displaced downward in FIGS. 3 and 4 by the elastic deformation of the leaf springs 36 and 37. Then, the lower surface of the second plate 33 contacts the stopper 3. At this time, the value of the counter is set to a predetermined value (for example, -0.7 mm) so that the value of the counter becomes "0" when the leaf springs 36 and 37 return to the original neutral positions. In this way, as shown in FIG. 5, the origin can be set at an intermediate position of the measurement range (1 mm).

After the origin is set in this way, the semiconductor laser 11 emits light. Then the light
After passing through the beam splitter 13 and the quarter-wave plate 14,
After being collimated by the collimator lens 12 and subsequently reflected by mirrors 15 and 16, the objective lens 1
The light is condensed on the measurement surface 18 of the DUT 17 by 9. The reflected light from the measurement surface 18 of the device 17 is
9, mirrors 16 and 15, collimating lens 12, 1/4
The light reaches the beam splitter 13 via the wave plate 14. The light reflected by the beam splitter 13 is split by the edge mirror 20 and then detected as an electric signal by the two-division light receiving elements 21 and 22.

If the focal position of the objective lens 19 and the measurement surface 18 match, the amount of light received by the two-divided light receiving elements 21 and 22 is the same, but the focal position of the objective lens 19 and the measurement surface If 18 does not match, there is a difference in the amount of light received by the two-divided light receiving elements 21 and 22. As a result, a signal corresponding to the amount of deviation from the focal position of the objective lens 19 to the measurement surface 18 is output from the detection circuit 23.
The objective lens 19 is moved in the optical axis direction based on the output. That is, the objective lens 19 is moved in the optical axis direction so that the amounts of light received by the two-divided light receiving elements 21 and 22 are the same. In this way, if the amount of movement of the objective lens 19 is detected by the displacement detecting means 50 while the measuring apparatus and the object 17 are relatively moved, the shape of the measurement surface 18 of the object 17 can be measured. can do.

According to the optical displacement measuring device of the present embodiment, the optical scale 51 constituting the displacement detecting means 50 is
Since the coil 39 and the magnet 40 are arranged at a position distant from the actuator 38, the coil 3
9 can be less affected. Moreover, since the optical scale 51 is disposed near the objective lens 19, the displacement of the objective lens 19 can be measured with high accuracy.

The driving means 30 comprises a holder 31 holding the objective lens 19 and this holder 31 is connected to the sensor body 2.
4 includes a pair of parallel leaf springs 36 and 37 that are supported so as to be displaceable in the optical axis direction of the objective lens 19, and an actuator 38 that includes a coil 39 and a magnet 40. Since the plate objective lens 19 is supported by the parallel plate springs 36 and 37, the plate objective lens 19 can be displaced in parallel in the optical axis direction.

The holder 31 is connected to a first plate 32 holding the coil 39, a second plate 33 holding the objective lens 19 and the optical scale 51, and is connected to hold both the plates 31, 32 at a predetermined interval. Since the configuration includes the shaft 34, the objective lens 19 and the optical scale 51 can be arranged away from the coil 39 with a simple structure. Moreover, these plates 32, 33
And the connecting shaft 34 is made of lightweight aluminum, and the coil 39 having the light weight among the coil 39 and the magnet 40 constituting the actuator 38 is attached to the holder 3.
Since the holder 31 is attached to the first plate 32, that is, the entire holder 31 on the movable side is reduced in weight.
Can be moved with good responsiveness.

Since the magnetic fluid 42 is filled between the coil 39 and the magnet 40, the magnetic fluid 42 functions as a damper for suppressing the generation of vibration, so that an improvement in responsiveness can be expected. In addition, since heat from the coil 39 can be released to the sensor main body 24 through the magnetic fluid 42 and the magnet 40, the optical scale 5
1 can be less affected by heat.

Since the stopper 3 is provided on the bottom wall of the case 1 and the value of the displacement detecting means 50 when the holder 31 abuts on the stopper 3 is set to a predetermined value, the leaf spring 3
6 and 37 when the displacement detecting means 50 returns to the neutral position.
Can be set to 0. That is, the origin of the displacement detection unit 50 can be set at an intermediate position in the measurement range. Therefore, the measurement ranges on the plus side and the minus side can be set equal to each other with respect to the origin and the center.

In the above embodiment, the objective lens 19
A pair of parallel plate springs 36 and 37
Parallel displacement in the direction of the optical axis of the objective lens 19, but is not limited to this. Any object can be used as long as the objective lens 19 can be displaced in the optical axis direction while being parallel. Also, if the objective lens 19 is a plastic lens, the entire movable holder 31 can be made lighter, so that the responsiveness can be further improved. Also, the measured surface 1 that has passed through the half mirror 15
If the reflected light from 8 is incident on the video camera, the measurement can be performed while confirming the measurement location on the measurement surface 18 with an image.

[0025]

According to the optical displacement measuring device of the present invention,
High-precision measurement is possible by preventing thermal effects on the optical scale.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of an optical displacement measuring device according to the present invention.

FIG. 2 is a diagram showing a configuration of a displacement sensor according to the embodiment.

FIG. 3 is a view as seen from a direction III in FIG. 1;

FIG. 4 is a view as seen from a direction IV in FIG. 1;

FIG. 5 is a view for explaining origin setting in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 3 Stopper 10 Displacement sensor 17 Object to be measured 18 Measurement surface 19 Objective lens 24 Sensor body 30 Driving means 31 Holder 32 First plate 33 Second plate 34 Connecting shaft 36, 37 Leaf spring 38 Actuator 39 Coil 40 Magnet 42 Magnetic fluid

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-26105 (JP, A) JP-A-63-21504 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00

Claims (3)

(57) [Claims] 1. A displacement sensor that includes an objective lens that projects light onto a measurement surface, and outputs a signal corresponding to the amount of displacement from the focal position of the objective lens to the measurement surface, and outputs a signal based on an output signal from the displacement sensor. Drive means for moving the objective lens to follow the measurement surface so that the measurement surface coincides with the focal position of the objective lens; and displacement detection means for detecting the amount of movement of the objective lens by the drive means. In the optical displacement measuring device, the driving unit includes : a holder holding the objective lens;
This holder is used as an object for the sensor body of the displacement sensor.
A pair of parallel plates supporting the lens so that it can be displaced in the optical axis direction
Actuator consisting of wire, coil and magnet
And the holder comprises the coil
A first plate holding the objective lens and the optics
The second plate holding the scale and both plates
A connection shaft that is held at a predetermined distance, and the displacement detection unit is configured to include an optical scale. The optical scale is disposed near the objective lens and at a position away from the actuator. An optical displacement measuring device. 2. The optical displacement measuring device according to claim 1 , wherein a magnetic fluid is filled between the coil and the magnet. 3. The optical displacement measuring apparatus according to claim 1 or claim 2, wherein the displacement sensor, the case containing the drive means and the displacement detecting means, the holder is in contact with the stopper is provided An optical displacement measuring device, characterized in that: