JPH0861917A - Position detecting device - Google Patents

Abstract

PURPOSE: To install a light reflection means of a simple constitution in a small space, and make a device compact and lightweight by providing the external surface of a measurement object with a light reflection means having a plurality of mirror surfaces along a direction orthogonal with the axis of the object, and projecting a laser beam to the mirror surfaces. CONSTITUTION: A right-angle reflection mirror 13 (light reflection means 4) having two mirror surfaces 11 and 12 orthogonal with each other is pasted to the external surface of a measurement object 3 movable in the vertical direction along z-axis and rotatable in arrow A direction having the z-axis as a rotation axis. When the object 3 moves vertically along the z-axis, a laser beam 5 from a light source 6 is reflected on the surface 11 of the mirror 13. Then, the beam is again reflected on the mirror surface 12 and made incident on a PSD element 10. Furthermore, the displacement of the object 3 is measured on the basis of the change of a signal corresponding to a change in the travel position of the beam 5 on the element 10. On the other hand, the rotational angle of the object 3 is measured on the basis of the lateral displacement of the incident position of the beam 5 incident on the element 10 resulting from the rotating travel of the mirror 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting a position change of an object to be measured which rotates and / or vertically moves as a position change of a one-dimensional area or a two-dimensional area. In particular, the present invention relates to a position detection device that detects a minute position change of an object to be measured with a small installation space.

[0002]

2. Description of the Related Art In the case of measuring the position change of the rotational movement of the object to be measured, it is known to attach a device such as an encoder to the object to be measured and measure the position change of the object to be measured as a rotation angle. . Furthermore, in the case of measuring the linear up and down movement separately from this rotational movement, the position change must be measured separately from the encoder using a position sensor. As described above, in the conventional case, the encoder and the position sensor have to be installed on the object to be measured, the installation space is small, and it is difficult to use in a small device.

For example, in order to read an optical disk memory, it is necessary to focus a spot having a diameter of about 1 μm condensed by a focus driving section on a pit on the disk. FIG. 7 shows an example of the focus drive unit 1. The eccentricity of the track when the disc rotates is about 1
00 μm, vertical movement of the disk surface is 100 μm to 500
μm. In order to perform accurate reading, the cylindrical focus drive unit 1 including the condenser lens 2 is driven, and the spot is always focused and controlled so as to be located within a predetermined track.

[0004]

By feeding back the signal of the position change when the focus drive section moves, it is possible to perform the control with higher accuracy. However, when the above-described encoder, position sensor, and the like are attached to the focus driving unit to operate, the device is inevitably increased in size, and it becomes difficult to use the device in such a small space. In particular, when an encoder and a position sensor are attached to a part of a focus drive unit having a precise structure for measurement, the weight of the encoder and the position sensor itself increases the total weight of the focus drive unit, resulting in a problem such as a center of gravity and a response speed. There is a problem that the delicate balance changes, and desired control cannot be performed.

The present invention has been made in view of the above problems, and provides a lightweight position detecting device which can be mounted in a small space with a simple structure and can detect a minute position. The task is to do.

[0006]

In order to solve the above problems, an object to be measured that is movable in an angular direction and an axial direction intersects with an object provided on the outer peripheral surface of the object to be measured and in a direction orthogonal to the axial direction. Light reflecting means having first and second mirror surfaces, and a laser for projecting a laser beam from the front surface onto the first mirror surface of the light reflecting means and reflecting the laser light through the second mirror surface. An apparatus and a two-dimensional position detection device that receives the laser beam reflected from the second mirror surface and detects the incident position of the laser beam in the biaxial directions of the angular direction and the axial direction.

Further, the light reflecting means comprises a right-angled reflecting mirror in which the first and second mirrors are provided so as to intersect at a right angle, and the laser beam is incident on the first mirror surface at an angle of 45 °. It is characterized in that a reflected light beam reflected by the second mirror surface at an angle of 45 ° is made incident on the detecting means in parallel with the incident light, and the detecting means can detect a two-dimensional area by a PSD (position sensitive). -Device: semiconductor position detecting element).

Further, the object to be measured is a focus driving section for reading an optical disk memory, and the light reflecting means is attached to the focus driving section for use. The light reflecting means prevents reflection on the incident surface. The prism is characterized by having a coating and a mirror surface coating on the back surface.

An object to be measured which moves in the angular direction, a light reflecting means fixed to the outer peripheral surface of the object to be measured, a laser device for injecting a laser beam from the front to the light reflecting means, and the light reflecting means. And a detecting means for detecting a position change of the reflected laser beam, wherein the light reflecting means has intersecting mirror surfaces that displace the reflection angle of the incident laser beam according to the position angle of the object to be measured, and the detecting means is And a one-dimensional position detecting device for detecting the angular displacement of the laser beam reflected from the light reflecting means.

An object to be measured that moves in the axial direction, a light reflecting means fixed to the outer peripheral surface of the object to be measured, and a laser device for injecting a laser beam from the front to the light reflecting means,
A detecting means for detecting a position change of the laser beam reflected from the light reflecting means, wherein the light reflecting means has first and second mirror surfaces intersecting in a direction orthogonal to the axial direction, Displace the reflection position based on the change in the incident position of the laser beam due to the movement of the measurement object in the axial direction,
The detecting means is a one-dimensional position detecting device for detecting the axial displacement of the laser beam reflected by the light reflecting means.

[0011]

In such a structure, the light reflecting means is fixedly arranged on the object to be measured which moves in the rotational direction and / or the axial direction. The laser beam output from the light source is projected onto the light reflecting means. The laser beam reflected by the light reflecting means is made incident on the detecting means, the positional displacement corresponding to the movement of the measured object is detected, and the movement amount of the measured object is detected by the signal processing section.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic view of a minute position detecting device according to the present invention. The cylindrical object 3 to be measured is vertically movable in the Z-axis direction, and is also rotatable in the arrow A direction with the Z-axis as a rotation axis. The side surface of the DUT 3 is provided with a light reflecting means 4 described later. On the other hand, a light source 6, a collimator lens 7, and a reflection mirror 8 are provided as means for emitting the laser beam 5, and a detection means 9 for detecting the laser beam 5 reflected by the light reflecting means 4 is provided. A PSD element (position sensitivity device: semiconductor position sensing element) 10 is provided.

When a light spot such as a laser beam is incident on the surface of the PSD element, a charge proportional to the light energy is generated at the incident position. This charge is a photocurrent on both ends of the PSD element (one-dimensional position detection PSD),
Alternatively, the position of the light spot that is output from the four sides (PSD for two-dimensional position detection) and is incident on the PSD surface can be specified by the external signal processing unit from the ratio of the respective photocurrents.

FIG. 2 shows a preferred example of the light reflecting means 4, which is a right-angled reflecting mirror 13 having a first mirror surface 11 and a second mirror surface 12, and the first mirror surface 11
And the second mirror surface 12 intersect each other and are formed so as to form a right angle. The right-angled reflection mirror 13 can be made of a conventionally known mirror material, but preferably,
The first mirror surface 11 and the second mirror surface 12 are made of a lightweight material such as a synthetic resin material, and are metal-coated by vapor deposition, sputtering, or the like. The surface on the opposite side where these mirror surfaces are formed is formed into a flat surface or a curved surface according to the shape of the DUT 3.

FIG. 3 shows an example of another light reflecting means 4. A rectangular prism 14 is used as the light reflecting means 4, an incident surface 15 of the laser beam 5 is provided with an antireflection coating, and a rear surface 16 is provided with a metal coating to form a mirror surface. The right-angle prism 14 has a mirror surface that is 4 with respect to the rotation axis.
It is fixed to the side surface of the DUT 3 by an auxiliary member or the like that makes the angle of 5 °. Alternatively, the rectangular prism 14 may be fixed by forming a groove or the like on the DUT 3.

The principle of the position detecting device having such a configuration will be described. FIG. 4 shows a method of detecting the displacement amount when the DUT 3 moves up and down in the axial direction. The laser beam 5 emitted from the light source 6 is reflected by the first mirror surface 11 of the right angle reflecting mirror 13 as the light reflecting means 4 shown by the solid line,
Towards the second mirror surface 12. Then the second mirror 12
The laser beam 5 (dashed-dotted line) reflected by the surface returns to the direction parallel to the emitted laser beam and enters the PSD element 10. Next, when the DUT 3 moves in the direction of arrow B as shown in the drawing, the right-angled reflection mirror 13 moves to the position shown by the broken line. The reflection path of the laser beam 5 after the movement of the right-angled reflection mirror 13 is displaced to the position shown by the chain double-dashed line and enters the PSD element 10. The change in the signal with respect to the change in the position of the laser beam that has moved on the PSD element 10 is sent to the signal processing unit 21, and the displacement amount of the DUT 3 is measured.

On the other hand, FIG. 5 shows a method of detecting the displacement amount of the DUT 3 in the rotation direction. Similar to FIG. 4, the laser beam 5 is emitted to the above-mentioned right-angled reflection mirror 13, is reflected by the first mirror surface 11 and the second mirror surface 12, and is PSD.
The light is incident on the position (X1) of the element 10. Next, when the DUT 3 rotates around the rotation axis in the direction of arrow A and the right angle reflection mirror 13 rotates, the laser beam 5 incident on the PSD element 10 moves from position (X1) to position (X2). Then, the position of the light beam is indicated by a chain line, and the rotation angle of the DUT 3 is measured by the signal processing unit 21 according to the displacement value of the incident position.

Since the right-angled reflection mirror 13 moves on the circumference of the object to be measured, it is not a linear position displacement, but the amount of movement of the right-angled reflection mirror 13 in the angular direction is minute (for example, about several hundreds of microns). ), It can be regarded as a linear movement and can be measured. Further, when a more precise measurement is required, it is possible to perform the correction by the signal processing means.

The amount of movement of the object 3 in the axial direction and the rotational direction is calculated according to the principle described above. FIG. 6 shows a preferred example of the position detection device. The position detecting device includes a light source 6, a control unit 18 including a light source drive circuit for sending a control signal to the light source 6, a light projecting lens 19 for condensing the laser beam 5,
A reflecting mirror 8 for directing the laser beam 5 to the light reflecting means 4.
A right-angled reflection mirror 13 fixed to the DUT 3, a condenser lens 20 for condensing the laser beam reflected by the reflection mirror 13, and a position P for detecting the position of the laser beam.
SD element 10 and signal processing unit 2 for calculating the detected signal
1 and a drive circuit that controls the movement of the DUT 3. The laser beam 5 directed from the light source 6 through the light projecting lens 19 by the reflection mirror 8 is reflected by the first mirror surface 11 and the second mirror surface 12 of the right-angle reflection mirror 13. The output laser beam 5 is returned in a direction parallel to and opposite to the input laser beam 5, condensed by the condenser lens 20 and incident on the PSD element 10. The laser beam 5 is displaced on the PSD element 10 by the movement of the DUT 3, that is, the above-mentioned movement of the right-angled reflection mirror 13, and the DUT 3 is displaced from the displacement amount.
The signal processing unit 21 measures the amount of movement of the two-dimensional area.

In the above embodiments, the cylindrical object is used as the object to be measured, but the present invention can be similarly applied to the object to be measured having a cylindrical shape, a polygonal shape, a spherical shape, or the like. Produce an effect. In the present specification, the "outer peripheral surface" is a general term including the circumferential surface of the above-mentioned cylinder, cylinder, and sphere, and the side surface of the polygon.

[0021]

The position detecting device of the present invention adopts a means of attaching, fixing or providing the above-mentioned light reflecting means of a specific shape to an object to be measured, thereby achieving downsizing of the device and a simple structure. The position can be detected more easily by using the light reflecting means, and since a light material can be used as the light reflecting means, it is possible to change the axial direction and the rotating direction without changing the weight of the measured object. It is also possible to perform minute position detection. Further, since the laser beam emitted from the light source is displaced and reflected, it is easy to set the mounting location of the PSD element which is the detection means, and the arrangement of the device can be made compact.

[0022]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment according to the present invention.

FIG. 2 is a perspective view showing a right angle reflecting mirror of the light reflecting means.

FIG. 3 is a diagram showing a prism of a light reflecting means.

FIG. 4 is a principle diagram showing a state in which a light reflecting means fixed to an object to be measured moves in an axial direction.

FIG. 5 is a principle diagram showing a state in which a light reflecting means fixed to an object to be measured moves in a rotation direction.

FIG. 6 is a schematic view showing another embodiment according to the present invention.

FIG. 7 is a diagram showing a focus drive unit as an object to be measured.

[Explanation of symbols]

 1 Focus Driving Section 2 Condensing Lens 3 Object to be Measured 4 Light Reflecting Means 5 Laser Beam 6 Light Source 7 Collimator Lens 8 Reflecting Mirror 9 Detecting Means 10 PSD Element 11 First Mirror Surface 12 Second Mirror Surface 13 Right Angle Reflecting Mirror 14 Right Angle Prism 15 Incident surface 16 Rear surface 18 Control unit 19 Projecting lens 20 Condensing lens 21 Signal processing unit

Claims (7)

[Claims] 1. An object to be measured that is movable in an angular direction and an axial direction, and first and second mirror surfaces provided on an outer peripheral surface of the object to be measured and intersecting in a direction orthogonal to the axial direction. A light reflecting means, a laser device for projecting a laser beam onto a first mirror surface of the light reflecting means, and reflecting the laser beam via the second mirror surface; and a laser beam reflected from the second mirror surface. Received,
A two-dimensional position detecting device for detecting incident positions of the laser beam in two axial directions, i.e., an angular direction and an axial direction, and a position detecting device. 2. The light reflecting means comprises a right-angled reflecting mirror in which first and second mirrors are provided so as to intersect at a right angle, and the laser beam is incident on the first mirror surface at an angle of 45 °. It is reflected by the mirror surface of 2 at an angle of 45 °,
The position detecting device according to claim 1, wherein a reflected light beam parallel to the incident light is made incident on the detection means. 3. A P which enables the detection means to detect a two-dimensional area.
SD (position sensitive device: semiconductor position detection element), characterized by the above-mentioned.
The position detection device described. 4. The position detection according to claim 1, wherein the object to be measured is a focus drive unit for reading an optical disk memory, and the light reflecting means is attached to the focus drive unit for use. apparatus. 5. The position detecting device according to claim 1, wherein the light reflecting means is a prism having an incident surface with an antireflection coating and a back surface with a mirror surface coating. 6. An object to be measured which moves in an angular direction, a light reflecting means fixed to an outer peripheral surface of the object to be measured, a laser device for injecting a laser beam from the front to the light reflecting means, and the light reflecting means. A detecting means for detecting a position change of the laser beam reflected from the means, the light reflecting means has intersecting mirror surfaces for displacing the reflection angle of the incident laser beam according to the position angle of the object to be measured, The means comprises a one-dimensional position detecting device for detecting an angular displacement of a laser beam reflected by the light reflecting means. 7. An object to be measured that moves in the axial direction, a light reflecting means fixed to the outer peripheral surface of the object to be measured, a laser device for injecting a laser beam from the front to the light reflecting means, and the light reflecting means. Detecting means for detecting a position change of the laser beam reflected from the means, wherein the light reflecting means has first and second mirror surfaces intersecting in a direction orthogonal to the axial direction, and the object to be measured. The one-dimensional position detecting device for displacing the reflection position based on the change of the incident position of the laser beam due to the movement in the axial direction and the detecting means for detecting the axial displacement of the laser beam reflected from the light reflecting means. Position detection device characterized by.