JPH1123221A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the output signal of a light receiving element by reducing the influence of unnecessary light on the output signal. SOLUTION: A luminous flux from a light emitting element is made incident to a fixed scale plate 13 faced oppositely to a mobile scale plate 12 through the light transmitting sections 12b of the mobile scale plate 12. The luminous flux made incident to the fixed scale plate 13 are split into luminous fluxes in three directions through the inclined surfaces 14a and 14b of V-shaped groove sections and the flat surface sections 15 of the plate 13 and the signal luminous fluxes which are made incident to the inclined surfaces 14a and 14b at angles of about 30 deg. are received by means of light receiving elements 16a and 16b oriented in the direction of the luminous fluxes with high sensitivity and the luminous flux passed through the flat surface section 15 advances straight and is received by means of the elements 15 with half sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a position detecting device for performing position detection using an optical element having a V-groove.

[0002]

2. Description of the Related Art Conventionally, in an imaging apparatus such as a video camera,
The lens must operate at a given speed and position accuracy for zoom and focus. Recently, a linear motor has been used as a lens drive control device for this purpose, and a control device for detecting the position of the lens is required to control the linear motor. As an example of the position detection device, an optical encoder that generates a plurality of signals having a plurality of repetitive periodic waveforms whose phases are shifted with respect to a position change is known, and is disclosed in Japanese Patent Application Laid-Open No. 1-123723.

FIG. 6 shows a side view of an optical encoder.
A condenser lens 2 is attached to the light emitting element 1, and a movable scale plate 3 attached to, for example, a lens portion of the device under test is disposed below the condenser lens 2. A light shielding portion having a slope and a light transmitting portion having a flat surface are periodically provided at regular intervals of a pitch P in a lattice pattern.

[0004] A fixed scale plate 4 is disposed on the lower side of the movable scale plate 3 so as to be opposed to the movable scale plate 3. A groove 4a and a plane portion 4b are provided. Also, below the fixed scale plate 4, two light receiving elements 5 for receiving light beams from each area of the fixed scale plate 4 are provided.
a and 5b are arranged such that the light-receiving and incident light are directed in the light beam direction in the straight traveling direction.

In the state shown in FIG. 6, the light flux from the light transmitting portion of the movable scale plate 3 is
The light is refracted by a and enters the light receiving elements 5a and 5b. On the other hand, in the state of FIG.
The light beam from the light transmitting portion of the movable scale plate 3 travels straight on the flat portion 4b of the fixed scale plate 4 and enters the light receiving elements 5a and 5b.

[0006]

However, in the above-mentioned conventional example, the light beam passing through the flat portion 4b of the fixed scale plate 4 is incident perpendicularly on the light receiving elements 5a and 5b, and the inclined surface of the V-shaped groove portion 4a is formed. There is a problem that harmful light becomes harmful to the transmitted light flux and affects the output level and phase of the output signals of the light receiving elements 5a and 5b.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a position detecting device that reduces the influence of unnecessary light and improves the output signal of a light receiving element.

[0008]

A position detecting device according to the present invention for achieving the above object divides a light beam from a light emitting element into at least two directions using a V-shaped groove, and splits the divided light beam. In a position detecting device for detecting a position by receiving light with a light receiving element, a direction in which the light receiving element having directivity has high sensitivity is directly opposed to the refracted light beam direction.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a side view of the embodiment. A movable scale plate 12 made of a parallel plate-shaped transparent material attached to, for example, a lens portion of an object to be measured (not shown) is arranged below a light emitting element 11. On the lower surface of the scale plate 12, light-shielding portions 12a formed of inclined surfaces and light-transmitting portions 12b formed of flat surfaces are periodically arranged at regular intervals of a pitch P in a grid pattern. Below the movable scale plate 12, a fixed scale plate 13 made of a parallel plate-shaped transparent material is provided.
Are arranged facing each other, and as shown in FIG. 2, the V-shaped groove portion 14 and the flat portion 15 which are both light transmitting portions are formed on the surface of the fixed scale plate 13 at intervals equal to the lattice pitch P of the movable scale plate 12. Are provided, and the inclined surface 14a of the V-shaped groove portion 14,
14b is at an angle of 45 degrees with respect to the plane portion 15.

Further, below the fixed scale plate 13, two light receiving elements 16a and 16b are arranged so as to be inclined toward the fixed scale plate 13 by about 30 degrees so as to face each other. The light beam refracted from the light beam 13 can be received almost directly. Further, the light receiving elements 16a and 16b have directivity in sensitivity, and the sensitivity to light incident from a direction inclined at 30 degrees is half that in the vertical direction.

FIG. 1 shows a light transmitting portion 12 of a movable scale plate 12.
b coincides with the V-shaped groove 14 of the fixed scale plate 13, and the light shielding portion 12 a of the movable scale plate 12
And the light-emitting element 11
The light flux from the light source passes through the light transmitting portion 12b of the movable scale plate 12, and is incident on the inclined surfaces 14a and 14b of the V-shaped groove portion 14 of the fixed scale plate 13 opposed thereto. When the inclined surfaces 14a and 14b of the V-shaped groove portion 14 are at an angle of 90 degrees to each other and the light refractive index of the fixed scale plate 13 is 1.58, the light is refracted after passing through the fixed scale plate 13 and becomes perpendicular to the vertical line. About 3
It becomes a light beam having an inclination of 0 degree, more precisely 30 degrees and 12 minutes.
These light beams are received by the light receiving elements 16a and 16b, respectively, from directions substantially perpendicular to each other.

FIG. 3 shows that the light transmitting portion 12b of the movable scale plate 12 coincides with the flat portion 15 of the fixed scale plate 13,
The light-shielding portion 12a of the movable scale plate 12 corresponds to the V-shaped groove portion 14 of the fixed scale plate 13, and the light-emitting element 1
1 from the light transmitting portion 12b of the movable scale plate 12.
And enters the opposed flat surface portion 15 of the fixed scale plate 13 and passes as it is.

When the movable scale plate 12 is positioned between FIG. 1 and FIG. 3 with respect to the fixed scale plate 13, FIG.
As shown in (2), the light flux passing through the light transmitting portion 12b of the movable scale plate 12 enters the V-shaped groove 14 and the flat portion 15 of the fixed scale plate 13. The light beam incident on the V-shaped groove portion 14 is refracted, and the light beam incident on the flat portion 15 goes straight. At this time, the light receiving elements 16a and 16b are both fixed scale plates 13
, And about 60 degrees with respect to the straight light, it has high sensitivity to the light flux refracted by the fixed scale plate 13, while the light beam that goes straight through the fixed scale plate 13 is Since the light is incident obliquely at an angle of 30 degrees with respect to the light receiving elements 16a and 16b, the sensitivity becomes half.

At this time, for example, the V-shaped groove 14 is
And the width of the two inclined surfaces 14a and 14b is equal and P / 4, respectively.
Is set to have a width equal to a half of the pitch P, the output signals Sa and Sb from the light receiving elements 16a and 16b have a phase difference of 90 degrees with respect to the change in the position of the movable scale plate 12, as shown in FIG. Is a repetitive signal with a period P shifted by By calculating the output signals Sa and Sb, the movable scale plate 12
Can be detected relative to the fixed scale plate 13.

As described above, by increasing the sensitivity to the signal light beam passing through the inclined surfaces 14a and 14b of the V-shaped groove portion 14 of the light beam divided into three directions and decreasing the sensitivity of the light beam transmitted through the plane portion 15, By improving the signal output of the light receiving elements 16a and 16b, a signal having a desired phase difference can be received.

Although the light beam is divided into three directions in the fixed scale plate 13 of the embodiment, the light beam may be divided into two directions, or the light beam may be further divided into a plurality of directions by setting the inclination angle of the slope to many floors. Can also. Further, there is no problem even if either of the two scale plates 12 and 13 is used as a fixed scale plate or a movable scale plate.

[0017]

As described above, the position detecting device according to the present invention divides the light beam from the light emitting element into at least two directions by using the V-shaped groove of the scale plate, and changes the angle of incidence on the light receiving element. As a result, the received light signal can have a gradient depending on the incident direction, and further, the light beam can be received with a desired phase difference without being affected by harmful light, so that accurate position detection can be performed. Become.

[Brief description of the drawings]

FIG. 1 is a side view of an embodiment.

FIG. 2 is a perspective view of a fixed scale plate.

FIG. 3 is a side view when the movable scale plate moves by a half pitch.

FIG. 4 is an explanatory diagram of a transmitted light beam.

FIG. 5 is a graph showing an output voltage of the light receiving element.

FIG. 6 is a side view of a conventional example.

FIG. 7 is a side view when the movable scale plate moves by ピ ッ チ pitch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Light emitting element 12 Movable scale plate 13 Fixed scale plate 14 V-shaped groove part 14a, 14b Inclined surface 15 Flat part 16a, 16b Light receiving element

Claims (2)

[Claims] 1. A position detecting device for dividing a light beam from a light emitting element into at least two directions using a V-shaped groove, and receiving the divided light beam by a light receiving element to detect a position.
A position detecting device, wherein a direction of high sensitivity of the light receiving element having directivity is directly opposed to the direction of the refracted light beam. 2. The position detecting device according to claim 1, wherein said light receiving element is tilted by about 60 degrees with respect to said light beam in the straight direction.