JPH01136021A - Optical displacement detector - Google Patents

Abstract

PURPOSE:To reduce the effect of the distortion of an irradiation at the time of molding, by preventing the generation of the shade of a light emitting diode in the parallel light illuminating a main scale and a reference scale. CONSTITUTION:The relative displacement quantity of the first member, which is composed of a light pervious material having a main scale 16 composed of vertical stripe like optical lattices at a constant pitch formed thereto, and the second member 22 is detected on the basis of the change of the output signal of a photodetector 26 caused by the repeated superposition of both of the main scale 16 and a reference scale 20. A light emitting diode 24 is arranged on a lead frame 28 and the concave reflecting mirror 32 for converting the light emitted from the light emitting diode 24 to parallel light to reflect the same toward the first and second members 18, 22 is arranged so as to be shifted in the relative moving direction of the first member 18 in order to prevent a center optical axis 30 from passing through the main scale 16, the reference scale 20 and the photodetector 26. By this method, the shade of the light emitting diode is not generated in the parallel light for illuminating the main scale and the reference scale.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical displacement detector, and in particular, a light receiving element converts changes in light caused by repeated overlapping of a main scale and a reference scale that are relatively displaced into an electrical signal, and the electric signal is used to generate the amount of relative displacement. This invention relates to an improvement of an optical displacement detector that detects

[Conventional technology]

Conventionally, as disclosed in JP-A-62-212516, for example, a main scale and a reference scale made of an optical grating are formed on a first member and a second member made of a light-transmitting material, and these first members and When the second member is relatively displaced, the illumination light from the light-emitting element that illuminates the main scale and the reference scale is received by the light-receiving element on the opposite side and converted into an electrical signal. There is an optical displacement detector called an optical encoder that detects the amount of relative displacement of a second member. Another example of such an optical displacement detector is an optical displacement detector as shown in FIGS. 5 and 6, which was proposed by the applicant in Japanese Patent Application No. 61-149073, although it is not publicly known. There is a detector. This optical displacement detector includes a first member 2 in which main scales 1 each consisting of a vertical striped optical grating with a constant pitch are formed in parallel in the longitudinal direction, and a first member 2 arranged so as to be relatively displaceable along the first member 2. and a second member 4 on which a reference scale 3 made of an optical grating is formed facing the main scale 1, and a second member 4 disposed on the opposite side of the second member 4 with the first member 2 in between. an illuminator 6 including a light emitting diode 5, and four receivers disposed on the opposite side of the first member 2 with the second member 4 in between.
- a light receiver 8 including optical elements 7A to 7D; Here, the main scale 1 and the reference scale 3 are formed adjacent to opposing surfaces of the first member 2 and the second member 4. Further, the light emitting diode 5 in the illuminator 6 is attached to the surface of the second member 4 opposite to the surface of the reference scale 3, with its light emitting surface facing in the opposite direction to the reference scale 3. The illuminator 6 includes the light emitting diode 5, a hemispherical light-transmitting resin mold 9 with the light-emitting diode 5 at the center of the sphere, and a spherical reflective mold formed on the outer surface of the light-transmitting resin mold 9. The illumination light emitted from the light emitting diode 5 in the radial direction is made up of a parallel light beam that illuminates the main scale 1 and the reference scale 3 in a direction perpendicular to the scale planes by the spherical reflection M9A. Here, in the light emitting diode 5, a slit-shaped light emitting portion 5A is formed by depositing a metal film having a slit-shaped opening on the light emitting surface of the light emitting diode 5. The slit-shaped light emitting section 5A is arranged parallel to the height direction of the main scale 1 and the reference scale 3 (see FIG. 6).
Also, on the surface of the second member 2 on the illuminator 6 side, a transparent conductive film 5B is provided as a power supply line to the light emitting diode 5.
, 5C are formed by vapor deposition. In the optical displacement detector as described above, the slit-shaped light emitting portion 5B of the light emitting diode 5 has a main scale 1 and a reference scale 3.
Because it is arranged parallel to the main scale 1 and the reference scale 3, the amount of illumination light can be increased without losing the parallelism of the illumination light in the direction perpendicular to the main scale 1 and the reference scale 3. 1
By widening the grid spacing S of the reference scale 3, a signal with a good S/N ratio can be obtained. Further, since the radiation emitted from the light emitting diode 5 is made into parallel light by the spherical reflection JA9A, the detector can be made smaller.

[Problem that the invention attempts to solve]

However, as mentioned above, the light beam emitted from the light emitting diode 5 is reflected by the spherical reflection M9A as a parallel light beam, and this is reflected by the main graduation 1 and the reference graduation TI! t3
Since the light emitting diode 5 casts a shadow when the light is incident on the light emitting diode 5, the positioning accuracy of the light receiving element 7 must be increased to avoid this shadow. When doing so, there is a problem that the parallelism of the parallel light beams to be formed by the spherical reflective film 9A is disturbed due to the distortion of the light emitting diode 5 itself and the distortion of its surroundings. Furthermore, as a power supply line for the light emitting diode 5,
As mentioned above, the surface of the second member 4 has a transparent conductive If! 5B
, 5C are provided, but a metal film deposition process is required to form the transparent conductive films 5B and 5C, which increases manufacturing costs and makes it difficult to increase the supplied current.

[Purpose of the invention]

The present invention has been made in view of the above problems, and is designed to prevent shadows of light emitting diodes from being cast on the parallel light beams illuminating the main scale and reference scale, and to eliminate the need for passing through a transparent conductive film. An object of the present invention is to provide an optical displacement detector that can supply a large amount of current to a light emitting diode.

[Means to solve the problem]

The present invention includes a first member made of a light-transmitting material on which main scales in the form of vertical stripes with a constant pitch are formed, and a reference scale corresponding to the main scales, which is movable relative to the first member. a second member made of a light-transmissive material arranged; an illuminator including a light emitting diode and illuminating the main scale and the reference scale from one side; and illumination light from the illuminator that passes through the main scale and the reference scale. a light receiver that receives the light and outputs an electric signal according to the amount of light received;
An optical displacement detector that detects the amount of relative displacement between the first member and the second member based on a change in an output signal of a light receiver based on repeated overlapping of a main scale and a reference scale due to relative displacement between the member and the second member. , the illuminator is arranged on the opposite side of the second member with the first member in between, and
a lead frame; and on the lead frame, the first
The light emitting diode is arranged facing in the opposite direction to the member, and the central optical axis is a straight line that passes through the light emitting diode and is orthogonal to the scale surface on which the main scale is formed, and the light emitted from the light emitting diode is converted into parallel light. a concave reflecting mirror that reflects in the direction of the first member and the second member;
The light emitting diode is provided with a slit-like light emitting section, and is arranged so that the slit-like light emitting section is parallel to the main scale and the reference scale, and the light emitting diode and the concave reflecting mirror have a central optical axis parallel to the main scale. The above object is achieved by arranging the scale, reference scale, and light receiver so as not to pass through them.

[Effect]

In this invention, only the part of the parallel light beam formed by the concave reflector that is shifted to one side from the light emitting diode is used, so there is no shadow of the light emitting diode in the illumination light, and therefore the reference scale There is no need to increase the positioning accuracy. Furthermore, the influence of distortion during molding of the illuminator can be reduced, and furthermore, since there is no need to use a transparent conductive film, manufacturing costs can be reduced and supply current can be increased.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, this embodiment includes a first member 18 made of a light-transmitting material on which a main graduation 16 made of an 8M-shaped optical grating with a constant pitch is formed, and a first member 18 made of a light-transmitting material. A reference scale 20 consisting of an optical grating corresponding to 16 is formed, and includes a second member 22 made of a light-transmitting material and arranged to be movable relative to the first member 18, and a light emitting diode 24, and includes a light emitting diode 24. An illuminator 25 that illuminates the scale 16 and reference scale 20 from one side; and an illuminator 25 that receives illumination light from the illuminator 25 that has passed through the main scale 16 and reference scale 20, and outputs an electrical signal according to the amount of received light. receiver 26
The change in the output signal of the light receiver 26 based on the repetition of the overlapping of the main scale 16 and the reference scale 20 due to the relative displacement of the first member 18 and the second member 22 causes the first member to 18 and a second member 22, the illuminator 25 is disposed on the opposite side of the second member 22 with the first member 18 in between, and A lead frame 28, a light emitting diode 24 disposed on the lead frame 28 facing in the opposite direction to the first member 18, and the insect eye passing through the light emitting diode 24! T! perpendicular to the scale plane where A16 is formed! A concave reflection 11A3 that takes the L line as the central optical axis 30 and reflects the light emitted from the light emitting diode 24 as parallel light toward the first member 18 and the second member 22.
2, the light emitting diode 24 includes a slit-shaped light emitting section 24A, and the slit-shaped light emitting section 24
A is arranged so that it is parallel to the main scale 16 and the reference scale 20, and the light emitting diode 24 and the concave reflecting mirror 3
2, the central optical axis 30 is the main scale 16 and the reference scale 2.
0 and the light receiver 26, the first member 18 is shifted in the direction of relative movement of the first member 18. Here, the light emitting diode 24 is connected to a lead frame 28.
It is molded in a light-transmissive resin 34 in a state where it is bonded to the surface. A circular recess 34A is formed on the surface of the light-transmissive resin 34 facing the light emitting diode 24, and a lens member 36 is fitted and bonded to the recess 34A. The end surface of the lens member 36 opposite to the recess 34A has a convex spherical shape, and the concave reflecting mirror 32 is formed by depositing a metal film such as aluminum on the convex spherical surface. The radius R of the convex spherical surface of the lens member 36 is equal to 2 of the distance between the concave reflecting mirror 32 and the light emitting diode 24 on the central optical axis 30.
'' times, so that the light rays emitted from the light emitting diode 24 in the radial direction are reflected by the concave reflection 832.
Therefore, the light beams are parallel to each other in a direction perpendicular to the main scale 16 and the reference scale 20. The light emitting diode 24, as shown in FIG.
The slit-shaped light-emitting portion 24A is formed by vapor-depositing gold ffM24B having a slit-shaped opening on the light-emitting surface. This light emitting diode 24 is made of a P-type Ga AS substrate 24a.
and an N-type GaAs substrate 24b, each having a square shape with a − side of 400 μl,
The shape of the slit-shaped light emitting section 24A has a width W=50μ1.
1. Length L = 350 μm, Ga AS substrate 24
a and 24b are arranged diagonally. Reference numeral 24C in the figure is a lead wire, and the lead wire to be connected to the surface opposite to the metal film 24B of the light emitting diode 24, which is connected to the metal film 24B which also serves as an electrode, is connected to the surface opposite to the metal film 24B. It is omitted because it is in contact with the lead frame 28. As shown in FIG. 2, the first member 18 is a so-called main scale in an optical displacement detector. On the other hand, the second member 22 is formed short and is a so-called index scale, and the reference scale 20 is composed of four optical gratings 20A to 20 whose phases are shifted by 90 degrees.
D (see Figure 4). These four optical gratings 20A to 20D are connected to the first member 18
It is arranged in a block shape, that is, in a box shape, at a position that can overlap with the main scale 16 in the figure. The illuminator 25 is connected to the four optical gratings 20A to 20A.
0D overlaps the circular illumination range of the lens member 36,
Moreover, a light emitting diode 24 placed at the center of the circular illumination range is placed so as to be offset from the four optical gratings 20A to 20D. Further, the lead frame 28 has optical gratings 20A to 20D forming the reference scale 20, as shown in FIG.
The transparent portion 28A is formed so as not to overlap with the transparent portion 28A. Further, the lead frame 28 is divided into upper and lower parts in FIG. 4, and the lead wire 24C from the light emitting diode 24 is connected to the upper part, and the back surface of the light emitting diode 24 is connected to the lower part. The light receiver 26 includes four light receiving elements 26A to 26D provided corresponding to the four optical gratings 20A to 20D,
It is composed of a lead frame 38 to which these light receiving elements 26A to 26D are die-bonded, and a light transmitting resin 40 which integrally molds the light receiving elements 26A to 26D and the lead frame 38. The light receiver 26 is integrally bonded to the surface of the second member 22 on which the reference scale 20 is formed using an adhesive 27. The input terminal of the light emitting diode 24 and the output terminal of the light receiver 26 are connected to a measuring circuit 42, as shown in FIG. This measurement circuit 42 processes the output signal from the light receiver 26, calculates the relative movement distance between the first member 18 and the second member 22, and outputs it to the display 44 to display the measured value. be. Reference numeral 46 in FIG. 1 indicates a probe connected to the first member 18 via a spindle 48, and 50 indicates a guide for guiding the spindle 48. This guide 50 is fixedly held within a cylindrical outer tube (not shown). In this embodiment, the illumination light emitted from the light emitting diode 24 enters the lens member 36 and is reflected by the concave reflector 32.
, and becomes a parallel light beam in a direction perpendicular to the first member 18 and the second member 22 . The optical gratings 20A to 20D of the reference scale 20 and the light receiving elements 26A to 26D in the light receiver 26 are connected to a central optical axis 3 passing through the center of the light emitting diode 24 and the concave reflecting mirror 32.
Since the arrangement is shifted from 0, it is formed by the concave reflection 9A32, and the transparent part 28A of the lead frame 28,
The shadow of the light emitting diode 24 is not formed in the illumination light that passes through the first member 18, the main scale 16, and the reference scale 20 and reaches the light receiving elements 26A to 26D. Further, since current is supplied to the light emitting diode 24 from the lead frame 28 through the lead wire 24C and the back surface of the light emitting diode 24, a large current can be supplied to the light emitting diode 24 to increase the amount of illumination light. Can be done. Furthermore, since a vapor deposition process for a transparent metal film or the like is not necessary, manufacturing costs can be reduced. Note that it is also possible to shift the light emitting diode 24 from the central optical axis 30, but in this case, the concave reflector 32
Since the reflected light is tilted with respect to the central optical axis 30, off-axis aberrations occur and the arrangement of the illuminator becomes complicated. , the illuminator becomes large. Also, when a light emitting diode is attached to a lead frame for boat fishing, not only the shadow of the light emitting diode itself but also the shadow of the lead frame will appear in the illumination light. Since only parallel light rays deviated from the central optical axis 30 are used, there is no shadow of the lead frame. In the above embodiment, the reference scale 20 on the second member 22 is formed on the light receiver 26 side, but it may be provided at a position facing the main scale 16. Further, in the above embodiment, the concave reflecting mirror 32 is formed in the lens member 36 which is provided separately from the light-transmitting resin 34, but the lens member may be formed integrally with the light-transmitting resin. good. Furthermore, although the concave reflecting mirror 32 in the above embodiment has a concave spherical surface, the lens member may be formed into a cylindrical lens shape to form a concave reflecting mirror in cross section, for example. Further, in the above embodiment, the light emitting diode 24 has a slit-like light emitting portion 24A formed by covering the light emitting surface with a metal film having a slit-like opening, but the present invention is not limited to this. For example, N-type Ga AS
It may also be one in which P-type GaAs is diffused into a slit shape on the substrate. Furthermore, in the above embodiment, the lead frame 28 in the illuminator 25 is shaped like a flat plate.
As shown by the two-dot chain line in the figure, the mounting part of the light emitting diode 24 on the lead frame 28 is bent clockwise in the figure so that the emitted light is concentrated on the right side in the figure rather than the central optical axis 30 of the concave reflector 32. In this way,
The efficiency of light use may be increased. Furthermore, although the above embodiment relates to an encoder that detects the relative linear displacement of two members, the present invention is not limited thereto, and can also be applied to a rotary encoder that detects a rotation angle. be.

【Effect of the invention】

Since the present invention is configured as described above, the shadow of the light emitting diode does not occur in the parallel light beam that illuminates the main scale and the reference scale, and furthermore, it is possible to supply power to the light emitting diode from the lead frame. As a result, it is possible to increase the amount of illumination light as a large current, and since there is no need to provide a transparent conductive film or the like, it has excellent effects in that manufacturing costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view including a four-part block diagram showing an embodiment of an optical displacement detector according to the present invention, and FIG.
FIG. 3 is an enlarged perspective view showing the light emitting diode in the same embodiment, and FIG. 4 is an enlarged sectional view taken along the line, FIG.
- A cross-sectional view taken along line IV, FIG. 5 is a cross-sectional view showing an optical displacement detector previously proposed by the applicant, and FIG.
FIG. 3 is a cross-sectional view taken along the line Vl-Vl in the figure. DESCRIPTION OF SYMBOLS 16... Main scale, 18... First member, 20... Reference scale, 22... Second member, 24... Light emitting diode, 24A-24D... Slit-shaped light emitting part, 25... ...Illuminator, 26... Light receiver, 26A to 26D... Light receiving element, 28... Lead frame, 30... Central optical axis, 32... Concave reflecting mirror, 34... Light transmission sex resin.

Claims (1)

[Claims] (1) A first member made of a light-transmissive material on which main scales in the form of vertical stripes with a constant pitch are formed, and reference scales corresponding to the main scales are formed, and are arranged so as to be movable relative to the first member. a second member made of a light-transmissive material, an illuminator including a light emitting diode and illuminating the main scale and the reference scale from one side, and an illumination light from the illuminator that passes through the main scale and the reference scale. a light receiver that receives light and outputs an electrical signal according to the amount of received light, the light receiver being based on repeated overlapping of a main scale and a reference scale due to relative displacement of the first member and the second member. Due to the change in the output signal of
In the optical displacement detector that detects the amount of relative displacement between the first member and the second member, the illuminator is disposed on the opposite side of the second member with the first member in between, and a frame, and the light emitting diode disposed on the lead frame in a direction opposite to the first member;
A concave reflection device that has a central optical axis that passes through the light emitting diode and is perpendicular to the scale surface on which the main scale is formed, and reflects the light emitted from the light emitting diode as a parallel beam toward the first member and the second member. a mirror, the light emitting diode is provided with a slit-like light emitting section, and the slit-like light emitting section is arranged parallel to the main scale and the reference scale, and the light emitting diode and the concave reflecting mirror An optical displacement detector arranged such that a central optical axis does not pass through the main scale, the reference scale, and the light receiver.