JP2004317357A - Light-receiving element and optical encoder equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical encoder wherein crosstalk is suppressed. <P>SOLUTION: In this optical encoder, a scale 3 wherein translucent parts 32 are arrayed at a pitch P is arranged between a light source 2 and this light-receiving element 1. In the light-receiving element 1 equipped with the first light-receiving region row wherein the first light-receiving regions A having the same shape are arrayed in one row at a pitch P/2 in the X-direction and the second light-receiving region row wherein the second light-receiving regions B having the same shape are arrayed in one row at the pitch P/2 in the X-direction, each second light-receiving region B is positioned between the adjacent first light-receiving regions A, and the first light-receiving region row and the second light-receiving region row are arranged with a step so that the first light-receiving regions A and the second light-receiving regions B are partially overlapped in the Y-direction perpendicular to the X-direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light receiving element and an optical encoder including the same.
[0002]
[Prior art]
In the conventional optical encoder, as described in Patent Document 1, a light-transmitting portion having a pitch P is provided on a scale, and light-receiving regions are arranged in a line in a light-receiving element at a pitch 1/4 times the pitch P of the light-transmitting portion. They are arranged.
[0003]
[Patent Document 1]
JP-A-61-292016
[Problems to be solved by the invention]
In the conventional optical encoder, since each light receiving region is adjacent to each other in the length direction, crosstalk that is affected by the adjacent light receiving region is likely to occur. By arranging the light receiving regions to be adjacent to each other vertically so that the light receiving regions are arranged in two rows, it is less likely to be affected by crosstalk. However, if the light receiving area is arranged in two stages vertically, the state of the output signal is likely to be unstable when an inclination occurs between the light transmitting part of the scale and the light receiving area due to a mounting error or the like. Further, the length of the element increases in the length direction of the light receiving region, the size of the element increases, and the number of elements that can be obtained from one wafer decreases.
[0005]
Accordingly, it is an object of the present invention to prevent the element shape from becoming large and to suppress the occurrence of crosstalk.
[0006]
[Means for Solving the Problems]
As described in claim 1, the light receiving element of the present invention has a first light receiving region row in which first light receiving regions of the same shape are arranged in a line in the X direction, and a second light receiving region of the same shape in a line in the X direction. And a second light receiving region row arranged in a row. The second light receiving region is located between the adjacent first light receiving regions, and the first light receiving region and the second light receiving region are arranged in a Y direction orthogonal to the X direction. The first light receiving area row and the second light receiving area row are arranged with a step so that the two light receiving areas partially overlap.
[0007]
The optical encoder of the present invention is an optical encoder in which a scale in which light-transmitting portions are arranged at a pitch P is arranged between a light source and a light-receiving element, wherein the light-receiving element has the same shape. A first light receiving region row in which one light receiving region is arranged in a line in the X direction at a pitch P / 2, and a second light receiving region line in which second light receiving regions having the same shape are arranged in a line in the X direction at a pitch P / 2. And the second light receiving region is located between the adjacent first light receiving regions, and the first light receiving region and the second light receiving region partially overlap in a Y direction orthogonal to the X direction. The first light receiving area row and the second light receiving area row are arranged with steps.
[0008]
An optical encoder according to the present invention is an optical encoder in which a scale in which light transmitting portions are arranged at a pitch P is arranged between a light source and a light receiving element, wherein the light receiving element has the same shape. A first light receiving region row in which one light receiving region is arranged in a line in the X direction at a pitch P / 2, and a second light receiving region line in which second light receiving regions having the same shape are arranged in a line in the X direction at a pitch P / 2. And the second light receiving region is located between the adjacent first light receiving regions, and the first light receiving region and the second light receiving region partially overlap in a Y direction orthogonal to the X direction. And the output of the adjacent first light receiving area is provided to a first comparator, and the output of the adjacent second light receiving area is provided to a second comparator.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of the optical encoder.
[0010]
This optical encoder is configured by disposing a scale 3 between a light receiving element 1 and a light source 2. The light source 2 uses a light emitting diode, but other light sources may be used. The light of the light source 2 may be arranged to be collimated by an optical means such as a collimator lens 21 and then irradiated to the scale 3.
[0011]
The scale 3 has a plurality of light transmitting portions 32 arranged at a pitch P (for example, 170 μm) on a base material 31. The base material 31 is formed of a light-shielding plate such as a metal plate, and a hole serving as the light-transmitting portion 32 may be formed therein. Alternatively, the base material 31 may be formed of a transparent plate such as glass or plastic. A light-shielding film may be patterned. The width of the light transmitting portion 32 is set to, for example, 85 μm, which is approximately half the length of the pitch P. The length of the light transmitting portion 32 is set to, for example, 2000 μm, which is sufficiently longer than the pitch P. The light-shielding portion located between the adjacent light-transmitting portions 32 is set to have the same shape as the light-transmitting portion 32. The scale 3 has an elongated plate shape that reciprocates in the X direction. However, the scale 3 may be formed of a circular plate in which the light transmitting portion rotates along the X direction.
[0012]
The light receiving element 1 includes a light receiving unit 11 having a plurality of light receiving areas A and B aligned. The light receiving element 1 is configured by integrating a light receiving unit 11 and a circuit unit 12. The light receiving section 11 arranges light receiving areas A and B having the same shape in one direction (X direction), and alternately protrudes the light receiving areas A and B in a Y direction orthogonal to the X direction. A and B are arranged in a zigzag shape. The protruding length L1 is set to be shorter than the length L of the light receiving regions A and B in the Y direction.
[0013]
The rows of the first light receiving areas A located at the first stage of the light receiving section 11 are arranged at a pitch (P / 2) that is half the pitch P. The rows of the second light receiving areas B located at the second stage of the light receiving section 11 are arranged at a pitch (P / 2) that is a half of the pitch P. The second light receiving area B is located between the adjacent first light receiving areas A. In the Y direction, the first light receiving area A and the second light receiving area B partially overlap, and the first light receiving area row and the second light receiving area row are arranged with a step (length L1).
[0014]
The width of the first and second light receiving regions A and B is set to, for example, 30 μm, which is slightly shorter than the length (P / 4) of the pitch P. The length L of the first and second light receiving areas A and B is set to, for example, 260 μm. Between the first and second light receiving areas A and B, an interval of a length obtained by subtracting the width of the first (second) light receiving area A (B) from P / 4, in this example, 12.5 μm An interval is provided.
[0015]
The length L2 where the first light receiving area A and the second light receiving area B partially overlap in the Y direction is set to be longer than half the length L of the first light receiving area A or the second light receiving area B. I have. The longer the overlapping length L2 is, the shorter the length of the light receiving element 1 in the Y direction can be set, so that the number of light receiving elements obtained from one wafer can be increased. However, as the length L2 becomes longer, a crosstalk phenomenon in which one light receiving signal affects the other is more likely to appear between adjacent light receiving regions. Therefore, if there is no restriction on the length of the light receiving element 1 in the Y direction, the overlapping length L2 should be shorter than half the length L / 2 of the length of the first and second light receiving areas A and B. Can be. By doing so, the crosstalk phenomenon can be further suppressed.
[0016]
The light receiving unit 11 covers the surface of the portion excluding the light receiving regions A and B with a light-shielding coating.
[0017]
The light receiving element 1 is configured such that a circuit section 12 having a configuration as shown in FIG. 2 is integrated on a semiconductor substrate so as to be adjacent to the light receiving section 11, and is integrally formed with the light receiving section 11 and the circuit section 12.
[0018]
On the circuit section 12, a Vcc terminal for power supply, a GND terminal for grounding, and VoutA and VoutB for output are provided.
[0019]
As shown in FIG. 2, the circuit unit 12 includes a light-receiving area A and a light-receiving area A- (where-represents an inverted output called a bar) for obtaining an output having an inverse relationship with the output. After that, each output is amplified by an amplifier and compared by a comparator COMP-A to obtain an output VoutA. Similarly, each output of the light receiving region B and the light receiving region B− that obtains an output having an inverted relationship with the output is amplified by an amplifier, and then compared by a comparator COMP-B to obtain an output VoutB.
[0020]
The light receiving areas B-, A, B, A- are composed of four continuous light receiving areas. When the adjacent light receiving areas B-, A overlap the light transmitting part 32 of the scale simultaneously, the adjacent light receiving areas B, A -Is configured to overlap the scale light-shielding portion. That is, one block composed of the light receiving areas B-, A, B, A- is arranged so as to be within the pitch P of the scale. This light receiving element 1 has a configuration in which a plurality of the blocks are arranged in the X direction, in this example, four blocks are arranged. The numbers assigned to the light receiving areas A and B indicate the numbers of the blocks. The number of blocks can be increased or decreased. The corresponding light receiving areas of each block are electrically connected so that they are in a parallel relationship. For example, an element (photodiode) indicated by A in FIG. 2 typically represents a state in which light receiving regions A1 to A4 are connected in parallel. The same applies to the elements indicated by A-, B and B- in FIG.
[0021]
FIG. 3 shows signal waveforms at various parts of the circuit shown in FIG. 2 when the scale 3 and the light receiving element 1 are relatively moved. FIG. 1A shows the output signals of the elements A and A−, FIG. 2B shows the output VoutA of the comparator COMP-A, and FIG. 3C shows the output signals of the elements B and B−. (4) shows the output VoutB of the comparator COMP-B. In this way, a phase difference of 90 degrees can be provided between the output VoutA and the output VoutB.
[0022]
As described above, the light receiving areas arranged in the X direction are alternately arranged in a zigzag shape with the adjacent light receiving areas overlapping in the Y direction, so that the light receiving elements (light receiving sections) , The crosstalk between adjacent light receiving regions can be suppressed.
[0023]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a light receiving element having small dimensions and suppressing crosstalk, or an optical encoder including the same.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an optical encoder showing an embodiment of the present invention.
FIG. 2 is a circuit diagram of the embodiment.
FIG. 3 is a signal waveform diagram in the circuit diagram of the embodiment.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 light receiving element 11 light receiving unit 12 circuit unit 2 light source 3 scale 32 light transmitting unit

Claims (3)

A first light receiving area row in which first light receiving areas of the same shape are arranged in a row in the X direction, and a second light receiving area row in which second light receiving areas of the same shape are arranged in a row in the X direction are adjacent to each other. The first light receiving region is located such that the second light receiving region is located between the first light receiving regions, and the first light receiving region and the second light receiving region partially overlap in a Y direction orthogonal to the X direction. A light receiving element, wherein a row and a second light receiving area row are arranged with a step. In an optical encoder in which a scale in which light transmitting portions are arranged at a pitch P is arranged between a light source and a light receiving element, the light receiving elements are arranged such that first light receiving regions of the same shape are arranged in a line in the X direction at a pitch P / 2. And a second light receiving region row in which second light receiving regions of the same shape are arranged in a line at a pitch P / 2 in the X direction, and the second light receiving region line is arranged between the adjacent first light receiving regions. A first light receiving area row and a second light receiving area row are arranged such that a second light receiving area is located and the first light receiving area and the second light receiving area partially overlap in a Y direction orthogonal to the X direction. An optical encoder characterized in that is disposed with a step. In an optical encoder in which a scale in which light transmitting portions are arranged at a pitch P is arranged between a light source and a light receiving element, the light receiving elements are arranged such that first light receiving regions of the same shape are arranged in a line in the X direction at a pitch P / 2. And a second light receiving region row in which second light receiving regions of the same shape are arranged in a line at a pitch P / 2 in the X direction, and the second light receiving region line is arranged between the adjacent first light receiving regions. A second light receiving region is located, and the first light receiving region and the second light receiving region are arranged so as to partially overlap each other in a Y direction orthogonal to the X direction. An optical encoder, wherein the output is supplied to one comparator, and the output of the adjacent second light receiving region is supplied to a second comparator.

Images