JP4307895B2 - Optical encoder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light receiving element and an optical encoder including the same.
[0002]
[Prior art]
As described in Patent Document 1, the conventional optical encoder is provided with a translucent portion having a pitch P on the scale, and the light receiving elements are arranged in a row with light receiving areas at a pitch 1/4 times the pitch P of the translucent portion. Arranged.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 61-292016 [0004]
[Problems to be solved by the invention]
In the conventional optical encoder, the respective light receiving areas are adjacent to each other in the length direction, so that crosstalk that is affected by the adjacent light receiving areas is likely to occur. If the light receiving regions are arranged in two rows by arranging the light receiving regions that should be adjacent to each other, it is less likely to be affected by crosstalk. However, if the light receiving area is arranged in two stages in the vertical direction, the state of the output signal is likely to become unstable when an inclination occurs between the light transmitting part of the scale and the light receiving area due to an attachment error or the like. In addition, 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 taken from one wafer decreases.
[0005]
Accordingly, it is an object of the present invention to prevent an increase in element shape and to suppress the occurrence of crosstalk.
[0007]
[Means for Solving the Problems]
Light encoder of the present invention as described in claim 1, scale transparent portion are arranged at a pitch P is the optical encoder disposed between the light receiving element and the light source, the light receiving element of the same shape the A first light receiving region array in which one light receiving region is arranged in a row in the X direction at a pitch P / 2, and a second light receiving region row in which second light receiving regions having the same shape are arranged in a row in the X direction at a pitch P / 2. 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 the Y direction orthogonal to the X direction. Further, the first light receiving region row and the second light receiving region row are arranged with a step.
[0008]
According to an optical encoder of the present invention, as described in claim 2 , in the optical encoder in which the scale in which the light transmitting portions are arranged at the pitch P is disposed between the light source and the light receiving element, A first light receiving region array in which one light receiving region is arranged in a row in the X direction at a pitch P / 2, and a second light receiving region row in which second light receiving regions having the same shape are arranged in a row in the X direction at a pitch P / 2. 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 the Y direction orthogonal to the X direction. And the output of the adjacent first light receiving region is supplied to a first comparator, and the output of the adjacent second light receiving region is supplied to a second comparator.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an optical encoder.
[0010]
This optical encoder is configured by arranging 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 can also be used. The light of the light source 2 can be configured to irradiate the scale 3 after being aligned with parallel light by optical means such as the collimating lens 21.
[0011]
The scale 3 has a plurality of light transmitting portions 32 arranged on a base material 31 at a pitch P (for example, 170 μm). The base material 31 is constituted by a light-shielding plate such as a metal plate, and a hole as the light transmitting portion 32 may be formed therein, or may be constituted by a transparent plate such as glass or plastic. A light-shielding film may be patterned. The width of the translucent part 32 is set to, for example, 85 μm, which is substantially half the pitch P. The length of the translucent part 32 is set to 2000 μm, for example, which is sufficiently longer than the pitch P. The light-shielding part located between the adjacent translucent parts 32 is set in the same shape as the translucent part 32. The scale 3 has a long and narrow 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 regions 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 unit 11 arranges the light receiving regions A and B having the same shape in one direction (X direction), and alternately projects the light receiving regions A and B in the Y direction orthogonal to the X direction, thereby the light receiving region. A and B are arranged in a zigzag shape. The protruding length L1 is set to be shorter than the length L in the Y direction of the light receiving areas A and B.
[0013]
The rows of the first light receiving regions A located at the first stage of the light receiving unit 11 are arranged at a pitch (P / 2) that is half the pitch P. The rows of the second light receiving regions B located in the second stage of the light receiving unit 11 are arranged at a pitch (P / 2) that is half the pitch P. The second light receiving region B is located between the adjacent first light receiving regions A. The first light receiving region A and the second light receiving region B partially overlap in the Y direction, and the first light receiving region row and the second light receiving region row are arranged with a step (length L1).
[0014]
The widths of the first and second light receiving regions A and B are set to, for example, 30 μm, which is slightly shorter than the length (P / 4) of ¼ of the pitch P. The length L of the first and second light receiving areas A and B is set to 260 μm, for example. Between the first and second light receiving areas A and B, an interval having a length obtained by subtracting the width of the first (second) light receiving area A (B) from P / 4, which is 12.5 μm in this example An interval is provided.
[0015]
The length L2 at which the first light receiving region A and the second light receiving region B partially overlap in the Y direction is set to be longer than half the length L of the first light receiving region A or the second light receiving region B. Yes. The longer the overlapping length L2, the shorter the length of the light receiving element 1 in the Y direction, so that the number of light receiving elements obtained from one wafer can be increased. However, as the length L2 is longer, a crosstalk phenomenon in which one received light signal affects the other is more likely to appear between adjacent light receiving regions. Therefore, if the length of the light receiving element 1 in the Y direction is not restricted, the overlapping length L2 is made shorter than the length L / 2 which is half the length of the first and second light receiving regions A and B. Can do. In this way, 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 film.
[0017]
In the light receiving element 1, the circuit unit 12 having the configuration shown in FIG. 2 is integrated on the semiconductor substrate so as to be adjacent to the light receiving unit 11, and the light receiving unit 11 and the circuit unit 12 are integrally formed.
[0018]
On the circuit unit 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 receives the light receiving area A, and the light receiving area A- (where-is an inverted output called a bar) to obtain an output that is in an inverted relationship with the output. The same is applied to the output, and the output VoutA is obtained by amplifying the outputs with an amplifier and comparing them with a comparator COMP-A. Similarly, each output of the light receiving region B and the light receiving region B- that obtains an output in an inverted relationship with the output thereof 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 at the same time, the adjacent light receiving areas B, A -Is configured to overlap the scale shading part. That is, one block constituted by the light receiving areas B-, A, B, A- is arranged so as to be within the pitch P of the scale. The light receiving element 1 has a configuration in which a plurality of the blocks are arranged in the X direction, four in this example. The numbers given to the light receiving areas A and B indicate the block numbers. 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, the element (photodiode) indicated by A in FIG. 2 represents a state in which the 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. (1) shows the output signals of the elements A and A-, (2) shows the output VoutA of the comparator COMP-A, and (3) shows the output signals of the elements B and B-. FIG. 4 (4) shows the output VoutB of the comparator COMP-B. In this manner, 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 overlapped in the Y direction, so that the light receiving elements (light receiving portions) The crosstalk between adjacent light receiving regions can be suppressed while suppressing the dimension in the Y direction.
[0023]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a light receiving element having a small size 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 same embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light receiving element 11 Light receiving part 12 Circuit part 2 Light source 3 Scale 32 Translucent part

Claims (2)

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

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