JPH06258100A - Absolute encoder - Google Patents

Abstract

PURPOSE:To obtain an absolute encoder having high resolution. CONSTITUTION:A plurality of photoreceivers 10, 11, 12, 13, 14 each having a width of 2l or more for a minimum reading unit l are provided in an absolute detector 3, and disposed in different continuous combination with a passing part 1a and a shielding part 1b of an absolute pattern 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute encoder, and more particularly to a detector for detecting an absolute pattern.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional absolute encoder.
And shown in FIG. FIG. 5 is a diagram showing a configuration of the absolute encoder, and FIG. 6 is a diagram showing an optical scale and a detector. As shown in FIG. 5, the absolute encoder includes an illumination unit 40 including a light source 33 and a condenser lens 34, an optical scale 31, and a detector 32. The illumination unit 40, the detector 32, and the optical unit It is configured to move relative to the scale 31.

As shown in FIG. 6, the optical scale 31 includes:
A 5-bit 1-track absolute pattern 41 including a white portion having a length of a minimum reading unit of λ and a hatched portion is formed. The white part indicates “1”, which is a transmissive part that transmits light, and the shaded part indicates “0”, which is a light shielding part that shields light. The number of bits of the pattern 41 (=
5 light receiving elements 35, 36, 37, which have the same number as 5),
38 and 39 are provided.

In the absolute encoder thus constructed, the light emitted from the light source 33 is collimated by the condenser lens 34 and projected on the optical scale 31, and the light transmitted through the pattern 41 of the optical scale 31 is detected by the detector 32. The absolute position was detected by making it incident on each of the light receiving elements 35, 36, 37, 38, 39.

[0005]

In the prior art as described above, the width of the light receiving element included in the detector is substantially the same as the minimum reading unit for the minimum reading unit of the absolute pattern. In recent years, the resolution of absolute encoders has increased, and the minimum reading unit of absolute patterns has become smaller.

Therefore, it becomes necessary to reduce the width of the light receiving element of the detector with respect to the absolute pattern.
However, if the width of the light receiving element becomes small, the effective light receiving area of the light receiving element also becomes small, and there is a possibility that the light passing through the minimum reading pattern cannot be received.

The present invention has been made in view of such conventional problems, and provides a light-receiving element capable of receiving the light passing through the transmitting portion of the absolute pattern even if the width of the minimum reading unit becomes small. The purpose is to obtain a high resolution absolute encoder.

[0008]

According to a first aspect of the present invention, a passage portion (1a) through which light passes and a light shielding portion (1b) that shields light are formed in a minimum reading unit λ. The optical scale (1) having an absolute pattern (7) whose absolute value is represented by a combination of the passing portion (1a) and the light shielding portion (1b), moves relative to the optical scale (1), and the passing portion (1a) A plurality of light receiving elements (1
0, 11, 12, 13, 14) and an absolute encoder having an absolute detection means (3), and a plurality of light receiving elements (10, 11, 12, 13,
14) each has a width of 2λ or more with respect to the minimum reading unit λ, and has a passage portion (1a) and a light shielding portion (1).
It was arranged for each of different continuous combinations with b).

According to a second aspect of the present invention, a plurality of light receiving elements (10, 11, 12, 13, 14) are provided between the optical scale (1) and the absolute detecting means (3) and the passing section (1a). ), An auxiliary scale (2) having an opening (15) formed therein to receive light from

[0010]

In the present invention, the plurality of light receiving elements included in the absolute detecting means are set to 2λ for the minimum reading unit λ.
Since it has the above width and is arranged for different continuous combinations of the passing portion and the light shielding portion, even if the minimum reading unit of the absolute pattern becomes small,
The absolute pattern can be detected.

[0011]

1 shows an optical scale 1, an auxiliary scale 2 and an absolute detector 3 according to a first embodiment of the present invention, and FIG. 2 includes the optical scale 1, the auxiliary scale 2 and an absolute detector 3 shown in FIG. It is a figure which shows the whole structure of the absolute encoder.

As shown in FIG. 2, the absolute encoder of the first embodiment includes an illuminating means 6 having a light source (for example, LED or laser diode) 4 and a condenser lens 5, an optical scale 1, an auxiliary scale 2, and , An absolute detector 3 and a signal processing circuit 8 connected to the absolute detector 3 by a wiring 9. The illuminating means 6 is provided on one side of the surface of the optical scale 1 on which the absolute pattern 7 is formed. Is arranged, and the auxiliary scale 2 and the detector 3 are arranged on the other side, and the auxiliary scale 2 and the detector 3 are configured to move relative to the optical scale 1. In this configuration, the auxiliary scale 2 is provided, but the optical scale 1 and the absolute detector 3 may be arranged close to each other without providing the auxiliary scale 2. In the first embodiment, a structure provided with the auxiliary scale 2 will be described.

As shown in FIG. 1 (a), a 1-track absolute pattern 7 of 5 bits is formed on the optical scale 1 in the minimum reading unit λ, and the absolute pattern 7 has a passing portion () through which light passes. It is generated by a polynomial of X ⁵ + X ³ + X ^{0 in which} the white part) 1a is “1” and the light-shielding part (hatched part) 1b for shielding light is “0”.

As shown in FIG. 1B, the absolute detector 3 has a width of 5λ or more with respect to the minimum reading unit λ of the absolute pattern 7, and has the same number of light receiving elements as the number of bits of the absolute pattern 7. 10, 11, 1
It has 2, 13, and 14. Here, each light receiving element 10,
The widths of 11, 12, 13, and 14 are 5λ or more in order to correspond to the spread of light.

Light receiving elements 10, 11, 12, 13, 14
Are arranged with a phase difference of λ in the relative movement direction between the optical scale 1 and the absolute detector 3, and are also arranged sequentially in the longitudinal direction of the absolute pattern 7 at a predetermined distance x. In FIG. 2B, each light receiving element 10,
11, 12, 13, and 14 are absolute patterns 7
Are sequentially arranged at a predetermined distance x in the longitudinal direction of
The light receiving elements 10, 11, 12, 13, and 14 may be arranged without a gap. As shown in FIG. 1C, each of the light receiving elements 10, 11, 12, 13, 1 is provided on the auxiliary scale 2.
Approximately the same as 4 (width of 5λ for minimum reading unit λ)
Further, an opening 15 having a phase difference of λ in the longitudinal direction of the absolute pattern 7 and continuous in the longitudinal direction of the absolute pattern 7 is formed.

The absolute encoder configured as described above will be described below. The light from the light source 4 is collimated into a parallel light flux by the condenser lens 5, passes through each white part of the absolute pattern 7 of the optical scale 1 and the opening 15 of the auxiliary scale 2, and each light receiving element 10, 11 of the detector 3 is detected. 1
It is incident on 2, 13, and 14. Each light receiving element 10, 1
The optical signals received by 1, 12, 13, and 14 are converted into electrical signals and sent to the signal processing circuit 8 via the wiring 9.

The signal processing circuit 8 includes the respective light receiving elements 10, 1
The absolute position data is detected based on the electric signals from 1, 12, 13, and 14. That is, when the optical scale 1 and the absolute detector 3 move relative to each other from the A position of the optical scale 1 and the B position of the light receiving element 10 of the absolute detector 3, the light receiving element 10 detects the light passing through the absolute pattern. It is possible to detect [5] representing the total sum (the amount of light that has passed through the passing portion through the absolute pattern 7). Further, the light receiving element 11 can detect [4] representing the total sum of the light from the passing portion 1a, and the light receiving element 12 can detect the [3] representing the total sum of the light from the passing portion 1a, The light receiving element 13 can detect [3] representing the total sum of the light from the passing portion 1a, and the light receiving element 14
Can detect [3], which represents the total sum of the light from the passage portion 1a. Each light receiving element 10, 11, 12, 13, 14
One absolute value can be obtained from the total sum of the light detected by. The absolute value in this case indicates "1".

Each light receiving element 10, 11, 12, 13, 14
Table 1 shows the relationship of the total sum of the light from the passage portion 1a detected by the and the relationship of the absolute values.

[0019]

[Table 1]

In this embodiment, each light receiving element 10, 1
Although the widths of 1, 12, 13, 14 are set to 5λ, the width may be 5λ or more, or 2λ, 3λ, 4λ. Table 1 above shows the case where the widths of the light receiving elements are 2λ, 3λ, and 4λ. As is clear from Table 1, 2λ, 3λ,
Even in the case of 4λ, as in the case of 5λ, the combinations of lights detected by the respective light receiving elements are all different, and the absolute value can be obtained.

Further, each of the light receiving elements 10, 11, 12, 1
Although 3 and 14 are arranged with a phase difference of λ,
There is no need to limit it to. FIG. 3 is provided with the optical scale 1 and the absolute detector 20 of the second embodiment. still,
Since the entire configuration of the absolute encoder is the same as that of the first embodiment, the description thereof is omitted and the same reference numerals are used. Here, the optical scale and the absolute detector will be described.

In FIG. 3, the absolute detector 20
Is a light receiving element 21, 22, 23, 2 having a width of 3λ.
4 and 25 have the same number as the number of bits of the absolute pattern 7. Light receiving element 21, 22, 23, 24, 25
Are arranged at a pitch of 4λ with respect to the relative movement direction of the optical scale 1 and the absolute detector 20.

The optical scale 1 and the absolute detector 20 configured as described above are combined with each other in the absolute pattern 7
Position A and the light receiving element 21 of the absolute detector 20
When the optical scale 1 and the absolute detector 20 are moved relative to each other from the position B, the light receiving element 21 detects [3], which represents the sum of the light that has passed through the absolute pattern 7, and the light receiving element 22 detects the absolute pattern 7. [3] representing the total sum of the light passing through is detected, and the light receiving element 23 represents the total sum of the light passing through the absolute pattern [2].
Is detected, the light receiving element 24 detects [1] representing the total sum of the light that has passed through the absolute pattern 7, and the light receiving element 25
Detects [1], which represents the sum of the light that has passed through the absolute pattern 7.

Each light receiving element 21, 22, 23, 24, 25
One absolute value can be obtained from the total sum of the light detected by, and the relationship is shown in Table 2.

[0025]

[Table 2]

As is clear from Table 2, each light receiving element 2
It can be seen that since the output data from 1, 22, 23, 24, and 25 have no overlap, the absolute value can be detected. When the auxiliary scale is arranged in the second embodiment, 3
Five openings having a width of λ and formed at a pitch of 4λ in the longitudinal direction of the absolute pattern 7 are formed in the auxiliary scale, and the openings are formed in the respective light receiving elements 21, 2 respectively.
It may be arranged between the optical scale 1 and the absolute detector 20 so as to face 2, 23, 24, 25.

FIG. 4 includes the optical scale 1 and the absolute detector 50 of the third embodiment. Since the entire configuration of the absolute encoder is the same as that of the first embodiment, the description thereof is omitted and the same reference numerals are used. Here, the optical scale and the absolute detector will be described. In FIG. 4, the absolute detector 50 includes light receiving elements 51, 52, 53 having a width of 3λ,
54 and 55 have the same number as the number of bits of the absolute pattern 7.

Light receiving elements 51, 52, 53, 54, 55
Are arranged so that adjacent light receiving elements are on a diagonal line with respect to the relative movement direction of the optical scale 1 and the absolute detector 20. The optical scale 1 and the absolute detector 50 having the above-described configuration are arranged so that the optical scale 1 and the absolute detector 50 are relatively positioned from the A position of the absolute pattern 7 and the B position of the light receiving element 51 of the absolute detector 50. When moving, the light receiving element 51 detects [3], which represents the total sum of light that has passed through the absolute pattern 7, and the light receiving element 22 detects [2], which represents the total sum of light that has passed through the absolute pattern 7. 23 detects [2], which represents the total sum of light that has passed through the absolute pattern 7, and the light-receiving element 24 detects [1], which represents the total sum of light that has passed through the absolute pattern 7.
The light receiving element 25 detects [1] representing the total sum of the light that has passed through the absolute pattern 7.

Each light receiving element 51, 52, 53, 54, 55
One absolute value can be obtained from the total sum of the light detected by, and the relationship is shown in Table 3.

[0030]

[Table 3]

As is clear from Table 3, each light receiving element 5
It can be seen that since the output data from 1, 52, 53, 54, 55 have no overlap, the absolute value can be detected. When the auxiliary scale is arranged in the third embodiment, 3
While having a width of λ, five openings are formed in the auxiliary scale so that adjacent openings are on a diagonal line with respect to the relative movement direction of the optical scale 1 and the absolute detector 50. Each light receiving element 51, 52, 5
It may be arranged between the optical scale 1 and the absolute detector 50 so as to face 3, 54, 55.

In the present invention, when the optical scale is formed with the absolute pattern and the incremental pattern, the auxiliary scale may be provided with both the absolute opening and the incremental opening. Further, in the embodiment, the 5-bit absolute pattern has been described, but other numbers of bits may be used.

Further, the case where the number of bits of the absolute pattern and the number of light receiving elements are the same has been described, but they do not have to be the same. In the present embodiment, since the auxiliary scale having the opening formed so that the plurality of light receiving elements receive the light from the passing portion is arranged between the optical scale and the absolute detecting means, the optical scale and the absolute detecting means are arranged. It becomes easy to adjust the distance between the optical scale and the absolute detecting means, and the distance between the optical scale and the absolute detecting means can be sufficiently separated. Also, the bonding portion of the light receiving element can be removed, and the detection portion itself can be downsized. Furthermore, even if dust enters between the optical scale and the light receiving element of the detector, the light receiving element is not damaged.

[0034]

As described above, according to the present invention, since the light passing through the absolute pattern can be detected even if the minimum reading unit of the absolute pattern is small, a high resolution absolute encoder can be realized. .

[Brief description of drawings]

FIG. 1 is a diagram showing an optical scale, an auxiliary scale, and a detector according to a first embodiment.

FIG. 2 is a configuration diagram showing an entire first embodiment according to the present invention.

FIG. 3 is a diagram showing an optical scale and a detector of a second embodiment.

FIG. 4 is a diagram showing an optical scale and a detector of a third embodiment.

FIG. 5 is a configuration diagram showing an entire conventional device.

FIG. 6 is a view showing a conventional optical scale, auxiliary scale and detector.

[Explanation of symbols]

 1 Optical Scale 2 Auxiliary Scale 3, 20, 50 Absolute Detector 6 Lighting Means 8 Signal Processing Circuit

Claims (2)

[Claims] 1. An absolute pattern in which a light passing portion and a light shielding portion which shields light are formed in a minimum reading unit λ, and one absolute value is represented by a combination of the light transmitting portion and the light shielding portion. An absolute encoder having an optical scale having, and an absolute detection unit having a plurality of light receiving elements that move relative to the optical scale and detect light from the passage portion, wherein the plurality of light receiving elements are each the minimum. An absolute encoder having a width of 2λ or more with respect to a reading unit λ and being arranged for different continuous combinations of the passing portion and the light shielding portion, respectively. 2. An auxiliary scale having an opening formed so that the plurality of light receiving elements receive the light from the passing portion is arranged between the optical scale and the absolute detecting means. The absolute encoder according to claim 1, which is characterized in that.