JPH0422261Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention controls the movement of a code plate provided with translucent slits in the circumferential direction by applying a certain phase difference to the arrangement pitch of the translucent slits. The present invention relates to an improvement of an encoder that performs detection using a group of light-receiving elements arranged in a row.

[Conventional technology]

An example of the above optical encoder is a device already filed as Japanese Patent Application No. 13951/1983 by the applicant of the present application. This detects the movement of a code plate provided with translucent slits using a group of light receiving elements (image sensors) arranged with a certain phase difference with respect to the arrangement pitch of the translucent slits. It is characterized by converting the rotation angle of the code plate into the amount of phase shift of the reference signal and measuring it with high precision.

FIG. 3 is a configuration diagram showing an example of an encoder having such a configuration. In the figure, 1 is a code plate, 2 is a translucent slit provided at a predetermined pitch on the code plate 1, 3 is a light source, 30 is a lens for converting the light beam irradiated from the light source 3 into a parallel beam, Reference numeral 4 denotes an image sensor that receives the light (slit image) that has passed through the light-transmitting slit 2. Here, in order to simply explain the operation, an example in which four light-receiving elements 41 to 44 are arranged in an array is shown. are doing. SW1 to SW4 are switches that sequentially take out signals from the light receiving elements 41 to 44 at a fixed timing, 5 is an amplifier that amplifies the signals applied via each switch SW1 to SW4, and 6 is a fundamental wave from the output signal of the amplifier 5. This is a bandpass filter that extracts components.

FIG. 4 shows the transparent slit 2 formed on the code plate 1 and the light receiving elements 41 to 4 in the image sensor 4.
4 is a diagram showing the arrangement relationship with 4. FIG. As shown in the figure, if the four light receiving elements 41 to 44 are assumed to be one group, and the pitch of this group is the basic pitch of the image sensor 4, this basic pitch is equal to the arrangement pitch P of the light-transmitting slits 2. It is formed. That is, the light-receiving elements 41 to 44 are arranged so that their phases are sequentially shifted by 90 degrees with respect to the arrangement pitch of the light-transmitting slits 2.

The operation of the encoder configured as described above will be described below with reference to the waveform diagram of FIG.

The light from the light source 3 is converted into a parallel beam by the lens 30, passes through the light-transmitting slit 2 of the code plate 1, and reaches the light receiving elements 41 to 44 of the image sensor 4.
An image of the transparent slit 2 is formed on top. In the image sensor 4, the switches SW1 to SW4 are sequentially turned on and off at the timings shown in FIGS.
.about.44 are sequentially applied to the amplifier 5. As a result, the output signal _e5 of the amplifier 5 has a staircase waveform whose magnitude changes each time the switches SW1 to SW4 are turned on, as shown in FIG. 5e. Therefore, when such a step waveform is added to the bandpass filter 6, the waveform shown in FIG.
A sine wave signal e ₆ (fundamental wave component) as shown in can be obtained.

Here, the fundamental frequency of this sine wave signal e ₆ is
It matches the repetition frequency of sequentially driving the switches SW1 to SW4, and when the code plate 1 rotates according to the rotation angle to be measured, the light receiving element 41
Since the Suit image formed on ~44 also moves,
Sine wave signal e 6 obtained from bandpass filter ₆
The phase of is shifted, for example, as shown by the broken line in the figure, depending on the amount of movement of the SWIT image, that is, the rotation angle of the code plate 1. Now, when the code plate 1 is rotated by the arrangement pitch P of the transparent slits 2, the amount of phase shift of the sine wave signal _e6 is 2π
only changes. Therefore, by measuring this phase shift amount, the rotation angle of the code plate 1 can be detected with high precision.

[Problem that the invention attempts to solve]

However, as described above, the plurality of light receiving elements 4
In an encoder that detects the moving state of the light-transmitting slit 2 by using the difference in voltages generated between the light receiving elements 41 to 44, if the light beam irradiated from the light source 3 is not uniform, the light receiving elements 41 to 44 may be Differences occur in the level of each output voltage depending on the position, making it impossible to perform highly accurate angle detection.

For example, if the light beam irradiated from the light source 3 is uniform and light of equal intensity is incident on all the light receiving elements 41 to 44, the light beams emitted from the light receiving elements 41 to 44 according to the rotation of the code plate 1 can be obtained. output voltage
As shown in FIG. 6, e ₁ to e ₄ are triangular waves having a phase difference of 90 degrees. However, if the light beam is not uniform and its intensity differs depending on the location, the output voltages e ₁ to e ₄ will be as shown in FIG.
The rotation angle of the code plate 1 and the phase shift amount of the sine wave signal e ₆ do not correspond accurately.
This will cause an error in the detection results. Furthermore, it is not easy to adjust such uneven output voltages using an optical system such as the light source 3 or an electrical means such as a variable resistor.

The purpose of this invention is to eliminate the drawbacks of conventional devices as described above, and to realize an encoder with a simple configuration that can equalize the output voltage level of each light receiving element without using complicated adjustment means. It is something.

[Means for solving problems]

The encoder of the present invention is an encoder in which the movement of a code plate provided with transparent slits is detected by a group of light receiving elements arranged with a constant phase difference with respect to the arrangement pitch of the transparent slits. , a plurality of light receiving elements that generate outputs of different phase components are placed adjacent to each other to form a unit light receiving element group, and at least one pair of unit light receiving element groups are arranged at equal distances from the center of the light beam, and each of these unit light receiving elements The light receiving elements in the group that generate outputs of the same phase component are respectively coupled.

[Effect]

In this way, the unit light receiving element group, which is a collection of multiple light receiving elements that generate outputs of different phase components, is arranged at equal distances from the center of the light beam, and
When light-receiving elements that generate outputs with the same phase component are connected, changes in output voltage due to non-uniformity of the light beam are compensated for among the connected light-receiving elements.
The sum of output voltages can be kept almost constant.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the encoder of the present invention. The figure shows the arrangement of light receiving elements in the encoder of the present invention. In the figure, the same parts as in FIG. 3 are designated by the same reference numerals. 41 ₁ ~ 41 ₄ , 42 ₁ ~ 42 ₄ , 43 ₁ ~
43 ₄ , 44 ₁ to 44 ₄ are light receiving elements, and C is the center of the light beam irradiated to the light receiving element groups 41 ₁ to 44 ₄ via the coat plate 1. The light-receiving elements 41 ₁ to 41 ₄ are, for example, light-receiving elements arranged at positions that generate outputs of phase components of 0° (reference);
2 ₁ to 42 ₄ , 43 ₁ to 43 ₄ , and 44 ₁ to 44 ₄ are light receiving elements arranged at positions that generate outputs of phase components of 90°, 180°, and 270°, respectively. The elements are connected in series, each generating an in-phase output. In addition, light receiving elements 41 ₁ , 42 ₁ , 43 ₁ , which generate outputs of each phase component,
44 ₁ are arranged adjacent to each other to form one unit light receiving element group, and similarly, the light receiving elements 41 ₂ to 4
4 ₂ , 41 ₃ to 44 ₃ , and 41 ₄ to 44 ₄ are also arranged adjacent to each other to form a unit light receiving element group.
Further, these unit light receiving element groups are arranged at equal distances from the center C of the irradiated light beam.

Here, the intensity of the light beam with which the light receiving element groups 41 ₁ to 44 ₄ are also irradiated is generally not uniform;
It has distribution characteristics as shown in FIG. That is, the light is strong near the center C of the light beam, and becomes weaker as it moves away from the center C. Therefore, the light receiving elements 41 ₁ to 4 arranged as described above
4 In ₄ , the position where each light receiving element is placed,
The intensity of the light beam received at that position is as shown in the figure. For example, the light receiving elements 41 ₁ and 41 ₃ are arranged at the closest position from the center C of the light beam, and the light receiving elements 41 ₂ and 41 ₄ are arranged at the closest position.

In this way, one series circuit includes the light receiving elements 41 ₂ , 41 ₄ arranged at positions with high light intensity, and the light receiving elements 41 ₁ . 4
1 and ₃ , and the magnitude (maximum value) of the output voltage at each photodetector is proportional to the intensity of the incident light beam, so the circuit in which four photodetectors are connected in series The output voltages Σe ₁ to _{Σe 4} have approximately equal values. Therefore, the outputs of each phase component can be made equal without using complicated adjustment means.

Also, considering the case where the irradiation position of the light beam shifts from this state, for example, if the output voltage of one unit light receiving element group increases due to eccentricity of the light beam, this and the target Since the output voltage of the unit light-receiving element group located at the position decreases, changes in the output of each light-receiving element compensate each other, and the overall output voltages Σe ₁ to Σe ₄ do not change significantly.

In addition, in the above explanation, the transparent slit 2
In this example, the movement of the light receiving elements is detected by the light receiving elements placed at positions with different phases by 90 degrees. However, the phase difference in which the light receiving elements are arranged is not limited to this. When used as one group, they may have a phase difference of 120°. Also, the center C of the light beam
The number of unit light-receiving element groups (number of light-receiving elements connected in series) arranged at equal distance from I can do it. Furthermore, the arrangement state of the light receiving elements 41 ₁ to 44 ₄ as shown in FIG. 1 may be directly realized by the formation positions on the substrate, or may be realized by a combination with a phase plate having a window portion of a constant phase. .

[Effect of idea]

As explained above, in the encoder of the present invention, the movement of the code plate provided with transparent slits is detected by a group of light receiving elements arranged with a certain phase difference with respect to the arrangement pitch of the transparent slits. In such an encoder, a plurality of light receiving elements that generate outputs of different phase components are arranged adjacently to form a unit light receiving element group, and at least one pair of unit light receiving element groups are arranged at equal distances from the center of the light beam. In each of these unit photodetector groups, the photodetectors that generate outputs with the same phase component are coupled, so changes in the output voltage due to non-uniformity of the light beam are absorbed between the connected multiple photodetectors. It is possible to realize an encoder with a simple configuration that can compensate each other and keep the sum of output voltages almost constant, and can even out the output voltage level of each light receiving element without using complicated adjustment means. .

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing one embodiment of the encoder of the present invention, and FIGS. 3 to 7 are block diagrams showing an example of a conventional encoder. 1... Code plate, 2... Translucent slit, 3...
Light source, 30...lens, 4...image sensor,
41 to 44, 41 ₁ to 44 ₄ ... Light receiving element, SW1
~SW4...Switch, 5...Amplifier, 6...Bandpass filter.

Claims (1)

[Scope of utility model registration request] In an encoder that detects the movement of a code plate provided with translucent slits in the circumferential direction using a group of light receiving elements arranged with a certain phase difference with respect to the arrangement pitch of the translucent slits, different phases are detected. A plurality of light receiving elements that generate component outputs are placed adjacent to each other to form a unit light receiving element group, and at least one pair of unit light receiving element groups are arranged at equal distances from the center of the light beam, and each of these unit light receiving element groups has the same An encoder that connects light-receiving elements that generate outputs of phase components.