JPH0376428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a photoelectric rotary encoder that detects rotational information such as the rotational speed and rotational direction of a rotating body using light-emitting and light-receiving elements.

Prior Art Conventionally, photoelectric devices have been used as devices to detect the speed of rotating bodies such as motors, which have a structure in which a rotating body with slits formed at regular intervals is rotated so as to block the optical path between the light emitting and light receiving elements. It has been developed as a type rotary encoder.

Fig. 1 shows the main parts of a conventionally developed photoelectric rotary encoder, with a rotating body ₁₀ having slits 1 ₁ , 1 ₂ . And a light emitting element (not shown)
A light receiving element 2 is arranged, and light from the light emitting element passes through the slit and is detected by the light receiving element. Normally, one light-emitting element is used as a light source, whereas the light-receiving element uses a first photo to obtain signals that are 90° out of phase with each other so that the direction and speed of rotation can be detected. A diode PD ₁ and a second photodiode PD ₂ are provided, and a third photodiode PD ₃ is provided for monitoring in order to stabilize the operation due to usage environment, aging, etc. These three types of photodiodes
The positional relationship of PD ₁ , PD ₂ , and PD ₃ is defined by a fixed mask placed on the light-receiving surface, and they are placed in the radial direction of the slit with respect to the rotating body as shown in the figure. Therefore, a relatively large area is required for installing the light-receiving element, which has the disadvantage that not only the light-receiving element substrate becomes larger, but also the encoder as a whole becomes larger accordingly. In addition, the positional relationship for creating signals with a 90° phase difference is determined by the first photodiode PD ₁ , which is defined by a fixed mask.
Second photodiode PD ₂ and rotating body slit 1
₁ , 1 _{2 .} . ., and the problem is that it is extremely difficult to adjust the position of the encoder. That is, it is necessary to adjust the distance between the first photodiode PD ₁ and the second photodiode PD ₂ to 1/4 pitch, and to adjust the radial arrangement of the rotating body slit and the light receiving areas PD ₁ and PD ₂ . Furthermore, the three types of photodiodes, especially the first photodiode PD ₁ and the second photodiode PD ₂ , have a constant light receiving area with a 1/2 pitch width, but because they are arranged in the radial direction, The light receiving area is the outer photodiode.
PD ₁ has the characteristic that it is larger than the inner photodiode PD ₂ , which inevitably causes an imbalance in the amount of optical signals. Therefore, in order to improve detection accuracy, structural and circuit improvements must be made to address the above-mentioned problems, and it is inevitable that the device will become complicated and expensive. It is difficult to obtain sufficient accuracy.

Purpose The present invention provides a photoelectric rotary encoder that eliminates the drawbacks of the conventional devices described above and is capable of forming highly reliable rotating body information with a simple mechanical configuration and circuit configuration. An embodiment of the present invention will be described in detail below with reference to the drawings.

Embodiment FIG. 2 is a diagram showing the relationship between a group of light receiving elements and a rotating body in which a slit is formed. In the figure, a constant pitch P is drilled along the circumference of a rotating body ₁₀ .
Four photodiodes Pb ₁ to Pd ₄ are provided to the slits 1 ₁ , 1 _{2 .} . . separated from each other.
The four photodiodes Pd ₁ to Pd ₄ have a width of approximately 1/4 pitch and are arranged at 1/4 pitch intervals in the arrangement direction of the slits 1 ₁ , 1 ₂ . . . , and are electrically connected to each other on the same semiconductor substrate. It is manufactured in an insulated state.
When the rotating body ₁₀ rotates in either direction, each photodiode Pd ₁ to _{Pd 4} passes through the slit.
Changes over time in the light-receiving area irradiated with light can be represented by graphs S ₁ to _{S 4} in FIG. 3. Each photodiode Pd ₁ ~ whose light receiving area changes as above
Photocurrents I _S1 to I _S4 proportional to the light receiving area are formed from Pd ₄ .

That is, since the four photodiodes Pd ₁ to _{Pd 4} are in a positional relationship shifted by 1/4 pitch from each other, the light receiving area for the incident light between them also changes by shifting by 1/4 pitch, and the photodiodes Pd ₁ and 90° for photodiode Pd ₂ , photodiode Pd ₃
A phase difference of 180° occurs.

The photocurrents I _S1 to I _S4 outputted from each of the photodiodes PD ₁ to _{PD 2} are applied to each input terminal of the operational amplifiers OP ₁ to OP ₄ of the signal processing circuit shown in FIG. 4 and amplified, for example. Output voltage of operational amplifier OP ₁
V _A is V _A if the feedback resistor r ₁ of operational amplifier OP ₁ is
= r ₁ ×I _S1 , and draw V _A shown by the sine wave in Figure 3. The outputs of the other photodiodes also show changes represented by curves V _B , V _A , and V ^B in the figure, which are out of phase by 90 degrees from each other.

The outputs V _A , V _B of each of the above operational amplifiers OP ₁ to _{OP 4} ,
V _A and V _B are the output V _A whose phase is reversed.
V _A , and V _B and V _B are paired and comparator Comp
1 or Comp2, and the levels of each input signal are compared. In the comparator Comp1, for example, the output V _A is compared with the output V _A as a reference signal, and a high level comparator output is derived when the output V _A is high, and the output V _A becomes lower than the output V _A. A low level comparator output is derived in the state, and eventually V _A ,
Outputs V _putA and V _putB shown as rectangular waves in Fig. 3 are formed corresponding to V _A , V _B , and V _B , and two outputs with a 90° phase difference are formed.
Two signals are obtained. These output signals V _putA
Rotation information of the rotating body can be obtained from V _putB .

In addition, in the photoelectric rotary encoder with the above structure, the photodiode output in the normal state is V _A ,
If the light-emitting diode efficiency decreases, temperature increases, changes over time, etc., the output of the photodiode decreases and becomes V _A ', as shown in Fig. 5.
It changes like the curve shown by V _A ′. Even if such a level change occurs, if you compare it with comparator Comp1, the reference signal side will also have a level change to the same extent, so the output signal will be the same output V _putA
is obtained. That is, the temperature characteristics and element deterioration of the encoder are compensated for, and there is no need to provide a complicated compensation circuit. In addition, in the above structure, a high-resolution slit structure with a slit width of 1/2 pitch can be used as is without degrading the resolution, and the semiconductor substrate forming the photodetector has a photodiode Pd within one pitch of the slit. ₁ ～
Since only Pd ₄ is formed, it is easy to integrate circuits on the same semiconductor substrate.

Effects According to the present invention, the light receiving element group for detecting light passing through the slit or reflected light is arranged along the slit arrangement direction, and each light receiving element group is positioned at a position shifted by 1/4 pitch from the slit pitch. Relatedly, by comparing these output signals, it is no longer necessary to arrange the light-receiving elements in the radial direction as in conventional devices, and it is possible to downsize the electric circuit components such as the light-receiving elements. It is possible to obtain a photoelectric rotary encoder that is easy to handle and has high reliability, since the burden on mechanical position adjustment with the other components is significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a plan view of a main part of a conventional device, FIG. 2 is a plan view of a main part of an embodiment according to the present invention, FIG. 3 is a signal waveform diagram for explaining the operation of the embodiment, and FIG. FIG. 5 is a circuit diagram of one embodiment of the present invention, and is a signal waveform diagram showing another operating state of the same embodiment. 1 ₀ : Rotating body, 1 ₁ , 1 ₂ ...; Slit, Pd ₁ ,
Pd ₂ ...; Photodiode.

Claims (1)

[Claims] 1. In a photoelectric rotary encoder that detects rotational information by passing a rotating body with a slit between a light emitting side and a light receiving side that are arranged opposite to each other, At least four electrically independent light receiving elements integrally formed on the same semiconductor substrate detect light emitted from the light emitting element through slits with a width of 1/2 pitch P, which are bored at intervals of P. The light receiving elements each have a width of approximately 1/4 pitch P on the same semiconductor substrate,
1/ in the arrangement direction of the above slits on the same circumference
They are arranged at an interval of 4 pitches P, and every other pair of light receiving elements is provided with a comparator that inputs and compares each light receiving signal of the light receiving element pair to form output signals with a 90° phase difference. A photoelectric rotary encoder characterized by the following: