JP3273201B2 - Optical incremental encoder device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to angle measurement, length measurement, movement amount,
It is used in a technical field where it is necessary to detect a rotation speed or the like.

[0002]

2. Description of the Related Art A general optical encoder has a main scale plate (main scale) and a sub scale plate (index scale).
By setting the sub-scale plate in a fixed state and converting the shutter operation caused by the relative movement of the two scale plates with the movement of the object to be measured into an electric signal, the number of times of the shutter operation is counted to measure the angle and the angle. Do the length etc.

When the dark portion on the main scale plate completely overlaps the bright portion on the sub-scale plate, the amount of light incident on the light receiving means has a minimum value, but that value is theoretically zero. On the other hand, when the bright portions of both scale plates completely overlap each other, the amount of transmitted light takes the maximum value, and the value is half of the value when no scale plate is present. In an optical incremental encoder, the amount of change per unit time between the minimum value and the maximum value of the amount of incident light is theoretically as long as it can be approximated that the measured object is moving at a constant speed. If the incident light amount during the period is constant and shown, it should form a triangular wave with respect to the time axis.

However, it is generally well known that the actual change in the amount of incident light is not a triangular wave but a sinusoidal wave due to the influence of reflection and diffracted light between the scale plate and the mask. is there.

In the optical encoder, the light receiving means outputs a sinusoidal signal in response to such a change in the sinusoidal light receiving amount, and the comparator compares the output signal with a predetermined threshold voltage (threshold). Voltage) to output a rectangular wave by performing waveform shaping.

[0006] The rectangular wave is converted into a pulse, and then the counter counts the number of pulses to obtain an angle,
It becomes possible to measure the amount of movement and the like.

[0007]

As described above, the comparator shapes the waveform of the sine wave signal output from the light receiving means according to the amount of received light. In general, a scale plate is used in an optical encoder. The transmitted light amount of the parallel light beam transmitted through the main scale plate fluctuates due to the presence of a defect on the upper portion, the non-uniform processing accuracy of the scale plate, and the like. Therefore, even if the bright portions of the main scale plate and the sub scale plate have the same overlapping amount, if the position of the main scale plate is different, the light amount of the transmitted light received by the light receiving means may vary.

Further, the amount of emitted light may fluctuate due to a change in temperature, a change over time of the light emitting element, or the like, and as a result, the amount of transmitted light received by the light receiving means may fluctuate.

In addition, the optical encoder has a main scale plate attached to the object to be measured and is in a movable portion, and the sub-scale plate 6 is in a fixed portion. Therefore, the optical encoder has a movable portion and a fixed portion in terms of its structure.
It cannot be completely sealed and an opening is created.
Therefore, for example, when the encoder is mounted on a machine tool, the amount of emitted light and the amount of transmitted light fluctuate due to the use environment and the like, such as contamination of dirt cutting oil and fine particles on the scale plate and the light receiving element. May fluctuate in the amount of light received.

When the incident light amount fluctuates, in the conventional encoder, the S / N ratio is lowered, and the threshold voltage is not controlled. In this case, the duty of the rectangular wave output from the device fluctuates, and as a result, the interval of the pulse width fluctuates, causing a serious error in the measured value.

The present invention addresses the various problems envisioned in the use environment of an optical encoder as described above,
It is an object of the present invention to provide an optical encoder capable of obtaining a precise detection result by minimizing a measurement error.

[0012]

According to the first aspect of the present invention,
The means for detecting the light amount of the parallel light flux transmitted only through the main scale plate detects fluctuations in the amount of transmitted light due to dirt or the like attached to the main scale plate, thereby controlling the threshold voltage, thereby stabilizing Outputting a square wave was realized.

According to the second aspect of the present invention, a stable rectangular wave is output by controlling the amount of emitted light by the detecting means.

According to the third aspect of the present invention, a more stable rectangular wave is output by controlling the threshold voltage and the amount of emitted light by the detecting means.

[0015]

According to the first aspect of the present invention, the emitted light emitted from the light emitting means is converted into a parallel light beam by the optical means and enters the parallel light beam transmitting means. The parallel light beam passes through the bright portions of the main scale plate and the sub-scale plate in the parallel light beam transmitting means and enters the light receiving means, and the light receiving means outputs a detection signal as positional information to the comparator.

On the other hand, the parallel light flux transmitted through only the main scale plate is detected by the incident light quantity fluctuation detecting means to detect the change in the transmitted light quantity. The incident light quantity fluctuation detecting means and the threshold voltage control means The threshold voltage input to the comparator is controlled in accordance with the increase or decrease in the amount of incident light, for example, when the threshold voltage is decreased.

As a result, the comparator outputs a stable rectangular wave without being affected by the fluctuation of the amount of incident light.

In the invention according to claim 2, the incident light amount fluctuation detecting means controls the light emitting means by the light emitting amount control means to increase the light emitting amount when the incident light amount decreases, for example. The light emission amount control means is controlled in accordance with the fluctuation of.

As a result, the amount of light incident on the light receiving means becomes constant, and the comparator outputs a stable rectangular wave.

According to the third aspect of the invention, by combining the above operations, the amount of emitted light and the threshold voltage are controlled,
The comparator outputs a stable square wave.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical incremental encoder according to an embodiment of the present invention, which generates a stable rectangular wave by controlling a threshold voltage.

The emitted light 2 emitted from the light emitting means 1 is converted into a parallel light flux 4 by the optical means 3 and enters the parallel light flux transmitting means 7. The main scale plate 5 in the parallel light beam transmitting means is:
Only the parallel light beam incident on the bright part on the scale plate is transmitted,
A part of the transmitted light is incident light amount fluctuation detecting means 11 as it is.
Incident on. The other portions are incident on the sub-scale plate 6, but of the parallel light beams transmitted through the main scale plate 5, only those incident on the bright portion of the sub-scale plate become the transmitted light 8 and are incident on the light receiving means 10. I do.

Since the main scale 5 moves with the movement of the object to be measured, the amount of overlap between the bright portions of the two scales also changes accordingly, and the amount of parallel light flux passing through both scales also increases. Changes with the movement of. Accordingly, the light receiving means 10
Although the amount of transmitted light 8 incident on the light
Outputs a signal corresponding to such a change in the amount of received light to the comparator 13.

The transmitted light 9 transmitted through only the main scale plate is incident on the incident light amount fluctuation detecting means 11. In general, the width of the bright and dark portions of the main scale plate of an optical incremental encoder is made equal, so the amount of light transmitted through only the main scale plate is theoretically irrespective of the moving speed of the DUT. Is ２ of the case where no scale plate is present.

The incident light quantity fluctuation detecting means 11 outputs a detection signal corresponding to the light quantity of the transmitted light 9 to the threshold voltage controlling means 12.

The amount of light incident on the light receiving means 10 depends not only on the amount of overlap between the bright portions of the main scale and the sub-scale, but also on the main scale due to variations in the amount of light emitted from the light emitting means 1 and contamination of the main scale. There are fluctuations due to the use environment, such as a decrease in the amount of light transmitted through the plate. Due to such usage environment,
For example, when the amount of emitted light decreases, both the amount of light incident on the light receiving unit 10 and the amount of light incident on the incident light amount fluctuation detecting unit 11 decrease. Fluctuations occurring in the light receiving means 10 and the incident light quantity fluctuation detecting means 11 are in the same direction, such as an increase in the light quantity. Further, if the light receiving means 10 and the incident light amount fluctuation detecting means 11 are arranged adjacent to each other, the fluctuation of the light amount of the transmitted light 8 due to the contamination of the main scale can be detected. Can be found at

The threshold voltage input to the comparator 13 is
The threshold voltage control unit 12 can increase or decrease the amount of transmitted light incident on the incident light amount fluctuation detecting unit 11 according to an increase or decrease. Therefore, even if the output signal output from the light receiving means 10 fluctuates, for example, the threshold voltage is set at the center of the amplitude of the signal voltage of the output signal output from the light receiving means 10 so that a correct rectangular wave can be obtained. It is possible to set the level.

However, since the comparator 13 can use a comparator with hysteresis, in this case, in addition to controlling the threshold voltage in accordance with the fluctuation of the incident light amount detected by the incident light fluctuation detecting means 11, At the same time, the hysteresis width can be controlled. Further, the fluctuation of the incident light amount can be controlled by calculating the average value over a certain period of time and controlling the threshold voltage based on the result by using an arithmetic unit.

The comparator 13 generates a rectangular wave by comparing the signal output from the light receiving means 10 with a threshold voltage. Although not shown in the figure, the rectangular wave is generally a pulse wave. After the conversion, it is counted by a counter or the like. Thereby, information such as the position and the moving speed of the measured object can be obtained.

The above effect can be further enhanced by disposing the light receiving means 10 and the incident light amount fluctuation detecting means 11 close to each other. However, as shown in FIG. 1 to FIG. In addition to the case where the scale plate is arranged side by side in the moving direction, the effect of further reducing the angle measurement error can be obtained by arranging the scale plate vertically and parallel to the moving direction and vertically.

FIG. 2 is a block diagram of an optical incremental encoder according to an embodiment of the present invention, which controls the amount of emitted light to generate a stable output voltage.

A part of the parallel light beam transmitted through the main scale plate 5 directly enters the incident light amount fluctuation detecting means 11, and the other part enters the light receiving means 10 through the sub scale plate 6. This is the same as the embodiment of the invention of item 1.

The incident light amount fluctuation detecting means 11 outputs a detection signal corresponding to the fluctuation of the incident light amount to the light emitting amount controlling means 14,
The light emitting amount control means controls the light emitting amount of the light emitting means 1 based on the detection signal so that predetermined incident light can be obtained, for example, by increasing the driving current of the light emitting means when the light emitting amount decreases. I do. As a result, according to the present invention, a stable rectangular wave can be obtained.

FIG. 3 shows an embodiment according to the third aspect of the present invention, in which the threshold voltage and the light emission amount are simultaneously controlled according to the change in the incident light amount detected by the incident light amount fluctuation detecting means 11. FIG. 1 is a block diagram of an optical incremental encoder capable of obtaining a more accurate rectangular wave.

[0036]

The advantages of the present invention are as follows.

That is, with a very simple circuit configuration, it is possible to prevent the occurrence of measurement errors in angle measurement, length measurement, and the like due to fluctuations in the amount of received light, and to obtain accurate measured values.

Accordingly, it is possible to obtain a high-precision optical incremental encoder which has a simple structure and is low in cost.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the invention described in claim 1;

FIG. 2 is a block diagram of an embodiment of the invention described in claim 2;

FIG. 3 is a block diagram of an embodiment of the invention described in claim 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Light-emitting means 3 Optical means 5 Main scale plate 6 Sub-scale plate 10 Light-receiving means 11 Incident light quantity fluctuation detecting means 12 Threshold voltage control means 13 Comparator 14 Light-emitting amount control means V0 Threshold voltage

Claims (3)

(57) [Claims] 1. A light emitting means, an optical means for converting the emitted light emitted from the light emitting means into a parallel light beam, and a bright portion which transmits the parallel light beam and a dark portion which blocks the parallel light beam are alternately provided on the surface. One having two scale plates formed at the same width and at the same interval, one of the scale plates being attached to the object to be measured, a main scale plate, and the other being placed in parallel with the main scale plate and having a sub scale plate. Comparing the output signal and a threshold voltage with a parallel light beam transmitting means, a light receiving means for receiving a parallel light beam transmitted through both the main scale plate and the sub scale plate, and outputting a signal corresponding to a received light amount. An optical incremental encoder having a comparator that outputs a square wave by detecting incident light amount fluctuation detecting means for detecting a light amount of a parallel light beam transmitted only through the main scale plate and outputting a detection signal; Controls threshold voltage according to Optical incremental encoder device which is characterized in that a threshold at a voltage control means. 2. A light emitting means, an optical means for converting the emitted light emitted from the light emitting means into a parallel light beam, and a bright portion which transmits the parallel light beam and a dark portion which blocks the parallel light beam are alternately provided on the surface. One having two scale plates formed at the same width and at the same interval, one of the scale plates being attached to the object to be measured, a main scale plate, and the other being placed in parallel with the main scale plate and having a sub-scale plate. Comparing the output signal with a threshold voltage, receiving the parallel light beam transmitted through both the main scale plate and the sub-scale plate, and outputting a signal corresponding to the amount of received light. An optical incremental encoder having a comparator that outputs a square wave by detecting incident light amount fluctuation detecting means for detecting a light amount of a parallel light beam transmitted only through the main scale plate and outputting a detection signal; Control the light emitting means according to Optical incremental encoder device which is characterized in that a means for controlling the Shako amount. 3. The optical incremental encoder device according to claim 1, further comprising: means for controlling a light emitting means in accordance with a detection signal output from said incident light quantity fluctuation detecting means.