JPH0212562Y2 - - Google Patents

Description

[Detailed description of the invention] A. Field of industrial application The present invention relates to an optical position measuring device that optically measures the edge position of a detected object using an image sensor (self-scanning one-dimensional photodiode array). More specifically, the detection section with a built-in image sensor, etc., and the control section, which uses a counting clock to count the measurement signals output by the detection section, are separated and connected using a long signal line, and the detection section is separated far from the control section. This invention relates to an optical position measuring device that can be installed at

B. Prior Art A device as shown in FIG. 3 is known as a device for precisely measuring the edge position of a detected object in a non-contact manner using an image sensor. In the same figure,
1 is an image sensor, 2 is a light source that irradiates parallel light L toward the light receiving window 1a of the image sensor, and 3 is a detected object whose edge position P is measured.

The optical position measuring device 4 causes the light source 2 to emit pulses, and immediately thereafter applies a sensor clock to the image sensor 1, and measures the width W of the light incident on the image sensor 1 (from one end of the image sensor to the edge position of the detected object). The absolute position of the edge position P of the object to be measured 3 with respect to the image sensor 1 is measured by taking out a measurement signal corresponding to the width (width) and counting the width of this measurement signal using a counting clock.

The measurement principle of the apparatus shown in FIG. 3 will be explained in more detail using the waveform diagram shown in FIG.

The image sensor 1 includes photocells 1b, 1b...
It has a shift register configuration in which cascade-connected photocells 1b, 1b... are irradiated with light L.
Charge is accumulated only in the When a start pulse a is generated immediately after the light source 2 emits a pulse, the sensor clock b is input to the image sensor 1, and from its output terminal (OUT) each photocell 1b, 1b...
The charges stored in ... are output as a pulse train c. A measurement signal d is obtained by binarizing the section of this pulse train c that is equal to or higher than a predetermined level. The falling edge d _D of the measurement signal d accurately captures the edge position P of the object 3 to be detected. However, the timing of the rise d _U is unstable due to the characteristics of the image sensor 1 . In other words, as shown in the figure, the output level of several bits of pulse train c immediately after start pulse a is unstable, and the rising edge d _U of measurement signal d obtained by binarizing this has a delay-lead error. . Therefore, accurate measurement cannot be performed depending on the width of the measurement signal d. Therefore, the time T from the generation of the start pulse a to the generation of the falling pulse e obtained by the falling edge _dD of the measurement signal d is counted by the counting clock f synchronized with the start pulse a and the sensor clock b. do. As a result, the edge position P of the object to be measured 3 can be accurately measured with the start bit position of the image sensor 1 as a reference.

By the way, as an application device of the optical position measuring device 4, there is a separate type optical position measuring device 7 as shown in FIG. In this system, a detection section 5 having an image sensor 1 etc. and a control section 6 that performs counting processing etc. are separated, so that measurement operations can be performed at a position far away from the detection position. In this case, the detection section 5 and the control section 6 are connected by a long signal line 8, and the control section 6 outputs a start pulse a and a sensor clock b.
In response, the pulse train c output from the image sensor 1 is sent from the detection unit 5 to the control unit 6, and is processed by the same means as described above on the control unit 6 side, and is processed by the counting clock f. I am counting.

However, with the above method, there is a limit to the distance that can separate the detection section 5 and the control section 6. This is because the sensor clock b of the image sensor 1 is normally as high as 2 to 5 MHz, so if the signal line 8 becomes long, the waveform of the sensor clock b to be sent out will be distorted, making transmission and reception impossible. The maximum distance that can be separated is about 20 meters when using twisted pair wires.

C. Problems to be solved by the invention For this reason, the inventor separately provided a sensor clock generator in the detection section 5 and a counting clock generator in the control section 6, and transmitted and received the sensor clock b through the signal line 8. I came up with the idea of making it unnecessary.

However, in this case, the following problems arise.

This measurement method will be explained based on the signal waveform diagram shown in FIG.

First, a control section start pulse j synchronized with the counting clock i of the control section 6 is created and sent to the detection section 5 through the signal line 8. At this time, the control unit side pulse j has a rough waveform k, so this is waveform-shaped at a constant slice level E to create a detection side start pulse, and after the generation of this start pulse, the detection unit 5 generates The sensor clock m that is currently running is input to the clock terminal of the image sensor 1. As a result, the image sensor 1 outputs a pulse train n. This pulse train n is binarized at a predetermined slice level to obtain a measurement signal O. Since the rise O _U of this measurement signal O is unstable as mentioned earlier, this measurement signal O is sent from the detection section 5 to the measurement section 6, and the difference between the fall O _D and the start pulse j on the control section side is determined. The time interval T' is counted by the counting clock i. However, the time when the control section side start pulse j is generated and the time when the supply of the sensor clock m on the detection section side is started are the control section side start pulse j.
There is a lag time t ₁ due to the rounding of the waveform when the signal is sent through the signal line 8 and the lack of synchronization between the sensor clock m and the counting clock i. Therefore, in the above measurement method, an error occurs by this lag time t of ₁ minute, and it cannot be put to practical use.

D. Means for Solving the Problem The present invention separates the detection section with a built-in image sensor and the control section that performs counting processing, etc., and installs an independent sensor clock generator and counting clock generator in the detection section and the control section, respectively. The optical position measuring device is provided so that the time width of the measurement signal sent from the detection section to the measurement section accurately represents the edge position of the detected object.

To achieve this, the device of the present invention includes an image sensor with one end of the light receiving window covered with a mask, a light source that irradiates the light receiving window with parallel light through the object to be detected, and a sensor clock that drives the image sensor to mask the mask. A detection section includes a detection circuit that generates a measurement signal representing the length from the edge of the detection object to the edge of the object to be detected. The control section counts the incoming measurement signals using a counting clock and measures the position of the edge of the object to be detected.

Embodiment One embodiment of the optical position measuring device 9 of the present invention is shown in FIG. 1. 10 is a detection section, 11 is a control section, 12 is a signal line, 13 is an image sensor,
1 is a mask that covers the start bit side of the light receiving window 13a of the image sensor; 15 is a light source that irradiates the light receiving window with parallel light L through the object to be detected 16; 17 is a detection circuit with a built-in sensor clock generator; 18 is a counting clock. This is a measurement circuit with a built-in generator.

The optical position measuring device 9 operates as follows.

A start pulse (not shown) is sent from the control section 11, a start pulse q synchronized with the sensor clock p is generated on the detecting section 10 side, and thereafter, when the sensor clock p is applied to the clock terminal of the image sensor 13, a pulse train r is output. Then the second
As shown in the figure, the mask 14 is connected to the image sensor 13.
The start bit of the light receiving window 13a is covered.
Therefore, the output from one end of the photocells 13b, 13b, . . . is not output from the unstable bit. The rising and falling edges of the measurement signal s obtained by binarizing the pulse train r accurately capture the edge position of the mask 14 and the edge position of the detected object 16, respectively, and since the sensor clock p has a constant frequency, The output period T'' accurately represents the edge position of the object to be detected 16 with respect to the edge position of the mask 14. Therefore, this measurement signal s is sent to the control unit 11 through the signal line 12, and the measurement circuit 18
, the output period T'' is determined by the counting clock t.
By counting , it is possible to accurately measure the edge position of the object to be detected 16 relative to the edge position of the mask. Since this counting clock t measures the time width T'' of the measurement signal s, it does not need to be synchronized with the sensor clock p, nor does it need to match their frequencies.For example, the frequency of the counting clock t is set to the sensor clock p. It is also possible to increase the measurement accuracy by several times the frequency of .

In the above embodiment, the mask 14 is provided on the start bit side of the image sensor 13, and the detected object 1 is
6 is moved in and out from the end bit side, but a mask may be provided on the end bit side and the object to be detected may be moved in and out from the start bit side.

F. Effects of the invention According to the invention, in a separate type optical position measuring instrument in which a detection part equipped with an image sensor and a control part equipped with a measurement circuit etc. are connected by a signal line, a sensor clock generator is installed in the detection part. In addition, a counting clock generator is provided in the control section to eliminate the need to send and receive clock pulses through the signal line, and to eliminate the need to transmit and receive clock pulses through the signal line. ), obtain a measurement signal representing the distance from the edge position of the mask to the edge position of the object to be detected, and send it to the control unit through the signal line.This measurement signal is counted by a counting clock to detect the object to be detected. Since the edge position of the object is measured, the signal line can be made much longer than in the past. Therefore, it becomes possible to install the detection section and the control section of the above-mentioned separate type optical position measuring device far apart.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical position measuring device showing an embodiment of the present invention, and FIG. 2 is a signal waveform diagram for explaining the operation of the optical position measuring device shown in FIG. FIG. 3 is a diagram for explaining the principle of the optical position measuring device, and FIG. 4 is a signal waveform diagram for explaining the operation of the optical position measuring device shown in FIG. FIG. 5 is a schematic diagram of a separate type optical position measuring device which is the premise of the present invention. FIG. 6 is a signal waveform diagram illustrating a problem when a sensor clock generator and a counting clock generator are simply provided in the detection section and the control section, respectively, in a separate type optical position measuring instrument. 9... Optical position measuring device, 10... Detection unit, 1
1...Control unit, 12...Signal line, 13...Image sensor, 13a...Light receiving window, 14...Mask,
15... Light source, 16... Object to be detected, 17... Detection circuit, 18... Measurement circuit.

Claims (1)

[Scope of utility model registration request] An image sensor with one end of the light-receiving window covered with a mask, a light source that irradiates the light-receiving window with parallel light beyond the object to be detected, and a sensor clock are used to drive the image sensor to detect the distance from the edge of the mask to the edge of the object to be detected. A detection section consisting of a detection circuit that generates a measurement signal representing the length, and a detection section connected to the detection section by a long signal line, and a counting clock that receives the measurement signal sent from the detection section through the signal line. An optical position measuring device consisting of a control section that counts and measures the position of the edge of an object to be detected.