JPH05306903A - Device and method for adjusting light receiving sensitivity of speckle length measuring gauge - Google Patents

Abstract

PURPOSE:To use a speckle displacement gauge as it is with high accuracy even when light receiving signals become weak when an object to be measured is changed to the one made of a different material. CONSTITUTION:The light receiving sensitivity adjusting device of speckle displacement gauge is connected with a light quantity monitor circuit 7 which detects a decline in light receiving quantity on the output side of a solid-state image pickup element 1 and reset pulse control section 6 for reset pulses B which resets signals accumulated during one-scanning period on the control side of the element 1 and makes the period of the reset pulses longer by an integer multiple. The light receiving sensitivity of the speckle displacement gauge is adjusted in such a way that, when a decline in the light receiving signals A received by the element 1 is detected, the signal accumulating period is prolonged by making the period of the pulses B for resetting the signals accumulated in one-scanning period of the element 1 longer so that the light receiving signals can be intensified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measurement method using the speckle correlation method. When the amount of reflected light from the object to be measured is insufficient and the received light signal weakens, the received light sensitivity is adjusted to change the received light signal. The present invention relates to a strengthening device and method.

[0002]

2. Description of the Related Art Conventionally, a laser beam emitted from a semiconductor laser is irradiated onto an object to be measured, and a speckle pattern generated by reflected and diffused light from the surface of the object to be measured is detected by cross-correlation processing to determine the moving and deforming speed of the object. There is known a speckle length measuring device for measuring such as the like (Japanese Patent Laid-Open No. 4-507).
08).

As shown in FIG. 4, a measuring head of a speckle length measuring device comprises a semiconductor laser (8) in a casing having a window (15) for emitting and receiving a beam, and a laser beam from the semiconductor laser (parallel laser beam). A collimator lens (81) to be molded into a solid-state image sensor (1) such as a one-dimensional image sensor for photoelectrically converting a speckle pattern formed by the laser beam diffused and reflected by the object to be measured (9) is arranged. Is configured. FIG. 1 shows the overall configuration of a speckle length measuring device according to the present invention. The conventional speckle length measuring device basically has the same configuration except for a part thereof. The configuration and operation of the length measuring instrument will be described.

As is well known, the solid-state image pickup device (1) provided in the speckle length measuring device uses a reset signal B and read signals C and D which are input from a timing generation circuit (5) through a driver (63) so that the CCD The scanning in the array direction is repeated at a constant cycle. The output signal of the element (1) is the first stage amplifier (1
It is connected to the sample hold circuit (12) via 1), and the noise peculiar to CCD is removed by this.

The output signal of the sample and hold circuit (12) is
It is sent to the binarization circuit (14) through the gain control amplifier (13)
Valued. Further, the binarized data is sent to the cross-correlation circuit (2), and the cross-correlation function of the speckle pattern at the reference position of the target object and the speckle pattern at the subsequent moving position determines the reference position. It is repeatedly calculated with appropriate shifts, and the result of this calculation is calculated by the microcomputer.
It is sent to (3). The microcomputer (3) calculates the moving distance of the object based on the peak position of the cross-correlation function sent from the cross-correlation circuit (2). At this time, the microcomputer (3) detects the time when the cross-correlation coefficient of the speckle pattern falls below a predetermined value, and switches the basic data, which is the basis of the cross-correlation function calculation, to the current data at the time of the fall. The control signal is generated and sent to the cross-correlation circuit (2). In response to this, the reference data in the cross-correlation circuit (2) is switched. The movement amount of the reference value due to the switching of the reference data is accumulated, converted into a distance or a speed, and displayed on the display (4).

[0006]

In order to accurately measure the relative amount of movement of the object by the speckle length measuring device, the solid-state image pickup device needs to receive an appropriate amount of light, which is not desirable. When the object to be measured is an object with low surface reflectance such as black rubber, the amount of reflected light is not sufficient, so the solid-state image sensor lacks the amount of received light in one scanning time, and the SN ratio is poor.
There is a problem that the measurement accuracy is lowered or measurement becomes impossible.

As one method of increasing the sensitivity of the solid-state image pickup device, it is possible to increase the sensitivity of the solid-state image pickup device by setting a long accumulation time of a signal for irradiating the light receiving portion. However, when the same measurement head for the object to be measured with low surface reflectance is used to measure a standard object to be measured next, the solid-state image sensor has a problem that the amount of light received is saturated and measurement becomes impossible. there were.

According to the present invention, when the quantity of accumulated light in the light receiving portion of the solid-state image pickup device is insufficient due to the difference in material of the object to be measured,
It is intended to clarify a light receiving sensitivity adjusting device of a speckle length measuring device and its method capable of enhancing the sensitivity of a solid-state image pickup device and strengthening a light receiving signal by the action of a control circuit.

[0009]

SUMMARY OF THE INVENTION The present invention provides a light amount monitor circuit for detecting a decrease in the amount of light received on the output side of a solid-state image sensor.
(7) is connected, and a reset pulse control section (6) for changing the cycle of the reset pulse B for resetting the signal accumulated during the scanning time is connected to the control side of the solid-state image sensor (1).
And a light receiving sensitivity adjusting device in a speckle displacement meter for extending the reset pulse period to an integral multiple by the detection signal of the light receiving monitor circuit (7).

Further, according to the present invention, when a decrease in the light receiving signal A of the solid-state image pickup device (1) is detected, a reset pulse B for resetting the light receiving signal A accumulated in one scanning time of the solid-state image pickup device (1). A light-receiving sensitivity adjusting method in a speckle displacement meter, characterized in that the light-receiving signal is strengthened by extending the period and extending the reset pulse period of the solid-state image sensor (1) to extend the accumulation time of the amount of light emitted. ..

[0011]

When the object to be measured having the standard surface reflectance is inspected, the reflected diffuse beam illuminating the solid-state image sensor (1) is accumulated during the reset period of the solid-state image sensor (1), The received light signal with appropriate strength is output. When the object to be measured has a low reflectance such as black rubber and the amount of light received by the solid-state image sensor (1) is insufficient, the light amount monitor circuit (7)
Detects insufficient light quantity and inputs a signal to the microcomputer.

When the insufficient light amount is detected, the microcomputer (3) extends the reset time of the solid-state image pickup device automatically or by seeing the display of the insufficient light amount and by manual operation.
Therefore, the amount of light accumulated in the solid-state image sensor during one reset cycle increases, so that the sensitivity is improved and a light receiving signal having an appropriate intensity can be output.

[0013]

EXAMPLE A solid-state image sensor (1), a sample hold circuit (12), a gain control amplifier (13) and a binarization circuit (1) shown in FIG.
4), the cross-correlation circuit (2) and the display (4) are the same as the conventional ones, and the description thereof is omitted here.

The timing signal generating circuit (5) outputs a reset basic pulse E at a period T0 of 20 microseconds for resetting the solid-state image pickup device (1) as shown in FIG. Further, in order to send data one pitch at a time from an analog shift register (not shown) incorporated in the solid-state image pickup device (1), a pair of read pulses C and D and a gate signal F which are deviated from each other by a half wavelength are formed. A reset pulse switching unit is provided on the control side of the solid-state image sensor (1) via a driver (63).
(6) and the timing signal generating circuit (5) are connected to receive the reset signal B from the reset pulse switching section (6) and read pulses C and D from the timing signal generating circuit (5).

The reset pulse switching section (6) is provided with a gate signal control circuit (62) and a gate (61) which are respectively connected to the microcomputer (3) and the timing signal generating circuit (5), and a light quantity monitor circuit. When (7) detects that the intensity of the received light signal A is within an appropriate range, "H
The gate signal F of "i" is output. The gate (61) is a reset basic pulse E created in the timing signal generation circuit (5) and the gate signal F from the gate signal control circuit (62).
Are input respectively, and the logical sum processing is performed and the reset pulse B
Is output.

When the light amount monitor circuit (7) senses that the light amount of the received light signal A is appropriate, the reset basic pulse E is the gate (6) because the gate signal F is "Hi".
After passing through 1), the reset pulse B is input to the solid-state image sensor (1). Therefore, the period T of the reset pulse B
1 corresponds to the period T0 of the reset basic pulse E.

Due to the replacement of the object to be measured or other reasons, the amount of reflected diffused light input to the solid-state image sensor (1) is insufficient,
When the received light signal A weakens, the light quantity monitor (7) detects it and outputs it to the microcomputer (3). The microcomputer (3) automatically controls the timing generation circuit (5) by the detection signal of the light quantity monitor circuit (7),
The gate signal F is generated at a period T2 which is an integral multiple of the period T0 of the reset basic pulse E.

In the example of FIG. 3, since the "Hi" of the gate signal F appears every fourth pulse of the reset basic pulse E, the reset pulse B passing through the gate (61).
Period T2 is three times the period T0 of the reset basic pulse E. Since the solid-state image sensor (1) is reset in a cycle three times as long as the previous one, the diffuse reflection light accumulates a signal in the solid-state image sensor (1) for a reset time T2 which is three times longer than T0. If the solid-state image sensor is reset at the reset pulse period T1 (see FIG. 2) when the solid-state image sensor (1) is receiving a reflected diffuse beam having an appropriate intensity, the light-receiving signal A
2 is weak as shown in FIG. 2, but when the reset period is extended as shown in FIG. In A, the intensity of the received light signal is tripled as compared with that in FIG. 2 by the amount that the light accumulation time is extended by three times.

In the embodiment of the present invention, the period of the reset signal pulse is automatically extended by the control operation of the timing generation circuit (5) and the gate signal control circuit (62) by the microcomputer (3). However, it is not possible for an operator to manually operate the timing generation circuit (5) by seeing the signal from the light amount monitor circuit (7) or the display on the display (4) via the microcomputer (3). Of course.

[0020]

According to the present invention, since the reset period of the solid-state image sensor (1) is variable, the material of the object to be measured has a high surface reflectance, followed by a material having a low reflectance. In the case of measurement, the problem associated with the change in the amount of received light can be dealt with only by the signal processing of the reset pulse switching unit (6), and the speckle displacement meter can be used as it is. There is no need to change the main body.

[0021]

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an apparatus according to the present invention.

FIG. 2 is a signal waveform diagram in each part when the amount of received light is appropriate.

FIG. 3 is a signal waveform diagram of each part when the amount of received light is insufficient.

FIG. 4 is a perspective view of a conventional speckle displacement meter.

[Explanation of symbols]

 (1) Solid-state image sensor (3) Microcomputer (5) Timing generation circuit (6) Reset pulse switching section (7) Light intensity monitor circuit

Continuation of the front page (72) Inventor Kazuya Minamino 2-13 Akita-cho, Takatsuki-shi, Osaka Inside Keyence Corporation

Claims (2)

[Claims] 1. A solid-state image sensor (1) detects a speckle pattern generated by reflected and diffused light from the surface of the object to be measured by irradiating the surface of the object to be measured (9) which is relatively displaced. However, in a speckle length measuring device that measures the amount of movement of an object by cross-correlation processing between reference data corresponding to the speckle pattern at the reference position of the object to be measured and current data corresponding to the speckle pattern at the subsequent movement position. At the output side of the solid-state image sensor, a light amount monitor circuit (7) that detects a decrease in the amount of received light is connected and
The control side of (1) is connected to a reset pulse control unit (6) that changes the cycle of a reset pulse B that resets the signal accumulated during the scanning time, and is reset by the detection signal of the light receiving monitor circuit (7). Light sensitivity adjustment device in a speckle displacement meter that extends the pulse period by an integral multiple. 2. A solid-state image sensor (1) detects a speckle pattern generated by reflected and diffused light from the surface of the object to be measured by irradiating the surface of the object to be measured (9) which is relatively displaced. However, in a speckle length measuring device that measures the amount of movement of an object by cross-correlation processing between reference data corresponding to the speckle pattern at the reference position of the object to be measured and current data corresponding to the speckle pattern at the subsequent movement position. Then, when a decrease in the light receiving signal A of the solid-state image sensor (1) is detected, a reset pulse B for resetting the light receiving signal A accumulated in one scanning time of the solid-state image sensor (1).
Of the solid-state imaging device (1) to extend the period of, and extend the accumulation time of the amount of light emitted by the extension of the reset pulse period of the solid-state imaging device (1),
A method for adjusting the light receiving sensitivity in a speckle length measuring device, which is characterized by enhancing a light receiving signal.