JPH11132730A - Dimension measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the dimension of a white turbid body such as a crystallized glass without being affected by the change of a dark current of a light receiver. SOLUTION: A period, in which a light receiver 27 comes into a non-light receive state is detected by a dark level period detection circuit 29, a dark level of a light receive signal S outputted from the light receiver 27 during this dark level period is detected by a dark level detection circuit 32, and a signal S' obtained by subtracting the detected dark level from the light receive signal S is turned into a binary number to calculate an outside diameter and an inside diameter of an object to be measured 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for reducing the influence of dark current of a light receiving element in a dimension measuring device for measuring the dimension of an article using light without contact.

[0002]

2. Description of the Related Art A conventional dimension measuring apparatus using light is shown in FIG.
As shown in FIG. 5, a laser beam scanned so that the optical axis moves in parallel on the same plane from the light projecting unit 11 is emitted, and the beam is condensed on the light receiver 14 by the lens 13 of the light receiving unit 12, The light reception signal S output from the light receiver 12 is binarized by a threshold value Vs set in advance by a binarization circuit 15, and based on the level inversion timing of the binarization signal, the beam of the light projecting unit 11 is changed. The outer diameter and the like of the DUT 1 arranged within the scanning range are calculated.

As shown in FIG. 6, a photodetector 14 used in such a conventional dimension measuring device has a power supply + B connected to one end of a photodetector 14a composed of a photodiode or a phototransistor, and a photodetector 14B connected to the other end. A load resistor R is connected, a current corresponding to the intensity of light incident on the light receiving element 14a flows through the load resistor R, and a voltage generated at both ends of the load resistor R is output as a light receiving signal S. The light receiving element 1
4a, a dark current id flows through the load resistor R as shown in FIG. 6 (a) when in a non-light receiving state, and a dark current id and a photocurrent i due to incident light as shown in FIG. 6 (b) when in a light receiving state.
Although p flows through the load resistor R, when the dark current id is small, the received light signal is almost proportional to the intensity of the incident light.

In general, the light receiving element 14a generally has
A silicon type having high sensitivity to a laser beam having a wavelength such as 80 nm or 680 nm is used.

When it is intended to measure the inner diameter of, for example, a cylindrical object to be measured by such a dimension measuring apparatus, the object to be measured is made to enter the light receiver 14 with a certain intensity so that a beam passes therethrough. It is necessary to catch the level change of the received light signal when the position of the beam passes through the edge position of the inner diameter of the measured object.

However, when the object to be measured is an opaque material such as crystallized glass, the attenuation by the object to be measured is large at the above-mentioned conventional laser wavelength, and the beam scanning position is smaller than the inner diameter of the object to be measured. The level change of the light receiving signal when passing through the edge position cannot be captured at all.

For this reason, a long wavelength (for example, about 1300 nm) having a small attenuation with respect to a cloudy substance such as crystallized glass.
It is conceivable to use a germanium-type light receiving element that can obtain high sensitivity to a long-wavelength beam while using the above laser beam.

[0008]

However, the dark current flowing in the non-light receiving state of the germanium type light receiving element is much larger than that of the silicon type light receiving element, and the dark current greatly changes with temperature change. Resulting in.

For this reason, the light receiving signal output from the light receiver is not proportional to the intensity of the incident light, and the level inversion timing of the binary signal obtained by binarizing the light receiving signal is determined by the fact that the optical axis of the beam is actually There is a problem that the timing is shifted from the timing of passing through the edge position of the measured object, and the dimensions of the measured object cannot be accurately measured. An object of the present invention is to provide a dimension measuring device that solves this problem.

[0010]

According to a first aspect of the present invention, there is provided a dimension measuring apparatus for projecting a beam whose optical axis moves parallel to a predetermined width range on the same plane. A light part, a condenser lens for condensing a beam emitted from the light projecting part, and a light condensed by the condenser lens received by a light receiving surface of a light receiving element, and according to an intensity of the received light. A light receiver that outputs a light receiving signal whose level changes, a dark period detection circuit that detects a dark period in which the light receiver is in a non-light receiving state, and a level of the light receiving signal output from the light receiver during the dark period. A dark level detection circuit for detecting, a subtraction circuit for subtracting a level detected by the dark level detection circuit from the light receiving signal, and a binarization circuit for comparing an output signal of the subtraction circuit with a threshold to binarize the signal And a binary output from the binarization circuit Based on the level inversion timing signal, and an arithmetic circuit for calculating the dimensions of the object located within the scanning range of the beam of the light projecting unit.

According to a second aspect of the present invention, there is provided a dimension measuring device which emits a beam whose optical axis moves in parallel over a range of a predetermined width on the same plane, and which emits a beam. A condenser lens for condensing the beam, a light receiver for receiving the light condensed by the condenser lens on a light receiving surface of a light receiving element, and outputting a light receiving signal whose level changes according to the intensity of the received light; A dark level signal output circuit for outputting a dark level signal substantially equal to a signal output by the light receiver when light is not received, the dark level signal output circuit comprising: A subtraction circuit for subtracting a dark level signal output from the signal output circuit from a light reception signal output from the photodetector; a binarization circuit for comparing an output signal of the subtraction circuit with a threshold to binarize the signal; , Output from the binarization circuit Based on the level inversion timing of the binary signal, and an arithmetic circuit for calculating the dimensions of the object located within the scanning range of the beam of the projector.

According to a third aspect of the present invention, there is provided a dimension measuring device which emits a beam whose optical axis moves in parallel within a range of a predetermined width on the same plane, and which emits the beam. A condenser lens for condensing the beam, a light receiver for receiving the light condensed by the condenser lens on a light receiving surface of a light receiving element, and outputting a light receiving signal whose level changes according to the intensity of the received light; A temperature sensor that outputs a signal corresponding to a temperature change of the light receiver, a cooling device that cools the light receiver, and controls the cooling device in accordance with a signal output from the temperature sensor; A control circuit for keeping the temperature constant, a binarization circuit for binarizing a light reception signal output from the photodetector with a threshold value, and a binarization signal output from the binarization circuit Based on the level inversion timing, the beam And a calculation circuit for calculating the dimensions of the object located within the range.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of the dimension measuring apparatus according to the first embodiment.

In FIG. 1, a light projecting section 21 deflects a laser beam of a long wavelength (for example, 1300 nm) emitted from a light source 22 by a deflector 23 of a vibrating mirror type or a rotating mirror type within a predetermined angle. The beam is scanned by the lens 24 so as to move in parallel on the same plane, and is emitted.

The beam emitted from the light projecting section 21 is condensed by a condenser lens 26 of a light receiving section 25 and received by a light receiver 27. Here, the light receiver 27 has a long wavelength (for example, 1
(300 nm) having a light receiving element composed of a germanium type photodiode or a phototransistor having a high sensitivity to the beam, and similar to the light receiving device shown in FIG.
The dark current id and the current ip corresponding to the intensity of the incident light flow through the load resistor R, and a voltage signal generated at both ends of the load resistor R is output as a light receiving signal S.

The light receiving signal S is input to a dark period detecting circuit 29. The dark period detection circuit 29 includes a binarization circuit 30 and a dark period threshold value output circuit 31. 2
The value conversion circuit 30 outputs the light receiving signal to the dark period threshold value output circuit 3.
The signal is binarized by comparing with a threshold value Vd output from 1 and, for example, a low-level signal indicating a dark period is output when the light receiving signal is smaller than the threshold value Vd. The dark period threshold value output circuit 31 is preset so as to output a threshold value Vd slightly larger than the maximum value of the voltage generated at the load resistor R due to the dark current of the light receiving element of the light receiving device 27.

The dark level detection circuit 32 includes a binarization circuit 30
, The bottom level of the light receiving signal while the low level signal is being output as the dark level Ld, and outputs it to the subtraction circuit 33.

The subtraction circuit 33 subtracts the dark level Ld detected by the dark level detection circuit 32 from the light receiving signal S output from the light receiving section 25 and outputs the result.

The outer diameter peak detection circuit 35 includes a subtraction circuit 3
3 and detects the peak level Lp1 of the output signal S '.
And outputs a threshold value Vs1 substantially equal to one half of the peak level Lp1 detected.

The outer diameter binarizing circuit 37 binarizes the output signal S 'of the subtracting circuit 33 with a threshold value Vs1. For example, when the subtraction output is smaller than the threshold value Vs1, the binarizing signal becomes a low level. Is output.

The peak level Lp1 of the signal S 'is
This is a value indicating the intensity of light that enters the light receiver 27 without the beam intersecting the DUT 1. The reason why the intensity of light that is incident on the receiver 27 is reduced by half is that the optical axis of the beam is Since the signal is at a position in contact with the outer peripheral surface, the signal obtained by binarizing the output signal S ′ of the subtraction circuit 33 with the threshold value Vs1 that is almost の of the peak level Lp1 is obtained when the optical axis of the beam is measured. 1, the level is inverted when passing through a position in contact with the outer peripheral surface of the light emitting element 1.

The outer diameter calculating circuit 38 is provided with an outer diameter binarizing circuit 3.
The outer diameter dimension φ1 of the DUT 1 is calculated from the relationship between the level inversion timing of the binary signal output from 7 and the optical axis position of the beam with respect to the time of the light projecting unit 21.

The inner diameter peak detection circuit 39 receives the binarized signal from the outer diameter binarization circuit 37 from the start of the beam scanning, and detects the period Ta during which the beam completely intersects the DUT 1. During this time, the peak level Lp2 of the output signal of the subtraction circuit 33 is detected.

The inner diameter threshold output circuit 40 outputs the peak level Lp detected by the inner diameter peak detection circuit 39.
A threshold value Vs2 substantially equal to 1/2 of 2 is output.

The inner diameter binarization circuit 41 binarizes the signal output from the subtraction circuit 33 with a threshold value Vs2.

The inner diameter calculating circuit 42 is provided with an inner diameter binarizing circuit 4.
From the relationship between the level inversion timing of the binary signal output from 1 and the optical axis position of the beam with respect to the time of the light projecting unit 21, the inner diameter dimension φ2 of the DUT 1 is calculated.

Next, the operation of the dimension measuring apparatus according to this embodiment will be described. As shown in FIG. 1, a cylindrical DUT 1 made of crystallized glass or the like is arranged within the scanning range of the beam of the light projecting unit 21 with its center substantially coincident with the scanning center. 2A, the light receiving signal S shown in FIG. 2A is repeatedly output from the light receiving unit 25 while the beam of the light projecting unit 21 is repeatedly scanned.

That is, from the scanning start time t0 at which the beam is farthest from the DUT 1, the beam is changed to the DUT 1
Since the beam from the light projector 21 is received by the light receiver 27 of the light receiving unit 25 without being attenuated until immediately before contacting the outer peripheral surface of the light receiving element 25, the light receiving signal includes a dark current id of the light receiving element and a large current ip due to the received beam. It is a big level corresponding to the sum.

When the beam reaches a position in contact with the outer peripheral surface of the DUT 1, a part of the beam is reflected on the outer peripheral surface of the DUT 1 and the level of the received light signal decreases. When the value exceeds the value Vd and the beam completely intersects the DUT 1, all of the beam is reflected on the outer peripheral surface, and the level of the light receiving signal becomes the lowest.

When the beam further moves inward of the DUT 1 and the angle between the beam and the outer peripheral surface of the DUT 1 reaches a certain angle, the beam passes through the DUT 1, When the level of the received light signal rises and exceeds the first threshold value Vd at t2, when the beam reaches a position in contact with the inner peripheral surface of the DUT 1, the beam is reflected by the inner peripheral surface and the level of the received light signal is increased. Decreases to exceed the first threshold value Vd at t3.

When the angle between the beam and the inner peripheral surface of the DUT 1 reaches a certain angle, the beam passes through the hollow portion of the DUT 1, and the level of the received signal rises to t4 Sometimes the level exceeds the first threshold value Vd, and the level of the received light signal increases until t5 when the beam passes through the center position of the DUT 1.

Hereinafter, the waveform from time t0 to time t5 intersects the time t5 before the beam is scanned away from the center of the DUT 1 to the farthest position (next scan start position). Appears almost symmetrically.

With respect to such a light receiving signal S, the level of the light receiving signal S exceeds the threshold value Vd from the binarizing circuit 30 of the dark period detecting circuit 29 as shown in FIG. A binary signal whose level is inverted every time is output, and the dark level detection circuit 32 detects the bottom level of the light receiving signal during a period when the binary signal is at the low level, and detects this as the dark level Ld
To the subtraction circuit 33.

For this reason, as shown in FIG. 2C, a signal S 'obtained by shifting the light receiving signal of FIG. 2A lower by the dark level Ld is output from the subtracting circuit 33. Output signal S 'of the subtraction circuit 33 from the
Is binarized by a threshold value Vs1 substantially equal to 1/2 of the peak level Lp1, and a signal is output as shown in FIG.

From the inner diameter binarizing circuit 41, the peak level Lp2 of the output signal S 'of the subtracting circuit 33 during the period when the position of the beam is completely mixed with the device under test 1 is reduced to approximately 1/2. The signal binarized by the equal threshold value Vs2 is shown in FIG.
(E).

The outer diameter calculating circuit 38 is provided with an outer diameter binarizing circuit 3.
7, the outer diameter φ1 of the device under test 1 is determined based on the timing t6 when the binary signal output from 7 is inverted from the high level to the low level at the beginning of the scanning period and the timing t7 when the binary signal is inverted from the low level to the high level at the end. Is calculated. In other words, when the beam is scanned so that the optical axis position of the beam of the light projecting unit 21 is represented by A cos ωt with reference to the center of the scanning range, the DUT 1 Outer diameter φ
1 is calculated. φ1 = A | cos ω (t6-t0) −cos ω (t7−t
0) |

When the optical axis of the beam is scanned at a constant speed v, the outer diameter is calculated by calculating φ1 = v (t7−t6).

On the other hand, the inner-diameter calculating circuit 42 outputs a second timing t8 at which the binarized signal output from the inner-diameter binarizing circuit 41 is inverted from a high level to a low level during one scanning period, and from a low level to a high level. Based on the timing t9 when the level is inverted to the third time, the inner diameter φ2 of the DUT 1 is calculated by the same calculation as described above.

As described above, the dimension measuring device of the first embodiment detects the dark level of the light receiving signal S output from the light receiving device, and subtracts the detected dark level from the light receiving signal S. S ′ is binarized to calculate the dimensions of the measured object.

For this reason, even when the dark current of the light receiving element is large, or even if the dark current greatly changes with temperature, the dark current component included in the light receiving signal is subtracted from the light receiving signal. There is no effect on the detection of the diameter or the inner diameter, and accurate dimensional measurement can be performed.

[0041]

[Second Embodiment] Next, a second embodiment of the present invention will be described. FIG. 3 is a diagram illustrating the configuration of the dimension measuring device according to the second embodiment.

In this dimension measuring device, a light receiver 50 having the same characteristics as the light receiver 27 is arranged in the light receiving part 25 in a light-shielding state by a light-shielding member 51, and is arranged close to the light receiver 50. Is output from the light receiver 27, and the dark level signal is subtracted from the light reception signal S output from the light receiver 27 by the subtractor 52. The subtracted output S 'is output to the inner diameter as in the first embodiment. The outer and inner diameters of the DUT 1 are obtained by binarization by the binarization circuits 37 and 41 for external and external diameters.

In the case of this embodiment, even if the dark current of the light receiving element of the light receiving device 27 is large, or even if the dark current greatly changes depending on the temperature, the light receiving device 5 having the same characteristics as the dark current.
Since the dark current component included in the received light signal is subtracted by the dark level signal output from 0, detection of the outer diameter and the inner diameter is not affected, and accurate dimension measurement can be performed.

In this embodiment, the light receiver 50 shielded by the light shielding member 51 is used as the dark level output circuit. However, instead of the light receiver 50, an element such as a germanium diode, a germanium transistor or a thermistor is used. The dark level output circuit may output a signal having the same temperature characteristic as the light receiver 27 and equal to the light receiving signal output by the light receiver 27 in the non-light receiving state.

[0045]

[Third Embodiment] Next, a third embodiment of the present invention will be described. FIG. 4 is a diagram illustrating a configuration of the dimension measuring device according to the third embodiment.

In this dimension measuring device, a cooler 55 composed of, for example, a Peltier element for cooling the light receiver 27 and a temperature sensor 5 for outputting a signal corresponding to the temperature of the light receiver 27 are provided.
6 and the cooler 55 based on the output signal of the temperature sensor 56.
And a control circuit 57 for controlling the temperature of the photodetector 27 to keep the temperature of the light receiver 27 constant, thereby suppressing a change in dark current due to a change in ambient temperature.

In this case, by keeping the light receiver 27 at a temperature lower than the lower limit of the ambient temperature (for example, 10 ° C.), the dark current of the light receiving element can be kept relatively small. The received light signal S is directly binarized by binarization circuits 37 and 41 for inner diameter and outer diameter,
The dimensions of the measured object can be measured.

In this embodiment, the temperature sensor 56
Is used to detect a change in the temperature of the light receiver 27, but the light receiver 27, the dark period detection circuit 29 and the dark level detection circuit 32 of the first embodiment are temperature sensors, and the dark level detection circuit The control circuit 57 may control the cooler 55 based on the output of the cooling device 32.

[0049]

As described above, according to the first aspect of the present invention,
The dimension measuring device detects the dark level of the received light signal output from the light receiver, and binarizes a signal obtained by subtracting the detected dark level from the received light signal to calculate the size of the object to be measured. ing.

For this reason, even when a germanium-type light-receiving element having a large dark current and a large change in the dark current due to temperature is used, it is not affected by the magnitude or change of the dark current.
It is possible to accurately measure the outer diameter and inner diameter of the object to be measured.

The dimension measuring apparatus according to claim 2 of the present invention has a dark level output circuit having the same temperature characteristic as the light receiver and outputting a signal equal to the signal output from the light receiver in the non-light receiving state. A signal obtained by subtracting the signal of the dark level output circuit from the light receiving signal of the light receiving device is binarized to calculate the dimension of the device under test.

For this reason, even when a germanium-type light receiving element having a large dark current and a large change in dark current due to temperature is used, it is not affected by the magnitude or change of the dark current.
It is possible to accurately measure the outer diameter and inner diameter of the object to be measured.

Further, in the dimension measuring apparatus according to the second aspect of the present invention, since the cooler is controlled by a signal from a temperature sensor for detecting a change in the temperature of the light receiver to keep the temperature of the light receiver constant, the ambient temperature is kept constant. , The dark current of the light receiving element of the light receiving device can be kept constant, and the dimensions of the object to be measured can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a signal diagram for explaining the operation of the first embodiment.

FIG. 3 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a conventional apparatus.

FIG. 6 is a diagram showing a configuration of a light receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Projection part 26 Condensing lens 27 Receiver 29 Dark period detection circuit 32 Dark level detection circuit 33 Subtraction circuit 37 Outer diameter binarization circuit 38 Outer diameter computation circuit 41 Inner diameter binarization circuit 42 Inner diameter computation circuit

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[Procedure amendment]

[Submission date] November 28, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG. 2

FIG. 6

FIG.

FIG. 3

FIG. 4

FIG. 5

Claims (3)

[Claims] 1. A light projecting unit for emitting a beam whose optical axis moves in parallel over a range of a predetermined width on the same plane, a condensing lens for condensing a beam emitted from the light projecting unit, A light receiver that receives light condensed by an optical lens on a light receiving surface of a light receiving element and outputs a light receiving signal whose level changes according to the intensity of the received light; and a dark period in which the light receiving device is in a non-light receiving state. , A dark level detection circuit for detecting a level of the light receiving signal output from the light receiver during the dark period, and subtracting the level detected by the dark level detecting circuit from the light receiving signal. A subtraction circuit, a binarization circuit that binarizes an output signal of the subtraction circuit with a threshold value, and a level inversion timing of the binarization signal output from the binarization circuit. Within the beam scanning range of the light emitting section A dimension measuring apparatus comprising: an arithmetic circuit for calculating a dimension of the placed object to be measured. 2. A light projecting section for emitting a beam whose optical axis moves in parallel over a range of a predetermined width on the same plane; a condensing lens for condensing the beam emitted from the light projecting section; A light receiving device that receives light condensed by an optical lens on a light receiving surface of a light receiving element and outputs a light receiving signal whose level changes according to the intensity of the received light; A dark level signal output circuit that outputs a dark level signal substantially equal to a signal output when the light receiver does not receive light, and a dark level signal output from the dark level signal output circuit. A subtraction circuit for subtracting from a light reception signal output from a light receiver, a binarization circuit for comparing an output signal of the subtraction circuit with a threshold value to binarize, and a binary output from the binarization circuit Signal level inversion timing There, the dimension measuring apparatus and an arithmetic circuit for calculating the dimensions of the object located within the scanning range of the beam of the projector. 3. A light projecting unit for emitting a beam whose optical axis moves in a predetermined width range in parallel on the same plane, a condensing lens for condensing a beam emitted from the light projecting unit, A light receiver that receives light condensed by an optical lens on a light receiving surface of a light receiving element and outputs a light reception signal whose level changes according to the intensity of the received light, and a signal corresponding to a temperature change of the light receiver. A temperature sensor for outputting, a cooling device for cooling the light receiver, a control circuit for controlling the cooling device in accordance with a signal output from the temperature sensor to make the temperature of the light receiver constant, and the light receiver A binarization circuit that binarizes a light reception signal output from the binarization circuit by comparing the light reception signal with a threshold value, and a level inversion timing of the binarization signal output from the binarization circuit. The dimensions of the DUT placed within the beam scanning range A dimension measuring device comprising a calculation circuit for calculating.