JPH1163917A - Optical system displacement sensor and optical system displacement measuring equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system displacement sensor having high resolution and a wide measuring range, and an optical system displacement measuring equipment using the sensor. SOLUTION: In this equipment, the image of a light spot cast on an object 5 to be measured from a light source 1 is formed on a displacement sensor 2 by an imagery lens 4, and displacement of the object 5 is measured by using the position of the light spot image formed on the displacement sensor 2. In this case, the displacement sensor 2 has three or more photoelectric transducers which are adjacently arranged, and a signal processing part which adds specific offset to the difference signal of the two adjacent photoelectric transducers and performs adding process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement sensor for detecting a displacement of an object to be measured from a displacement of a light spot position and an optical displacement measuring instrument using the same, and more particularly to a displacement sensor for detecting a wide range with high resolution. The present invention relates to a sensor and an optical displacement measuring device.

[0002]

2. Description of the Related Art Light from a light source is projected as a light spot on an object to be measured by a light projecting lens, and the light spot is formed as an optical image spot on a displacement sensor by an imaging lens. 2. Description of the Related Art A displacement measuring device using a triangulation method for detecting a displacement of an object to be measured based on a displacement of an optical imaging spot is known.

A displacement sensor of the triangulation method uses a two-part photoelectric conversion element, and detects a zero cross point as a predetermined position from a differential signal of each photoelectric conversion element. Or, a nearly linear portion of the differential signal of each photoelectric conversion element, ie,
The displacement of the object to be measured is detected using a portion where the displacement-voltage characteristic is nearly linear.

FIG. 5 shows the movement of a light imaging spot of a conventional displacement sensor and the waveform of a displacement detection process performed by the displacement sensor at this time.

FIG. 5A simultaneously shows a state in which an optical imaging spot (optical imaging) 103 on the displacement sensor 100 is displaced from x1 to x5 in the direction of displacement 104. The optical image 103 is displaced in a displacement direction 104 by an optical system (not shown) in accordance with the displacement of the measured object. The displacement sensor 100 is divided into a sensor 101 and a sensor 102,
Each of the sensors 101 and 102 independently outputs a signal proportional to the amount of received light.

The position of the light image 103 is detected by the sensor 10
1 and the output of the sensor 102 is obtained by the following equation (1).

[Equation 1] S = (ba) / (b + a) where a is the output of the sensor 101 and b is the output of the sensor 102. In addition, the denominator (b + a) in Equation 1 is for normalization for reducing the influence of the light amount change, and can be omitted.

FIG. 5B shows the sensor 101 of FIG.
And the difference between the output of the sensor 102 and the output of the sensor 102 and the output of the sensor 101. The output a of the sensor 101 is
The waveform 105 is plotted as a triangle. The waveform 105 is
The peak level is at a position near the displacement x1 at which the optical image 103 is formed on the central portion of the sensor 101, and before and after the displacement, the optical image 103 attenuates gradually as the distance from the central portion increases. The output b of the sensor 102 is shown in a waveform 106 plotted by a square. The waveform 106 has a peak level near the displacement x5.

The waveform S is the difference (ba) between the output of the sensor 102 and the output of the sensor 101.
Corresponding to The zero cross point of waveform S is
02 corresponds to the position of the displacement x3 where the amount of light received by the sensor 101 is equal. In addition, the waveform S has a substantially straight line before and after the zero cross point, and the displacement of the measured object can be detected by using this linear portion.

[0010]

From the viewpoints of ease of use and measurement accuracy, a displacement sensor having a wide measurement range and high resolution is desired. However, in the above-described related art, in order to increase the resolution of displacement detection of the optical image 103, the displacement sensor 100 must be minute relative to the optical image 103. Then, the output waveform 105 of the sensor 101 and the output waveform 1 of the sensor 102 in FIG.
06 peak point approaches in the horizontal axis direction and the sensor 10
2, the slope of the linear portion of the waveform S, which is the difference between the output of the sensor 101 and the output of the sensor 101, increases, and the resolution of displacement detection of the light image 103 can be increased.

However, if the displacement sensor 100 is made minute and the resolution of displacement detection is increased, a slight displacement of the optical image 103 will exceed the sensor output peak point.
That is, the interval between the negative peak point and the positive peak point of the waveform S in FIG. 5B in the horizontal axis direction becomes small, and the measurement range of the displacement of the optical image 103 is narrowed.

For this reason, when the resolution is increased, FIG.
The displacement measuring device has to be driven up and down in accordance with the height of the object to be measured so that the optical image 103 of (1) falls within the measurement range of the displacement sensor 100, and has to be adjusted again and again.

Conversely, if the inclination of the linear portion of the waveform S in FIG. 5B is reduced in order to widen the measurement range of the displacement of the optical image 103, the resolution of displacement detection is reduced.

An object of the present invention is to solve such a conventional problem and to provide an optical displacement sensor having a high resolution and a wide measurement range, and an optical displacement measuring device using the same.

[0015]

According to the present invention, there is provided an optical displacement sensor for determining a displacement of a position of a light spot projected on a photoelectric conversion element. An optical displacement sensor comprising: at least two photoelectric conversion elements; and a signal processing unit that adds a difference signal between two adjacent photoelectric conversion elements by adding a predetermined offset to each other. This is achieved by:

That is, according to the displacement sensor of the present invention, high resolution can be obtained by the adjacent minute photoelectric conversion elements, and
By continuously connecting the differential signals of all the adjacent photoelectric conversion elements, displacement detection in a wide measurement range becomes possible.

The above object is also achieved by forming an image of a light spot projected from a light source on an object to be measured on a displacement sensor by an image forming lens, and determining the position of the light spot formed on the displacement sensor by the position of the light spot. In an optical displacement measuring device for measuring a displacement of a measured object, the displacement sensor is configured to determine a difference signal between three or more photoelectric conversion elements arranged adjacent to each other and two photoelectric conversion elements adjacent to each other in a predetermined manner. This is also achieved by providing an optical displacement measuring device having a signal processing unit for adding and adding an offset.

That is, according to the displacement measuring device of the present invention, it is possible to detect displacement in a wide measurement range with high resolution. For this reason, for example, when measuring the height of the object to be measured, the displacement detection area becomes wide, and high-resolution measurement can be performed at high speed without driving the displacement measuring device up and down in accordance with the height of the object to be measured. it can.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, such embodiments do not limit the technical scope of the present invention.

FIG. 1 shows a configuration example of a displacement detection system according to an embodiment of the present invention. Light 9 from the light source 1 such as a laser diode forms a light spot on the DUT 5 via the light projecting lens 3. The device under test 5 is displaced in the direction of displacement 13, and this displacement is detected by the displacement sensor 2. The positions of the DUT 5 are indicated by 6, 7, and 8.

The light spot projected on the object to be measured forms an image on the displacement sensor 2 via the imaging lens 4. The displacement sensor 2 is divided into seven from the sensor 20 to the sensor 26,
Each sensor independently outputs a signal proportional to the amount of received light.

When the object 5 is located at the position 6, the light 10 reflected by the object 5 passes through the imaging lens 4 and forms an image between the sensors 24 and 25. When the DUT 5 is at the position 7, the reflected light 11 forms an image between the sensor 23 and the sensor 24. When the DUT 5 is at the position 8,
The reflected light 12 forms an image between the sensor 22 and the sensor 23.

As described above, the displacement sensor 2 of the present embodiment
Has a wide measurement range for the displacement of the DUT 5. That is, since the conventional displacement sensor is a two-divided sensor, it has only a measurement range corresponding to, for example, the sensors 23 and 24 in FIG. 1 and can only detect the positions 6 to 8 of the measured object 5. In order to measure a larger displacement, the displacement measuring device is driven up and down in accordance with the height of the object to be measured or the like, and readjusted so that the optical image enters the measurement range of the sensors 23 and 24. Had to be measured.

On the other hand, the displacement sensor 2 of the present embodiment
Since the displacement range of optical imaging can be made large by a large number of sensors as shown in FIG. 1, even if the relative position between the displacement measuring device and the object 5 is fixed, the position of the object 5 shown in FIG. Larger displacements beyond positions 6 to 8 can be measured. Therefore, unlike the related art, the displacement measuring device is not driven up and down to refocus according to the displacement of the object 5. In addition, since a large number of small sensors for securing high resolution are used, high-resolution and wide-range measurement can be performed at high speed.

FIG. 2 shows a configuration of an optical displacement sensor according to an embodiment of the present invention. The displacement sensor 2 is, as described above,
The sensor 20 is divided into seven from the sensor 26, and each sensor independently outputs a signal corresponding to the amount of received light.

The output S20 of the sensor 20 is
0 is input to the negative input terminal, and the output S21 of the sensor 21
Is input to the positive input terminal of the differential amplifier 50. Therefore, the output S50 of the differential amplifier 50 is the difference between the output S21 of the sensor 21 and the output S20 of the sensor 20.

The outputs of the adjacent sensors from the sensor 21 to the sensor 26 are similarly input to the differential amplifiers 51 to 55, and the respective differential outputs S51 to S55 are output. Expression 2 shows the difference outputs S50 to S55.

[Equation 2] S50 = (S21-S20), S51 = (S22-S21) S52 = (S23-S22), S53 = (S24-S23) S54 = (S25-S24), S55 = (S26- S25) The difference outputs S50 to S55 are input to the linear part selecting means 60 to 65, respectively. Each difference output is shown in FIG.
As shown in the waveform S of (2), S having positive and negative peaks
It has the characteristic of a character curve. Therefore, the linear part selecting means 60
To 65 select only a linear part of a predetermined range around the zero cross point of the difference outputs S50 to S55,
The linear outputs S60 to S65 are output. In order to select a linear portion, for example, it is detected that the sum of the received light amounts of two adjacent sensors is equal to or more than a certain value, and signals within that range are passed.

Next, in this embodiment, the differential signals whose linear portions are selected are continuously connected. This enables displacement detection with high resolution and a wide measurement range.

The linear outputs S60 to S65 are input to offset adding means 70 to 75, respectively. The voltage change range of the linear outputs S60 to S65 corresponds to the photoelectric conversion output of each sensor and is almost the same range. Therefore, a predetermined offset is added to the linear outputs S60 to S65 so that the voltage change range changes continuously.

The offset adding means 70 to 75
Are output to the adding means 80,
The differential output of the adjacent sensor is output as a continuously connected displacement detection output S80.

FIG. 3 shows the movement of the optical imaging of the displacement sensor according to the embodiment of the present invention and the waveform of the displacement detected by the displacement sensor at that time.

FIG. 3A shows that the light image 30 is shifted in the displacement direction 3.
A state where the optical imaging 30 is displaced on the displacement sensor 2 in response to the displacement from x1 to x11 in the direction of 1 is also shown. The position of the light image 30 is detected between two adjacent sensors based on the difference between the outputs of the two sensors as in the related art.

The difference between adjacent sensors is given by the above equation (2).
From S50 to S55. Differential output S of each sensor
50 to S55 are input to the linear part selecting means 60 to 65 shown in FIG. 2 as described above.

FIG. 3B shows the waveforms of the outputs S60 to S65 of the linear portion selecting means 60 to 65. In the selection of the linear portion, a predetermined range around the zero cross point of each waveform is selected according to the required linear accuracy.

S60 in FIG. 3 (2) is the difference between the sensor 21 and the sensor 20, and its zero cross point is
The case where the optical image 30 of (1) is at the displacement x1 is shown. In addition, S61, S62, S63, S64, S61 in FIG.
The zero crossing point of 65 corresponds to the light image 30 of FIG.
Are located at x3, x5, x7, x9, and x11.

Outputs S60 to S6 with the linear part selected
5 is input to the offset adding means 70 to 75.
For example, the following methods are available for giving an offset that makes the differential output of each sensor continuous.

When centering on the linear output S62 in FIG. 3B, the offset amount of the offset adding means 72 in FIG. 2 is set to zero. Then, a linear range of the sensor output, that is, “40” which is a change range of the vertical axis in FIG. 3B is set as an offset amount (offset). Then, the offset amount “40” is subtracted in S61, and the offset amount “8” is subtracted in S60.
"0" is subtracted. In S63, the offset amount “4” is set.
"0" is added, and offset amounts "80" and "120" are added to S64 and S65, respectively.

The offset adding means 70 to 75
The outputs S70 to S75 are all added by the adding means 80 to form a continuous displacement detection output S80. Equation 3 shows the displacement detection output S80.

[Equation 3] S80 = (S60−2 * offset) + (S61−offset) + S62 + (S63 + offset) + (S64 + 2 * offset) + (S65 + 3 * offset) FIG. Detection output S80
3 shows the signal waveforms of FIG. As described above, in the present embodiment, the displacement detection by the displacement sensor 2 is continuously connected, and the displacement can be detected with a high resolution and a wide measurement range.

[0041]

As described above, according to the displacement sensor of the present invention, high resolution can be obtained by the adjacent minute photoelectric conversion elements, and the linear part of the differential signal of all adjacent photoelectric conversion elements can be selected. By connecting the linear portions continuously, it is possible to detect displacement in a wide measurement range.

According to the displacement measuring device of the present invention, it is possible to detect a displacement with a high resolution and a wide measurement range. High-resolution measurement can be performed at high speed without driving the measuring device up and down in accordance with the height of the object to be measured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a displacement detection method according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical displacement sensor according to an embodiment of the present invention.

FIG. 3 shows a light imaging spot and a displacement detection waveform of the displacement sensor according to the embodiment of the present invention.

FIG. 4 is a displacement detection processing waveform of the displacement sensor according to the embodiment of the present invention.

FIG. 5 shows a light imaging spot and a displacement detection processing waveform of a conventional displacement sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Displacement sensor 3 Projection lens 4 Imaging lens 5 DUT 50-55 Differential amplifier 60-65 Linear part selection means 70-75 Offset addition means 80 Addition means

Claims (2)

[Claims] 1. An optical displacement sensor for determining the displacement of the position of a light spot projected on a photoelectric conversion element, comprising: three or more adjacent photoelectric conversion elements; and two adjacent photoelectric conversion elements. An optical displacement sensor, comprising: a signal processing unit that adds a predetermined offset to the difference signal of the photoelectric conversion element and adds the signal. 2. A light spot projected from a light source onto an object to be measured is imaged on a displacement sensor by an imaging lens, and a displacement of the object to be measured is determined by a position of the light spot imaged on the displacement sensor. In an optical displacement measuring device for measuring, the displacement sensor adds a difference signal between three or more photoelectric conversion elements arranged adjacent to each other and two photoelectric conversion elements adjacent to each other by adding a predetermined offset. An optical displacement measuring device, comprising: