JPH1183430A - Position detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detection device having high resolution, high precision, and high responsiveness, with a simple structure. SOLUTION: A moving body 120 is moved by an actuator 140 so as to search for the position of a differential type light receiving element 130, where the significant value of the sum output (R+L) of the differential type light receiving element 130 is obtained when a point light source image hits the same. Then, the encode portion 150 of the moving body 120 is detected by an image pickup type absolute position detection device 160 so as to obtain an position information output A. When the point light source image hits the differential type light receiving element 130, the center point position of the point light source image are obtained by the difference output (v=R-L) of respective light receiving elements 130R, 130L as a distance x+v/k from the center line of differential type light receiving element 130. Where, (k) is a position conversion factor. The absolute position of the center position of the point light source image is obtained by A+x=A+v/k.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting the absolute positions of various objects via a point light source.

[0002]

2. Description of the Related Art Conventionally, in a position detecting device using a light source image obtained by detecting a point light source, a semiconductor PSD (photodetector), CCD (charge coupled device), or the like is used as a light receiving element. However, the resolution and accuracy are low and the response speed is low.
Since the PSD of a semiconductor is an analog output, it should be able to perform high-resolution detection originally. However, the resolution is low due to noise and the like, and the accuracy is also about 10 ⁻³ mm because of the temperature drift of the characteristic. However, it is very difficult to increase the precision by another digit.

On the other hand, a solid-state imaging device using a CCD or CMOS has a pixel size of one due to the progress of semiconductor technology.
It has been halved in about 10 years, and has been reduced from 10 μm to about 5 μm, but it is considered that it will take much longer to reach about 0.1 μm. Further, if the number of pixels is increased, the accuracy is higher, but the cost of the element is higher. Further, in the case of a CCD, when the number of pixels increases, it takes a long time to read, and there is a problem that a response speed is also reduced. In addition, a position detecting device in which low-resolution and low-precision elements are simply integrated becomes large as a whole and is not practical.

[0004]

As described above, it is difficult to obtain a small and high-performance device in the conventional position detecting device using a light source image depending on the resolution and accuracy of the light receiving element. Was. Therefore, an object of the present invention is to provide a simple configuration
An object of the present invention is to provide a high-resolution, high-accuracy, high-responsive position detecting device.

[0005]

In order to achieve the above object, the present invention provides a point light source attached to a position detecting object, a lens system for collecting and forming an image of the point light source, and a focal light of the lens system. A movable body disposed on a surface, a differential light receiving element provided on the movable body and detecting a focal position of light from a point light source, and by linearly moving the movable body within the focal plane. Detecting, based on an output signal of the differential light-receiving element, an actuator that controls the differential light-receiving element so that the image of the point light source hits the light-receiving element, an encoder provided on the movable body, and the encoder. And an absolute position detecting device for detecting the position of the movable body, and the point is detected based on detection information of the absolute position detecting device and difference output information of the differential type light receiving element. One-dimensional position to detect light source position Characterized by comprising a detection device.

In the above-described position detecting device of the present invention,
The movable body is moved linearly by the operation of the actuator,
The light source image of the point light source is moved to a position where it is formed on the differential type light receiving element. At this time, the moving amount of the movable body is detected at the level of the resolution and accuracy by the encoding unit by reading the encoding unit provided on the movable body with the absolute position detecting device. In addition, when the light source image of the point light source is formed on the differential light receiving element, the position of the point light source can be adjusted within the field of view of the differential light receiving element by the differential output output from the differential light receiving element. Detect with higher resolution and higher accuracy. Then, the position of the point light source is calculated by synthesizing the detection information from the absolute position detection device and the difference output information from the differential light receiving element.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a position detecting device according to the present invention will be described below. First, a first embodiment in which a position detection target moving on a straight line is detected by the position detection device of the present invention will be described. FIG. 1 is an explanatory diagram showing a configuration example of a one-dimensional position detection device of a position detection device according to the present invention, and FIG. 2 is a diagram illustrating position detection of a position detection target to be detected by the one-dimensional position detection device shown in FIG. It is explanatory drawing which shows a possible area.

The one-dimensional position detecting device of this embodiment includes a point light source 100 attached to a position detection target (not shown), a lens system 110 for collecting and forming an image of the light from the point light source 100, and a lens system 110. A movable body 120 disposed on the focal plane 110A, and a point light source 100 provided on the movable body 120;
Light receiving element 130 for detecting the focal position of light from
And an actuator 140 that linearly moves the movable body 120 within the focal plane 100A, an encoding unit 150 provided on the movable body 120, and an absolute position detection device 160 that detects the position of the movable body 120 by the encoding unit 150. Have.

In this embodiment, the object to be detected moves linearly in a linear area as shown in an area E1 in FIG. 2, and the point light source 100 attached to the object to be detected also has a straight line in the area E1. Moving. The point light source 100 is configured by, for example, an LED. The lens system 110 is
It is formed by a combination of a spherical or cylindrical lens or a reflecting mirror for condensing and imaging the point light source 100.

The movable body 120 is formed in a plate shape as a whole, and is disposed on the focal plane 110A of the lens system 110 so as to face the above-mentioned area E1, and a position detection target is provided by a guide mechanism (not shown). Object (point light source 100)
And movably supported in the same direction. Movable body 120
Mounts a differential light receiving element 130 at the center thereof, provides a movable element 170 for an actuator 140 at one end with respect to the moving direction of the movable body 120, and attaches an encode section 150 to the other end. It is provided.

The actuator 140 is composed of, for example, a linear motor such as a voice coil motor, and applies a thrust to the movable element 170 made of a magnetic material to move the movable body 120. The operation of the actuator 140 is controlled based on the output signal of the differential light receiving element 130, and controls the movement of the movable body 120 to a position where the light source image from the point light source 100 hits the differential light receiving element 130. The encoding unit 150 is provided by attaching an encoding plate to the movable body 120, for example. The encode plate is provided with a scale pattern of a stripe pattern and a code pattern, and by reading this scale pattern by the absolute position detection device 160,
The absolute position of the movable body 120 is detected.

The absolute position detecting device 160 captures and decodes the scale pattern of the encoding plate using a CCD, a photodiode, or the like, and outputs absolute position information A of the movable body 120. The absolute position detecting device 16
0 is described in, for example, JP-A-6-0944.
An absolute position detection device disclosed in Japanese Patent Application Publication No. 18 can be adopted.

FIG. 3 is an explanatory diagram showing the configuration and operation of the differential light receiving element 130. The differential type light receiving element 130 is shown in FIG.
As shown in the figure, two light receiving elements 130R and 130R having the same characteristics
0L are juxtaposed and arranged close to each other along the moving direction of the movable body 120. In the following description, the output of the light receiving element 130R will be described as R, and the output of the light receiving element 130L will be described as L.

FIG. 4 is a block diagram showing a circuit configuration of the one-dimensional position detecting device of this embodiment. The one-dimensional position detecting device includes the light receiving elements 130R, 13R of the differential light receiving element 130.
A differential amplifier 210 for obtaining a difference output (RL) of 0 L
And the sum output (R + L) of each light receiving element 130R, 130L
And an actuator control circuit 230 that drives and controls the actuator 140 based on the difference output (RL), the sum output (R + L), and the output A from the absolute position detection device 160, and a difference output v. = (RL) multiplied by a coefficient 1 / k to be described later to obtain position information x = v / k, and the position information x is used as the absolute position detection device 1
An adder 250 that adds the output A from the output 60 and outputs it as absolute position information A + x; and an adder 250 that has an absolute value of the difference output (RL) that is less than a certain value and an absolute value of the sum output (R + L) that is more than a certain value. A determination circuit 260 for determining whether or not the position information x is valid.

Next, the functions and operations of the above-described one-dimensional position detecting device will be described in detail. First, the movable body 120 is moved by the actuator 140, and the point light source image at which the sum output (R + L) of the differential light receiving element 130 becomes a significant size hits the differential light receiving element 130, that is, as shown in FIG. Find the loop control range. Next, if the difference output is moved in the direction in which the sign output is reversed in accordance with the sign of the difference (RL), loop control is performed. Converge to the center position.

In this feedback loop established state,
Even when the point light source 100 moves, the differential light receiving element 1 is actuated by the actuator 140 in accordance with the output of the differential light receiving element 130.
The movement of 30 is controlled so as to follow the point light source image, so that the point light source image can always be captured. The difference output at that time is near the zero cross point (for example, in FIG. 3, within the position detection range of ± 0.5 μm). The difference output (RL) in this state
= V) is proportional to the distance x between the center point (light intensity center of gravity) of the point light source image and the center line of the differential type light receiving element 130, and since the light receiving elements having the same characteristics are arranged close to each other, a straight line is obtained. Extremely high. Therefore, v = kx can be set. Here, k is a position conversion coefficient.

As described above, the center point position of the point light source image is given as the distance x = v / k from the center line of the differential light receiving element 130, and the position of the center line of the differential light receiving element 130 is Imaging type absolute position detection device 1 directly connected to the light receiving element 130
Since 60 is detected as the output A at the same time, the absolute position of the center point of the point light source image can be output as A + x = A + v / k.

The output x from the differential light-receiving element 130 is obtained by reducing the point light source image as much as possible to make the width of the differential light-receiving element 130 in the x direction small and small, thereby obtaining the position conversion coefficient k and S / N. And it is easy to achieve high resolution and high-speed response. On the other hand, the actuator 140
By moving the differential light receiving element 130 having a narrow detection range, it is possible to detect a wide range, and the imaging type absolute position detecting device 160 can determine the position A of the differential light receiving element 130 with high resolution, high accuracy, and high speed. Response, detect with high reliability. This is equivalent to a state in which a large number of differential light receiving elements are arranged at a high resolution and a high precision pitch, and A + x is advanced absolute position information that cannot be obtained by the differential light receiving element 130 alone.

In the position detecting device of the present embodiment as described above, the position detection information A of the imaging type absolute position detecting device 160 capable of detecting the absolute position of the differential light receiving element 130 moved by the actuator 140 with high resolution and high accuracy. By combining (A + x) with position detection information x of the differential light receiving element 130 that can be detected with high resolution and high accuracy only in a narrow range by reducing the size of the differential light receiving element 130, a large length measurement range is obtained. A high-resolution, high-precision light source image one-dimensional position detecting device can be obtained. Further, the output x of the differential type light receiving element 130, which has been reduced in size for higher resolution, has a high-speed response due to the effect of the smaller element.
By combining (A + x) with the output A of the high-speed response type imaging absolute position detection device disclosed in Japanese Patent No. 94418, a high-speed response light source image one-dimensional position detection device can be obtained.

Next, FIG. 5 is an explanatory diagram showing how a point light source (position detection object) moving on a plane is detected by the position detection device according to the second embodiment of the present invention. The above-described one-dimensional position detection device uses the area E2 on the XY plane.
The lens system 11 is detected by detecting a point light source moving
The amount of deviation of the detection position from the optical axis of 0 is calculated, and X of the point light source is calculated.
-It is possible to detect an angle on the Y plane. Also,
As an application example in this case, two position detection outputs (A + x) are provided by providing two one-dimensional position detection devices described above and individually detecting the position of the common point light source 100 from different angles on the XY plane. ) Can be used to calculate the position of the point light source moving on the XY plane.

FIG. 6 is an explanatory diagram showing how a position detecting device according to the third embodiment of the present invention detects a point light source (position detecting object) moving in a solid. In the above-described one-dimensional position detecting device, for example, by using a spherical lens for the lens system 110, the visual field of the position detecting device
By expanding in the direction, the region E in the XYZ space is obtained.
3 is detected. And the lens system 11
The amount of deviation of the detection position from the optical axis of 0 is calculated, and X of the point light source is calculated.
-It is possible to detect an angle on the Y plane. Also,
As an application example in this case, three one-dimensional position detection devices described above are provided, and the position of the common point light source 100 is individually detected from different angles in the XYZ space, thereby providing three position detection outputs. It is also possible to calculate the position of the point light source moving in the XYZ space from (A + x).

Next, a modified example of the above-described one-dimensional position detecting device will be described. First, as a first modification,
A solution in a case where the value of the position conversion coefficient k fluctuates greatly and is difficult to fix will be described. The value of k fluctuates greatly due to a change in the light emission intensity of the point light source, a change in the distance between the point light source and the lens, and a change in the amount of light received by the differential light receiving element 130 in inverse square of the distance. , This is a gradual change and hardly fluctuates within a short time.

Therefore, the actuator 140
Is slightly fluctuated (wobbled) to instantaneously determine the value of k at that time. Assuming that a change in A + v / k at two time points when the time interval is Δt is △ A + △ v / k, △
t × (point light source image speed) = △ A + △ v / k holds. △
At the three time points of the t interval, {A ₁ + {v ₁ / k, {A ₂ +}
If v ₂ / k, the speed is assumed to be constant in a short time Δt, and ΔA ₁ + Δv ₁ / k = ΔA ₂ + Δv ₂ / k holds, so that k = − (Δv ₁ − Δv ₂ ) / (ΔA ₁ − △
A ₂ ) can be determined every moment.

In this way, with respect to the fluctuation of the output characteristic of the differential type light receiving element 130, the latest detection is instantaneously performed based on the position detection information output A of the imaging type absolute position detection device 160, which is guaranteed to have high reliability. Can be detected. As described above, the position detection information A of the imaging type absolute position detection device 160 is guaranteed to have high reliability, and the combined output (A + x) is constant when the point light source to be detected is considered to be stationary. Therefore, when the movable body 120 is wobbled and A is slightly changed, the value to be taken for x can be found.
The characteristic of the output x of the differential light receiving element 130 can be diagnosed and corrected, a highly reliable output x can be obtained, and a highly reliable point light source image one-dimensional position detecting device can be obtained.

Next, as a second modified example, by storing the position conversion characteristic value k of the differential output of the differential light receiving element as described above, it is possible to compare with the typical data in the past. An abnormality in the characteristic value can be determined, an abnormality such as a failure can be diagnosed, and a highly reliable one-dimensional position detecting device for a point light source can be configured.

Next, as a third modification, the point light source 100
Is flashed at a high frequency, and only the signal component by the light of the point light source 100 is extracted by the processing as shown in FIG.
The signal processing step of the differential light receiving element 130 as shown in FIG. 8 does not become complicated. Also, since it is hard to be affected by unnecessary light or the like, it can be used anywhere. FIG. 8A shows an example of an output signal of the differential light receiving element 130 when there is no background light, and FIG. 8B shows an example of an output signal of the differential light receiving element 130 when there is background light. I have.

In FIG. 7, the frequency signal for detecting the output signal of the differential light receiving element 130 is set as shown in FIG. 7C in accordance with the pulse of the point light source 100 (FIG. 7A). Thus, the signal component of the background light (FIG. 7D) and the signal component of the point light source light (FIG. 7E) are compared with the output signal of the differential light receiving element 130 (FIG. 7B). To separate.
Accordingly, even when there is background light as shown in FIG. 8B, the same processing as when there is no background light can be performed.

As described above, since the differential light receiving element 130 receives only light in a narrow range around the point light source 100, noise components due to unnecessary light are small and S / N is high. In particular, at the time of the point light source tracking operation, since only reflected light in a narrow range around the point light source 100 attached to the position detection target is received,
The one-dimensional position detecting device is hardly affected by disturbance light, can be used anywhere, and is convenient. Further, by blinking the point light source 100 at a specific high frequency, detecting the specific frequency, determining a gate timing, and extracting a signal component by the point light source 100 from the output signal of the differential light receiving element 130,
It is possible to provide a one-dimensional position detecting device which can remove a signal component due to unnecessary light and is hardly affected by disturbance light.

Next, as a fourth modification, as shown in FIG. 9, by providing sub-differential light-receiving elements 132L and 132R on both sides in the moving direction of the differential light-receiving element 130, respectively, Moving the light receiving element 130 at a high speed,
It is possible to solve the problem that the point light source image is missed when the point light source image is searched, and the loop light source is easily deviated from the loop control. The differential light receiving element 130 functions as if it has spread to the width of the sub differential type light receiving elements 132L and 132R, a point light source image can be searched at a high speed, and it is difficult to deviate from loop control. Further, for example, a point light source 100
Approaches the lens system 110, the point light source image becomes large,
When the value of the position conversion coefficient k of the differential output of the differential light receiving element 130 becomes too small and v / k becomes rough, the operation can be switched to the sub differential light receiving elements 132L and 132R.

This is particularly the case in the configuration in which the point light source 100 moves on a plane or in a three-dimensional object as in the above-described embodiments shown in FIGS.
The movement area in the direction (Y direction) of contacting / separating from 30 can be widened, which advantageously functions in providing a position detecting device with a wide field of view.

Next, as a fifth modified example, when the lens is a sphere and the operating area in the Z direction in FIG. 6 is enlarged, the dimension of the differential light receiving element 130 in the Z direction is increased, and the response frequency of the light receiving element is increased. Is to solve the problem of falling. FIG.
0, the light receiving element array 13 divided into eight equal parts in the Z direction
By selecting one set that provides the maximum signal by forming 4L and 134R, an eightfold response frequency can be obtained.

Next, as a sixth modification, a differential light-receiving element 130 is arranged at the center of a plate-shaped movable body 120, and an actuator 140 and an imaging type absolute position detecting device 1 are arranged on both sides thereof.
11, the differential light receiving element 130 and the actuator 140 are close to each other to increase the rigidity, the loop control characteristic frequency is increased, and the differential light receiving element 130 and the imaging type Absolute position detection device 160
And the output information A indicating the position of the center line of the differential light receiving element 130 is less likely to include expansion and contraction errors due to temperature, and a highly reliable device can be configured.

Further, in each of the above configurations, by increasing the reduction magnification of the lens system, the moving range of the point light source image is obtained by multiplying the operating range of the point light source attached to the position detection target by the reduction ratio. Since the size and size of the point light source one-dimensional position detecting device can be extremely small and the length and amount can be reduced, and the speed and acceleration of the point light source image are multiplied by the reduction rate, the actuator 140 that moves the movable body can be obtained. Can also be made extremely small.

[0034]

As described above, the position detecting apparatus according to the present invention comprises a movable body disposed on a focal plane formed by a lens system of a point light source, a differential light receiving element for detecting a point light source image, and an absolute position. An encoding unit read by the detection device,
By moving the movable body linearly by the actuator, it is controlled so that the point light source image hits the differential light receiving element,
A one-dimensional position detection device for detecting the position of the point light source based on detection information of the absolute position detection device and difference output information of the differential light receiving element. For this reason, the detection information of the absolute position detection device that can detect the absolute position of the differential light-receiving element with high resolution and high precision, and the differential light-receiving element that detects the point light source image with high resolution and high precision in a narrow range. By synthesizing the detection information, it is possible to provide a high-resolution, high-accuracy, and high-speed responsive position detection device having a simple configuration, a large length measurement range, and no large number of light receiving elements. effective.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration example of a one-dimensional position detection device of a position detection device according to the present invention.

FIG. 2 is an explanatory diagram showing a position detectable area of a position detection target to be detected by the one-dimensional position detection device shown in FIG.

FIG. 3 is an explanatory diagram showing the configuration and operation of a differential light receiving element provided in the one-dimensional position detecting device shown in FIG.

FIG. 4 is a block diagram showing a circuit configuration of the one-dimensional position detecting device shown in FIG.

FIG. 5 is an explanatory diagram showing a position detectable area when a position detection target to be detected by the one-dimensional position detection device shown in FIG. 1 moves on a plane.

FIG. 6 is an explanatory diagram showing a position detectable area when a position detection target to be detected by the one-dimensional position detection device shown in FIG. 1 moves in a three-dimensional space.

FIG. 7 is a timing chart showing signal processing for removing background light when a point light source is detected by the one-dimensional position detection device shown in FIG. 1;

8A is a waveform diagram illustrating an example of an output signal of a differential light receiving element when there is no background light, and FIG. 8B is a waveform diagram illustrating an example of an output signal of the differential light receiving element when there is background light. is there.

9 is an explanatory diagram showing an example in which sub differential light receiving elements are provided on both sides of the differential light receiving element of the one-dimensional position detecting device shown in FIG.

FIG. 10 is an explanatory diagram showing an example in which the differential light receiving element of the one-dimensional position detecting device shown in FIG. 1 is divided into a plurality of parts in a direction perpendicular to the moving direction.

FIG. 11 is an explanatory diagram showing the structure of the one-dimensional position detecting device shown in FIG.

[Explanation of symbols]

100 point light source 110 lens system 110A
Focal plane, 120: movable body, 130: differential light receiving element, 130R, 130L: light receiving element, 140: actuator, 150: encoding unit, 160: absolute position detecting device, 170: movable 210, a differential amplifier, 220, an adding circuit, 230, an actuator control circuit, 240, a multiplier, 250, an adder, 260
... Judgment circuit.

Claims (14)

[Claims] 1. A point light source attached to a position detection target, a lens system that collects and forms light from the point light source, a movable body disposed on a focal plane of the lens system, and provided on the movable body. And a differential light receiving element for detecting a focal position of light from a point light source, and by linearly moving the movable body in the focal plane, based on an output signal of the differential light receiving element, An actuator that controls the image of the point light source to impinge on the differential light receiving element; an encoding unit provided on the movable body; and an absolute position that detects the position of the movable body by detecting the encoding unit. A one-dimensional position detecting device configured to detect the position of the point light source based on detection information of the absolute position detecting device and difference output information of the differential type light receiving element. Position detection characterized by Apparatus. 2. The one-dimensional position detecting device outputs information obtained by combining detection information of the absolute position detecting device and difference output information of the differential light receiving element as position information of the point light source. The position detecting device according to claim 1. 3. At least two one-dimensional position detecting devices for detecting a position of a common point light source from directions different from each other, and a plane of the point light source based on position detection information from each of the one-dimensional position detecting devices. 2. The position detecting device according to claim 1, wherein the position is detected. 4. At least three one-dimensional position detecting devices for detecting the position of a common point light source from mutually different three-dimensional directions, and the point light source is based on position detection information from each of the one-dimensional position detecting devices. 2. The position detecting device according to claim 1, wherein the position detecting unit detects a position in a three-dimensional space. 5. The position detecting device according to claim 1, wherein the encoding unit is provided with a scale pattern on the movable body along a moving direction of the movable body. 6. The differential light-receiving element includes a pair of light-receiving elements arranged close to each other in parallel along a moving direction of the movable body, and detects a position of the point light source according to output information of each light-receiving element. 2. The position detecting device according to claim 1, wherein the position is detected. 7. The position detecting device according to claim 1, wherein the actuator is constituted by a linear motor, and the movable body has a mover made of a magnetic material driven by the linear motor. 8. The position detecting device according to claim 1, wherein the absolute position detecting device is an image pickup type absolute position detecting device that detects the position of the movable body by imaging the encoding unit. 9. A micro vibration is applied to the differential light receiving element by the absolute position detecting device and the actuator,
From the change in the output of the absolute position detection device and the change in the difference output of the differential light receiving element, a position conversion characteristic value of the difference output of the differential light receiving element is determined. 2. The position detecting apparatus according to claim 1, further comprising means for applying a current value of the position conversion characteristic value to the output and outputting the result. 10. A memory for storing a position conversion characteristic value of a differential output of the differential type light receiving element, wherein a current characteristic value is compared with a past typical characteristic value read from the memory, 10. The position detecting device according to claim 9, further comprising means for diagnosing an abnormality in the differential output of the light receiving element. 11. A means for pulsing the point light source at a high frequency, and a high frequency for pulsing the point light source is detected from an output signal of a light receiving element of the differential type light receiving element. 2. The position detecting device according to claim 1, further comprising: means for extracting the component. 12. The position detection device according to claim 1, further comprising a sub differential type light receiving element disposed on both sides of the differential type light receiving element with respect to a direction of linear movement of the movable body. apparatus. 13. A light-receiving device comprising: means for dividing the differential light-receiving element into a plurality of parts in a direction orthogonal to the direction of linear movement of the movable body, and switching and selecting a signal of each of the divided differential light-receiving elements. The position detecting device according to claim 1, wherein: 14. The movable body is formed by one plate,
The differential type light receiving element is provided at the center of the one plate, a mover for the actuator is provided at one end of the one plate, and a scale pattern is provided at the other end of the one plate. The position detecting device according to claim 1, wherein the encoding unit is formed and provided.