JPH0666518A - Position detector - Google Patents

Abstract

PURPOSE:To make the intensity of an incident light uniform and thereby to prevent the occurrence of an error in detection by a construction wherein a V-shaped groove made up of two reflecting surfaces intersecting a plane perpendicular to the direction of movement of an object of measurement, at a specified angle, respectively is formed to be a displacement member. CONSTITUTION:A V-shaped groove 21 made up of reflecting surfaces 21a and 21b intersecting a plane perpendicular to the direction of movement of a displacement member 20 at an angle of 45 degrees respectively is formed in the member. When an irradiation light from a light- applying part 10 is cast on the bottom part of the groove 21, it is reflected on the cast on bottom part and cast on the central part of PSD 30 with the optical path changed at an angle of 180 degrees. When the member 20 moves to the right, the irradiation light is cast on the reflecting surface 21a at an angle of 45 degrees, cast on the reflecting surface 21b with the optical path changed at an angle of 90 degrees, emitted in the direction reverse to the direction of incidence with the optical path changed at an angle of 90 degrees likewise, and cast on the right peripheral part of the PSD 30. Although the position of the groove 21 changes with the movement of the member 20, the optical path from the light-applying part 10 to the PSD 30 and a radiant solid angle are always unvaried. Therefore the intensity of the reflected light cast on the PSD 30 is made uniform and an error in measurement is reduced.

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 using an optical position detecting element such as PSD, and more particularly to a position detecting device for detecting the position of a focus lens of a camera.

[0002]

2. Description of the Related Art FIG. 12 shows the configuration of a conventional position detecting device using an optical position detecting element. LED 10 constituting a light source
The light flux emitted from the No. 1 is reflected by the thin reflection plate 103 provided on the surface of the detection target 102, and is a PSD that is a detection element.
It is incident on 104. By moving the detection target 102,
The position on the PSD 104 where the light reflected by the reflection plate 103 enters changes. The PSD 104 generates the currents I ₁ and I ₂ at a current ratio different depending on the position of the incident light, and the position of the detection target 102 can be detected by calculating the current ratio.

[0003]

By the way, as shown in FIG. 13, in the conventional position detecting device, as the LED 101 and the reflecting plate 103 are separated from each other, the light emitted from the LED 101 becomes P
The optical path length until it enters the SD 104 becomes long. Further, as shown in FIG. 14, the conventional position detecting device is
The radiation solid angle θ ₁₂ at the position where the reflector 103 is away from the LED 101 is narrower than the radiation solid angle θ ₁₁ at the position where the reflector 103 is close to D101.

Thus, the farther the incident position on the PSD 104 is from the LED 101, the longer the optical path and the narrower the solid angle of emission. Therefore, there is a problem in that the light intensity on the light receiving surface of the PSD 104 becomes weak, and the difference in the intensity distribution causes an error in the detection position.

An object of the present invention is to provide a position detecting device in which the intensity distribution of incident light on the PSD 104 is made uniform and a detection error is unlikely to occur.

[0006]

In order to solve the above-mentioned problems, the position detecting device of the present invention moves one-dimensionally in accordance with the movement of the object to be measured, and with respect to a plane perpendicular to this movement direction. V consisting of two reflective surfaces that intersect at an angle of 45 °
A displacement member having a V-shaped groove, a light irradiation unit that irradiates the groove of the displacement member with light along a plane perpendicular to the moving direction of the displacement member, and irradiation light from the light irradiation unit is generated by the groove of the displacement member. And a light position detector arranged on the optical path of the reflected light and detecting the incident position of the reflected light.

Further, the light irradiating section is provided with a light source and a slit plate in which a slit perpendicular to the moving direction of the displacing member is formed, and the irradiating light from the light source irradiates the groove of the displacing member through the slit. good.

[0008]

Since the position detecting device of the present invention is constructed as described above, the irradiation light emitted along the plane perpendicular to the moving direction of the displacement member is the base where the two reflecting surfaces of the groove of the displacement member intersect. The light is incident on the part or on one of the reflecting surfaces of the groove of the displacement member.

When incident on the bottom of the groove, the irradiation light is incident on the bottom of the groove at an angle of 45 ° with respect to the two reflecting surfaces. Then, the optical path is changed by 180 ° at the bottom surface portion, and the reflected light is emitted in the direction opposite to the direction of the irradiation light and at the same angle as the incident angle of the irradiation light.

When incident on one reflecting surface of the groove, the irradiation light is incident on one reflecting surface of the groove at an angle of 45 °. The incident light is reflected by this reflecting surface and the optical path is changed by 90 °. Furthermore, this reflected light is 45 ° on the other reflecting surface.
Is incident at an angle of. The incident light is also reflected by this reflecting surface and the optical path is changed by 90 °. Therefore, the reflected light from this reflecting surface has the same angle as the incident angle of the incident light in the direction opposite to the direction of the incident light.

The reflected light emitted from the groove in this way is incident on the optical position detecting section arranged on the optical path of the reflected light, and the incident position of the reflected light is detected.

In the position detecting device of the present invention, the position of the groove into which the irradiation light from the light irradiation section is incident changes due to the movement of the displacement member, but the optical path of the irradiation light from the light irradiation section to the light position detection section is changed. The length is constant. Further, regardless of the movement of the displacement member, the irradiation angle of the irradiation light from the light irradiation unit is constant, so that the radiating solid angle is also constant. Therefore, regardless of the movement of the displacement member, the light intensity of the reflected light incident on the light position detection unit is always the same.

Next, the principle that the optical path length of the irradiation light from the light irradiation unit to the light position detection unit becomes constant regardless of the movement of the displacement member will be described with reference to FIG.

In FIG. 11, the displacement member 60 is shown as a light irradiating section 61.
It shows a change in the optical path of the irradiation light when moving in a direction away from (rightward in the figure). Here, 2 of the groove before moving
One surface is the reflecting surface 62, 63, and the two surfaces of the groove after the movement are the reflecting surfaces 62 ', 63', and the reflecting surface 62 for reflecting the irradiation light
The position above ′ is the reflection portion 62a.

First, the optical path length from the light irradiating section 61 to the reflecting section 62a is l ₁ , the optical path length from the reflecting section 62a to the base 64 is l ₂ , and the optical path length from the reflecting section 62a to the optical position detecting section 65 is. If l ₃ is set, the optical path length from the light irradiating section 61 to the light position detecting section 65 when reflected by the base 64 is (l ₁
+ 2 × l ₂ + l ₃ ).

Further, the optical path length to the light reflected by the reflecting portion 62a and reaches the reflecting surface 63 'l _4, when the optical path length from the reflection surface 63' to the light position detector 65 and l _5, reflective surface The optical path length from the light irradiation unit 61 to the light position detection unit 65 when reflected by 62 ′ and 63 ′ is (l ₁ + l ₄ + l ₅ ).

Here, the angle between the light reflected by the reflecting surface 62 'and this reflecting surface 62' is 45 °, and this reflected light and the reflecting surface 6
The angle with 3'is also 45 °, and the reflecting surface 62 'and the reflecting surface 6
Since the angle of intersection with 3 ′ is 90 °, the optical path of the light reflected by the reflecting surface 62 ′ and the triangle (hatched portion 66) surrounded by the reflecting surfaces 62 ′ and 63 ′ form an isosceles right angle. Optical path length l
₂ is equal to the height of this triangle, so the optical path length l ₂ is 2
The multiplied distance is equal to the optical path length l ₄ . Further, since the optical path is changed by 90 ° on the reflecting surface 62 ′ and the optical path is changed by 90 ° on the reflecting surface 63 ′, the irradiation light from the light irradiation unit 61 is reflected by the two reflecting surfaces 62 ′ and 63 ′. The quadrangle (the shaded portion 67) surrounded by the optical path until reaching the light position detection unit 65 becomes a rectangle. Therefore,
The optical path length l ₃ and the optical path length l ₅ are equal. From the above, the bottom part 6
Optical path length when reflected at 4 (l ₁ + 2 × l ₂ + l ₃ )
And the optical path length (l
It was verified that ₁ + l ₄ + l ₅ ) are equal.

Further, when the light irradiating section is provided with the light source and the slit plate, it has the following effects. Since a slit is formed in the slit plate perpendicularly to the moving direction of the displacement member, the irradiation light from the slit plate becomes a light beam having a rectangular cross section that is long in the direction perpendicular to the moving direction. The cross section of the reflected light when this light flux is reflected by the groove of the displacement member and is incident on the light position detection unit is also a rectangular shape that is long in the direction perpendicular to the movement direction. Therefore, even if the distance between the light irradiation unit or the light position detection unit and the displacement member fluctuates, and the incident position of the reflected light on the light position detection unit shifts in the direction perpendicular to the moving direction, the rectangle If part of the reflected light of the shape can be received by the light position detector, the position can be detected.
A certain distance variation does not affect the position detection. In this case, the permissible range of the incident position change due to the distance change is (width of the light position detecting portion in the direction perpendicular to the moving direction) + 2 × (width of the light beam incident on the light position detecting portion in the direction perpendicular to the moving direction)
Is.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the position detecting device of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the configuration of an embodiment of the position detecting device according to the present invention. The position detecting device according to the present embodiment includes a light irradiating unit 1 including an LED 11 and a slit plate 12.
0, a displacement member 20 having a V-shaped groove 21, and a PS which is an optical position detection unit for injecting the light reflected by the displacement member 20.
And D30. LED 11 and slit plate 12
Are spatially fixed by means not shown so that the irradiation light from the LED 11 irradiates the groove 21 of the displacement member 20 through the slit plate 12. Similarly, P
The SD 30 is also spatially fixed by means (not shown) so that the light reflected by the groove 21 of the displacement member 20 can be received.

The displacing member 20 moves in accordance with the movement of the object to be measured.
Performs dimensional movement. This movement changes the position where the reflected light from the groove 21 is incident on the PSD 30. Two reflecting surfaces 21a and 21b are formed in the groove 21 of the displacing member 20 and intersect with the plane perpendicular to the moving direction of the displacing member at an angle of 45 °. Therefore, the reflective surface 2
The angle between 1a and the reflecting surface 21b is 90 °.

Further, the light emitted from the LED 11 becomes a light flux which illuminates the light in a limited area by the slit plate 12 having slits formed perpendicular to the moving direction of the displacement member 20. The irradiation direction of the LED 11 is adjusted so that this light flux forms an optical path along a plane perpendicular to the moving direction of the displacement member 20. Since the reflecting surfaces 21a and 21b of the groove intersect at an angle of 90 °, the reflecting surfaces 21a and 21b are reflected by these reflecting surfaces and PSD.
The light incident on 30 also has an optical path along a plane perpendicular to the moving direction of the displacement member 20.

Further, the PSD 30 generates I ₁ and I ₂ at a current ratio corresponding to the position of the incident light, and the movement of the displacement member 20 can be detected by calculating this current ratio.

Next, the operation of the position detecting device of this embodiment will be described. With reference to the position of the displacement member 20 when the irradiation light from the light irradiation unit 10 is incident on the bottom portion 21c where the reflecting surfaces 21a and 21b of the groove 21 intersect, the optical path of the irradiation light at this reference position is shown in FIG. And shown in FIG. And
4 and 5 show the optical path of the irradiation light when the displacement member 20 moves from the reference position to the right side of the drawing, and FIG. 6 shows the optical path of the irradiation light when the displacement member 20 moves from the reference position to the left side of the drawing. Each is shown in FIG.

First, the optical path of the irradiation light when the displacement member 20 is at the reference position will be described with reference to FIGS. 2 and 3. In FIG. 2A, the irradiation light from the light irradiation unit 10 is supplied to the groove 21.
2B is a perspective view showing an optical path when reflected by the bottom portion 21c of FIG. 2A, and FIG. 2B, FIG. 3A, and FIG.
It is a figure which shows the optical path seen from 3 directions of arrow 41-43 of FIG.

As shown in FIG. 2A, the LED 11 (L
The irradiation light emitted from the point 30) is reflected by the bottom portion 21c (point O) of the groove 21 through the slit plate 12 and the PSD 30
Is incident on the incident point 30a (point P) at the center of the. Figure 2
From the front view of (b), the incident light to the groove 21 is the displacement member 20.
It can be seen that the light is incident perpendicularly on the upper surface 20a of the.
At this time, the incident light and the two reflecting surfaces 21a, 21 of the groove 21 are
The angle with b is 45 °. And the bottom part 2
The reflected light reflected by 1c is emitted at the same angle as the incident light.
Further, from the side view of FIG. 3C, it can be seen that the incident light on the groove 21 is incident at an angle of θ with respect to the perpendicular of the bottom portion 21c. Then, the reflected light whose optical path is changed by 2θ at the bottom portion 21c is emitted at an angle of θ with respect to the perpendicular of the bottom portion 21c. Further, from the top view of FIG. 3D, it can be seen that the irradiation light emitted from the LED 11 has an optical path along the bottom portion 21c.

Next, the optical path of the irradiation light when the displacement member 20 moves to the right side of the drawing from the reference position will be described with reference to FIGS. 4 and 5. FIG. 4A is a perspective view showing an optical path when the irradiation light from the light irradiation unit 10 is reflected by the reflecting surfaces 21a and 21b of the groove 21, FIG. 4B and FIG.
4B is a diagram showing an optical path seen from three directions of arrows 41 to 43 in FIG.

As shown in FIG. 4A, the LED 11 (L
The irradiation light emitted from the point 21) passes through the slit plate 12 and the reflecting surface 21a (point A) and the reflecting surface 21b (B) of the groove 21.
Incident point 30b on the right periphery of the PSD 30
It is incident on (point P). From the front view of FIG.
It can be seen that the incident light on is incident on the reflecting surface 21a at an angle of 45 °. And the optical path is changed by 90 °,
It is incident on the reflecting surface 21b. Similarly on the reflecting surface 21b, 90
° The optical path is changed and the light exits in the direction opposite to the incident direction. This emitted light is incident on the right peripheral portion 30b of the PSD 30. From FIG. 4B, if the moving distance of the displacement member 20 is d,
It can be seen that the optical path length between points A and B is 2d. next,
From the side view of FIG. 5C, the incident light on the groove 21 is
It can be seen that the light is incident at an angle of θ with respect to the perpendicular of 1c. Then, the light reflected by the reflecting surface 21a is further reflected by the reflecting surface 21b, and this reflected light is incident on the PSD 30 at an angle of θ with respect to the vertical line of the bottom portion 21c. Further, from the top view of FIG. 5D, the irradiation light emitted from the LED 11 travels in parallel with the bottom portion 21c, the optical path is changed (θ + 90 °) on the reflecting surface 21a, and further (θ + 90 °) on the reflecting surface 21b. ) It can be seen that the optical path is changed and the optical path becomes parallel to the bottom portion 21c. This reflected light is incident on the incident point 30b of the PSD 30.

Similarly, FIG. 6A is a perspective view showing an optical path when the irradiation light from the light irradiation unit 10 is reflected by the reflecting surfaces 21b and 21a of the groove 21, FIG. 6B and FIG. c),
FIG. 6D is a plan view showing an optical path seen from three directions of arrows 41 to 43 in FIG.

As shown in FIG. 6A, the LED 11 (L
The irradiation light emitted from the reflection surface 21b (point B) and the reflection surface 21a (A) of the groove 21 passes through the slit plate 12.
Incident point 30c on the left peripheral part of PSD 30
It is incident on (point P). From the front view of FIG. 2B, it is understood that the optical path length between the points B and A is 2d, where d is the moving distance of the displacement member 20. Further, from the side view of FIG. 7C, the incident light to the groove 21 and the reflected light from the groove 21 are
It can be seen that the light is incident and emitted at an angle of θ with respect to the perpendicular of the bottom portion 21c. Furthermore, from the top view of FIG.
The light emitted from D11 is reflected by the reflecting surface 21a and the reflecting surface 2
The optical path is changed twice at 1b, and the light is incident on the incident point 30c of the PSD 30.

As shown in FIG. 7D, the incident point of the reflected light on the light receiving surface of the PSD 30 as the displacement member 20 moves is
It moves on a straight line 44 including the incident points 30a, 30b, 30c. The straight line 44 is parallel to the moving direction of the displacement member 20. Therefore, it is desirable that the PSD 30 is arranged such that its longitudinal direction is parallel to the moving direction of the displacement member 20.

Further, it can be seen that the optical path between points A to O and B shown in FIG. 7C is equal to the optical path between points A and B shown in FIG. 7D. Therefore, the optical path (point L → point O → point P
Point) and the optical path (point L → point A → point B → point P) have the same optical path length. Thus, in the configuration of this embodiment, the light irradiation unit 10
The optical path length from to PSD 30 is constant regardless of the movement of the displacement member 20.

Next, the features of this embodiment will be described.
The first feature of the present embodiment is that the light intensity and intensity distribution of the incident light incident on the PSD 30 are equal. this is,
As described above, the optical path length from the light irradiation unit 10 to the PSD 30 is constant regardless of the movement of the displacement member 20,
This is because, as shown in, the radiation solid angles θ ₁ of the irradiation light from the light irradiation unit 10 are the same regardless of the movement of the displacement member 20.

The second characteristic of this embodiment is that, even if the distance between the PSD 30 and the displacement member 20 changes, as shown in FIG.
The change in the incident position of the reflected light on the PSD 30 is perpendicular to the detection direction (the moving direction of the displacement member 20), and the detection position error does not occur. The allowable range of incident position change of reflected light is (width of PSD 30 in the direction perpendicular to the detection direction)
+ 2 × (width of light flux in the direction perpendicular to the detection direction). Also, if the light source is a minute spot light such as laser light,
The allowable range is approximately (PSD30 in the direction perpendicular to the detection direction.
Width).

FIG. 10 shows an autofocus camera and a VT.
It shows an application example to the position detection of the focus lens in an R camera or the like. In the figure, the fixed lens 51 and the focus lens 52 form an optical system, and the focus lens 52 is moved in the optical axis direction of the focus lens 52 by an actuator (not shown) to perform focusing. The side surface of the focus lens 52 is provided with a displacement member 53 whose upper surface is a V-shaped groove. Further, the LE is placed at a position where the groove of the displacement member 53 can be irradiated.
The D54 and the slit plate 55 are spatially fixed by means not shown. Further, the PSD 56 is spatially fixed by means (not shown) at a position where reflected light from the groove of the displacement member 53 can enter. Then, the movement of the focus lens 52 is detected by the position change of the incident light incident on the PSD 56.

The present invention is not limited to the above embodiment. For example, a multi-division PD or the like can be used instead of the PSD 30.

If a light source having a high directivity such as a laser is used for the light irradiation section 10, a large signal output can be obtained by driving a small light source.

[0038]

As described above, in the position detecting device of the present invention, the optical path length until the irradiation light emitted from the light emitting portion is incident on the optical position detecting portion is the moving position of the displacement member. It is constant regardless of. Further, the radiation solid angle of the irradiation light emitted from the light irradiation unit is also constant. Therefore, the incident light has the same light intensity regardless of the incident position of the incident light incident on the light position detection unit. Therefore, the intensity distribution of the incident light becomes uniform, and an error due to the detection position of the light position detection unit hardly occurs.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a position detection device of this embodiment.

FIG. 2 is a diagram showing an operation of the position detection device of the present embodiment.

FIG. 3 is a diagram showing an operation of the position detection device of this embodiment.

FIG. 4 is a diagram showing an operation of the position detection device of this embodiment.

FIG. 5 is a diagram showing an operation of the position detection device of this embodiment.

FIG. 6 is a diagram showing an operation of the position detection device of this embodiment.

FIG. 7 is a diagram showing an operation of the position detection device of this embodiment.

FIG. 8 is a diagram showing a radiation solid angle of irradiation light.

FIG. 9: PSD for a change in distance between PSD and displacement member
It is a figure which shows the incident position change to.

FIG. 10 is a perspective view showing an application example of the present invention.

FIG. 11 is a plan view showing the principle that the optical path length of the irradiation light from the light irradiation unit to the light position detection unit becomes constant.

FIG. 12 is a perspective view showing a configuration of a conventional position detection device.

FIG. 13 is a plan view showing the relationship between the position of a reflector and the position of incidence on a detection element.

FIG. 14 is a plan view showing a radiation solid angle of light incident on a reflection plate.

[Explanation of symbols]

10 ... Light irradiation part, 11 ... LED, 12 ... Slit plate, 2
0 ... Displacement member, 21 ... Groove, 30 ... PSD.

Claims (2)

[Claims] 1. A one-dimensional movement is made according to the movement of the object to be measured, and each of them is 45 ° with respect to a plane perpendicular to the movement direction.
A displacement member having a V-shaped groove composed of two reflecting surfaces that intersect at an angle of, a light irradiation unit that irradiates the groove of the displacement member with light along a surface perpendicular to the moving direction of the displacement member, A position detecting device, comprising: a light position detecting unit arranged on an optical path of light reflected from a groove of the displacement member, and a light position detecting unit detecting an incident position of the reflected light. 2. The light irradiating section includes a light source and a slit plate in which a slit perpendicular to the moving direction is formed, and irradiates the irradiating light from the light source to the groove of the displacing member through the slit. The position detecting device according to claim 1, wherein