JPH04358107A - Position detection device - Google Patents

Abstract

PURPOSE:To detect position information on a moving body with high accuracy while expanding a detection range by using a PSD element and an opening member which has a curve opening part. CONSTITUTION:The luminous flux from a projection means 3 is guided to a photodetecting means 2 through the opening part of the opening member provided as to the moving body and the position detection device which detects the position information on the moving body by utilizing a signal outputted corresponding to the incidence position of the luminous flux on the photodetection surface of the photodetecting means is constituted so that the opening part of the opening member is formed of a curve opening part which makes a projection image on the photodetection surface curved; as the moving body moves, the curved opening part image on the photodetection surface moves in a specific direction.

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, and relates to a position detecting device that detects a position on the optical axis of a lens group in a lens barrel when the lens group is moved along the optical axis when focusing or changing magnification, for example in a camera. The present invention relates to a position detection device that can detect a position with high accuracy.

0002

[Prior Art] Conventionally, in photographic cameras, video cameras, etc., the position on the optical axis of a movable lens group for focusing or variable magnification in a lens barrel is detected by a position detection device. This signal is used, for example, in automatic focus detection. Detection means in this position detection device include, for example, a potentiometer, a gray code pattern and a brush, an element that utilizes capacitance change, and a position sensor (PSD element) that outputs a signal corresponding to the incident position of the light beam.
There are some that use photoelectric conversion elements such as.

Among these, position detection devices using PSD elements have the advantage of relatively high position detection accuracy and easy signal processing because the output signal is obtained as a voltage, and are widely used.

However, since the detection surface (light-receiving surface) of the PSD element is relatively small, it has the disadvantage that a wide position detection range cannot be achieved.

On the other hand, it is conceivable to provide a slit opening that crosses the surface of the PSD element obliquely to the direction of movement so that the movement detection range is longer than the length of the light receiving surface of the PSD element.

FIG. 4A is a schematic diagram of the main parts of a position detection device using a PSD element and a slit plate (opening member).

In the figure, a slit plate 41 connected to a moving object
A light projecting means 43 and a light receiving means 4 consisting of a PSD element are sandwiched between the
2 are placed facing each other. The slit plate 41 has a
A slit opening 41a as shown in ) is formed obliquely at an angle θ with respect to the moving direction shown by an arrow 44. This allows P.S.
Position detection is possible within a length range a/tan θ of the length a of the detection surface 42a of the D element 42 in the position detection direction.

[0008]

[Problem to be Solved by the Invention] When changing the magnification by moving the lens group (variator lens) on the optical axis in a zoom lens, in many cases, the amount of movement of the variator lens on the optical axis and the magnification change are The amount (magnification ratio) is non-linear. Especially on the telephoto side, the zoom ratio changes greatly with a small amount of movement of the variator lens on the optical axis.

Furthermore, there are various focusing methods for zoom lenses. Among these methods, a focusing method using a so-called varifocal lens, which performs focusing using a relatively small and lightweight lens group that is part of the variable power system or a part behind the variable power system, is said to be easy to perform focus operations. It has its features.

FIG. 5 is a schematic diagram of the main part of the paraxial refractive power arrangement of a zoom lens using a conventional varifocal lens. In the figure, lens groups 51 and 53 are fixed. When changing the magnification from the wide-angle end to the telephoto end, the lens group for changing the magnification (variator lens) 52 and the so-called varifocal lens 54, which functions to correct image plane fluctuations and focus, are moved as shown by the arrows. There is.

Note that curves 54a, 54b, and 54c show the locus of movement of the varifocal lens 54 as the magnification changes when focusing on a close object, an intermediate object, or an infinitely distant object.

Even if the subject distance is constant, the varifocal lens 54 needs to change its position on the optical axis as the magnification changes, as shown by curves 54a, 54b, and 54c. Furthermore, the movement locus at that time varies depending on the distance to the subject.

FIG. 6 is an explanatory diagram of the movement locus (cam locus) of the varifocal lens at this time. In the figure, the horizontal axis represents the zoom position, and the vertical axis represents the position on the optical axis of the varifocal lens. As shown in the figure, the slope θ of the cam trajectory when the varifocal lens moves is large at the telephoto end, becomes approximately 0 at the middle, and at the wide-angle end, the sign and negative are reversed, and the slope is gentler than at the telephoto end. .

[0014] Also, the slope is gentle at close range and steep at infinite distance. As described above, in the zoom lens having the configuration shown in FIG. 5, it is necessary to move the varifocal lens a large amount on the optical axis in response to a small change in the zoom ratio on the telephoto side. Therefore, when using such a zoom lens to perform automatic focusing, for example, the position of the variator lens 52 on the optical axis must be detected at the telephoto side during the entire magnification range, and at infinity during the entire object distance. It is necessary to perform particularly high-precision detection at a long distance, and to control the varifocal lens 54 on the optical axis based on the detection.

However, the position detection device shown in FIG. 4 has uniform resolution (detection accuracy) over the entire detection range. When using such a position detection device, it is necessary to configure each element in accordance with the detection accuracy of the region where the highest resolution is required. For this reason, there was a problem that it was overspecified in other areas and was not efficient.

[0016] The present invention uses a PSD element and an aperture member having an aperture with an appropriately set aperture shape.
In addition to expanding the position detection range, we separate areas that require high position detection accuracy from areas that do not require high position detection accuracy, and perform position detection with the detection accuracy that suits each area. This allows for efficient position detection. The purpose of the present invention is to provide a position detection device that has been developed.

[0017]

[Means for Solving the Problems] The position detecting device of the present invention guides a luminous flux from a light projecting means to a light detecting means through an opening of an aperture member provided in relation to a moving object. In a position detection device that detects position information of a moving object using a signal output according to the incident position of a light beam onto a light receiving surface, the aperture of the aperture member is arranged such that the projected image onto the light receiving surface is It is characterized in that it consists of a curved aperture that forms a curve, and that an image of the curved aperture on the light-receiving surface moves in a predetermined direction as the moving object moves.

Further, as a position detection device in which the present invention is applied to a lens barrel of a camera, when the lens group held in the lens barrel is moved along the optical axis, the position detection device detects the position information of the lens group on the optical axis. An aperture member provided for detection with respect to the lens group, a light projecting means and a light detecting means are arranged facing each other with the aperture of the aperture member in between, and the light beam from the light projecting means is transmitted through the aperture to the light beam. In a position detecting device that detects with a detection means and uses a signal output from the light detection means in accordance with the incident position of a light beam onto the light receiving surface, the aperture has a curved aperture. The moving speed of the center of gravity of the curved aperture image projected onto the light receiving surface of the light detecting means of the curved aperture is different between the position detection direction of the light receiving surface and the direction perpendicular thereto. It is characterized by

In particular, in the present invention, the aperture member moves by the same amount in the same direction as the moving direction of the lens group, and at this time, the amount of movement of the center of gravity of the curved aperture image on the light receiving surface is equal to the amount on the light receiving surface. It is characterized by being different in the position detection direction and in the direction orthogonal thereto.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a main part of Embodiment 1 when the present invention is applied to a lens barrel, and FIG. 2 is an enlarged explanatory view of a portion of FIG. 1.

In the figure, reference numeral 4 denotes a variator lens, which is one element constituting a zoom lens as a moving object. 5 is a lens moving frame that holds the variator lens 4;
It is driven by an actuator (not shown). 6,
Each guide bar 7 slides and guides the lens moving frame 5.

Reference numeral 1 denotes an opening member, which is integrally fixed to a part of the lens moving frame 5 with screws, adhesive, or the like. The opening member 1 is provided with a curved opening 1a as shown in FIG. 2 as an opening (transparent part). Reference numeral 3 denotes a light projecting means, which is composed of an infrared light emitting diode (IRED) or the like. Reference numeral 2 denotes a light detection means, which is composed of a position sensor (PSD element). The light projecting means 3 and the light detecting means 2 are arranged opposite to each other with the curved opening 1a of the aperture member 1 interposed therebetween.

The light detecting means (PSD element) 2 is the light projecting means 3
The center of gravity of the light beam passing through the curved opening 1a and incident on the light receiving surface in the direction of the arrow 2a onto the light receiving surface is detected. Note that FIG. 2 shows the relationship between the curved opening 1a of the opening 1 and the PSD element 2.

In FIG. 2, the direction of the arrow 2a is the PSD element 2.
is the position detection direction. The arrow 1b is the moving direction of the aperture member 1, and is perpendicular to the position detection direction 2a of the PSD element 2. In FIG. 2, the PSD element 2 is located at the center of gravity 1c in the direction of the arrow 2a of the light beam that has passed through the curved aperture 1a of the aperture member 1, which corresponds to the curved aperture image projected onto the light-receiving surface.
is being detected.

In this embodiment, the aperture member 1 moves integrally by the same amount in the same direction as the moving direction (optical axis direction) of the lens group 4. At this time, as shown in FIG. 2, the curved aperture 1a provided in the aperture member 1 moves in the direction of the arrow 16 on the surface of the PSD element 2 as the lens group 4 moves.

1c indicates the position of the center of gravity of the curved aperture image 1a' of the curved aperture 1a when projected onto the PSD element surface. When the center of gravity position 1c moves in the direction of the arrow 1b, the amount of movement in the direction of the arrow 1b is different from the amount of movement in the direction of the arrow 2a (position detection direction of the PSD element 2) perpendicular thereto.

That is, by appropriately setting the curved shape of the curved aperture 1a, a region where the position detection resolution of the aperture member 1 (lens group 4) is improved (for example, at the zoom position on the telephoto side or when photographing an object at infinity) In this case, even when the aperture member 1 moves slightly in the direction of the arrow 1b, the curved aperture image (center of gravity position 1c) on the light receiving surface of the PSD element 2 moves relatively much. On the other hand, in a region where the position detection resolution can be low (for example, an intermediate zoom position), even if the aperture member 1 moves, the curved aperture image (center of gravity position 1c) on the light receiving surface of the PSD element 2 does not move much. I have to.

Note that in FIG. 2, the moving direction 1 of the opening member 1
Position detection resolution Δ at the opening position with angle θ relative to b
R is ΔR=Δa/t, where the resolution of PSD element 2 is a
It becomes anθ. (However, 0<θ<90°) In this example, by appropriately changing the aperture shape of the curved aperture 1a, a region where the position detection resolution can be improved and a region where it cannot be separated are separated, and the detection resolution can be effectively improved using one PSD element. It has improved significantly.

In addition, in this embodiment, in a zoom lens using a varifocal lens having the cam locus characteristic shown in FIG. This is particularly true on the telephoto and wide-angle sides, where varifocal lenses rapidly change position when changing magnification. And the PSD obtained at this time
The position of the varifocal lens on the optical axis is driven and controlled with high precision based on the signal from the element, that is, the position information of the variator lens. For example, specifically, the slope θ of the curved opening 1a in FIG. 2 is changed to the slope θ of the cam trajectory for an object at infinity in FIG.
It is set accordingly.

[0030] Furthermore, the setting may be made in accordance with the conditions of each system, for example, in accordance with a cam locus with an object distance of 5 m or 1 m. As a result, in this embodiment, a good image can be obtained over the entire magnification range.

Furthermore, when the zoom position is fixed in a zoom lens as shown in FIG. 5 and focusing is performed using a varifocal lens, the position resolution is relatively coarse on the close object side and very fine on the infinite object side. It becomes necessary.

Therefore, in such a case, the curved opening 1
It is preferable that the slope θ of a is small on the close object side and large on the infinite object side. Specifically, it is preferable to set the inclination to obtain the highest positional resolution required at each focus position.

For example, in the curve of FIG. 7 shown similarly to FIG. 6, when the position on the optical axis of the focus lens (varifocal lens) is at position b1, the slope θ1 is, when it is at position b2, the slope θ2 is, and when it is at position b3, the slope is θ1. The slope θ3 is the largest. Therefore, it is preferable to determine the curved shape of the curved opening 1a in accordance with these inclinations θi.

In the above embodiments, the position detection device of the present invention was described for detecting the position on the optical axis of the variator lens of a zoom lens. It can be similarly applied as a means.

For example, as shown in FIG. 8, if a curved aperture is provided in accordance with the slope θ of a curve 81 showing the relationship between the position of the diaphragm blades and the F number (FNo) of the photographing lens, the same result as in the previous embodiment can be obtained. Effects can be obtained. That is, it is possible to perform position detection with a fine aperture diameter in a region with a large F number where high positional resolution is required, and to perform position detection with a coarse aperture diameter in a region with a small F number.

In addition, the present invention can be similarly applied to, for example, detecting the position of a carriage mechanism of a printer or detecting the position of other moving objects.

[0037]

[Effects of the Invention] According to the present invention, the PS configured as described above
By providing a D element and an aperture member for a moving object, the position detection range (stroke) can be expanded, and position detection can be performed in areas where high position detection accuracy is required and areas where it is not. A position detection device that enables efficient position detection can be achieved.

[Brief explanation of drawings]

[Figure 1] Schematic diagram of main parts of Example 1 of the present invention

[Figure 2]
Enlarged explanatory diagram of a portion of Figure 1

[Figure 3] Explanatory diagram showing the relationship between the slope θ of the curved opening in Figure 2 and the position detection resolution ΔR

[Figure 4] Schematic diagram of a position detection device using a conventional PSD element

[Figure 5] Explanatory diagram of the paraxial power arrangement of a conventional zoom lens

[Figure 6] Explanatory diagram of the movement trajectory of the varifocal lens as it changes magnification

[Figure 7] Explanatory diagram of the movement trajectory of the varifocal lens as it changes magnification

[Figure 8] Explanatory diagram showing the relationship between the position of the aperture blades and the F number

[Explanation of symbols]

1 Opening member 1a Curved opening 1c Center of gravity position of luminous flux 2 PSD element 3. Light projecting means 4 Lens group 5 Lens movement frame 6,7 Guide bar

Claims (3)

[Claims] 1. A light beam from a light projecting means is guided to a light detecting means through an opening of an aperture member provided in relation to a moving object, and the light beam is guided to a light detecting means according to the incident position of the light beam onto a light receiving surface of the light detecting means. In a position detection device that detects position information of the moving object using an output signal, the aperture of the aperture member is formed of a curved aperture whose projected image onto the light receiving surface is a curve, and A position detection device characterized in that an image of a curved aperture on the light-receiving surface moves in a predetermined direction as the light-receiving surface moves. 2. Detection of positional information on the optical axis of a lens group held in a lens barrel when the lens group is moved on the optical axis by an aperture member provided with respect to the lens group, and an aperture member provided for the lens group; A light projecting means and a light detecting means are arranged opposite to each other with an opening in between, and the light beam from the light projecting means is detected by the light detecting means through the opening, and the light from the light detecting means is detected on the light receiving surface. In a position detection device that uses a signal output according to the incident position of a luminous flux to A position detection device characterized in that the moving speed of the center of gravity of the curved aperture image projected inward is different between the position detection direction of the light receiving surface and the direction perpendicular thereto. 3. The aperture member moves by the same amount in the same direction as the moving direction of the lens group, and at this time, the amount of movement of the center of gravity of the curved aperture image on the light receiving surface is in the position detection direction on the light receiving surface. 3. The position detection device according to claim 2, wherein the position detection device differs in the direction perpendicular thereto.