JP3162757B2 - Camera lens position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a lens position of a camera, and more particularly to an apparatus for detecting the position of a lens to be moved during focus control and zoom control.

[0002]

2. Description of the Related Art In a camera, the position of a lens to be moved at the time of focus control or zoom control such as inner focus and auto focus is detected. For this lens position detection, conventionally, for example, a potentiometer, Various detection devices such as an encoder, a position detection switch, and a device using a resistor are used.

FIG. 8 shows an example of a lens position detecting device using a resistor as an example of the lens position detecting device. As shown in the drawing, a lens 1 is held by a lens frame 2 and this lens frame 2 is guided by a guide. Guided by 3a, 3b. Therefore,
When the lens frame 2 is driven by driving means (not shown), the lens 1 is moved in the left and right directions in the figure along the guides 3a and 3b. A resistor 4 is arranged in parallel with the guide 3b, and a brush 5 is arranged at one end of the lens frame 2 so as to be in contact with the resistor 4. Therefore,
For example, the lens position can be specified by measuring the resistance value R of the resistor 4 from the left end.

[0004]

However, in the conventional lens position detecting device, for example, in the example of FIG. 8, by securing a space for disposing the resistor 4 and the brush 5, the diameter of the lens barrel becomes large. There is a problem that the camera cannot be downsized. This is the same for other conventional detection devices such as a potentiometer, an encoder, and a position detection switch.

In addition, a camera often has a plurality of lenses to be driven, and when detecting the positions of the plurality of lenses, the above-described detection device is disposed for each of them. Not
The configuration becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the size of a camera while ensuring that there is no need to secure a space for lens position detection. It is an object of the present invention to provide a camera lens position detecting device capable of simplifying a configuration for detecting a camera lens position.

[0007]

To achieve the above object of the Invention The present invention includes a guide for guiding the back and forth movement of the lenses, wound around the lens movement direction of the guide, and double
Consists of a primary coil and a secondary coil placed one on top of the other
A differential coil, is slidably disposed on the outer periphery of the differential coil, and a metallic support sleeve for supporting the lens, the lens by the output value of the differential coil when the support sleeve moves A lens position detecting device for detecting a position, wherein the guide has a plurality of differential coils in a lens moving direction, and a plurality of support sleeves corresponding to the differential coils are provided, and a plurality of lens positions are provided. It is characterized in that it is detected. The differential coil includes a primary coil and two secondary coils set in reverse winding, which constitute a differential transformer. In the above case, the primary coil among the plurality of differential coils provided on the guide can be formed by one winding.

[0008]

According to the above arrangement, the primary coil and the secondary coil constituting the plurality of differential coils are doubled in the guide.
A plurality of differential transformers are formed by this guide and a plurality of support sleeves arranged at respective portions of the guide on which the differential coil is formed. In the above differential coil, an induced voltage is generated on the secondary coil side by applying an AC voltage to the primary coil. When each support sleeve moves together with the lens by driving the lens, the voltage value induced in the secondary coil changes with the movement of the support sleeve. Thus, by the child measuring a voltage value of the secondary coil,
Each lens position is specified.

[0009]

FIG. 1 shows a schematic configuration of a camera lens position detecting apparatus according to an embodiment. As shown, two first lenses 10a and second lenses 10b are held by resin lens frames 12a and 12b.
Guides 13a, 13b, and 13c are provided for guiding the front and rear movements (left and right in the drawing) of the first lens 10a, and the first lens 10a is moved by the guides 13a and 13b.
b is guided by guides 13a and 13c. The guide 13a is provided with a stopper 11, which restricts the movement range of the lens 10. And
In the embodiment of the guide 13, two differential coils are wound inside the guide 13a in the embodiment, and the lens frame 12 is attached to the guide (hereinafter referred to as a differential coil guide) 13a.
The supporting sleeves (hereinafter simply referred to as sleeves) 14a and 14b attached to the a and 12b are arranged. Therefore, two differential transformers are formed by the differential coil guide 13a and the sleeves 14a and 14b, and the sleeves 14a and 14b are formed of non-ferrous metal such as copper, brass, and aluminum. Is preferred. The other guides 13b and 13c are connected to the respective lens frames 12 as in the prior art.
a, 12b.

FIG. 2 is a radially enlarged view of the differential coil guide 13a, and FIG. 3 shows a detailed configuration of the differential transformer. In FIG. 2, a shaft 16 is provided in the differential coil guide 13a.
First, the primary coil 17 is wound around the entire shaft. Then, the first lens 10a
In FIG. 3, two secondary coils 18a and 18b are wound, and the secondary coils 18a and 18b are wound so as to be opposite to each other as shown in FIG. In the second lens 10b, secondary coils 18c and 18d, which are opposite to each other, are wound around the primary coil 17. Therefore, when a current flows through the primary coil 17, an induced current is generated in the four secondary coils 18a, 18b, 18c, and 18d. In this case, two sets of coils wound in opposite directions are formed. In each of the secondary coils 18a and 18b and the secondary coils 18c and 18d, voltages having opposite polarities are generated separately. Since the metallic sleeves 14a and 14b are arranged on the differential coil guide 13a, a voltage value that changes linearly with the movement of the position can be obtained as shown in FIG. Such a differential coil guide 13a and the sleeve 14
a, differential transformer consists of 14b, the sleeve 14
A moving range having almost the same length as that of the moving range can be detected.

FIG. 4 shows a circuit configuration for detecting the above-described lens position. In FIG. 4, a driving circuit 21 is connected to an oscillator 20 for generating a sine wave, and the driving circuit 21 is connected to the driving circuit 21. The primary coil 17 is connected. A preamplifier 22a is connected to the secondary coils 18a and 18b for the first lens 10a that are wound in opposite directions, and a first detector 23a including a low-pass filter and the like is connected to the preamplifier 22a. On the other hand, a preamplifier 22b is connected to the secondary coils 18c and 18d for the second lens 10b, and a second detector 23b is connected to the preamplifier 22b. Accordingly, when an AC voltage is applied to the primary coil 17 by the drive circuit 21, the secondary coils 18a, 18b
And the AC voltages induced by 18c and 18d are output to preamplifiers 22a and 22b, and the voltages amplified by respective preamplifiers 22a and 22b are taken out as DC voltages by first and second detectors 23a and 23b.

The embodiment has the above configuration.
The operation will be described with reference to FIG. First, during operation of the camera, the oscillator 20 shown in FIG. 4 is driven, and the AC voltage shown in FIG. 5A is applied to the primary coil 17. When attention is paid to the first lens 10 a, the first lens Assuming that 10a is located at the base position (zero position), as shown in FIG. 4, the sleeve 14a supporting the first lens 10a is placed at the position indicated by the solid line. At this time,
As shown in FIG. 5B, in the secondary coils 18a and 18b, a voltage having a negative phase waveform (negative voltage) is induced, and the induction of a voltage having the same phase waveform is suppressed. The output is, for example, -2.5 V as shown in FIG. When the first lens 10 is driven, for example, forward by the inner focus control or the like, the sleeve 14a moves accordingly.
The movement of the position 4a gradually suppresses the voltage induction of the opposite phase waveform, while the voltage of the in-phase waveform is induced. As shown in FIG. 6, the output voltage of the first detector 23a becomes a straight line. Rise. The sleeve 14 is positioned at the lens movement end position indicated by a chain line 101 shown in FIG.
5 mm, only the voltage (positive voltage) of the in-phase waveform is induced in the secondary coils 18a and 18b, as shown in FIG. The signal is output from the first detector 23a.

Also, for the second lens 10b, a voltage value corresponding to the movement of the lens can be obtained from the second detector 23b by the same operation as described above. As shown, the sleeve 14b (center position) is connected to the secondary coils 18c and 18c.
At the transition point of the winding d, the positive and negative voltages cancel each other, and the induced voltage becomes 0V. In this manner, the moving positions of the first lens 10a and the second lens 10b are detected by the output voltage of the differential transformer that changes with the movement of the sleeves 14a and 14b. Generally, it is high, so that the lens position can be detected with high accuracy.

In the above embodiment, since the primary coil 17 constituting the differential coil is constituted by a single winding, it is not necessary to separately provide the primary coil 17 and the circuit configuration is simplified. There is an advantage. In the above embodiment, the first and second lenses 10a and 10b are about 20 m.
Although the case of moving over the range of about m has been described, this detection range has a limitation that the length of each sleeve 14 is half the length of the secondary coil 18 for each. The length can be increased by increasing the lengths of the guide 13a and the sleeves 14a and 14b.

The first and second lenses 10a, 10a,
10b can be two lenses moved for performing focus control such as inner focus control and auto focus control and zoom control, and the number of lenses for position detection can be two or more. is there. For example, in a camera composed of two group lenses, the positions of the front lens and the rear lens can be detected. In a camera composed of four group lenses, the present invention can be applied to the lens shown in FIG. it can.

In FIG. 7, an objective lens 25, a zoom (magnification) lens 26 for performing zoom control, and a correction lens 2 are shown.
7, and a focus (inner) lens 28 are provided, and the objective lens 25 is supported by an outer cylinder 29. On the other hand, the zoom lens 26, the correction lens 27, and the focus lens 28 are slidable by a differential coil guide 32 and a guide 33 provided with the primary coil 17 and the secondary coil 18 via sleeves 31a, 31b, 31c. Supported. A cam cylinder 34 is disposed inside the outer cylinder 29, and a cam 35 attached to the sleeve 31a is mounted on the cam cylinder 34.
The cam 36 attached to 1b is engaged.

According to this detailed example, the rotation of the cam barrel 34 causes the zoom lens 26 to move along the illustrated locus 100, the correction lens 27 to move along the locus 101, and the focus lens 28 to move along the locus 102 at an infinite distance. Will be moving. Therefore, the position of the zoom lens 26 moved on the movement locus is determined by the position of the sleeve 31a and the position of the differential coil guide 32.
And the position of the focus lens 28 is
1c and the differential coil guide 32.

[0018]

As described above, according to the present invention,
A guide for lens movement in which a primary coil and a secondary coil having a double configuration as a differential coil are wound in the lens movement direction,
A metal support sleeve slidably disposed on the outer periphery of the guide, and a device for detecting a lens position based on an output value of a differential coil when the support sleeve moves. A plurality of differential coils are provided in the lens movement direction, and a plurality of support sleeves are provided so that a plurality of lens positions can be detected. There is an advantage that the position can be easily detected simply by providing the sleeve, and it is not necessary to provide a space for detecting the lens position. Therefore, the lens barrel can be formed small, and it is possible to reduce the size of the camera and simplify the configuration when detecting a plurality of lens positions.

Further, by forming the primary coil of the differential coil with a single winding, there is an advantage that the coil can be easily formed and the circuit configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a lens position detecting device of a camera according to an embodiment of the present invention, wherein FIG. 1 (a) is a side view and FIG. 1 (b) is a front view.

FIG. 2 is an enlarged partial cross-sectional view of the differential coil guide shown in FIG.

FIG. 3 is a cross-sectional view showing a detailed configuration of a differential coil guide and a support sleeve of the embodiment.

FIG. 4 is a diagram showing a circuit configuration for detecting a lens position in the embodiment.

FIG. 5 is a diagram showing voltage waveforms at a primary coil and a secondary coil.

FIG. 6 is a graph illustrating an example of a voltage value obtained by the configuration of the differential coil guide and the support sleeve according to the embodiment.

FIG. 7 is a sectional view of the inside of a lens barrel showing an example of a specific configuration of the embodiment.

FIG. 8 is a configuration diagram illustrating an example of a conventional lens position detection device.

[Explanation of symbols]

1 ... lens, 2, 12a, 12b ... lens frame, 3a, 3b, 13b, 13c, 33 ... guide,
10a: first lens, 10b: second lens, 1
3a, 32 ... differential coil guides, 14a, 14b,
31a, 31c ... support sleeve, 17 ... primary coil, 18a, 18b, 18c, 18d ... secondary coil, 23a ... first detector, 23b ... second detector.

Claims (2)

(57) [Claims] [Claim 1] and a guide to guide the back-and-forth movement of the lenses,
Wound in the lens movement direction of this guide, and double weight
Differential consisting of primary coil and secondary coil arranged
A coil is the outer circumference slidably disposed in the differential coil, and a metallic support sleeve for supporting the lenses, the lens position by the output value of the differential coil when the support sleeve moves A lens position detecting device for detecting, wherein a plurality of differential coils are provided on the guide in a lens moving direction, and a plurality of support sleeves are provided corresponding to the differential coils to detect a plurality of lens positions. A camera lens position detecting device characterized in that: 2. The camera lens position detecting device according to claim 1, wherein a primary coil of said plurality of differential coils is formed by a single winding.