JPH0593841A - Device for detecting position of lens for camera - Google Patents

Abstract

PURPOSE:To eliminate the need of securing space for detecting the position of a lens and to miniaturize a camera. CONSTITUTION:This device is provided with a differential coil guide 13a for guiding a lens, which is obtained by winding a differential coil consisting of a primary coil and a secondary coil which are wound reversely to each other in a lens moving direction, and a supporting sleeve 14 for supporting the lens, which is made of metal and arranged on the outer periphery of the guide 13a so as to freely slide, and a voltage value induced to the secondary coil from the primary coil when the sleeve 14 is moved is fetched to detect the position of the lens. Therefore, the space is saved by using the conventional guiding guide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera lens position detecting device, and more particularly to a structure of a device for detecting the position of a lens which is moved during focus control, zoom control and the like.

[0002]

2. Description of the Related Art In a camera, the position of a lens to be moved is detected during focus control such as inner focus and auto focus, or zoom control. For this lens position detection, for example, a potentiometer, Various detection devices such as encoders, position detection switches, and resistors are used.

FIG. 6 shows an example of the lens position detecting device using a resistor. As shown in the drawing, the lens 1 is held by a lens frame 2 and the lens frame 2 is guided by the lens frame 2. Guided by 3a and 3b. Therefore,
When the lens frame 2 is driven by driving means (not shown), the lens 1 is moved in the left-right direction in the drawing 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 come into 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. 6 described above, the diameter of the lens barrel is increased by securing the space for disposing the resistor 4 and the brush 5. There was a problem that the camera could not be downsized. This also applies to other conventional detection devices such as potentiometers, encoders, and position detection switches.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a structure that does not require a space for detecting a lens position, and can reduce the size of a camera lens. It is to provide a position detection device.

[0006]

In order to achieve the above object, the present invention provides a guide in which a differential coil is wound in the lens movement direction and which guides the lens to move forward and backward, and slides on the outer circumference of the guide. And a support sleeve made of metal for freely supporting the lens, the lens position being detected by the output value of the differential coil when the support sleeve moves. The differential coil comprises a primary coil and a reverse winding, which constitute a differential transformer.
It is composed of two secondary coils.

[0007]

According to the above construction, the primary coil and the secondary coil forming the differential coil are formed inside the guide, for example, and the guide and the metal support sleeve form the differential transformer. Become. In the above differential coil,
By applying an AC voltage to the primary coil, an induced voltage is generated on the secondary coil side. When the support sleeve moves together with the lens by driving the lens, the voltage value induced in the secondary coil changes as the support sleeve moves. Therefore, the lens position is specified by measuring the voltage value of the secondary coil.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration of a lens position detecting device for a camera according to an embodiment. As shown in the figure, a lens 10 is held by a lens frame 12 made of resin. Guides 13a and 13b for guiding the front and rear (left and right in the figure) movement of the are provided. And this guide 13
Among them, in the embodiment, the differential coil is wound inside the guide 13a, and the guide (hereinafter referred to as the differential coil guide) 13a is attached to the lens frame 12 and the supporting sleeve (hereinafter simply referred to as the sleeve). Place 14 Therefore, the differential coil guide 13a and the sleeve 14 form a differential transformer.
4 is preferably formed of a non-ferrous metal such as copper, brass, or aluminum. Note that one guide 13b is directly penetrated through the lens frame 12 as in the conventional case (this guide 13b
May be provided with a differential coil).

FIG. 2 shows a detailed structure of the differential transformer, in which the shaft 16 is provided in the differential coil guide 13a.
The primary coil 17 is first wound around the shaft 16. Then, two secondary coils 18a and 18b are wound on the primary coil 17 so as to overlap each other, and the secondary coils 18a and 18b are wound so as to be opposite to each other. Therefore, when a current is passed through the primary coil 17, an induced current is generated in the secondary coils 18a and 18b, and voltages having opposite phase waveforms are generated in both coils 18a and 18b wound in opposite directions. Will be done. Since the metallic sleeve 14 is arranged in the actuating coil guide 13a, a voltage value that linearly changes due to the movement of the sleeve 14 can be obtained as shown in FIG. Such differential coil guide 13a and sleeve 14
The operating transformer constituted by can detect a moving range having substantially the same length as the sleeve 14.

FIG. 3 shows a circuit configuration for detecting the above lens position. In the figure, a drive circuit 21 is connected to an oscillator 20 for generating a sine wave, and the drive circuit 21 is connected to the drive circuit 21. The primary coil 17 is connected. In addition, the secondary coils 18a and 18b which are reversely wound with each other,
The preamplifier 22 is connected, and the preamplifier 22 is connected to a detector 23 including a low-pass filter and the like. Therefore, the driving circuit 21 supplies an AC voltage to the primary coil 17
AC voltage induced by the secondary coil 18 is output to the preamplifier 22, and the voltage amplified by the preamplifier 22 is extracted as a DC voltage by the detector 23.

The embodiment is constructed as described above, and is shown in FIG.
The operation will be described with reference to FIG. First, during operation of the camera, the oscillator 20 of FIG. 3 is driven, the AC voltage having the waveform shown in FIG. 4A is applied to the primary coil 17, and the lens 10 is at the base position (zero position). , The sleeve 14 supporting the lens 10 is placed at the position of the chain line 101, as shown in FIG. At this time, in the secondary coil 18, as shown in FIG. 4B, a voltage (negative voltage) having an antiphase waveform is induced,
Since the induction of the voltage having the in-phase waveform is suppressed, the output of the detector 23 becomes, for example, −2.5 V as shown in FIG. Then, when the lens 10 is driven forward, for example, by inner focus control or the like, the sleeve 14 moves accordingly, but due to the movement of the position of the sleeve 14, voltage induction of an antiphase waveform is gradually suppressed. Meanwhile, the voltage of the in-phase waveform is induced, and as shown in FIG.
As shown in, the output voltage of the detector 23 increases linearly. The sleeve 14 corresponds to the chain line 10 shown in FIG.
As shown in FIG. 4 (d), only the voltage of the in-phase waveform (positive voltage) is induced in the secondary coil 18 at the movement end position of the second lens 10, that is, the position of 20 mm. Then, a voltage of + 2.5V is output from the detector 23. In addition, the sleeve 14 (center position) is the secondary coil 1
When it is located at the turning point of windings 8a and 18b,
As shown in (c), the positive and negative phase voltages are canceled out, and the induced voltage is 0.
It becomes V.

In this way, the moving position of the lens 10 is detected by the output voltage of the differential transformer which changes according to the movement of the sleeve 14, but the sensitivity of this differential transformer is generally high, and therefore the lens position is high. Can also be detected with high accuracy.

In the above embodiment, the lens 10 is about 20 mm.
Although the case of moving within a range of about a certain degree has been described, in this detection range, the length of the sleeve 14 is equal to
Although it is limited to half the length of a, it can be increased by increasing the length of the differential coil guide 13a and the sleeve 14. Therefore, the present invention can be used not only for focus control such as inner focus control and auto focus control, but also for position detection of zoom control.

[0014]

As described above, according to the present invention,
A guide for lens movement, in which a differential coil is wound in the lens movement direction, and a metal support sleeve slidably arranged on the outer periphery of the guide are provided, and the differential coil when the support sleeve moves Since the lens position is detected by the output value of, the position can be detected only by providing the support sleeve on the lens frame part using the guide that has been conventionally arranged, and the space for detecting the lens position is opened. It has the advantage of not being necessary. Therefore, the lens barrel can be made small and the camera can be made compact.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a lens position detecting device for a camera according to an embodiment of the present invention, FIG. 1A is a side view, and FIG. 1B is a front view.

FIG. 2 is a cross-sectional view showing a detailed configuration of a differential coil guide and a support sleeve of the embodiment.

FIG. 3 is a diagram showing a circuit configuration for detecting a lens position in the embodiment.

FIG. 4 is a diagram showing voltage waveforms in a primary coil and a secondary coil.

FIG. 5 is a graph showing an example of voltage values obtained by the configurations of the differential coil guide and the support sleeve of the example.

FIG. 6 is a configuration diagram showing an example of a conventional lens position detection device.

[Explanation of symbols]

 1, 10 ... Lens, 2, 12 ... Lens frame, 3a, 3b, 13b ... Guide, 13a ... Differential coil guide, 14 ... Support sleeve, 17 ... Primary coil, 18a, 18b ... Secondary coil, 23 ... Detector .

Claims (1)

[Claims] 1. A differential coil is wound in a lens moving direction, and a guide for guiding the lens back and forth is provided, and a metal support sleeve slidably arranged on the outer periphery of the guide for supporting the lens. A lens position detecting device for a camera, which has a lens position detected by an output value of a differential coil when the support sleeve moves.