JPS6165214A - Camera - Google Patents

Abstract

PURPOSE:To perform high-resolution control over the movement extent of a photographic lens and the quantity of a shift in image plane by determining the movement extent of the photographic lens on the basis of the wave number of a high frequency voltage inputted to a surface wave motor for the driving of the photographic lens. CONSTITUTION:The movement extent of the photographic lens 6 is expressed as the angle of rotation of an interlocking motor 8, and its angle of rotation is determined on the basis of the wave number of the high frequency voltage inputted to the surface wave motor 7. An oscillator 20 as a source for the high frequency voltage for driving the photographic lens 6 is used and the number of pulse signals used for the driving of the photographic lens 6 is counted by a focus control circuit 15 to detect the actual movement extent of the photographic lens 6 accurately. Thus, the oscillator 20 for driving the surface wave motor 7 is used, so the movement extent of the lens is calculated accurately. Consequently, the movement extent of the photographic lens and the quantity of deviation in image plane are controlled with high resolution.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) Is the present invention a photographic lens? This relates to a camera that uses an ultrasonic motor to drive it.

(Background of the Invention) Conventionally, there has been a focus detection device disclosed in Japanese Patent Application Laid-Open No. 54-11101, which measures the transmitted light of a photographic lens and detects the amount of sea level deviation between a predetermined focal plane of the photographic lens, such as a film plane, and an actual object imaging plane. -15
It is disclosed in Japanese Patent Application Laid-open No. 9259 or Japanese Patent Application Laid-open No. 104859/1983.

By using this method, it is possible to obtain an in-focus state by driving the photographing lens by an amount corresponding to the detected sea level shift t. That is, as shown in FIG. 3, the sea level deviation Δxk between the predetermined focal plane 2 of the photographic lens and the actual object imaging plane 3
Detects and shifts the photographing lens 1 by a predetermined lid Δd corresponding to this shifted lid ΔX? By driving, the object imaging plane 3 can be made to coincide with the predetermined focal plane 2. Note that when the detected sea level deviation amount ΔX is large, it cannot be detected as an accurate value. Therefore, the detection of the deviation area and the driving of the photographing lens l are repeatedly performed, and the photographing lens 17 is gradually This will bring the camera closer to the in-focus position.

On the other hand, autofocusable photographic lens barrels for reflex cameras have a motor inside the photographic lens barrel and a motor that decelerates the rotation of the motor in order to automatically focus the photographic lens of the photographic lens barrel. It has a built-in speed reducer that drives the photographic lens, and this motor rotates in response to the focus detection signal to drive the photographic lens. It has a structure that allows it to be driven.

Therefore, in order to drive the photographing lens by a predetermined amount Δd corresponding to the one-plane deviation ΔX, a pulse generator that generates a number of pulses corresponding to the amount of motor rotation, that is, the amount of movement of the photographing lens is provided in the reducer. Drive control is performed by detecting the pulse signal. Since the pulse signal generated from this pulse generator is for guiding the photographing lens 1 into focus, the amount of image plane deviation ΔX corresponding to the l pulse is t (for example, about 50 μm) which can be considered to be in focus. Must-have. Therefore, the movement 1 of the photographing lens also needs to be controlled at a resolution as high as the controllable precision of the pulse generator. Therefore, as a means to satisfy the low cost i/lever condition, the amount of movement of the photographing lens is detected by detecting the rotation of the pulse generator from a stage in the reducer that is not decelerated much (for example, the first stage of the gear train). The best method is to install it like this.

However, since a conventional auto-focusable photographic lens barrel incorporates a reduction gear, the overall size becomes large and efficiency decreases due to the reduction gear. Also,
Considering the efficiency of the motor and reducer, is it possible to shoot lenses with limited power sources (e.g. batteries)? There were many problems that needed to be solved, such as the impossibility of driving at high speeds.

In order to solve these problems, the present applicant proposed a method for fully driving the photographing lens using a motor that utilizes ultrasonic vibration (hereinafter referred to as a surface wave motor).
It was disclosed in Publication No. 111609. This surface wave motor is highly efficient, and has the advantage of being a high-torque, low-rotation type that allows the photographic lens to be driven at high speed without the need for a reduction gear. There has been little research into methods for accurately detecting the movement i- of the photographing lens in the lens barrel, and this has led to the problem that it is difficult to control the amount of lens movement and the amount of image plane deviation with high resolution. It arises.

(Object of the invention) Is the present invention a surface wave motor? It is an object of the present invention to provide a camera in which the amount of movement and the amount of surface deviation of the photographing lens can be controlled with high resolution in a camera configured to drive the photographing lens using the lens.

(Summary of the Invention) The present invention provides a camera configured to drive a photographic lens using a hexagonal wave motor, in which the amount of movement of the photographic lens is controlled by a high frequency voltage input to the surface wave motor to drive the photographic lens. The technical point is that the amount of movement of the photographing lens and the amount of image plane shift can be controlled with high resolution by making decisions based on the applied wave number.

(Example) Fig. 1 and Fig. 2 show an embodiment of the present invention, and Fig. 1 illustrates a case where an autofocusable photographing lens barrel 4 is attached to a camera body 5 having a focus detection structure a. Full figure shown, M
FIG. 2 shows a circuit diagram of a lens drive circuit for the photographing lens barrel 4. As shown in FIG. In FIG. 1, a photographing lens 6 in a photographing lens barrel 4 is driven in the direction of its original axis in conjunction with a rotor 8 which is pressed against an elastic body of a surface wave motor 7. The luminous flux from the subject passes through the photographing lens and reaches the semi-transparent mirror 11 of the camera body 5, and part of the luminous flux is reflected by the semi-transparent mirror 11 and passes through the pentaprism 12 to be guided to the eye of person i. It will be done.

Also, part of the light flux passes through the semi-transparent mirror 11, and a part of the light beam passes through the total reflection mirror 13.
, and is guided to the distance measuring photoelectric conversion section 14Vc. The output signal from this photoelectric converter 14 is a known focusing control circuit 1.
5, and this circuit 15 determines the driving direction of the photographing lens 6 and the amount Δd to be driven. The lens drive signal instructing the determined drive direction is expressed by a lens angle via terminals 9c and 9d'i, and its rotation angle is
It can be determined based on the wave number of the high frequency voltage input to the surface wave motor 7. That is, in the input high-frequency voltage, the number of waves applied to drive the photographing lens 6 is counted, and this is multiplied by the slip rate between the elastic body of the surface wave motor 7 and the rotor 8.
movement of t? You can ask for it. Here, slight errors may occur due to changes in the slip rate, etc., but even in that case, the focusing system that brings the photographic lens 6 into focus uses a feedback control system between distance measurement and driving. If configured, it is possible to obtain a highly accurate focusing state by repeating distance measurement and driving several times.

In this embodiment, a signal of the same frequency as the high-frequency voltage input to the surface wave motor before being amplified is divided in the lens drive circuit 9 and inputted to the focus control circuit 15 as a lens movement amount signal. are doing. In the focus control circuit 15, the lens drive signal ? until the lens movement amount signal corresponds to the amount to be driven Δd. It continues to be output to the lens drive circuit 9.

Then, when the driving is completed, the in-focus state is detected again, and if the in-focus state is not found, the above-mentioned operation is repeated until the in-focus state is achieved. The IJ mint circuit 10 is a device that functions like a limit switch to input this information to the focus control circuit 15 and reverse the driving direction of the photographic lens 6 when the photographic lens 6 reaches an infinite or close position. It is. Further, 16 is a known shutter, and F is a film surface.

Next, the lens drive circuit 9 will be fully explained using FIG. Note that symbols 9a to 9f representing input/output terminals are
The same symbol as in the figure is used.

The oscillator 20 outputs a high frequency signal that drives the surface wave motor 7, and the waveform shaper 29 and the analog switch 27. The signals are input to phase shifters 21 and 22, respectively. The phase shifter 21 outputs an AC signal with a phase lead of π/2 relative to the AC signal from the oscillator 20 and inputs it to the analog switch 23 . Further, the phase shifter 22 outputs an AC signal delayed by π/2 in phase with respect to the AC signal from the oscillator 20, and inputs it to the analog switch 24.

Now, let us consider a case where the driving direction of the photographic lens 6 is instructed from close range to infinity. At this time, input terminal 9cVc
The H level signal (hereinafter abbreviated as H1) is also input to the input terminal 9.
d contains an L level signal [hereafter.

] are input respectively. As a result, OR gate 28
outputs H1 and turns on the analog switch 27, so the AC signal output from the oscillator 20 is input to the amplifier 25. In addition, the analog switch 24 is turned on and the analog f-circuit 23 is turned off, so that the amplifier 26 receives an AC signal from the phase shifter 22 that is delayed by 1r/2 phase with respect to the AC signal input to the amplifier 25. be done. amplifier 2
5.26 are each supplied with the power supply voltage from the input terminal 9b, and have a phase difference of π/2? The two alternating current signals are amplified and output as motor drive voltages.

This motor drive voltage is supplied to the surface wave motor 7 via the resonance coil Li and the output terminals 9a and 9fi. Next, there is a case where the driving direction of the photographic lens 6 is instructed from infinity to the close-up direction. In this case, the input terminal 9dVcH1 is input to the input terminal 9c, and the surface wave One turf is driven. moreover,
When stopping the photographing lens 6, use the input terminal 9e.

9d, both analog switches 23, 24, and 27 are turned off, and the power supply to the surface wave motor is prohibited and stopped. Also, the waveform shaper 29 The alternating current signal output is shaped into a pulse signal, outputted, and input to the frequency divider 30.The signal for one pulse divided by the frequency divider 30 is determined by the amount of movement of the photographing lens 6 corresponding to the one pulse signal. The amount that can be considered to be in focus corresponds to the image shift amount ΔX.In this way,
The divider 30 divides the frequency of the pulse signal sound from the waveform shaper 29). The frequency-divided pulse signal X' is then transmitted to the focus control circuit 15 via the output terminal 98. The focus control circuit 15 transmits lens drive signals to the terminals 9c and 9d of the lens drive circuit 9, and at the same time starts counting the pulse signal The movement tTh is being calculated.

In addition, the divider 30 monitors the drive voltage supplied to the surface wave motor 7 via the gold pin 31, and is designed to detect changes in this drive voltage so that the frequency is constantly divided. ] A function is also provided to control the frequency division ratio so that the movement wJt of the photographing lens 6 of the pulse signal valve becomes an amount corresponding to the image plane deviation ijx that can be regarded as in-focus.

In the focusing control circuit 15 in the camera body 5, the photographing lens 6 is driven by an amount Δ based on the image plane shift ΔxVC of the subject image on the film F produced by the photoelectric conversion unit 14 for distance measurement.
Since d is calculated, it is calculated based on the lens movement f signal X' from the terminal 9 mentioned above, and the movement of the photographing lens 6 is calculated based on the above-mentioned lens movement f signal X' from the terminal 9. When the distance Δd and the distance Δd to be driven are compared and match, the stop signal for the photographing lens 6 is issued at the next point in time. It is input to terminals 9e and 9d of the lens drive circuit 9. Note that, depending on the difference in the taking lens barrel, the value of the amount Δd to be driven of the taking lens corresponding to the image plane deviation ΔX differs, so when the lens drive circuit 9 is disposed inside the camera body 5, The configuration may be such that the frequency division ratio of the frequency divider 30 can be changed depending on the photographic lens barrel.

Therefore, in the embodiment, the oscillator 20, which is a source of high frequency voltage that drives the photographing lens 6, is used, and the number of pulse signals that are taken from this oscillator 20 and contributes to driving the lens 6 is determined by the focus control circuit 15. By counting, the photographing lens 6 actually moves and the movement of the lens 6 is accurately detected.

In this way, in the embodiment, there is no need to provide a new companion detector 'a for detecting the amount of movement of the photographic lens 6, and since it is used for the oscillator 20 for driving the surface wave motor 7, There is an advantage that the lens movement t'tf# can be determined with good accuracy.

What does the camera of the present invention mean: a photographic lens barrel and a camera body? This is a general term, and it may be a single-lens reflex camera with an interchangeable lens barrel as in this embodiment, or a lens shutter camera with an integrated lens barrel.
It does not limit the type.

(Effects of the Invention) As described above, according to the present invention, the movement t of the photographic lens is determined based on the wave number of the high frequency voltage input to the surface wave motor that is applied to drive the photographic lens. Due to this, the amount of movement of the photographic lens and the deviation of the image plane! It becomes possible to control gold with high resolution.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of a camera system according to the present invention, and FIG. 2 is a circuit diagram of a lens driving circuit of the camera shown in FIG. FIG. 3 is an explanatory diagram showing the relationship between the amount of movement of the photographing lens and the amount of movement of the subject image. (Explanation of symbols of main parts) 4...Shi/Z lens barrel 5...Camera body 6...Photographing lens 7...Surface wave motor 9...Lens drive circuit 14...Photoelectric conversion unit 15... Focusing control circuit 29... Waveform shaper 30... Branching unit

Claims (1)

[Claims] In a camera configured to drive a photographic lens using a surface wave motor that utilizes ultrasonic vibrations, the amount of movement of the photographic lens is input to the surface wave motor and used to drive the photographic lens. A camera characterized by comprising a movement amount determination means that determines the amount of movement based on the wave number of a high-frequency voltage.