JPS5986016A - Automatic focusing adjusting device - Google Patents

Abstract

PURPOSE:To prevent erroneous range finding by using an ultrasonic-wave motor as the driving source of an optical system which adjusts a body to a proper focusing position and operating the ultrasonic-wave motor mutually different in time zone. CONSTITUTION:When a power source is turned on, a timing control circuit 21 operates an oscillation circuit 16 and a transmitter and receiver 11 functions as a transmitter to transmit ultrasonic pulses for distance measurement to the body. Then, the circuit 21 operates a receiving circuit 17 to receive reflected pulses by the transmitter and receiver 11. The circuit 21 put a range finder circuit 18 in clocking operation to hold a final value. A signal indicating the position of a focusing lens 12 is supplied from a position sensor 14 to a data processing circuit 19 to generate a defocusing signal. The circuit 21 drives the ultrasonic wave motor 15 through a motor driving circuit 20 a maximum distance measurement time later. Consequently, the lens 13 is shifted to the focusing position and the defocusing signal decreases.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an automatic focusing device, and more particularly, to an automatic focusing device that transmits an ultrasonic signal and receives the reflected wave signal to determine the proper focusing position of an optical system with respect to an object. The present invention relates to an automatic focus adjustment device.

(Prior Art) It is well known that various active automatic focusing devices using ultrasonic waves as described above have already been proposed, and have been implemented in some cameras and the like.

Incidentally, although this is not limited to active automatic focusing devices using ultrasonic waves, general automatic focusing devices often use a motor as a driving source for the lens. In that case, the problem is often small size and high performance (high output).
This means that the lens device inevitably becomes significantly larger by incorporating the motor.

To address this problem, some attempts have been made to assemble a motor directly using a lens barrel, but there are still many technical difficulties and it is difficult to put it into practical use. The current situation is that this has not been achieved yet.

On the other hand, in recent years, something called a supersonant wave motor has been invented, which solves the above-mentioned problems.

An ultrasonic motor includes a fixed body and a movable body, and at least one of the fixed body and the movable body includes at least one vibrator driven by a plurality of electrostrictive elements, and the ultrasonic motor includes at least one vibrator driven by a plurality of electrostrictive elements. The extraction lead is connected to the driving surface 1 source, and the fixed body and the movable body are pressed against each other at at least one point on the surface of the vibrator in order to transmit torque, and the ultrasonic electric energy applied to the electrostrictive element is mechanically applied. It is a monitoring device that converts the mechanical vibration energy into unidirectional motion of a moving object.
This is disclosed in Japanese Patent No.-29192 and the like.

In particular, surface acoustic waves are used as mechanical vibration energy, and the moving body is frictionally driven by the elastic waves, and at that time,
An ultrasonic motor configured to generate a standing wave by the vibration of at least one electrostrictive element will be described.

Figure 1 shows the driving principle of the motor, where 1 is a moving object and 2 is a moving object.
Let be an elastic oscillator. The X-axis indicates the traveling direction of surface waves generated on the surface of the vibrator 2. When vibration is applied to the electrostrictive element of the 2-elastic vibrator, an elastic wave is generated on the surface and propagates on the surface of the vibrator. go. This elastic wave is a surface wave with longitudinal waves and transverse waves, and the motion of the mass point oscillates in an elliptical orbit.

Focusing on the mass point A, it is performing a circular motion with a vertical vibration lJu and a lateral vibration width W, and if the direction of travel of the surface wave is the +X direction, the elliptical motion rotates counterclockwise. This surface wave has vertices A, A', etc. for each wavelength, and its apex velocity is only the X component, V==2πfu (however, f
is the frequency of vibration). When the surface of the movable body 1 is brought into pressure contact with the surface of the vibrator 20, the surface of the movable body becomes a vertex.

Since the movable body 1 contacts only A', the movable body 1 is driven in the direction of the arrow N due to the frictional force between the movable body 1 and the vibrator 2.

The moving speed of the moving body 1 in the direction of arrow N is proportional to the frequency f. Furthermore, since frictional drive is performed by pressurized contact, it depends not only on the vertical oscillation width U but also on the lateral oscillation width W. That is, the moving speed of the moving body 1 is proportional to the size of the elliptical motion, and the larger the elliptical motion is, the faster the speed is. Therefore, the speed of the moving body is proportional to the voltage applied to the electrostrictive element.

FIG. 2 is a diagram illustrating the principle of generating surface waves in the elastic vibrator 2 shown in FIG. 1. 3a and 3b are attached to the elastic vibrator 2 at intervals such that elastic waves can be obtained most efficiently from the resonance frequency of the elastic vibrator 2, for example, P.
If it is a lightning/distortion element such as ZT, 3a is line A, 3b is line B
It is connected to the. 4 is the power supply for driving the motor and supplies the voltage υ, V − Vosinωt, and as is clear from the figure, ↓ MA A has V =: Vo
A voltage of sin oJt is applied. aB has a 90° phase shifter 5 V = Voein (ωt-1:2)
voltage is applied.

+ and - are switched depending on the moving direction of the moving body. That is, when the phase is shifted by +90° by the 90° phase shifter 5, and -90°
The moving direction of the moving body differs depending on the case where the phase is shifted.

(a) ~) shows the vibration state of the vibrator (elastic body) 2 according to time, (a) is 1 = ,, (b) is t = 'l
a+''o>, (c) is t knee 10~, and ni) is t- + t state ω ω .

The elastic wave propagates in the right direction, but any mass point on the drive surface of the vibrator 2 performs an elliptical motion in the counterclockwise direction.

Therefore, the moving body (not shown) that is pressed against the drive surface moves to the left.

To apply such an ultrasonic motor to a lens HA job, for example, the above-mentioned pendulum 2 is attached to a part of the fixed lens barrel, and the movable lens barrel holding the focusing lens is attached to the above-mentioned moving body 1. It is possible to construct an ultrasonic motor by directly using the lens barrel by forming a part of the lens barrel in pressure contact with the surface of the vibrator 2, or vice versa. This makes it possible to solve the problems mentioned above. In this case, the movable barrel may be moved relative to the fixed lens barrel by a rotary drive using a well-known helicoid mechanism or a cam groove, or alternatively, the movable barrel may be moved with respect to the fixed lens barrel. It may also be obtained by N-line driving along a straight guide.

By the way, when such an ultrasonic motor is used as a lens drive source in the above-mentioned automatic heat point adjustment device using ultrasonic waves, the following problems arise. That is, it is
If the receiving circuit that receives reflected ultrasonic signals from an object and the aforementioned ultrasonic motor are operated at the same time, the receiving circuit will receive the ultrasonic signals generated by the operation of the ultrasonic motor, causing an error. The problem is that it causes distance measurement. This is a serious concern, especially when the ultrasonic signals generated during operation of the ultrasonic motor are included in the frequency band of signals that can be received by the receiving circuit. Considering the performance aspects of both the ultrasonic motor and the ultrasonic motor, it is technically difficult to clearly differentiate the frequency band of the ultrasonic signal handled between the two, and therefore, the above-mentioned problem almost inevitably occurs. I will have to do it.

(Purpose) The present invention was made in view of the above-mentioned circumstances, and is an active automatic focusing device using ultrasonic waves.
By solving the above-mentioned problems that arise when using an ultrasonic motor as a lens and drive source, accurate distance measurement can be performed without being affected by the ultrasonic signals emitted by the ultrasonic motor. It is an object of the present invention to provide an active automatic focusing device A using ultrasonic waves, which is advantageous in that the load is averaged out without being concentrated all at once, and therefore only requires a small-capacity 'α source.

(Example) Hereinafter, a preferred embodiment of the present invention will be described in Section 3.4.5.
This will be explained with reference to the figures.

First of all, referring to FIG. 3, this figure shows a Q example of the present invention, in which 11 is an ultrasonic pulse generator/receiver for distance measurement;
2 is a horn for increasing the directivity of the ultrasonic transmitter/receiver 11; 16 is a focusing lens movable along the optical axis; 14 is a position sensor for detecting the position of the focusing lens 13; Reference numeral 15 denotes the aforementioned ultrasonic motor as a lens driving source, which is provided so as to be able to move the lens 13 along the optical axis in a manner as if it were previously tilted up. 16 is a transmitter/receiver 11 and a transmitting circuit for transmitting ultrasonic pulses; 17 is a receiving circuit for receiving reflected ultrasonic pulses from an object through the transmitter/receiver 11; 1B is an ultrasonic pulse for distance measurement. A distance measuring circuit 19 includes, for example, a pulse counter, etc., to detect the distance to an object by measuring the time from transmission to reception of the distance measuring circuit 18 and the position sensor 14. a data processing circuit that inputs lens position information and outputs a focus control signal based on the information;
0 is a motor drive circuit that controls the ultrasonic morph 15 based on the focus control signal from the data processing circuit 19, and 21 is a timing control circuit that controls the operation timing of each circuit shown by 16 to 20. Here, the data processing circuit 20, motor drive circuit 21, and ultrasonic motor 15 constitute a heating point adjusting means for the lens 15. Furthermore, Fig. 4 is a timing chart when the device of this embodiment is operated in servo focus mode, and Fig. 5 is a timing chart when it is operated in one-shot focus mode. be.

First, the operation in servo focus mode will be explained based on FIGS. 3 and 4. Servo focus mode is a focusing mode in which the focusing lens is continuously controlled to always follow changes in the distance to the object, and is always in focus even on moving objects. Suitable for cine cameras and video cameras.

When the power of this device is turned on by operating a switch (not shown), the timing control circuit 21 switches to the transmitting circuit 1.
6 is activated to cause the transmitter/receiver 11 to function as a transmitter and transmit distance measuring ultrasonic pulses toward an object as shown in FIG. 4a. The transmission period of this pulse is, for example, approximately 3.3
It is about m5eQ, and the pulse itself is 40~1Q Q KH
The signal is modulated to about 2.0 and is used to distinguish between external noise and transmitted wave pulses. After transmitting the outgoing wave pulse, the timing control circuit 21 activates the receiving circuit 17, causing the emitter/receiver 11 to function as a receiver and receive the reflected wave pulse from the object. The received wave pulse is shown in Figure 4.

At this time, the time delay between the transmission of the ultrasonic pulse and the receiver is proportional to the distance to the object. The timing control circuit 21 converts this τ to R as shown in FIG.
1 o'clock and hold the final value. On the other hand, a signal indicating the position of the focusing lens 13 is applied from the position sensor 14 to the data processing circuit 19 which receives the above-mentioned hold value, that is, the distance measurement signal, and here the distance measurement signal and the lens position are combined. After the difference, that is, the defocus signal (shown at θ in FIG. 4) is calculated, the timing control circuit 21 calculates the maximum distance measurement time τMkK.
After waiting (corresponding to the longest measured distance), the motor drive circuit 20 is activated. τ in Figure 4d. , indicates the time period in which the ultrasonic motor 15 is driven. During this period, as the lens position changes toward the in-focus position, the defocus signal decreases as shown in FIG. 4 and 8. The timing control circuit 21 operates the motor drive circuit 20 for a certain period of time (τ.N) to drive the motor 15 once, and then
As shown in FIG. d, the motor 15 is stopped, and then the transmission circuit 16 is activated again to emit ultrasonic pulses for distance measurement. Here, the air flow is about BOmsec, and τ.

, 4 is also set around +)QmsθC. After that, by repeating this cycle, it becomes Zapo Focus mode. In addition, in order to smoothly decelerate the lens 13 as it approaches the merging point, a defocus signal (θ
) by the magnitude of τ. , may be changed to control the speed of the motor 15. Further, the timing for driving the motor 15 may be any time after the reception signal is generated without waiting for τMAX.

Next, based on Figures 3 and 5, one-shot focus
The operation in this mode will be explained. The one-shot focus mode is a mode in which distance measurement and lens control are performed only once based on a single trigger, and is suitable for, for example, a still camera.

When a switch (not shown) is operated, the timing control circuit 21 activates the transmitting circuit 16 to transmit an ultrasonic pulse for distance measurement as shown in FIG. 5a, and then activates the receiving circuit 17. As shown in Figure 5, the reflected wave pulse is received. During this time, the timing control circuit 21 causes the distance measuring circuit 18 to detect the time delay τ as shown in FIG. 5C. The hold output is then applied to the data processing circuit 19 together with a signal indicating the current position of the lens 13 from the position sensor 14 to form a defocus signal (FIG. 50). Thereafter, the motor and drive circuit 20 are operated to drive the ultrasonic motor 15 until this defocus signal becomes zero.

The timing control circuit 21 includes, for example, a reference clock oscillator, a counter, a logic circuit, etc., and is configured to apply pulses or signals that determine the above-mentioned timings to each circuit.

(Effects) As explained above, according to the present invention, by shifting the time period of receiving the reflected wave from the object of the ultrasonic pulse for distance measurement during distance measurement and the time period of driving the ultrasonic motor, This has the effect of reliably preventing the receiving circuit from receiving ultrasonic pulses generated by the ultrasonic motor and erroneously measuring distance. That is, it is preferable that the frequency of the pulses for the ultrasonic motor and the frequency of the pulses for distance measurement are both about 40 to 1QQKHz, and even if the frequencies are changed within this range, high frequency distortion and distortion will occur on the low frequency side. However, the present invention can reliably prevent such inconveniences.

Note that when both frequencies are made the same, the same oscillation circuit and drive circuit can be shared in time division, which is advantageous in terms of cost and space. Moreover, since both of them are operated in a time-sharing manner, a large load is not applied to the power supply at once and is averaged out, which has the advantage of reducing the capacity of the power supply.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of the ultrasonic motor, Fig. 2 is also an explanatory diagram of the driving of the ultrasonic motor, Fig. 3 is a block diagram showing one embodiment of the present invention, and Fig. 4 is the present embodiment. A timing chart showing the operation of IFb under the mode consisting of the following: - Figure 5 is a timing chart showing the operation under the other modes of the example. 13...Optical system (focusing lens) 11
... Ultrasonic pulse generator/receiver for distance measurement 16 ... Transmission circuit 17 ... Receiving circuit 1B ... Distance measurement circuit

Claims (1)

[Claims] a transmitting circuit for transmitting an ultrasonic signal; a receiving circuit for receiving the ultrasonic signal reflected by an object after being transmitted by the transmitting circuit; and a receiving circuit for receiving the ultrasonic signal reflected by an object based on the output of the receiving circuit. A distance measuring circuit that outputs a distance-related signal, an optical system that adjusts the optical system to a proper focusing position for the object based on the output of the distance measuring circuit, and a focus adjustment including an ultrasonic motor as a driving source. and a control circuit for controlling the receiving circuit and the ultrasonic motor so as to operate them at mutually consistent time periods.