JPH0524486B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lens barrel drive device that automatically performs focus alignment based on an output signal from a focus detection means.

[Conventional technology]

Conventionally, lens barrel drive devices for cameras of this type are configured to drive and control the lens barrel by lens barrel drive control means that is energized by an output signal from a focus detection circuit.

[Problem that the invention seeks to solve]

As described above, in the lens barrel drive device in which the lens barrel is driven and controlled by the drive control means based on the output signal of the focus detection circuit, the focus detection circuit is used to detect objects whose focus cannot be detected or to detect the focus. The drawback is that if it takes a long time, you may miss the chance to take a picture.

In particular, in the case of automatic focusing devices for single-lens reflex cameras, it is recommended to use a TTL-type focus detection circuit using a passive light-receiving element such as a CCD line sensor due to lens exchange, operation, distance, etc. When measuring a horizontal pattern, a subject with low contrast, a low-luminance subject, etc., the above-mentioned drawbacks tend to occur.

For example, if you are filming a baseball game,
During the game, you are photographing various subjects such as first base, pitcher, fielders, etc., and at a certain moment, when the runner goes around third base and heads towards home plate, you try to photograph the runner rushing into home plate, but the runner is not at home plate. Since there is no subject, the focus detection circuit cannot perform a focusing operation.

Conventionally, in JP-A No. 53-96828, when the focus lens is driven based on the output signal of the focus detection means, the focus lens is moved to the manually set lens position by switching a switch. It is proposed to forcefully move the A similar proposal was also made in Japanese Patent Application Laid-open No. 128505/1983.

However, in the conventional proposals, the position of the focus lens is regarded as absolute value information, so although it is theoretically possible to move the focus lens to the lens position set manually, it is not possible to accurately and instantaneously move the focus lens. It is difficult to return the lens to a preset lens position, and in particular, when the depth of field is narrow due to the aperture value and focal length settings, there may be cases where it is not possible to obtain focus after returning the lens.

[Means for solving the problem] The present invention generates a pulse signal every time a lens barrel for focus adjustment moves by a predetermined amount, detects the amount of movement of the lens barrel as a relative value, and performs the first operation. The movement position storage means is set to a preset value based on the operation of the means, and the subsequent movement position of the lens barrel is determined as the movement direction and movement amount based on the pulse signal and the output of the movement direction determining means. and prohibiting the lens barrel driving operation by the output signal of the focus detection means based on the operation of the second operation means, and moving the lens barrel until the value reaches the preset value in the movement position storage means. Accordingly, the present invention is characterized by a lens barrel driving device that can accurately and instantaneously move the lens barrel to the position at which the first operating means was operated. As a result, when recording a baseball game as exemplified above, if the first operating means is operated while focusing on the batter standing at home plate in advance, other subjects can be controlled by the focus detection means. If the runner goes around third base while shooting based on the output signal, the second base
By operating the operating means, it is possible to keep aiming at the runner while focusing on home plate, and release the ball at a decisive moment.

〔Example〕

The invention will now be described with reference to illustrative embodiments. FIG. 1 is a diagram showing a basic embodiment of the present invention.
1 is an imaging optical system and a lens barrel that supports it; 2 is a drive control circuit that includes a drive member and its control circuit for extending or retracting the lens barrel to perform focusing; and 3 is for performing distance measurement. A distance measuring optical system that exchanges the necessary optical system and the input of the optical system into an electrical signal, and 4 a defocus that detects the difference between the current lens barrel position and the true focus position from the electrical output of the distance measuring optical system. These constitute an automatic focusing system. This can be constructed using various types of circuits that are conventionally known. 5 is a position detection circuit for detecting the position of the lens barrel; 6 is a storage circuit for detecting the output of the position detection circuit; 7 is storage command means for storing the output of the position detection circuit in the storage circuit; These circuits constitute a lens barrel position storage system. Reference numeral 8 denotes a difference detection circuit for detecting the difference between the position detection circuit 5 and the storage circuit 6.

The difference detection circuit 8 that detects the difference between the outputs of the position detection circuit 5 and the storage circuit 6 in the above-mentioned lens barrel position storage system and the output of the defocus amount detection circuit 4 in the above-mentioned automatic focusing system are selected. A selection circuit 9 for transmitting information to the cylinder drive control circuit 2, and selection command means 10 for commanding selection to the selection circuit 9 are provided.

The storage command means 7 is preferably a storage switch in the form of a push button switch, and the selection command means 10 is a home position switch in the form of a push button switch which selects the output of the difference detection means 8 when pressed. good.

The operation of the above device is as follows.

Focus start button (not shown) (for normal single-lens reflex cameras, the first shutter release button
The differential focus of the subject passing through the photographic lens is calculated by the differential focus amount detection circuit 4 via the distance measuring optical system 3. Based on this amount of defocus, the lens barrel drive control circuit 2 operates to drive the lens to the in-focus position. The lens barrel may be provided with a position detection circuit, and the output of this detection circuit may be fed back to the drive control circuit 2 to control the lens barrel position, but in the illustrated example, the signal from the ranging optical system is simplified. Focusing is performed using open-loop control. When the storage command means 7 (memory switch) is operated, the lens barrel position information is stored in the storage circuit 6. As you can easily see,
This memory mechanism has nothing to do with automatic focusing, so even if the focus is manually adjusted, it will remain in a position unrelated to focusing (e.g. at infinity, hyperfocal distance, etc.). It doesn't matter if you are in a state where you are.

Using this stored position information and after automatically or manually moving the lens barrel to various framing points, when the selection command means 10 (home position switch) is operated, the lens drive control circuit 2 is immediately driven to the position where the memory switch was previously pressed and then stopped so that this error becomes 0 according to the difference between the stored lens position and the current lens position.

In the automatic focusing system of a typical TTL single-lens reflex camera, the distance measurement result is calculated as the amount of defocus, so the control of the lens barrel is also controlled according to the amount of defocus, that is, from the current lens barrel position to the in-focus position. Control is performed based on the difference in lens barrel position. Therefore, the lens barrel position signal does not have a complicated absolute position signal,
It is often determined by generating and counting a simple pulse train based on the unit of the defocus amount. Therefore, in the case of such a system, an absolute position signal can be constructed by installing a counter in the position detection circuit and maintaining the power supply, but generally the system power supply is turned on and off frequently. If the configuration is left as is, problems will occur. A specific embodiment of the present invention that takes measures for this purpose is shown in FIG.

This is an UP/DOWN counter that retains memory regardless of whether the entire power is turned on or off, or
A non-volatile memory that saves the UP/DOWN counter data when the power is turned off, and a UP/DOWN counter that preloads the value of the non-volatile memory when the power is turned on.
It is equipped with a DOWN counter.

In the system shown in FIG. 2, the automatic focusing system includes a lens barrel 1, a lens barrel drive control circuit 2, a distance measuring optical system 3, and a defocus amount detection circuit 4, similar to that shown in FIG. In this example, the direction in which the focus point is located is indicated. That is, the defocus amount detection circuit 4 is configured to output two types of data: forward or backward, and in-focus or out-of-focus. , controls the forward, reverse, and stop of the lens barrel according to the output signal.

The lens barrel position detection means is constituted by a relative position pulse generator 5', and the memory means is constituted by an UP/DOWN counter 6', which is operated by a command from a memory command means (memory switch) 7. this
The UP/DOWN counter 6' is reset when the memory switch 7 is pressed, and thereafter, each time the automatic focusing system operates, it counts up when moving forward and counts down when moving backward. 10 is a selection command means (home position switch), and when this home position switch is pressed, a positive value is given if the lens barrel is moving forward compared to when the memory switch was pressed, and a negative value is given if it is backward. value remains. Therefore, by inverting the sign bit of the UP/DOWN counter and driving the counter in that direction until it reaches φ, it is possible to return to the position where the memory switch was pressed.

[Effects of the Invention] As explained above, the present invention replaces the movement of the lens barrel with a pulse signal, detects it as relative position information, and moves the lens barrel at the position desired to be stored based on the operation of the first operating means. Since the position storage means is set to a preset value and the subsequent movement position of the lens barrel is stored based on the pulse signal and the output of the movement direction determination means, When returning the lens barrel to the previously memorized position,
It is only necessary to move the lens barrel until the movement position storage means reaches the preset value, and the front of the lens barrel can be moved to the stored position instantaneously and accurately. In addition, the movement of the lens barrel can be detected by simply generating a pulse signal every time the lens barrel moves by a predetermined amount, and it is not necessary to detect the deviation of the lens barrel from the reference position as in the past, or to detect complicated components such as potentiometers and encoders. Not only is there no need to use a mechanism, but the movement of the lens barrel can be detected in detail and returned to the memorized position extremely accurately at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a basic embodiment of the invention, and FIG. 2 is a block diagram showing a specific embodiment of the invention. 1... lens barrel, 2... lens barrel drive control circuit, 3...
... Distance measuring optical system, 4... Defocus amount detection circuit,
5...position detection circuit, 6...memory circuit. 7...Storage instruction means, 8...Difference detection circuit, 9...Selection circuit, 10...Selection instruction means.

Claims (1)

[Scope of Claims] 1. A lens barrel drive device that operates a lens barrel drive means based on an output signal of a focus detection means to move a lens barrel and automatically perform focus alignment, comprising: a movement amount detection means that generates a pulse signal for each movement; a movement direction determination means that determines the movement direction of the lens barrel; a first operation means; Based on the outputs of the movement amount detection means and the movement direction determination means, the movement position of the lens barrel after the operation of the first operation means is determined from the time when the first operation means was operated. a second operation means; and based on the operation of the second operation means, prohibiting the operation of the lens barrel drive means based on the output signal of the focus detection means. A lens barrel driving device, further comprising a control means for driving the lens barrel driving means until the value reaches the preset value in the movement position storage means.