JP2556010Y2 - Camera auto focus device - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an automatic focusing device for a camera. More specifically, when a motor is controlled at a low speed when a taking lens approaches a target position, a battery voltage is reduced. The present invention relates to an automatic focus adjusting device for a camera in which the lower the motor speed, the shorter the low-speed control range of the motor and the shorter the time required for the taking lens to reach the target position.

[Conventional technology]

2. Description of the Related Art Conventionally, there has been known a method in which a photographing lens of a camera is driven to a target position by a motor, and as the photographing lens approaches the target position, the motor is gradually driven at a low speed.

FIG. 4 is a characteristic diagram showing a relationship between a lens moving amount and a motor driving speed for explaining such a motor driving method, and uses battery voltages of 4 V, 5 V, and 6 V as parameters.

In the figure, L1 is the first low-speed control range of the motor, L2
Is a second low-speed control range of the motor, and L3 is a target drive position of the photographing lens.

As is apparent from FIG. 4, the first low-speed control range
L1 and the second low-speed control range L2 are constant at any of the battery voltages 4V, 5V, and 6V. Therefore, the rotation speed of the motor decreases due to the decrease in the battery voltage, and it takes a long time for the photographing lens to reach the target position L3. That is, the focusing speed is low.

For example, Japanese Patent Laid-Open Publication No. 61-193439 (hereinafter, referred to as “1st Embodiment”) is configured to control the motor at a low speed as the photographing lens approaches the target position.
Japanese Patent Application Laid-Open Publication No. HEI 9-205 (1995) discloses an example in which three or more stages of low-speed control are performed.

That is, according to the technique disclosed in the first publication, the focus deviation detecting means detects a deviation of the photographing lens from the in-focus position with respect to the subject when the switching means is closed,
Based on the deviation, the focus determining unit determines whether or not the photographing lens is at the in-focus position. Based on the determination result, the camera moves the photographing lens by the driving unit. Is determined by the deviation area discriminating means, and the moving speed of the photographing lens by the lens driving means is focused on the photographing lens based on the discrimination result. The lens drive control means changes the speed to a plurality of stages of three or more stages in which the speed becomes lower as the position is in the deviation region closer to the position.

Japanese Patent Application Laid-Open No. S59-59980 discloses a configuration in which the motor is switched from high speed to low speed when the taking lens approaches the target position.
-26709 (hereinafter referred to as "second publication").

The second publication discloses a signal indicating a moving distance to a position where a photographing lens detected by a first detection unit is brought into a focus-matching state and a signal corresponding to a rotation speed of a motor output from a monitor unit. An input to the second detecting means, the second detecting means detects that the moving distance to the position at which the taking lens is brought into the focus matching state becomes equal to or less than a predetermined value, and outputs the outputs of the first detecting means and the monitor means to the second detecting means. The detection signal is input to the third detection means, the position at which the photographing lens is brought into the focus matching state is detected, and the output signal of the monitor means and the detection signal of the second detection means and the third detection means are output by the comparison means. A first comparison signal is output by comparing a first reference signal serving as a reference of the rotation speed of the motor, and when a detection signal is output from the second detection means, the output of the monitoring means and the first reference signal are compared with each other. Is compared with a different second reference signal A second comparison signal is output, a motor driving unit controls driving of the motor based on the first comparison signal so as to drive the photographing lens at high speed, and the motor control unit based on the second comparison signal. , The motor is controlled so that the photographing lens is driven at a low speed, and the motor is stopped by the motor control means in accordance with the output of the third detection means.

Further, in the case of Japanese Patent Application Laid-Open No. 58-223108 (hereinafter, referred to as "third publication"), when the taking lens approaches the focal point, the controller interrupts the energization of the motor so that the closer to the focal point. The focus adjustment is performed in a short time by shortening the energization time and decelerating the motor.

That is, the defocus amount ΔL output from the distance measuring unit
And a signal indicating the extension direction of the taking lens are input to the controller.
The amount of extension Δd of the photographing lens for defocusing is calculated based on L, and the amount of extension Δd of this photographing lens is calculated.
d is converted into digital data and output to an up / down counter.

Further, a signal for driving the motor is output from the controller to the drive circuit, and a pulse generated by the pulse generator is input to the up / down counter for each unit distance of movement of the photographing lens driven by the motor. . The up / down counter decrements the resetting amount Δd of the photographing lens which is reset each time a pulse generated from the pulse generator is input.

When the up / down counter becomes zero by this subtraction, that is, when the taking lens reaches the focal point, the controller controls the drive to stop the motor.

[Problems to be solved by the invention]

In the case of the first publication, since low-speed control of three or more stages is performed, not only the control becomes complicated, but also when the battery power is lowered, it takes a long time to reach an in-focus position.

Further, in the case of the second publication, since the switching control is merely performed from the high speed to the low speed, the focusing speed becomes slow as in the case of the first publication.

Further, also in the case of the third publication, the closer to the in-focus position,
It only shortens the energizing time to the motor.

That is, none of the first to third publications shows that the low-speed control range is changed with respect to the fluctuation of the battery voltage. As shown in FIG. Drive control. Therefore, as the battery voltage decreases, the rotation speed of the motor decreases,
There is a drawback that long-time useless low-speed control is performed and the focusing time is delayed.

The present invention has been made in view of the above circumstances, and its purpose is to shorten the time required for the photographing lens to reach the target focusing position even when the battery voltage is reduced, thereby achieving faster focusing adjustment. It is an object of the present invention to provide an automatic focusing device for a camera, which enables the automatic focusing.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a distance measuring means for measuring a distance from an exposure surface of a film to a subject,
A motor for driving the taking lens to a target position, lens motor driving means for controlling the driving of the motor, analog / digital converting means for converting the battery voltage into digital, and moving the taking lens toward the target position High speed driving of the lens motor driving means in the process,
A first low-speed drive that is slower than the high-speed drive and a second low-speed drive that is slower than the first low-speed drive are sequentially performed, and the digital information of the battery voltage output from the analog / digital conversion means and the distance measurement. Control means for changing a photographing lens moving range in which the photographing lens is moved by the first low-speed drive according to an output of the means, wherein the control means moves the photographing lens by the second low-speed drive The moving range of the photographing lens to be controlled is always constant, and the moving range of the photographing lens in the first low-speed driving is controlled so as to be smaller as the battery voltage is lower and to be larger as the battery voltage is higher. It was done.

[Action]

In the camera configured as described above, the photographic lens is moved to the target position by the motor based on the distance measurement result obtained by the distance measurement means, and the photographic lens is moved at a high speed first (hereinafter, the photographic lens movement range (hereinafter referred to as "the moving range"). In the "high-speed control range", the image pickup lens is driven at a high speed, but enters a photographic lens moving range (hereinafter, referred to as "first low-speed control range") in which the photographic lens is moved by the first low-speed drive close to the target position. And a photographic lens moving range (hereinafter referred to as “second driving speed”) in which the photographic lens is driven at a speed lower than the high-speed driving and the photographic lens is moved by a second low-speed driving approaching the target position.
In the "low-speed control range", drive control is performed at a speed even slower than the first low-speed drive.

The first low-speed control range is configured such that the battery voltage information obtained by digitizing the battery voltage by the analog / digital conversion means is input to the control means, and the control means changes the battery voltage information based on the battery voltage information.

The second low-speed control range is not changed regardless of the battery voltage information.

The control means changes the first low-speed control range (the number of pulses) to the motor driving means based on the battery voltage information,
For example, as the battery voltage decreases, the first low-speed control range is shortened so that the time required to reach the target position is not increased.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the camera according to the present invention.

In FIG. 1, reference numeral 1 denotes a central processing unit (hereinafter, referred to as “CPU”) as control means.

When the release button 2 of the CPU 1 is depressed one step, a release signal of the first release switch 2a is input to the CPU 1 and the CPU 1 causes the distance measuring means 3 to measure the distance. This distance measurement data is taken into the CPU1.

The CPU 1 calculates the moving amount (defocus amount) of the photographing lens 7 to the target position based on the distance measurement data.

By this calculation, the lens motor driving means 5
, Thereby moving the taking lens 7 toward the target position. The movement amount is measured by counting pulses output from the position detecting photointerrupter 8 by a counter (not shown) in the CPU 1 in accordance with the extension position of the photographing lens 7 by the motor 6.

Reference numeral 4 denotes an analog / digital converter for converting the voltage of a battery for supplying a voltage to the motor 6 and the like from analog to digital.
Digital conversion means (hereinafter referred to as "A / D conversion means")
The digital signal obtained by A / D conversion of the battery voltage by the A / D conversion means 4, that is, the battery voltage information is transmitted to the CPU 1.
To be sent to

The CPU 1 compares the count number calculated based on the battery voltage information with the first low-speed control range L1 (L1a, L1b, L1c,
..) Is counted whether or not the number of pulses output from the position detecting photointerrupter 8 matches.

FIG. 2 is a characteristic diagram showing the relationship between the amount of lens movement and the motor drive speed, and shows the case where the battery voltage is 4 V, 5 V, and 6 V as parameters.
The low-speed control range L2 indicates a second low-speed control range, and L3 indicates a target position.

Regarding the second low-speed control range L2, a count value is temporarily stored in a storage means (not shown) in the CPU 1 so as to always have a constant count number without depending on the battery voltage.

When the counter in the CPU 1 counts the pulses output from the position detecting photointerrupter 8 in the first low-speed control range L1 and measures the lens movement amount, CP
U1 issues a photometry command to the photometry means 11, and the photometry data measured by the photometry means 11 is sent into the CPU1.

The CPU 1 performs an exposure calculation based on the photometric data from the photometric means 11.

Further, when the release button 2 is pressed two steps, the second release switch 2b is turned on and a shutter start signal is output, and the CPU 1 opens and closes the shutter driving means 9 at the shutter speed determined by the exposure calculation. It is supposed to do.

When one frame of the film is exposed by the opening / closing drive of the shutter driving means 9, the CPU 1 controls the feeding driving means 10
Is driven to wind up one frame of the film.

The operation of the embodiment configured as described above will be described with reference to the flowchart shown in FIG.

First, in the "release first stage ON" of the flowchart, the operator presses the release button 2 by one stage, so that the first release switch 2a is turned on.
A release signal of the release switch 2a is sent to the CPU 1.

As a result, the processing shifts to the "distance measurement" processing in the flowchart, in which the CPU 1 sends a distance measurement command to the distance measurement means 3, and the distance measurement means 3 receiving the distance measurement instruction measures the distance from the exposure surface of the film to the object. Start distance measurement and send distance measurement data to CPU1.

The CPU 1 calculates the defocus amount of the distance measurement data by “Lens movement amount calculation (total photo interrupter count number)” in the flowchart, and replaces the defocus amount with the count number of the position detection photo interrupter 8. .

Next, the process proceeds to the process of “battery voltage A / D conversion” in the flowchart, where the battery voltage is converted into a digital value by the A / D converter 4 and digital battery voltage information is sent to the CPU 1. The process proceeds to the process of “calculation of count number of low-speed control range 1 from data”.

In this processing step, the CPU 1
The first low-speed control range shown in FIG. 2 from the battery voltage information
The count number of L1 (the number of pulses of the position detection photointerrupter 8) is calculated.

Here, the first low-speed control range L1 and the second low-speed control range L2 will be described with reference to FIG.

The first low-speed control range L1 is L1a at a battery voltage of 4V and L1a at a battery voltage of 5V.
The amount of movement of the photographic lens 7 is changed so that L1c at 1b and 6V, that is, the lower the battery voltage, the less the amount of movement of the photographic lens 7 in the first low-speed control range. This change in the moving amount actually changes the number of pulses to be counted by the position detecting photointerrupter 8.

Also, the second low-speed control range L2 is constant, as is clear from FIG. 2, since there is almost no variation with the battery voltage. The pulses in the second low-speed control range L2 are stored in the storage unit in the CPU 1.

Here, returning to the flowchart of FIG. 3 again, after calculating the number of counts to be counted by the position detecting photointerrupter 8 in the first low-speed control range L1 as described above, the “photometry” in the flowchart is performed. In the processing step, the CPU 1 gives a photometry command to the photometry means 11.

Thereby, the photometry means 11 performs photometry of the subject,
By sending the photometric data to the CPU 1, the CPU 1 performs an exposure calculation from the photometric data in a processing step of “exposure calculation” in the flowchart, and determines a shutter opening / closing speed and / or an aperture value.

Next, the process proceeds to the processing step of “release second stage ON” in the flowchart. When the release button 2 is depressed by two stages, the second release switch 2b is turned on, and when the shutter start signal is output to the CPU 1, the CPU 1 Controls the driving of the lens motor driving means 5.

Along with this, the motor 6 is driven by the lens motor driving means 5, and the photographing lens 7 starts moving toward the target position L3 in FIG.

With the movement of the photographing lens 7, the process proceeds to the processing step of “photo interrupter, count start” in the flowchart, and the position detecting photo interrupter 8 generates a pulse as the photographing lens 7 moves. This pulse starts counting by a counter in the CPU1.

Next, in the flowchart, “(total count number−
The processing step moves to "Count of low-speed control range count), and CPU 1 counts only the count obtained by subtracting the count of the first low-speed control range L1 and the second low-speed control range L2 from the count of pulses to the target position L3. Then, the processing shifts to the processing step of “starting low-speed control range 1” in the flowchart.

In this processing step, the CPU 1 recognizes that the motor 6 has reached the first low speed control range L, and instructs the lens motor driving means 5 to set the driving speed of the motor 6 to a predetermined constant speed (first low speed control range L). Speed). After this state, “low speed control range 1” in the flowchart is used.
When the counter in the CPU 1 counts up the count number of the first low-speed control range L1 in the “count number count”, the process shifts to the “start of low-speed control range 2” process in the flowchart.

In this processing step, after reducing the speed of the motor 5 to a drive speed even lower than the drive speed in the first low-speed control range L1, the counter in the CPU 1 next reads the second value stored in the storage means in the CPU 1. The counting of the low-speed control range L2 is started, and the taking lens 7 moves to the second low-speed control range L2.
Start moving.

Next, in the processing step of “counting the count of the low-speed control range 2 (constant count)” in the flowchart, the constant count of the second low-speed control range L2 stored in the storage means is counted up. The process proceeds to the “motor shunt” processing step in the flowchart.

In this processing step, the CPU 1 causes the lens motor driving means 5 to cut off the current supplied to the motor 6 and shunt both poles of the motor 6 to stop the rotation of the motor 6 suddenly. Accordingly, the taking lens 7 is moved to the target position shown in FIG.
It stops at L3, and at this time, a focused state is obtained for the subject.

Next, the process proceeds to the processing of “shutter control” in the flowchart, in which the CPU 1 controls the driving of the shutter driving means 9 and causes the shutter driving means 9 to open and close the shutter based on the shutter speed calculated by the exposure calculation. Expose to film.

When the exposure of the film is completed, the control moves to the process of “feed control” in the flowchart, and the CPU 1 controls the feed driving unit 10. As a result, a feed motor (not shown) is driven, and one frame of the exposed film is taken up.
Preparations for photographing the next one frame are made.

As described above, according to this embodiment, the battery voltage is digitally converted by the battery voltage A / D conversion means 4 and the battery voltage information is sent to the CPU 1 as the control means. When moving in the direction of the target position L3, the low-speed drive amount in the first low-speed control range L1,
The duration in the low-speed state is changed, for example, as the battery voltage is lower, the first low-speed control range is shortened. Therefore, the time required to reach the target position of the photographing lens 7 can be shortened. There is an advantage that can be as fast as possible.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention.

[Effect of the invention]

As described above in detail, according to the present invention, in the process of moving the photographing lens toward the target position, high-speed driving is performed on the lens motor driving unit, a first low-speed driving that is slower than the high-speed driving, and The second, slower than the first low-speed drive
And control means for sequentially changing the first low-speed control range in accordance with the digital information of the battery voltage output from the analog / digital conversion means and the output of the distance measuring means. The control means is configured such that the second low-speed control range is always constant, and the first low-speed control range is controlled so as to decrease as the battery voltage decreases and increase as the battery voltage increases. A simple circuit configuration is sufficient to change and control the lens movement range (low-speed control range), and even if the battery voltage drops, the time required for the photographic lens to reach the target position does not need to be lengthened. It is possible to provide an automatic focusing device of a camera capable of quickly performing a focusing operation and accurately stopping a photographing lens at a focusing position as a target position.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of an automatic focusing apparatus for a camera according to the present invention, and FIG. 2 explains the relationship between the amount of lens movement and the motor driving speed applied to the embodiment. FIG. 3 is a flowchart for explaining the operation flow of the embodiment, and FIG. 4 is a characteristic diagram for explaining a relationship between a lens moving amount and a motor driving speed in a conventional camera. It is. 1 ... CPU, 2 ... Release button, 2a ... First release switch, 2b ... Second release switch, 3 ... Distance measuring means, 4 ... Battery voltage A / D conversion means, 5 ... Lens motor Driving means, 6 ... motor, 7 ... photographing lens, 8 ...
Photo interrupter for position detection, 9: shutter driving means, 10: feeding driving means.

Claims (1)

(57) [Scope of request for utility model registration] 1. A distance measuring means for measuring a distance from an exposure surface of a film to a subject, a motor for driving a photographing lens to a target position, a lens motor driving means for controlling driving of the motor, and a battery. Analog / digital conversion means for converting a voltage into a digital signal; high-speed driving of the lens motor driving means in the course of movement of the taking lens toward a target position; first low-speed driving slower than the high-speed driving; The second low-speed drive, which is slower than the first low-speed drive, is sequentially performed, and the first low-speed drive performs the first low-speed drive according to the digital information of the battery voltage output from the analog / digital conversion means and the output of the distance measuring means. Control means for changing a photographing lens moving range for moving the photographing lens, wherein the control means controls the photographing lens by the second low-speed drive. The moving range of the photographing lens to be moved is always constant, and the moving range of the photographing lens in the first low-speed driving is controlled to be smaller as the battery voltage is lower and to be larger as the battery voltage is higher. Automatic focus adjustment device for cameras.