JP2891355B2 - Displacement conversion system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a displacement conversion system, and more particularly, to a method in which a current position of a moving object displaced by a predetermined drive source is driven from a reference position by the drive source. The present invention relates to a displacement conversion system identified by a displacement conversion amount.

[Related Art] In an autofocus device, when distance measurement is performed, a target position to drive a focus lens is obtained from the distance measurement value. Then, in order to drive the lens to the target position, a difference between the target position and the current position is obtained, and the lens output is driven toward the target position with the difference output. Here, after the focus lens reaches the target position, the same position becomes the current position, but this memory of the current position will be erased when the power is turned off, so the current position is reset when the power is turned off. Need to detect. Therefore,
Generally, when the power is turned on, the focus lens is once driven to an initial position regardless of the position of the focus lens, and a lens reset operation is performed to reset the initial position as the current position.

[Problems to be Solved by the Invention] However, since the lens reset operation performs the lens drive while checking the initial position sensor, the lens drive is a low-speed drive, and therefore, the lens drive is performed at a position far from the initial position. If the power is turned off after being performed, the lens reset operation when the power is turned on next takes a long time, and the focus lens reaches the target position and focusing is completed It takes a lot of time to do so.

Such a thing is not limited to the autofocus device alone, but generally also refers to a displacement conversion system in which the current position of the moving object is identified by a drive displacement conversion amount from the reference position. it can. In other words, if the main power is turned off after the moving object is at a position far from the reference position and the driving displacement is performed, the moving object moves to the reference position when the main power is turned on next time. It will take a long time.

It is an object of the present invention to provide a displacement conversion system in which a moving object is quickly reset to a reference position whenever a main power supply is turned on in view of such a problem.

[Means and Actions for Solving the Problems] In the displacement conversion system of the present invention, the current position of the moving object to which the driving displacement from the predetermined driving source is transmitted and displaced is set to the absolute position with respect to the moving object. A displacement conversion system that is identified by a drive displacement conversion amount in the drive source from a predetermined reference position for recognition, wherein a current position of the moving object is stored by a storage unit during an ON time of a main power supply. It is memorized. Then, when the main power supply off command is given, a signal for driving the moving object to the vicinity of the reference position is provided within a time period from when the main power supply is actually turned off after receiving the off command. Provided to the drive source by the control means.

Embodiment FIG. 1 is a schematic block diagram showing an embodiment of an autofocus apparatus to which the present invention system is applied. In FIG. 1, an initial position sensor 1 is constituted by a mechanical microswitch or the like as described later, and is turned on and off when an initial position is detected.
It is off at other times. One end of the initial position sensor 1 is connected to one input port of a CPU (Central Processing Unit) 3 to which the pull-up resistor 2 is connected, and the other end of the initial position sensor 1 is grounded. The CPU 3 is for calculating the amount of drive of the focus lens, and a motor drive circuit 4 is connected to its output port. An output terminal of the motor drive circuit 4 is connected to an excitation coil of a stepping motor 5 driven by four phases.

FIG. 2 shows a schematic configuration of a drive mechanism of the autofocus device. In FIG. 2, a pinion gear 10 fixed to the output shaft of the stepping motor 5 meshes with a sector gear 12 formed on the outer periphery of a cam ring 11. A cam 13 is formed on a part of the outer periphery of the cam ring 11. The cam 13 has a lens frame for the focus lens 14
A cam follower 16 provided integrally with 15 extends,
Since the lens frame 15 is urged in the direction of the cam ring 11 in parallel with the optical axis O by urging means (not shown), the cam follower 16 is pressed against the cam 13. Further, a projection 17 is integrally formed on the cam ring 11, and the projection 17 is formed on the initial position sensor 1 attached to the immovable member.
You can work with. That is, the projection 17 is provided at a position where the contact 1a of the initial position sensor 1 formed of a micro switch is activated to turn on the sensor 1 when the cam ring 11 reaches the rotation angle position of the initial position.

Here, the stepping motor 5 is driven in the forward direction to rotate in the direction of the cam ring 11 or the arrow a, and the cam follower 16 follows the cam 13 so that the focus lens
Reference numeral 14 moves in the direction of arrow b, and when the cam ring 11 rotates in the direction of arrow c by driving the stepping motor 5 in the reverse direction, the focus lens 14 moves in the direction of arrow d. Assuming that the number of auto-focusing steps (hereinafter referred to as the number of AF steps) at which the focus lens 14 moves from the initial position is n, the initial position is n = 0.

Next, the operation of the autofocus device will be described with reference to the flowcharts shown in FIGS.

First, when a power switch (not shown) of the autofocus device is turned on, the CPU 3 performs a <lens reset> processing operation shown in FIG. When entering the <lens reset> processing routine, the CPU 3 first checks whether or not the initial position sensor 1 is on by checking the level of the input port to which the initial position sensor 1 is connected. As can be seen from the configuration shown in FIG. 2, the initial position sensor 1 is turned on when the cam ring 11 rotates in the direction of arrow c and the projection 17 activates the contact 1a (n = 0). However, since the protruding portion 17 is provided over a range on the outer periphery of the cam ring 11, the cam ring 11 further has an arrow c.
The initial position sensor 1 is turned on even in the state of rotation in the direction. Therefore, when it is determined that the initial position sensor 1 is turned on, the stepping motor 5 is driven one step in the forward direction (the cam ring 11 is in the direction of the arrow a), and then waits for a certain period of time. Return to the recheck of 1,
The operation of this flow is repeated until the initial position sensor 1 is turned off. After that, the stepping motor 5 is driven one step in the reverse direction, and then waits for a certain period of time. ). Also,
If it is determined that the initial position sensor 1 has been turned off, then the stepping motor 5 is driven one step in the reverse direction (the cam ring 11 in the direction of arrow c), waits for a certain period of time, and starts again. The position sensor 1 is checked. Until the initial position sensor 1 is turned on, the operation of driving the stepping motor 5 in the reverse direction by one step and checking the weight and the initial position sensor 1 are repeated. And
If it is determined in this operation that the initial position sensor 1 has been turned on, the CPU 3 stores the AF of the initial position in the storage unit as the current position.
Set the number of stages to 0. In other words, this <lens reset>
By the processing operations described above, the relationship between the initial position sensor 1 and the number of AF steps is as shown in FIG. In FIG. 6, the hatched area indicates the ON area of the initial position sensor 1.

After the <lens reset> operation, the CPU 3 executes the <AF drive> processing operation shown in FIG. 3 based on a distance measurement signal from a distance measurement device (not shown). That is,
When entering the <AF drive> processing routine, the CPU 3 sets the target position data (the number of steps) as the distance measurement result to A, then sets the current position data (the number of steps) to B, and thereafter,
The number of driving steps C is obtained by performing the calculation of (AB). As for the current position data, B = 0 due to the <lens reset> process, so C = A in this case. Then, it is checked whether or not the obtained number of driving steps C is 0. As a result of this check, if C = 0, the stepping motor 5 is not driven, the target position is immediately set to the current position, and this < The process of <AF drive> is ended.

If C ≠ 0, it is further checked whether C> 0. If C> 0, the stepping motor 5 is driven trapezoidally in the forward direction by the number of steps C. Also, C
If <0, the stepping motor 5 is trapezoidally driven in the reverse direction by the number of steps C. Here, the trapezoidal drive is, as shown in FIG. 7, a motor drive control in which a speed diagram with respect to time has a trapezoidal shape, and the drive speed initially increases in proportion to time, When a certain high speed is reached, this high-speed driving state is maintained at the same time, and the driving speed gradually decreases in proportion to time and stops before the target position.
On the other hand, the motor drive control in which the forward (reverse) one-step drive and the weight are repeated in the <lens reset> process is a constant speed drive as shown in FIG. 8, but the drive speed is low. It is clear from a comparison between the two that the trapezoidal drive method has a higher drive speed.

When the focus lens reaches the target position as a result of the trapezoidal drive, this target position is set as the current position and this <AF drive>
Is completed.

Thereafter, when the power switch of the autofocus device is turned off, the processing of <power off> shown in FIG. 5 is performed. In the <power-off> processing routine, 1 is set as the number of steps of the target position, and then the <AF>
Drive> processing operation is performed again. Therefore, when the processing operation of <AF drive> during the processing of <power off> is completed,
The focus lens is driven to the position of the step number 1, the step number 1 of the target position is set as the current position, the power is turned off, and the <power off> processing ends. At the time of <AF driving> during the processing of <power off>, since the power has not been turned off yet, high-speed driving with trapezoidal driving is possible.

Therefore, after this, when the power switch is turned on again for the next autofocus operation, the above-described <lens reset> process is performed. In this case, since the number of steps at the current position is 1, the The position sensor 1 is off. When one-stage driving in the reverse direction and weighting are performed once,
The initial position sensor 1 is turned on to reach the initial position, and 0 is set as the current position. That is, in the <lens reset> process, the shortest flow of the <lens reset> is selected and executed because the current position stage number is set to 1 in the previous <power off> process, and the focus is reduced in the shortest time. The lens 14 is reset to the initial position.
Therefore, the subsequent auto-focus drive control is quickly started.

Although the initial position sensor 1 of the above embodiment is a mechanical switch, it can be formed by a non-contact type switch such as a photo interpreter.

In addition to the autofocus device, in general, for a displacement conversion system in which the current position of a moving object is identified by a drive displacement conversion amount from a reference position, the position of the moving object If the main power supply is given an off command even when the main power supply is turned off, the mobile body is moved to the vicinity of the reference position before the storage of the current position of the mobile body is reset, and then the main power supply is turned off. become. Therefore, after this, when the main power supply is turned on next, the moving object is driven and displaced to the reference position in a short time.

[Effects of the Invention] As described above, according to the present invention, when the main power supply is turned off, the main power supply is actually turned off after the moving object reaches the vicinity of the reference position. When turned on, the moving object is reset to the reference position in a short time, and therefore, the time required to drive the moving object to the target position is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing an embodiment of an autofocus apparatus to which the present invention system is applied. FIG. 2 is a schematic configuration of a drive mechanism of the autofocus device shown in FIG. 1; FIGS. 3 to 5 are flowcharts for explaining the operation of the autofocus device shown in FIG. 1; FIG. 6 is a diagram showing the relationship between the initial position sensor and the number of AF steps at the time of lens reset. FIG. 7 is a speed diagram of trapezoidal drive during <AF drive> processing shown in FIG. FIG. 8 is a velocity diagram of the constant speed drive during the <lens reset> processing shown in FIG. 1. Initial position sensor 3. CPU (storage means, control means) 5. Stepping motor (drive source) 14. Focus lens (moving object)

Claims (1)

(57) [Claims] 1. A driving method according to claim 1, wherein the current position of the moving object to which the driving displacement from the predetermined driving source is transmitted and displaced is a predetermined reference position for recognizing an absolute position of the moving object. In the displacement conversion system identified by the displacement conversion amount, a storage means for storing the current position of the moving object during the ON time of the main power supply, Control means for supplying a signal for driving the moving object to the vicinity of the reference position to the driving source within a time until the power is turned off.