JPS63285522A - Position controller for photographing lens - Google Patents

Abstract

PURPOSE:To rapidly decide a photographing position even if the voltage of power source lowers and to improve the precision of position by providing a command means, a driving means, a position detection means and a driving control means, etc. CONSTITUTION:When a photographing optical system 101 is in a reset position and the command means 102 is set in a wide-angle position, the driving means 103 is made to normally rotate under the control of the driving control means 105 so as to draw the optical system 101 out. And if the position detection means 104 detects that the optical system 101 reaches a wide-angle photographing position, the means 105 inverts the means 103. Next, if the wide-angle photographing position is detected 104 again, the application of pulse is executed after the means 103 is made to normally rotate to control the means 103 at low speed. When the means 104 detects the wide-angle photographing position, the means 103 is stopped by cutting the application of pulse, so that the optical system 101 is set in the wide-angle photographing position. Meanwhile, if the optical system 101 is in a telephotographing position and the means 102 is set in the wide-angle position, the means 103 is inverted under the control of the means 105 so as to put the optical system 101 in. Thus, the photographing position is rapidly decided even if the voltage of power source lowers, so that the precision of position can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention provides a position control device that is capable of moving a photographing optical system in one direction of light using a drive source such as a motor and setting the photographing optical system at a plurality of command positions. Regarding.

B. Conventional technology A multifocal camera with this kind of position control device.

For example, a guide tube that is rotatably supported by the camera body and has a helicoid engraved on its inner surface, a lens barrel that has a helicoid engraved on its outer surface that engages with the helicoid of the guide tube and that houses the photographic optical system, and a guide tube that is rotatably supported by the camera body. It has a drive motor that rotates and drives the lens barrel, and an encoder that is interlocked with the guide barrel, and the position of the lens barrel is determined based on a position signal from the encoder, and the lens barrel is moved to a predetermined photographing position.

By the way, the applicant has previously developed a camera that can take three positions: a reset position in which the lens barrel is almost completely retracted into the camera body, a wide-angle shooting position in which it is extended to an intermediate position, and a telephoto shooting position in which it is extended to the maximum. We are proposing a multifocal camera with In this camera, the position of the lens barrel is controlled as follows.

A substrate on which a conductive pattern is formed is fixed to the guide tube.
For example, three terminals (encoder brush) that slide on the conductive pattern are attached to the camera-side member fixed to the guide tube.
is provided to constitute an encoder, and a position signal corresponding to the position of the lens barrel is obtained from each terminal of this encoder. Therefore, the guide barrel is rotationally driven by a drive motor to extend or retract the lens barrel via both helicoids. For example, the position of the lens barrel is known by comparing the position signal of the lens barrel output from a changeover switch (not shown) such as a wide-angle or telephoto selection switch with the position signal from the encoder, and the drive motor is activated at a predetermined position. Stop and guide the lens barrel to the specified position.

In this type of position control device for a photographic optical system, when stopping the photographic optical system at each position, overrun due to inertia after cutting off power to the drive motor must be taken into consideration.

For this reason, the applicant first proposed a position control device in which a marking pattern is provided before the encoder pattern indicating the stop position, and the motor speed is reduced in response to the detection of this marking pattern, thereby preventing the effects of overrun. did.

Problems to be solved by the C0 invention When determining the position of such a marking pattern, take into consideration the overrun region from the fully energized state to the stop, and the speed control region from the low speed control of the motor to the stop. are doing.

FIGS. 9(a) and 9(b) show the time from when full energization is stopped at time 1 to when the motor shaft stops.

The cumulative rotational speed of the motor shaft during that period is shown as a parameter of the motor shaft rotational speed. As you can see from this figure, the faster the motor shaft rotation speed.

In other words, the higher the power supply voltage, the higher the motor shaft cumulative rotation speed.Here, if the marking pattern position is determined based on the high voltage value, as the power supply voltage decreases, the overrun amount will decrease and the motor low speed control section will become longer. There is a problem that it takes a long time to determine the position.

On the other hand, as shown in FIGS. 10(a) and (b).

Helicoid 201 on the driving side and helicoid 202 on the driven side
There is always a backlash between them.

When the lens barrel is extended, backlash as shown in FIG. 10(ca) occurs, and when retracted, backlash as shown in FIG. 10(b) occurs. This causes the following problems.

The horizontal axis in FIG. 11 indicates the positions of the terminals in the encoder; Et is the telephoto position, Ew is the wide angle position, and Er is the reset position. In addition, the vertical axis indicates the position of the lens barrel, and Re
is the reset position, W is the wide-angle shooting position, and T is the telephoto shooting position. Subscripts 1 to 4 in the diagram indicate the case where the lens barrel is extended from the reset position to the telephoto position, and 5
-8 indicates the case of retracting from the telephoto position to the reset position.When retracting from the reset position, the wide-angle position E
It can be seen that when the encoder reaches w, the lens barrel also reaches wide-angle position W from position 3 on the diagram.

However, when retracting from the telephoto position to the wide-angle position, even if the encoder reaches the wide-angle position i1Ew, the line position is 6, and the lens barrel has not reached the wide-angle position W. As a result, the encoder signal When the drive motor is stopped,
The distance from the film surface to the photographic optical system is off, and the correct subject image is not formed on the film surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photographing lens position control device that can quickly determine a photographing position and improve positional accuracy even when the power supply voltage decreases.

Means for Solving Problem D5 As shown in FIG. 1, which is a diagram corresponding to the claims, the position control device according to the present invention includes a command means 102 for commanding the position of the photographing optical system 101, and a command means 102 for commanding the position of the photographing optical system 101. Based on a driving means 103 that drives in the optical axis direction, a position detecting means 104 that detects the position of the photographing optical system 101 on the optical axis, a position command from the command means 102 and a detection result from the position detecting means 104. The photographing optical system 10 is driven by controlling the driving means 103.
Drive control means 105 for setting 1 from the current position to the command position
If the commanded position is in the first movement direction from the current position, the drive control means 105 continues until the commanded position is detected once, or if the commanded position is in the first movement direction from the current position. If the commanded position is in the second movement direction opposite to the first movement direction, the driving means 103 is moved every time the commanded position is detected by the position detection means 104 until the commanded position is detected n+1 times. After the photographing optical system 101 is alternately driven back and forth in the first and second movement directions, the driving means 103 is driven at a low speed, whereby the photographing optical system 101
is configured to move in a first movement direction and stop at a commanded position.

A reset position in which the 80-effect lens barrel is almost completely retracted into the camera body, and a wide-angle shooting position in which it is extended to an intermediate position.
The present invention will be described in detail by taking as an example a multifocal camera that takes three positions including the most extended telephoto shooting position and sets the position in the lens extension direction (first movement direction).

The photographing optical system 101 is at the reset position and the command means 101
When the camera is set to the wide-angle position, the drive unit 103 is rotated in the normal direction under the control of the drive control unit 105, and the photographing optical system 101 is extended. When the position detection means 104 detects that the photographing optical system 101 has reached the wide-angle photographing position, the drive control means 105 reverses the driving means 103. The photographing optical system 101 is extended for a while due to inertia, but is then retracted. When the position detecting means 104 detects the wide-angle photographing position again, the driving means 103 is rotated in the normal direction and then pulsed energized to control the driving means 103 at a low speed. Then, when the first position detection means 104 detects the wide-angle photographing position, the pulse energization is cut off to stop the driving means 103, and the photographing optical system 103 is set to the wide-angle photographing position.

Further, when the photographing optical system 103 is at the telephoto photographing position and the command means 101 is set to the wide-angle position, the drive control means 105
The driving means 103 is reversed under the control of the photographing optical system 1.
01 is renormalized. When the position detection means 104 detects that the photographing optical system 101 has reached the wide-angle photographing position, the drive control means 105 rotates the drive means 103 in the normal direction. The photographing optical system 101 is retracted for a while due to inertial force, but is then retracted. When the position detection means 104 detects that the photographing optical system 101 has reached the wide-angle photographing position again, the drive control means 105 reverses the driving means 103. The photographing optical system 101 is extended for a while due to inertia, but is then retracted. When the position detecting means 104 detects the wide-angle photographing position again, the driving means 103 is rotated in the normal direction and then pulsed energized to control the driving means 103 at a low speed. When the first position detection means 104 detects the wide-angle photographing position, the pulse current is cut off and the drive means 104 detects the wide-angle photographing position.
3, the photographing optical system 103 is set to the wide-angle photographing position.

F. Example An embodiment of the present invention will be described with reference to FIGS. 2 to 8.

In FIG. 2(a), which shows a cross section of the wide-angle photographing position of the lens barrel, and FIG. 3, which shows the view from the line ■-m, the guide barrel 1 is rotatably supported by the camera body (not shown). . A helicoid 1a is carved on the inner surface of the guide tube 1 almost up to the tip, and a gear 1b is formed on the outer peripheral surface. This gear 1b is connected to a motor 55 provided in the camera body.
A drive gear 5 that is rotationally driven by the gears 5 and 5 is in mesh with each other.

Reference numeral 10 denotes a lens barrel that moves forward and backward in the optical axis direction with respect to the guide barrel 1, and has a lens barrel outer barrel 11 having a helicoid lla carved on its outer circumferential surface that engages with the helicoid. A holding plate 12 is screwed onto the inner middle part of this lens barrel outer barrel 11, and lenses 20a, 20b, 20
c, and the support member 21.c. A main photographing optical system 20 supported by a holding cylinder 22 in which a focusing mechanism and a shutter drive mechanism are built in is screwed onto the lens 2 at the rear of the camera.
A sub-photographing optical system 23 having 3a, 23b, and 23e and held by a holding member 24 is provided so as to be insertable and removable within the optical path. The insertion/removal mechanism of the sub-photographing optical system 23 is well known and will not be described here.

As shown in FIGS. 2(a) and 3, a terminal support plate 30a is fixed to a support member 3 fixed to the camera body in correspondence with the outer peripheral wall of the tip of the guide tube 1. Terminals 31, 32, and 33 are supported on the terminal support plate 30a, and a circuit board 4 on which these terminals 31 to 33 slide is fixed to the peripheral wall at the tip of the guide tube 1.

The circuit board 4 is composed of a flexible printed circuit board, and has a conductive pattern 41 shown in FIG. In area A, only the 00M terminal 31 is in contact with the conductive pattern 41, and the fourth
As shown in Figure (a), a high level (hereinafter referred to as "H") signal is obtained from the X terminal 32 and the Y terminal 33.

In region B between Ew indicating the wide-angle shooting position and Er indicating the reset position, the 00M terminal 31 and the X terminal 32 are in contact with the conductive pattern 41, and "L" is output from the X terminal 32 and the Y terminal 33, respectively.

rH1 signal is obtained. In the area C between Et indicating the telephoto shooting position and Ew indicating the wide-angle shooting position, all the terminals 3] and 33 are in contact with the conductive pattern 41, so the "L" signal is output from the X terminal 32 and the Y terminal 33. can get. In addition, in the area to the right of Et indicating the telephoto shooting position, 0
Since the 0M terminal 31 and the Y terminal 33 are in contact with the conductive pattern 41, "H" is output from the X terminal 32 and the Y terminal 33, respectively.
.

An "L" signal is obtained. Furthermore, discard patterns 42 to 44 are provided before transitioning from area A to area B, before transitioning from area B to area C, and before transitioning from area RI to area C, respectively.

Although these discarded patterns 42 to 44 have no electrical meaning, they bring about effects such as keeping the contact positions with the +x and Y terminals 32 and 33 constant.

Next, the control system of this embodiment will be explained based on FIG.

51 is a control circuit having a well-known microcomputer consisting of RAM, ROM, CPU, etc.

52 is a main switch; 53 is a changeover switch (TV switch) for setting the lens barrel to either a wide-angle shooting position or a telephoto shooting position; position signals corresponding to each position are input to the control circuit 51; These switches are provided on the camera body. 54 is the encoder mentioned above, and signals are inputted to the control circuit 51 from the X terminal 32 and the Y terminal 33.

As mentioned above, 55 is a motor installed in the camera body, which rotates the drive gear 5 shown in FIG. 2(a) to rotate the guide barrel 1, thereby moving the lens barrel 10 to a prescribed position. The drive is controlled by a motor drive signal output from the motor drive circuit 56 based on the processing procedure described later.

Next, the processing procedure for driving the lens barrel and the operation of each part will be explained with reference to FIGS. 6(a) to 6(d).

(I) Reset position→wide-angle shooting position When the main switch 52 is turned on, FIGS. 6(a) to (d)
) is started, and the lens barrel 10 is extended from the reset position (hereinafter referred to as R position) to the wide-angle photographing position (hereinafter referred to as W position) through steps 81 to SIO. 6th
In Figure (a), the power supply is held in step S1, and thereafter, the power supply to the motor drive circuit 56 is maintained regardless of the state of the main switch 52 until the power supply hold is released.Then, the motor drive circuit 56 is driven in step S2. The motor 55 is rotated forward until the area C is detected in step S3.
5 continues to rotate in the normal direction, and if step S3 is affirmed, the motor 55 is reversely rotated in step S4.

The motor 55 continues to rotate in reverse until region B is detected in step S5, and when step S5 is affirmed, the motor 55 is rotated in the normal direction again in step S6. After continuing the forward rotation of the motor by full energization for a predetermined time in step S7, the motor 55 is energized in pulses in step S8. Then, when region C is detected in step S9, the pulse current to the motor 55 is cut off and the motor 55 is stopped.

Through the above processing, the lens barrel 10 is set from the R position to the W position. The movement of the lens barrel 10 at this time, the signals from the X and Y terminals 32 and 33 of the encoder, and the voltage at both terminals of the motor 55 will be explained with reference to FIGS.

Normal rotation of the motor 55 to which + voltage is applied (step S2)
Accordingly, the lens barrel 10 moves in the extending direction from the R position toward the W position. When the encoder detects region C at time t (step 83), one voltage is applied to the motor 55 (step S4) and a reverse current brake is applied, but it is still extended due to inertia, and from a certain time 0 time At t2, the encoder detects region B (
Step S5) Then, the 6 motors 55 are activated for a predetermined time T.
A voltage is applied (steps S6 to S7) and a reverse energization brake is applied. At this time, until a certain time the lens barrel].

0 is renormalized due to inertia. After a predetermined period of time has elapsed, the + voltage is pulsed and the motor 55 is rotated forward at a low speed (step S8). The lens barrel 10 is extended at a lower speed than when fully energized up to time t. When the encoder detects region C at time t (step S9), the pulse energization is cut off, the motor 55 stops, and the lens barrel 10 stops at the W position (step 510).

(n) Wide-angle shooting position→telephoto shooting position When the TV changeover switch 53 is switched to rTJ, the lens barrel 10 is extended from the W position to the telephoto shooting position (hereinafter referred to as the T position) in steps 82 to S21. In FIG. 6(b).

It is determined in step Sll whether or not the main switch 52 is on, and if an affirmative determination is made, in step S12 the TV
It is determined whether the switch 53 is switched to "T". If it is in the "T" position, the process advances to step S13, where the motor 55 is rotated in the normal direction, and the motor 55 continues to rotate in the normal direction until the area is detected in step 314. If step S14 is affirmative, the motor 55 is rotated in the normal direction in step S15. Reverse. The motor 55 continues to rotate in reverse until region C is detected in step S16, and when step 816 is determined, step S17
The motor 55 is rotated normally again. After continuing the forward rotation of the motor by full energization for a predetermined time in step 818, the motor 55 is energized in pulses in step S19. and,
When the area is detected in step S20, the lens barrel 10 is set to the T position by one or more processes of cutting off the pulse current to the motor 55 and stopping the motor 55.

(III) When the telephoto shooting position→wide-angle shooting position TW changeover switch 53 is switched to rWJ, the lens *ii is changed through steps 822 to 825 and steps 82 to S10.

is extended from the T position to the W position. Figure 6(c),
In (a), in step S22 the main switch 52
It is determined whether or not the TW switch 53 is turned on, and if the determination is affirmative, it is determined in step S23 whether or not the TW switch 53 has been switched to rWJ. If it is in the “W” position, step S
24, the motor 55 is reversed, and the motor 55 continues to rotate in reverse until region B is detected in step 825. If step S25 is affirmed, the process proceeds to step S2, where the motor 55 is rotated in the normal direction, and the motor 55 continues to rotate in the normal direction until area C is detected in step S3. If step S3 is affirmed, the motor 55 is rotated in the normal direction in step S4. Reverse. Step S
The motor 55 continues to rotate in reverse until region B is detected at step 5.
If step S5 is affirmed, the motor 55 is
Rotate forward again. After continuing the forward rotation of the motor by full energization for a predetermined time in step S7, the motor 55 is energized in pulses in step S8. Then, when region C is detected in step S9, the pulse current to the motor 55 is cut off and the motor 55 is stopped.

Through the above processing, the lens barrel 10 is set from the T position to the W position. The movement of the lens barrel 10 at this time, the signals from the X and Y terminals 32 and 32 of the encoder, and the voltage at both terminals of the motor 55 will be explained with reference to FIGS. 8(a) to 8(d).

Reverse rotation of the motor 55 to which one voltage is applied (step 524
) When the encoder detects region B at time t1 when the lens barrel 10 moves in the retraction direction from the T position toward the W position (step 525), ten voltages are applied to the motor 55 (step S2) and reverse energization is performed. The brakes apply.

When the encoder detects region C at 0 time t2, which is extended from a certain time due to inertia (step S3), one voltage is applied to the motor 55 (
Step 84) The reverse energization brake is applied, but it is still extended due to inertia and is retracted from a certain time. At time t, the encoder detects region B by smell (step S5
) Then, ten voltages are applied to the motor 55 for a predetermined time T (steps S6 and S7), and a reverse energization brake is applied. At this time, the lens barrel 10 is retracted due to inertia until a certain time. After a predetermined period of time has elapsed, a pulse of 10 voltage is applied (Step 88) to rotate the motor 55 forward at a low speed. At time 0, when the lens barrel 10 is extended at a lower speed than when fully energized up to time t, the encoder detects region C (step 89), the pulse energization is cut off, the motor 55 is stopped, and the lens barrel The cylinder 10 stops at the W position (step 510).

Further, if it is determined that the main switch 52 is turned off in each of the above steps Sll and S22, as shown in FIG. 6(d), steps 831 to S40 are performed.
The lens barrel 10 is set to the R position. That is, in step S31, the motor 55 is reversed,
When area A is detected in step S32, step S33
Then, the motor 55 is rotated in the normal direction. When region B is detected in step S34, the motor 55 is
After a predetermined time has elapsed in step 836, the motor 55 is energized in pulses in step S37, and when area A is detected in step S38, the energization to the motor 55 is cut off in step S39 to stop the motor 55. Finally, in step S40, the hold on the power supply is released.

Note that the time measured in step S36 is the same as that in step S7.
The time is set to be longer than the time of 818.

This is because the lens barrier is also closed by the force of the lens drive motor when moving to the R position.

Note that step S6. S7. Step S17°818 and step S35. S36 may be omitted, but in this case, the reverse energization brake does not work, so the time until low speed control is entered becomes a little longer.

Next, the effects of the above control procedure will be explained. As in the past, when pulse energization is performed from time ti in FIG. 8(d) in response to a marking plate in front of a predetermined photographing position, for example, the pulse current is applied from time ti in FIG. As shown, the lens barrel 10 due to inertia after time t4
The retracting is completed, and the lens barrel 10 is extended at a low speed by normal rotation of the motor due to pulsed energization, and then reaches the W position at time t and is stopped. On the other hand, according to the above-mentioned control procedure, the lens barrel 1o is set at W position at each time tit tzvt.
Since the pulse current is applied after the position has been crossed a total of three times, it is possible to control the motor at low speed by pulse current application without providing a marking plate. Here, the amount of overrun when detecting the W position and reverse energization increases as the power supply voltage increases, but the movement speed of the lens barrel when moving from the overrun position to the W position again also increases as the a source voltage increases. Therefore, the time required for overrun and the time from the overrun position to return to the W position do not depend on the power supply voltage. In other words, the time from W position detection to the next W position detection does not depend on the power supply voltage. , since the setting time to the desired photographing position is not dependent on the power supply voltage, even if the power supply voltage drops, the lens barrel 10 can be quickly moved to the position W [t T
Can be set to any position.

As shown in FIGS. 7(a) to 7(d), when setting from the R position to the W position, after crossing the W position twice, the motor enters low speed control by pulse energization. That is,
In the above embodiment, the photographing position is set in the extending direction of the lens barrel 10 both from the R position to the W position and from the T position to the W position. Pulse energization is performed after crossing the W position three times, and pulse energization is performed to stop the motor after the motor has crossed the W position three times to reach the imaging position on the retraction side, thereby eliminating positional deviation due to backlash etc. Improves position accuracy.

Note that the present invention can also be applied to a position control device that drives an autofocus photographing optical system to a focusing position. In this case, the command means corresponds to a focus detection circuit, and the position command depends on the defocus amount and its direction.

G0 Effects of the Invention According to the present invention, after the photographing optical system crosses the commanded position n times or n+1 times, the driving means is controlled at low speed and set at the commanded position. The photographing optical system can be stopped by low-speed control without the need for a power supply voltage, and it can always be positioned at a commanded position in a constant time without being affected by the power supply voltage. Further, since the lens barrel is positioned by driving it in only one direction, the positioning of the lens barrel due to play such as backlash of the drive mechanism is prevented, and positioning accuracy is improved.

[Brief explanation of the drawing]

FIG. 1 is a complaint correspondence diagram. Figures 2 to 8 show one embodiment, and Figure 2 (
(a) and (b) are cross-sectional views of a multifocal camera to which the present invention is applied, where (a) shows wide-angle shooting and (b) shows telephoto shooting;
Figure 3 is a side view of Figure 2 (a), Figure 4 (a) is a diagram showing the relationship between the position of the rotary encoder and the outputs of the X and Y terminals, and Figure 4 (b) is a view of the rotary encoder. FIG. 5 is a plan view of the conductive pattern constituting the encoder, FIG. 5 is a schematic configuration diagram of the control system, FIGS. 6(a) to (d) are flowcharts showing the processing procedure, and FIGS. 7(a) to (d) and Figure 8 (a
) to (d) are movements of the lens barrel. FIG. 3 is a diagram showing an encoder signal and a voltage across the motor. FIG. 9(a) is a graph showing the relationship between motor shaft rotational speed, cumulative rotational speed, and time, FIG. 9(b) is a time chart of motor applied voltage, and No. 10@(a). (b) is a diagram explaining helicoid backlash, and FIG. 11 is a diagram showing the positional relationship between the encoder position and the lens barrel when the lens barrel is photographed in two directions. 1: Guide tube 1a, lb: Helicoid 10: Lens barrel 11a: Helicoid 20: Main photographing optical system 23: Sub-photographing optical system 31: 00M terminal 32: X terminal 33: Y terminal 41: Conductive pattern 51: Control circuit 52 : Main switch 53: Changeover switch 54: Encoder 55: Motor 101: Photographing optical system 102: Command means 103: Drive means 104: Position detection means 105: Drive control means Patent applicant: Nippon Kogaku Kogyo Co., Ltd. Representative Patent Attorney Nagai Figure 2 ((1) Figure 2 Cb) Figure J Figure 4 ((1) (b) (C) (d) Figure 6

Claims (1)

[Scope of Claims] 1) A commanding means for commanding the position of the photographing optical system, a driving means for driving the photographing optical system in the optical axis direction, and a position detecting means for detecting the position of the photographing optical system on the optical axis. , a photographing lens comprising a drive control means for driving and controlling the driving means based on a position command from the command means and a detection result from the position detection means to set the photographing optical system from the current position to the command position. In the position control device, the drive control means operates until the commanded position is detected n times when the commanded position is in a first movement direction from the current position, or until the commanded position is detected n times, or If the position is in a second movement direction opposite to the first movement direction from the current position, the commanded position is detected by the position detection means until the commanded position is detected n+1 times. The driving means is controlled to drive the photographing optical system back and forth alternately in the first and second movement directions each time the photographing optical system is moved, and then the driving means is driven at a low speed to move the photographing optical system in the first movement direction. A position control device for a photographic lens, which is capable of moving and stopping at a commanded position. 2) In the control device according to claim 1,
The low speed control of the drive means is performed by pulse energization to the drive means, and the commanded position is n times or n+1 times.
The position of the photographing lens is characterized in that the pulse energization is performed after the photographing optical system is fully energized for a predetermined period of time in response to the first movement direction being detected. Control device.