JP2006171150A - Lens barrel controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve, using a simple configuration, accuracy of focus stop, without increasing soft capacity. <P>SOLUTION: In addition to the determination of a stop parameter based on the conventional detection of a speed in steady state, the speed during damping at the end of stop is detected, and thus correction is added at the final stage of control. Short circuiting or energization turn off is conducted with respect to reverse energization brake for damping. This enables reduction in the a speed reduction ratio and makes it effective to increase the driving speed of the lens barrel and to eliminate noise. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical apparatus such as a camera, and relates to drive stop control of a variable magnification photographing optical system.

(Conventional example 1)
Conventional zoom lenses generally have a configuration in which each group moves in the direction of the optical axis while satisfying each zooming condition and performs a zooming operation. At the time of focus adjustment, the focus lens group independently performs focus adjustment. The type of zoom lens barrel has two types of driving means for zooming and focusing.

In recent years, as disclosed in Japanese Patent Laid-Open No. 61-259237, a configuration that performs a focus adjustment operation in a zooming operation has also been put into practical use, and simplification of the mechanism and simplification of the control system can be realized. To take advantage of low cost and compact. (This method is called a step zoom method)
FIG. 4 is a conceptual diagram showing an example of the control method. Reference numeral 101 denotes a first lens group, and reference numeral 102 denotes a second lens group. The trajectories 103 and 104 are at the infinite focus position during normal zooming. On the other hand, in the step zoom method, the second lens group moves on the locus 105, and includes a focus adjustment region in which the focal position continuously changes from infinity to the close and a zoom region in which the zoom region moves to the next zoom region. . In FIG. 4, there are a total of five zoom regions between f = 35 and 90 mm. The reference pulse is configured to output one cycle for each zoom region. For example, a method of intermittently generating pulses in conjunction with the gear in the middle of a drive transmission gear system that performs zoom driving, or an optical axis of a lens barrel Some generate signals directly from movement in the direction or direction of rotation. The required pitch of the focus pulse is determined by the focus accuracy. If the first group performs focus in the two-group optical system of f = 35 to 90 mm as shown in FIG. 4, it is usually several μm to several tens μm. Stop accuracy is required. In other words, it is difficult to obtain a signal directly from the lens barrel because it requires a fineness several hundred times that of the reference pulse, and the signal is obtained at an increased speed. Therefore, the signal is generally generated on the first stage side of the zoom drive gear, that is, the gear near the motor or the motor direct.

  The operation of the above configuration will be described.

  An operation in which a photographer operates a zoom operation button (not shown) to set a desired focal length will be described. For example, when f = 35 mm is set to f = 50 mm (when the wide angle side is set to the telephoto side), when the photographer operates the zoom operation button and finishes the operation before the operation reference pulse 106, the lens barrel is further telephoto. After the reference pulse 106 is detected, the focus pulse starts to be counted and a predetermined value (Tele pulse) is counted, and then the movement of the lens barrel is reversed to drive to the wide angle side. Further, after detecting the pulse 106, the focus pulse starts to be counted, and after a predetermined value (Wide pulse) is counted, the lens barrel is stopped and positioned at the standby position 107. Also, when setting from the telephoto side to the wide-angle side, the pulse 106 is detected after the reverse of the lens barrel moving direction described above, and then the Focus pulse count is started and a predetermined value (Wide pulse) is counted. It stops and is located at the standby position 107.

  As described above, the photographer performs photographing after setting the photographing lens at a desired focal length, and the operation is as follows.

  When the photographer operates a release button (not shown), the photographing operation is started. First, the brightness and distance of the subject are measured, the lens extension amount corresponding to the subject distance is calculated, and the photographing lens is extended to a predetermined position based on the calculated value of the lens barrel. This will be described in detail with reference to FIG. When energization of the motor is started in order to drive the lens barrel, the motor reaches a steady speed through a rising section, and then the reference pulse 106 is detected. Focus pulse counting is started with the reference pulse 106 as a reference, and control is performed so as to stop the photographing lens at a position based on the calculated value. The current motor speed is measured in a state where the steady speed has been reached, and a stop control pulse necessary for stopping the motor is obtained from the measured value by a predetermined calculation method, before the stop control pulse for the target stop position. The stop control is performed from the beginning to stop at the target position.

  Thereafter, appropriate exposure based on the luminance of the subject is performed, and then the motor is energized in the opposite direction to reset the lens barrel, the lens barrel is driven to the wide-angle side, and after detecting pulse 106, Focus After the pulse count is started and a predetermined value (Wide pulse) is counted, the lens barrel is stopped and positioned at the standby position 107.

  As described above, the zooming operation and the focus adjustment operation are performed. The control will be described in more detail.

  In order to improve the stop accuracy at the time of Focus, the current speed is measured and the stop control pulse necessary for the stop is calculated. For that purpose, the speed measurement value must be accurate. Normally, the method of obtaining the motor speed using the Focus pulse set with the highest resolution is used, but the average value for several pulses is used so that it is difficult to be affected by measurement errors and signal disturbance noise. The motor must be in a sufficiently steady state of rotation, so the Wide pulse must be greater than the rise when the motor reaches steady state rotation. FIG. 5 shows a standard control pattern, but actually there are variations due to errors in the reference pulse, and there are differences in focus positions due to individual variations in the photographing optical system. It is necessary to determine the values of the reference pulse, the wide pulse, and the tele pulse in consideration of these, and this will be described with reference to FIG.

  FIG. 6 is a control diagram showing various variations. 108 is the fastest motor speed, 109 is the standard motor speed, 110 is the slowest motor speed, 111 is the standard infinite focus position, and 112 is the rearmost pin side. , The infinite focus position of the photographic lens shifted to, 113 is the infinite focus position of the photographic lens shifted to the most front focus side, 114 is the standard closest focus position, and 115 is the closest focus position of the photographic lens shifted to the most rear focus side, Reference numeral 113 denotes the closest focus position of the photographic lens that is shifted to the most front side.

  106 is the standard reference pulse, and 117 and 118 are the reference pulse positions when the error is most significant.

  Here, the Wide pulse must be larger than the rise at which the motor reaches steady rotation, and the rise of the fastest speed 108 must be taken into consideration. Next, since the stop control of the lens barrel is performed after the reference pulse is detected, the longest stop control is required at the timing of the reference pulse 117 when the error of the reference pulse is on the slowest side. It is necessary to set the reference pulse at such a position that it can stop at the infinite focus position 113 that is the closest focus position in the case of the highest speed.

  In addition, as shown in FIG. 6, the tele pulse described above is set at the closest focus position 115 of the photographing lens most shifted to the rear pin side for the following reason.

  In the step zoom method, as described above, since focus adjustment is performed as part of the zooming operation, the finder also performs zooming operation according to the operation, which may cause the photographer to feel uncomfortable. As a countermeasure, as shown in Japanese Patent Laid-Open No. 08-015318, the viewfinder is not interlocked during Focus operation. As a configuration, a predetermined amount of non-interlocking section is set by providing play in the interlocking of the lens barrel and the finder, and the finder is not operated in this section during the focus operation. Therefore, it is necessary to postpone the playfinder finder mechanism, and the amount of movement is the largest, and the tele pulse is determined so that the finder does not operate even in the case of the closest focus position 115 of the photographing lens shifted to the rear pin side.

(Conventional example 2)
Japanese Patent Publication No. 7-49455 discloses drive control aimed at improving the focus adjustment stop system. As this control method, a method has been proposed in which the driving speed is constantly measured during stop control, and compared with the target stop drive, the stop control is fed back from the difference to stop at the target position.

(Conventional example 3)
US Pat. No. 5,565,28 proposes a method in which a steady speed driving state having a low speed is created at the end of stop control, the speed is measured again, and the final stop control is performed based on the measured value as an improvement of the above conventional example 1. ing.
JP 61-259237 JP Japanese Unexamined Patent Publication No. 08-015318 Japanese Patent Publication No.7-49455 USP5652928 Publication

  In the configuration of (Conventional Example 1) described above, control is performed based on the speed measured in the steady state before the stop control. Therefore, if the steady state speed is unstable due to a disturbance or the like, the measured speed error Therefore, there is a problem that the stop position varies. In addition, there is a problem that the stop characteristic is affected by a change from a predetermined characteristic due to a disturbance such as a change in load state due to a mechanism variation for each camera, resulting in a variation in stop accuracy.

  In the configuration of (Conventional Example 2), high-accuracy stop control is possible. However, since the drive speed is constantly measured during stop control and compared with the target stop drive, the stop control is fed back from the difference. There is a drawback that the capacity of the control software is large and a high-performance microcomputer capable of high-speed computation is required, which makes it expensive.

  In the configuration of (Conventional Example 3), the stop position accuracy is improved because two-step stop control is performed, but there is a disadvantage that the control time becomes longer because a steady drive region is provided during the stop control. Yes.

  According to the present invention, a zoomable photographic optical system having at least two or more lens groups, a barrel mechanism that moves the photographic lens group in the optical axis direction, and a barrel drive mechanism that drives the barrel mechanism, A lens barrel control device that controls the lens barrel driving mechanism, and measures the driving speed at the time of focus adjustment driving, performs stop control based on the measured value, and drives the speed during the stop control at the time of focus adjustment. The stop control position system can be improved by correcting the stop control based on the measured value.

  As described above, according to the present invention, a zoom optical system having at least two or more lens groups, a barrel mechanism that moves the zoom lens group in the optical axis direction, and driving the barrel mechanism It has a lens barrel drive mechanism and a lens barrel control device that controls the lens barrel drive mechanism, measures the drive speed during focus adjustment drive, performs stop control based on the measured value, and stops during focus adjustment By measuring the driving speed during the control and correcting the stop control based on the measured value, it is possible to improve the stop control position system and realize a photographing device with higher focus accuracy. .

  Further, if the focus accuracy is set to the conventional level, the reduction ratio can be reduced by the drive mechanism with the improved stop control position system, so that it is possible to realize a photographing apparatus with a short control time (ie, a small time lag). It becomes possible.

  FIG. 1 is a basic block diagram of an embodiment of the present invention. 1 is a control circuit (microcomputer) for controlling the entire sequence of the camera, 2 is a memory circuit, 3 is a lens barrel drive circuit for driving the lens barrel, 4 is a lens barrel drive motor for driving the lens barrel, 5 is a reference pulse detection circuit for detecting a reference pulse, 6 is a focus pulse detection circuit for detecting a focus pulse, 7 is a zoom switch, 8 is a release switch, and 9 is a subject switch. A photometric circuit for measuring the luminance, 10 a distance measuring circuit for measuring the distance of the subject, and 11 a shutter driving circuit for driving the shutter.

  FIG. 2 is a flowchart showing the lens barrel control sequence, and the sequence from the zoom operation of the camera will be described. First, when it is detected that the photographer performs a zoom operation, the lens barrel drive circuit is activated according to the operation state to drive the lens barrel. In FIG. 2, driving to the telephoto side is performed. Thereafter, the zoom drive is continued even after the photographer releases the zoom operation switch when the desired zoom ratio is achieved, and the reference pulse is detected, and when the pulse is detected, the count of the Focus pulse is started. When the count value of the Focus pulse reaches a predetermined Tele pulse, the driving direction of the lens barrel is reversed, and the reference pulse is further detected. When the pulse is detected again, the Focus pulse starts counting and the predetermined Wide pulse is detected. The lens barrel is stopped when is counted. The zooming operation is thus completed, and a release switch or another zoom operation standby state is entered. When the release switch is pressed, the camera starts a shooting operation, and first the brightness and distance of the subject are measured. After that, the lens barrel driving circuit is activated and the lens barrel driving for the focus control is started, and the amount of feeding according to the subject distance is calculated, and after detecting the reference pulse for feeding out the amount of feeding, The drive speed is measured, stop control calculation is performed to perform stop control suitable for the current speed, and stop control is performed to stop at the target position based on the calculation result. Thereafter, when the value approaches the target value, the drive speed is measured again, and correction control is performed by performing correction control calculation so that the target position is accurately stopped based on the measured value. Thereafter, when the lens barrel reaches the target position, the motor is short-circuited for a certain time, and the focus adjustment operation is completed. Thereafter, appropriate exposure control based on the photometric value is performed by the shutter driving circuit, and then the lens barrel driving circuit is driven again to reset the lens barrel to the original standby position, thereby completing the photographing operation.

  FIG. 3 is a diagram showing the focus adjustment control of the present plan, and the drive stop target corresponding to the subject distance is point E. The driving is started from the point A, the steady speed is reached at the point B, and the speed measurement (1) is performed in the steady state. After that, in order to stop at point E, a reverse energizing brake is applied to perform stop control. The start of reverse energization braking is calculated based on the measured value of the speed measurement (1). In the most standard case, reverse energization braking is started from point F, followed by a locus indicated by a dotted line, and stopped at point E. In the control in this embodiment, reverse energization braking is started from point C before point F, speed measurement (2) is performed in the middle of the braking, and a correction amount is calculated based on the measured value. For a predetermined period based on the calculated correction amount, the stop control is changed from reverse energization to energization off or short energization, and correction is performed to stop at the original stop target store E point.

Basic block diagram of the present invention The barrel drive flowchart of the present invention The figure explaining the drive control of this invention Illustration of step zoom Diagram showing conventional drive control Diagram for explaining conventional control parameters

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control circuit 2 Memory circuit 3 Lens barrel drive circuit 4 Lens barrel drive motor 5 Reference pulse detection circuit 6 Focus pulse detection circuit 7 Zoom switch 8 Release switch 9 Distance measuring circuit 10 Photometry circuit 11 Shutter drive circuit

Claims (5)

  A variable-magnification photographing optical system having at least two lens groups, a lens barrel mechanism that moves the photographing lens group in the optical axis direction, a lens barrel drive mechanism that drives the lens barrel mechanism, and the lens barrel drive mechanism A lens barrel control device for controlling, and measuring the drive speed during focus adjustment drive and performing stop control based on the measured value, and measuring the drive speed during stop control during focus adjustment and measuring the drive speed A lens barrel control device that corrects the stop control based on a value. In claim 1,
The lens barrel control device, wherein the lens barrel mechanism is configured to alternately move the zooming movement area and the focus adjustment area of the photographing optical system. In claim 2,
3. The lens barrel control device according to claim 1, wherein the stop control is braking by reverse energization, and the correction control is short energization. In claim 2,
3. The lens barrel control device according to claim 1, wherein the stop control is braking by reverse energization, and the correction control is power off. In claim 2,
The lens barrel control device according to claim 1, wherein the stop control is braking by short-circuit energization, and the correction control is power-off or reverse energization.

Images