JP2004317997A - Device and method for controlling driving of zoom lens barrel for camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling the driving of a zoom lens barrel capable of stably acting in a short moving range between a standby position, a lens cover opening position and a focus position. <P>SOLUTION: The device for controlling the driving of the zoom lens barrel is constituted of the zoom lens barrel 1, a DC motor 2 driving the lens barrel 1, an encoder 6 detecting the moving amount of the lens barrel 1 in accordance with the rotational amount of the motor 2 and outputting a corresponding moving amount detection signal, a position detector 5 outputting a corresponding reference position detection signal when the lens barrel 1 passes through a specified reference position, and a control part 7 controlling the motor 2. The control part 7 switches the driving of the motor 2 to constant speed driving in advance before the reference position detection signal is outputted, and starts counting the moving amount detection signal outputted from the encoder 6 when the reference position detection signal is outputted, and switches driving from the constant speed driving to braking driving when judging as the result of counting that the lens barrel 1 reaches a specified position. Therefore, the lens barrel 1 is stopped at an aimed stopping position. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drive control device and a drive control method for a camera zoom lens barrel. More specifically, the present invention relates to a drive control method capable of shortening the operation range of a zoom lens barrel to achieve downsizing while maintaining operation stability.
[0002]
[Prior art]
With the miniaturization of cameras, the zoom lens barrel has also been reduced in size by shortening the focal length. For this reason, the operating range of the zoom lens barrel is narrowed. For example, in a structure in which both zooming and focusing operations are performed by a single lens barrel, control must be performed so that the lens can be driven between the standby position, the lens cover open position, and the focus position within a small operation range. For this purpose, accurate control using a pulse motor is possible, but high-speed driving is required, for example, when zooming out to a zoom position. For this purpose, a high-torque high-speed pulse motor is required. Such a high-performance pulse motor has a large size and has a problem in price.
[0003]
Therefore, a method of controlling the moving amount of the zoom lens barrel using a DC motor and a deceleration wheel train and using an encoder that detects the rotation of the DC motor is often used. This drive control method detects a moving amount of the zoom lens barrel according to a rotation amount of the DC motor for a DC motor that drives the zoom lens barrel via a wheel train, and detects a corresponding moving amount detection signal. The DC motor is controlled to be switched among full drive, constant speed drive, and brake drive based on the movement amount detection signal using an encoder that outputs the DC motor.
[0004]
[Patent Document 1] Japanese Patent No. 2830277 [Patent Document 2] Japanese Patent Application Laid-Open No. 10-239589 [Patent Document 3] Japanese Patent Application Laid-Open No. 11-341318 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-131615 [0005]
[Problems to be solved by the invention]
Unlike the pulse motor, the DC motor does not stop rotating immediately even when the driving is stopped, and an overrun occurs. In order to make this overrun constant, a method of controlling the DC motor at a constant speed and then applying a brake to stop the DC motor is used. However, in order to make the DC motor have a constant speed by the constant speed control, an approaching section is required to some extent. Therefore, it has been difficult to accurately perform stop control at the standby position and the focus position in a short operation range. If the stop control cannot be performed accurately, various problems occur. For example, if the lens barrel does not stop exactly at the standby position, the lens cover will open halfway. Further, if the focus position is not accurately stopped, a focus shift occurs.
[0006]
[Means for Solving the Problems]
In view of the above-mentioned problems of the related art, the present invention relates to a zoom lens barrel for a camera that performs zooming and focusing, and can stably operate in a short movement range between a standby position, a lens cover open position, a focus position, and the like. It is an object to provide a drive control device and a drive control method. The following measures have been taken to achieve this objective. That is, a zoom lens barrel for a camera, a DC motor that drives the zoom lens barrel via a wheel train, and a movement amount of the zoom lens barrel corresponding to a rotation amount of the DC motor are detected and corresponded. An encoder that outputs a movement amount detection signal to be output, a position detector that outputs a corresponding reference position detection signal when the zoom lens barrel passes a predetermined reference position, the movement amount detection signal and the reference position detection A drive unit for controlling switching of the DC motor between full drive, constant speed drive, and brake drive based on the signal, wherein the control unit detects the reference position. First control means for previously switching the DC motor to constant speed driving before a signal is output, and output from the encoder during constant speed driving when the reference position detection signal is output Second control means for starting counting of the movement amount detection signal, and, when the zoom lens barrel reaches a predetermined position as a result of the counting, switching from constant speed drive to brake drive, whereby the zoom lens barrel And a third control means for stopping at a target stop position. For example, the zoom lens barrel is extended and driven from a stop position for standby for zooming or focusing, and the control unit is configured to extend the zoom lens barrel by the first control unit to the third control unit. To the stop position for standby. Further, the position detector is constituted by electrical contacts comprising a combination of a slide plate fixed to the camera body corresponding to the reference position and a slider attached to the zoom lens barrel side. Have been.
[0007]
Further, the present invention detects a movement amount of the zoom lens barrel according to a rotation amount of the DC motor and outputs a corresponding movement amount detection signal to a DC motor that drives the zoom lens barrel via a wheel train. An encoder that outputs a signal, and a position detector that outputs a corresponding reference position detection signal when the zoom lens barrel passes a predetermined reference position, based on the movement amount detection signal and the reference position detection signal. A drive control method for a zoom lens barrel for a camera, wherein the DC motor is controlled to be switched among full drive, constant speed drive and brake drive, before the reference position detection signal is output. A first control procedure for switching to driving, and a second control procedure for starting counting of the movement amount detection signal output from the encoder during constant speed driving when the reference position detection signal is output. When the zoom lens barrel reaches a predetermined position as a result of the counting, a third control procedure of switching from constant speed drive to brake drive and stopping the zoom lens barrel at a target stop position is performed. It is characterized by the following.
[0008]
According to the present invention, a camera zoom lens barrel is driven by a DC motor and a speed reduction train. For detecting the position of the zoom lens barrel, an electrical contact composed of a combination of a slider mounted on the barrel side and a slide plate mounted on the camera body side and indicating a reference position is used. In order to measure the amount of movement of the zoom lens barrel from the detected reference position (detection position), an encoder that detects the amount of rotation of the DC motor is used. A control unit (CPU) that calculates a movement amount based on information output from the electrical contacts and the encoder and performs drive control at the same time is provided. The CPU controls the zoom lens barrel in advance at a constant speed from before the reference position carved on the slide plate to secure the approaching section. Thereafter, the distance between the reference position and the target stop position is reduced by performing the constant speed drive and the braking drive based on the reference position. At the same time, the stability (accuracy) of the stop position can be improved. Rather than shifting to constant-speed drive for the first time after detecting the reference position, constant-speed drive is started before the reference position is reached, and a sufficiently stable constant-speed state is guaranteed when the reference position is reached. . Here, by stopping the driving at a constant speed continuously for a predetermined distance from the reference position and then applying the braking, accurate stop position accuracy is obtained. Since braking is applied from a sufficiently stable constant speed state, the amount of overrun is always constant, and the stability of the stop position can be ensured. Further, since the approach section has already passed before reaching the reference position, the constant speed section between the stop position and the reference position can be shortened. As a result, the operating range of the zoom lens barrel can be shortened, which leads to downsizing.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a schematic block diagram showing the entire configuration of a drive control device for a camera zoom lens barrel according to the present invention. As shown in the figure, the apparatus includes a lens barrel 1, a DC motor 2, a wheel train 3, a driving unit (driver) 4, a position detector 5, an encoder 6, and a control unit (CPU) 7. The DC motor 2 drives the zoom lens barrel 1 via a deceleration wheel train 3. The encoder 6 is attached to the wheel train 3 or the rotating shaft of the DC motor 2, detects the moving amount of the zoom lens barrel 1 according to the rotating amount of the DC motor 2, and outputs a corresponding moving amount detection signal to the control unit 7. Output to The position detector 5 is attached to the lens barrel 1 and outputs a corresponding reference position detection signal when the zoom lens barrel 1 has passed a predetermined reference position. The control unit (CPU) 7 fully drives the DC motor 2 via the drive unit (driver) 4 based on the movement amount detection signal output from the encoder 6 and the reference position detection signal output from the position detector 5. Switching control is performed between constant speed driving and brake driving. As a characteristic feature, the control unit 7 includes first control means for switching the DC motor 2 to constant speed driving before the reference position detection signal is output, and constant speed driving when the reference position detection signal is output. A second control means for starting counting of the movement amount detection signal output from the middle encoder 6; and, when the zoom lens barrel 1 reaches a predetermined position as a result of the counting, switching from constant speed drive to brake drive. Third control means for stopping the zoom lens barrel 1 at a target stop position. Note that these first to third control means are means or procedures realized by a program executed by the CPU 7.
[0010]
FIG. 1B is a schematic perspective view showing the configuration around the zoom lens barrel. In the present embodiment, the zoom lens barrel 1 is driven out from a stop position (standby position) for standby for zooming or focusing. The CPU returns the zoom lens barrel 1 from the advanced position extended for zooming or focusing to the stop position (standby position) for standby by the first to third control units described above.
[0011]
In the present embodiment, the position detector is an electric device comprising a combination of a sliding plate 5z fixed to the camera body corresponding to the reference position and a slider 5a attached to the zoom lens barrel 1 side. It is composed of a passive contact. Specifically, pieces 5b and 5c made of a metal conductor are formed on the sliding plate 5z. When the slider 5a passes over these sections 5b and 5c, the electrical contacts are turned on / off and a predetermined reference position is detected. The section 5b is for detecting a wide position, and may be referred to as a wide detection plate in this specification. The section 5c is for detecting the retracted position. For example, when focusing on the section 5b, both ends 5b1 and 5b2 define the reference position. That is, when the slider 5a passes through both ends 5b1 and 5b2, the respective electrical contacts are turned on / off.
[0012]
Each operating position is indicated by a dotted line along the sliding plate 5z. From the near side to the front, the retracted position (lens cover closed), the lens cover open position, the standby position, and the infinite focus 1 are arranged in this order. When the power switch of the camera is turned on, the zoom lens barrel 1 is extended from the retracted position to the standby position through the lens cover open position. In the camera operation, the lens is extended forward for zooming or focusing with the standby position as a form position. When focusing on a subject at infinity, the subject is moved from the standby position to the infinite focus position. When the subject is at a short distance, the zoom lens barrel 1 is focused on the subject beyond the infinite focus position accordingly. Of course, in the case of zooming, it is largely extended forward from the standby position. When the photographing operation is completed, the zoom lens barrel 1 is returned from the focus position to the standby position. At that time, constant-speed driving is started before reaching the reference position 5b1, and the constant-speed state is stabilized in advance. Then, when the pulse passes the reference position 5b1 of the contact 5b, the counting of the pulses output from the encoder is started, and when the vehicle is moved backward by a predetermined distance in a constant speed state, the mode is switched to the brake drive. Thereby, it is possible to accurately return to the target stop position (standby position). Since the vehicle has already passed through the approach section for stabilizing the constant speed state, the distance between the standby position and the reference position 5b1 can be reduced. Thereby, the zoom lens barrel 1 can be reduced in size. In addition, since the brake is applied in a sufficiently stable constant speed state, the accuracy of the stop position increases.
[0013]
Hereinafter, a drive control method for a camera zoom lens barrel according to the present invention will be specifically described. FIG. 2 is a table showing control parameters used in the present drive control method and their contents. The parameter WIDTH_PI represents the number of pulses in the wide position detection signal ON section. This pulse is output from the encoder, and the movement distance of the lens barrel can be determined by counting the pulses. DCNST_PI is the number of pulses for performing constant speed control in the retracting direction. BREAK_TA represents a brake time during zoom driving. BREAK_TB represents the brake time at the time of the feed reverse rotation. BREAK_TF represents a braking time during focusing. WAIT_PI indicates the number of pulses from the standby position to the wide detection plate reference position 5b1. FCNST_PI represents the number of pulses for constant speed control during focusing. MASK_TM is a chattering removal time of the wide position detection signal. FOCUS_PI indicates the number of pulses of the zoom movement distance during focusing.
[0014]
FIG. 3 is a schematic diagram illustrating a drive control method of the camera zoom lens barrel when the power of the camera is turned on. The zoom lens barrel is once extended forward from the retracted position beyond the standby position, and is then driven to reverse and set to the standby position. In FIG. 3, the movement trajectory of the zoom lens barrel is indicated by a line with an arrow, and the reference positions 5b1 and 5b2 at both ends of the wide detection plate 5b are also displayed in a superimposed manner. When passing through one reference position 5b1, the reference position detection signal WonP1 is turned on / off. When passing through the other reference position 5b2, the reference position detection signal WonP2 is turned on / off. In this specification, these reference position detection signals are referred to as wide position detection signals.
[0015]
FIG. 4 is a flowchart showing the drive control mode shown in FIG. For ease of understanding, each step of the flowchart is represented by a numeral in a box, and the corresponding travel process in FIG. 3 is also represented by the same numeral in a box. Hereinafter, the standby position drive control mode will be described based on the flowchart of FIG. 4 with reference to the diagram of FIG. In this specification, the standby position may be called a wide end position in some cases. First, in step (1), full driving is performed until the wide position detection signal WonP1 is turned on. At step (2), only MASK_TM waits for chattering. In step (3), full drive is performed only by DCNST_PI-WAIT_PI. In step (4), the brake is applied only for BREAK_TB. In the above steps (1) to (4), zoom feed control is performed.
[0016]
Next, inversion is performed, and in step (5), the full drive is performed by (DCNST_PI-WAIT_PI) / 2. In step (6), the motor is driven at a constant speed until the wide position detection signal WonP1 is turned off. In step {circle around (7)}, the motor is further driven at a constant speed by WAIT_PI. When the wide position detection signal WonP1 is turned on due to backlash or the like, the counting is restarted from the off state. Finally, in step (8), brake is applied only for BREAK_TA. Through the above steps (5) to (8), the zoom inversion wide end stop control is completed.
[0017]
FIG. 5 is a timing chart of the drive control mode shown in FIGS. In the timing chart, the drive signal A and the drive signal B represent two-phase drive signals applied to the DC motor via the driver. When the level relationship between the drive signal A and the drive signal B is L (low level) / L (low level), brake drive is performed, and when H (high level) / L (low level), full drive (retreat) is performed. When L / H, the drive is full (forward), and when H / H, the DC motor is stopped. The on / off state of the wide position detection signal WonP1 is also shown corresponding to the level change of the drive signals A and B. Further, the pulses output from the encoder are also displayed. For ease of understanding, numbers (1) to (8) are attached to the horizontal axis of the timing chart corresponding to the steps in the flowchart shown in FIG.
[0018]
As shown in the figure, in steps (1), (2) and (3), the lens barrel is fully advanced and fully extended from the retracted position. After the brake is applied in step (4), the operation shifts to the inversion drive. That is, the reverse full drive is performed in step (5), and thereafter, the process proceeds to the constant speed drive in step (6). As is clear from the timing chart, this constant speed drive is performed by PWM-modulating the drive signals A and B. By executing PWM while monitoring pulses output from the encoder, constant speed control of the DC motor is realized. When the wide position detection signal switches from ON to OFF, the final constant speed control is performed while counting the encoder output pulses in step (7), and then the brake is applied in step (8) to reach the standby position. . In this way, a stable stop operation can be ensured while shortening the distance ΔL from the reference position to the stop position.
[0019]
FIG. 6 is a diagram showing a drive control mode in a case where the zoom lens barrel is returned from the telescopic position where the zoom lens barrel is largely extended to the standby position. To facilitate understanding, parts corresponding to those in FIG. 3 are denoted by corresponding reference numerals. FIG. 7 is a flowchart of the drive control mode shown in FIG. This drive control mode will be described based on the flowchart of FIG. 7 with reference to the diagram of FIG. In step (1), reverse full drive is performed until the wide position detection signal WonP2 is turned on. In step (2), the system waits for chattering for only MASK_TM. In step (3), reverse full drive is performed by WAIT_PI + WIDTH_PI-DCNST_PI. Thereafter, in step (4), the reverse full drive is switched to the reverse constant speed control, and the process is continued until the wide position detection signal WonP1 is turned off. In step (5), the encoder output pulses are counted, and the constant speed drive is performed by WAIT_PI. When WonP2 is turned on due to backlash or the like, the encoder output pulse is counted again after WonP1 is turned off again. Finally, in step (6), the brake is applied only by BREAK_TA and stopped at the target standby position.
[0020]
FIG. 8 is a diagram showing a drive control for returning from the standby position to the infinite focus position and returning to the standby position again. FIG. 9 is a flowchart of the drive control mode shown in FIG. This drive control mode will be described based on the flowchart of FIG. 9 with reference to the diagram of FIG. First, in step {circle around (1)}, full forward drive is performed from the standby position by FOCUS_PI + WAIT_PI-FCNST_PI. Next, in step (2), the motor is driven at a constant speed until the wide position detection signal WonP1 is turned on. In step (3), the motor is further driven at a constant speed by FOCUS_PI. Thereafter, in step (4), the brake is applied only by BREAK_TF, and the brake is accurately stopped at the target infinite focus position. With the above steps (1) to (4), the focus position drive stop control is completed. In this case, too, the control is shifted to the constant speed control before reaching the reference position 5b1, and the brake is applied after continuing the constant speed control for a predetermined number of pulses, thereby shortening the operation range and increasing the accuracy of the stop position. Has been realized.
[0021]
After the shutter drive for photographing is performed in step (5), the backward constant speed drive is started in step (6), and continues until the wide position detection signal WonP1 is turned off. In step {circle around (7)}, constant-speed driving is performed for WAIT_PI. When the wide position detection signal WonP2 is turned on due to backlash or the like, WonP1 is turned off and counting is performed again. Finally, in step (8), a brake is applied only for BREAK_TA, and the lens barrel is stopped at the standby position. With the above steps (6) to (8), the zoom wide end drive stop control is completed.
[0022]
FIG. 10 shows a drive control mode in which the lens is extended from the standby position to the short-distance focus position (for example, corresponding to 2.5 m) beyond the infinite focus position, and then returned to the standby position again. FIG. 11 is a flowchart of the drive control mode shown in FIG. Hereinafter, the present drive control mode will be described based on the flowchart of FIG. 11 with reference to the diagram of FIG. First, in step (1), forward full drive is performed until the wide position detection signal WonP1 is turned on. In step {circle around (2)}, further forward full drive is performed by FOCUS_PI-FCNST_PI. In step (3), the control is shifted to the constant speed drive by FCNST_PI. In step (4), brake is applied only for BREAK_TF. This completes the focus position drive stop control for extending the lens barrel to the target focus position.
[0023]
Then, after the shutter is driven in step (5), the process shifts to zoom wide end drive stop control. First, in step (6), reverse full drive is performed by FOCUS_PI + WAIT_PI-FCNST_PI. If the wide position detection signal WonP2 is still off, full driving is continued until it is turned on. At step {circle around (7)}, the operation shifts to constant speed driving, and continues until the wide position detection signal WonP1 is turned off. In step (8), the constant speed drive is continued by WAIT_PI. At this time, when the wide position detection signal WonP2 is turned on due to backlash or the like, the encoder output pulse is re-counted after WonP1 is turned off. Finally, in step (9), a brake is applied by BREAK_TA to stop the zoom lens barrel at the standby position. Thus, the zoom wide end drive stop control is completed.
[0024]
【The invention's effect】
As described above, according to the present invention, the first control procedure in which the DC motor is switched to the constant speed drive before the reference position detection signal is output, and the first control procedure when the reference position detection signal is output, A second control procedure for starting counting of a movement amount detection signal (pulse) output from the encoder during the high-speed driving, and when the zoom lens barrel reaches a predetermined position as a result of the pulse counting, the constant-speed driving is switched to the brake driving. A third control procedure is performed to switch the zoom lens barrel to the target stop position in response to the switching. With such a drive control method, it is possible to move between a target stop position such as a standby position and a focus position within a small operation range, while ensuring stability of the stop position control. As a result, it has become possible to provide a high-speed, compact, and low-priced zoom lens barrel for a camera.
[Brief description of the drawings]
FIG. 1A is a schematic block diagram illustrating an entire configuration of a drive control device of a zoom lens barrel for a camera according to the present invention, and FIG. 1B is a schematic diagram illustrating a configuration around a zoom lens barrel. FIG.
FIG. 2 is a table showing control parameters and their contents used in a drive control method of a zoom lens barrel for a camera according to the present invention.
FIG. 3 is a schematic diagram illustrating a drive control method of a camera zoom lens barrel when the power of the camera is turned on.
FIG. 4 is a flowchart showing a drive control mode shown in FIG.
FIG. 5 is a timing chart of the drive control mode shown in FIGS. 3 and 4.
FIG. 6 is a diagram illustrating a drive control mode in a case where the zoom lens barrel is returned from a telescopic position where the zoom lens is largely extended to a standby position.
FIG. 7 is a flowchart of the drive control mode shown in FIG.
FIG. 8 is a diagram showing a drive control for returning from a standby position to an infinite focus position and returning to a standby position again.
FIG. 9 is a flowchart of the drive control mode shown in FIG.
FIG. 10 is a diagram illustrating a drive control mode in which a lens is extended from a standby position to a short-distance focus position beyond an infinite focus position, and then returned to the standby position.
11 is a flowchart of the drive control mode shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Zoom lens barrel, 2 ... DC motor, 3 ... Wheel train, 4 ... Drive part, 5 ... Position detector, 5a ... Slider, 5b ... Intercept, 5b1... Reference position, 5b2... Reference position, 5c... Intercept, 6... Encoder, 7... Control unit (CPU)

Claims (4)

A zoom lens barrel for a camera, a DC motor that drives the zoom lens barrel via a wheel train, and a corresponding movement by detecting a movement amount of the zoom lens barrel according to a rotation amount of the DC motor An encoder that outputs an amount detection signal, a position detector that outputs a corresponding reference position detection signal when the zoom lens barrel passes a predetermined reference position, and an encoder that outputs the movement amount detection signal and the reference position detection signal. A drive unit for controlling the switching of the DC motor between full drive, constant speed drive, and brake drive based on the DC motor,
The control unit, a first control unit that switches the DC motor to constant speed drive in advance before the reference position detection signal is output,
When the reference position detection signal is output, a second control unit that starts counting the movement amount detection signal output from the encoder during constant speed driving,
When the zoom lens barrel reaches a predetermined position as a result of the counting, the control means switches from constant-speed drive to brake drive, thereby stopping the zoom lens barrel at a target stop position. A drive control device for a zoom lens barrel for a camera. The zoom lens barrel is driven out from the stop position for standby for zooming or focusing,
2. The zoom lens barrel for a camera according to claim 1, wherein the control unit returns the zoom lens barrel from the extended position to the stop position for standby by the first control unit to the third control unit. Drive control device. The position detector is configured by an electrical contact made of a combination of a sliding plate fixed to the body of the camera corresponding to a reference position and a slider attached to the zoom lens barrel side. 2. A drive control device for a camera zoom lens barrel according to claim 1, wherein: An encoder for detecting a movement amount of the zoom lens barrel according to a rotation amount of the DC motor and outputting a corresponding movement amount detection signal for a DC motor that drives the zoom lens barrel via a wheel train; A position detector that outputs a corresponding reference position detection signal when the zoom lens barrel passes a predetermined reference position, and controls the DC motor based on the movement amount detection signal and the reference position detection signal. In a drive control method of a camera zoom lens barrel that controls switching between full drive, constant speed drive, and brake drive,
A first control procedure in which the DC motor is switched to constant speed drive before the reference position detection signal is output;
When the reference position detection signal is output, a second control procedure to start counting the movement amount detection signal output from the encoder during constant speed driving,
When the zoom lens barrel reaches a predetermined position as a result of the counting, a third control procedure of switching from constant speed drive to brake drive and stopping the zoom lens barrel at a target stop position is performed. A drive control method for a zoom lens barrel for a camera, comprising:

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