JPH05181051A - Lens position controller - Google Patents

Abstract

PURPOSE:To reduce the circuit scale of a lens position controller which can obtain rapid and proper response characteristic at the time of moving a lens or stopping it and to make production cost low. CONSTITUTION:This controller is provided with lens groups 2 and 3 which move an optical axis direction, driving means 7 and 14 which drive the lens groups 2 and 3, storage means 12 and 15 which previously store the relation between the input in the driving means 7 and 14 and the response of the lens groups 2 and 3, and a control means 5 which selects the driving condition of the lens groups 2 and 3 based on data read out from the storage means 12 and 15 and controls the driving means 7 and 14, and also detects the positions of the lens groups 2 and 3 based on the data, the past driving condition and lens driving time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens position control device for optical devices such as video cameras and cameras.

[0002]

2. Description of the Related Art In a conventional lens position control device of this type, a DC motor, a step motor or the like is used as a driving device. Also, for example, Japanese Patent Laid-Open No. 61-175606
JP-A-61-97616, JP-A-61-97616
As disclosed in Japanese Patent No. 244911, etc., a coil is wound around a movable lens holding frame and a permanent magnet is provided on a fixed lens barrel, and the driving force generated by energizing the coil causes the lens to vibrate slightly, 2. Description of the Related Art A micro-vibration device or the like is used that performs focus amount modulation and focus adjustment by slightly changing the optical path length in the axial direction.

[0003]

However, in the above-mentioned conventional lens position control device, when a rotary motor such as a DC motor or a step motor is used as a drive device, a rotation-linear motion conversion mechanism is required, and therefore, the device is required. There is a problem that it will become larger. Also, when using the microvibration device, the microvibration for focus amount modulation and the lens movement for focus adjustment are performed using different actuators, so the control mechanism becomes complicated and large, and the cost increases. There are problems such as

Therefore, as a structure not requiring a rotation-linear motion conversion mechanism, a coil and a permanent magnet are arranged relatively to the fixed lens barrel and the movable part, respectively, and the movable part is moved by energizing the coil. So-called voice coil motors have been considered.

However, when this boil coil motor is used in a lens position control device, in order to obtain a quick response characteristic, a position or speed feedback circuit network or the like is required, which causes a problem that the circuit scale increases. there were.

It is an object of the present invention to obtain a lens position control device that solves the above conventional problems.

[0007]

According to the present invention, a lens group moving in the optical axis direction, a driving means for driving the lens group, a relationship between an input to the driving means and a response of the lens group. And a drive means for controlling the drive means of the lens group based on the data read out from the storage means and controlling the drive means. By including the control means for detecting the position of the lens group, it is possible to obtain a quick and appropriate response characteristic when the lens is moved or stopped. Further, since the lens position can be detected, it is possible to reduce the lens position detection device, the position or speed feedback circuit network, etc., and it is possible to reduce the circuit scale and the manufacturing cost.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a view best showing the features of the present invention.
The illustrated example shows an embodiment in a lens position control device of a video camera using a rear focus zoom as an optical system.

In FIG. 1, 1 is a first lens group, 2 is a variator that moves in the optical axis direction to perform zooming, and 3 is moved in the optical axis direction to compensate for the focusing action and the focus movement associated with zooming. This is a focus lens group that simultaneously performs focus correction.

Reference numeral 4 is a zoom switch for instructing the zoom direction, 5 is a CPU as control means, and 6 is a zoom motor for driving a zoom motor 7 as drive means based on an output signal from the CPU 5 to move the variator 2. A driver, 8 is a variator position detection circuit that reads the position of the variator 2 and sends the information to the CPU 5, 9 is a CCD
An autofocus (AF) circuit for detecting focus information included in the image signal from the image pickup member 10 such as a camera circuit 11 is a camera circuit for processing the image signal and then sending it to a recorder unit (not shown).

Reference numeral 12 denotes a first data storage device in which movement data of the focus lens group 3 associated with zooming is stored in advance, and reference numeral 13 drives a focus motor 14 based on an output signal from the CPU 5 to drive the focus lens. Focus motor driver as driving means for moving the group 3, 1
Reference numeral 5 denotes a second data storage device in which information regarding the relationship between the drive signal for driving the focus motor 14 and the movement amount of the focus lens group 3 is stored in advance.

The CPU 5 simultaneously selects driving conditions according to the situation based on the data read from the first and second data storage devices 12 and 15 and detects the focus lens position from past driving conditions. To do.

FIG. 2 is a perspective view showing a lens moving mechanism in the present embodiment. In FIG. 2, 51 is an outer lens barrel to which a coil (not shown) is wound around the entire inner circumference and adhered, 52.
Reference numerals a and 52b are guide bars provided in the outer lens barrel 51 in parallel with the optical axis, 53 is sleeves 54a and 54b fitted to the guide bars 52a and 52b, and a semicircular magnetic member 55a,
55b is a lens holding frame formed in a cylindrical shape by 55b.
The magnetic members 55a, 55b are magnetized in a radial direction outward from the optical axis 56, and by applying a voltage to the coil, the lens holding frame 53 holding a lens group (not shown) is moved in the optical axis direction. Move to.

FIG. 3 is a diagram showing a lens position detecting device in this embodiment. In FIG. 3, 101 is an A electrode also serving as a guide bar, 102 is a B electrode also serving as a guide bar, and 103a and 103b are cylindrical. Make A electrode 10
1, outer electrodes 104a and 104b facing the B electrode 102 to form a capacitor, 104a and 104b are sleeves of a lens holding frame holding a lens group (not shown), and are fitted to the A electrode 101.

FIG. 4 is a signal processing circuit diagram for processing a detection signal from the position detecting device of FIG. In FIG. 4, 15
1 generates a rectangular wave to generate a timer 152 and resistors R ₁ and R ₂
Is a pulse generator for generating pulses to be applied to the variable capacitors VC ₁ and VC ₂ respectively. The variable capacitors VC ₁ and VC ₂ correspond to the capacitors composed of the A electrode 101, the electrode B 102, and the outer electrodes 103a and 103b in FIG. 3, respectively. The electric capacity of each is changed by.

The timer 152 starts time counting at the same time when a pulse is applied from the pulse generator 151,
After a certain period of time, a trigger is output to the voltage reading circuit 153 and the voltage reading circuit 154. The voltage reading circuit 153 and the voltage reading circuit 154 supplied with this trigger.
Reads the voltage corresponding to the variable capacitors VC ₁ and VC ₂ , respectively. 155 is a voltage reading circuit 153 and 15
4 is a differential circuit that outputs a signal corresponding to the lens position from the voltage values of the above-mentioned variable capacitors VC ₁ and VC ₂ received from the circuit 4.

FIG. 5 shows, as curves A and B, the voltage changes at the terminals A and B after the pulse is output from the pulse generator 151 in FIG. In this way, since the time constant changes with the variable capacitors VC ₁ and VC ₂ ,
The position of the lens can be detected by detecting the voltages V _A and V _B of the terminals A and B after a fixed time and taking the difference between them.

FIG. 6 is a diagram for explaining the properties of the optical system in this embodiment, where the horizontal axis represents the variator position and the vertical axis represents the focus lens position. As is clear from the figure, such an optical system has a property that a focal point shift occurs due to changes in the variator position and the subject distance.
For this reason, when the magnification is changed during shooting of the same subject, the focus lens is out of focus unless the focus lens is moved.

Curves a, b, and c shown in FIG. 6 represent the movement paths of the focus lens necessary for maintaining the focus during zooming, and the curves a, b, and c are the subject distance infinity and 5 m, respectively. , 1 m is shown.

As described above, in such an optical system, the focus lens follows the above-mentioned movement locus during zooming,
In addition, it becomes necessary to change the movement locus according to the object distance and move the movement.

Therefore, in this embodiment, for example, according to the characteristic diagram shown in FIG. 7, the zone is divided into a plurality of zones, and the speed of the representative focus lens is preset for each zone and stored in the data storage device. Therefore, if the in-focus state is maintained before the start of zooming, the speed of the representative focus lens can be read from the data storage device by the variator, focus lens, and information on the zooming direction. Since the moving speed of is determined, it is possible to perform the zooming operation while maintaining the in-focus state.

FIG. 8 shows an AF circuit. In FIG. 8, 201 is a bandpass filter for extracting a frequency component of a constant band contained in a luminance signal separated from an image signal, and 202 is a bandpass filter 201. A full-wave rectifier circuit 203 that outputs the absolute value of the output, 203 is a full-wave rectifier circuit 2
This is a peak hold circuit that holds the maximum value of the output of 02 for a certain period of time.

The output of the band-pass filter 201 has a pass band set so that a constant high-frequency component in the luminance signal is included, and the high-frequency component has a signal amplitude depending on the degree of focusing. Since it changes, this will be described with reference to FIGS.

In FIG. 9, reference numeral 210 denotes the entire screen area, and 211 is a range in which a signal for focusing operation is obtained. If the luminance distribution is as shown in FIG. 9, A
The signal in the F circuit is processed as shown in FIGS. (A) is a luminance signal, (b), (c), and (d) are a bandpass filter 201, a full-wave rectification circuit 202,
This is the output of the peak hold circuit 203.

Here, the amplitude A of the output signal of the peak hold circuit 203 shown in FIG. 10 (d) is as shown in FIG.
In FIG. 11, the horizontal axis represents the focus lens position, and the vertical axis represents the above-mentioned amplitude A. Since this amplitude A has a mountain-shaped output value with the in-focus point as the maximum value with respect to the focus lens position, the output signal Automatic focus adjustment can be realized by moving the focus lens to the focus lens position that takes the maximum value and stopping it.

FIG. 12 shows the waveform of a signal applied to the coil in the lens moving mechanism of FIG. 2. This signal is a continuous pulse train, the period of which is high level time t ₁ ,
The low level time t ₂ , the high level voltage V _H , and the low level voltage 0.

FIG. 13 is a diagram showing the response to the above-mentioned signal application, and the period T when V _H and t / T are constant.
Shows the relationship between the lens speed after a certain period of time and
The curves a, b, and c have t ₁ / T of 0.2, 0.4, and
The case of 0.6 is shown. Further, FIG. 14 shows the above V
The relationship between the time and the lens position when _H , t ₁ / T ₁ and T are constant is shown. Curves a, b, c and d show t ₁ / T of 0.1, 0.2 and The response is shown for 0.4 and 0.6.

If such a response is stored in the data storage device in advance and the moving speed of the focus lens is controlled by the data read from the data storage device according to the situation, the target speed can be quickly followed. Further, since the integrated travel distance can be calculated from the past control conditions, the data when the control conditions are taken, and the response data described above, the position can be detected.

In the case of this embodiment, there is an advantage that the timer output in the variator position detection circuit can be used as the time information. When the capacity of the data storage device is small and only a small amount of data can be stored, part of the data may be stored and the other data may be calculated by interpolation calculation.

The operation of the embodiment according to the present invention will be described below with reference to the flow chart of FIG. When the processing is started (step ST1), it is determined whether zooming is in progress (step ST2), and if YES is determined, the zoom direction is W →
It is determined whether it is T (step ST3). If YES in the W → T direction, the direction flag is set to 1 (step ST
4) If NO in the T → W direction, the direction flag is cleared to zero (step ST5).

After that, the position of the variator is detected (step ST6), and the variator speed is calculated from the previous variator position, the current variator position, and time information (not shown) (step ST7). Next, after detecting the AF signal and calculating the fine adjustment amount of the drive speed (step ST8),
The position of the focus lens is calculated from the past drive history and time information (step ST9).

Next, the area in the aforementioned zone division is determined from the obtained variator position and focus lens position, and the representative speed is read (step ST10).
Then, the parameters (V _H , t ₁ / T, T described above) for driving the focus lens are determined based on the AF signal detection result, the representative speed, the response data, the variator speed, and the like (step ST11).

Then, it is determined whether or not the zoom is started (step ST12). If YES is determined at the zoom start, the focus lens is driven in accordance with the direction flag and the parameter value described above, and the variator is driven after a predetermined time has passed ( Step ST13). This is for accelerating the focus lens to near the target speed to enhance the apparent speed responsiveness, and its time delay changes depending on the target speed. If the result of the determination in step ST12 is NO and it is not the time to start zooming, the focus lens is driven according to the above-mentioned direction flag and parameter value (step ST14).

On the other hand, if the decision result in the step ST2 is NO and zooming is not in progress, an AF signal is detected (step S
T15), after calculating the focus lens position (step ST16), the target speed is calculated from the result of step ST15 (step ST17), and the focus lens drive parameter is calculated from this calculation result (step ST1).
8) The focus lens is driven according to this parameter (step ST19).

As described above, a quick speed response can be obtained,
The position of the focus lens can be detected without an encoder.

The focus lens moving mechanism does not have the structure shown in FIG. 2, but may be a DC motor, for example.
Other rotary type motors may be used. Further, the position detector of the variator includes variable capacitors VC ₁ and VC ₂
It is also possible to use, for example, a PSD, a photo interrupter, a gray scale, a resistance type encoder, or the like instead of using the above. Further, the data stored in the data storage device is not necessarily speed data, but may be stored as position data and converted into speed data.

[0037]

As described above, according to the present invention,
Since the lens driving device is configured to be controlled on the basis of the relational data between the input and the response of the lens driving device stored in advance, a quick and appropriate response characteristic when the lens is moved or stopped is obtained. be able to. Also,
Since the lens position is calculated and detected from the above-mentioned stored contents, the lens driving condition, and the lens driving time information, the lens position detecting device, the feedback network such as the position or speed, etc. can be reduced, and the circuit scale can be reduced. And the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a lens moving mechanism in the embodiment.

FIG. 3 is a diagram showing a lens position detection device according to an embodiment.

FIG. 4 is a signal processing circuit diagram from the lens position detection device of FIG.

5 is a terminal voltage change curve diagram of the variable capacitor of FIG.

FIG. 6 is a movement locus diagram of a focus lens required for maintaining focus during zooming.

FIG. 7 is a change characteristic diagram of the focus lens position with respect to the variator position.

FIG. 8 is a block diagram showing an autofocus circuit.

FIG. 9 is a screen area diagram.

FIG. 10 is a signal waveform diagram in the autofocus circuit of FIG.

11 is an output signal waveform diagram of a peak hold circuit in the autofocus circuit of FIG.

12 is a signal waveform diagram applied to the coil in the lens moving mechanism of FIG.

FIG. 13 is a characteristic diagram showing a change in lens speed with respect to time according to a coil current.

FIG. 14 is a characteristic diagram of a change in lens position with time according to a coil current.

FIG. 15 is a flowchart for explaining the operation of the embodiment.

[Explanation of symbols]

 2 lens group 3 lens group 5 CPU (control means) 7 zoom motor (drive means) 12 data storage device (storage means) 14 focus motor (drive means) 15 data storage device (storage means)

Claims (1)

[Claims] 1. A lens unit that moves in the optical axis direction, a drive unit that drives this lens unit, and a storage unit that stores in advance the relationship between the input to the drive unit and the response of the lens unit. Control means for selecting the driving condition of the lens group based on the data read from the storage means to control the driving means and detecting the position of the lens group from the data, the past driving condition and the lens driving time. And a lens position control device.