JPH11281872A - Lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the contents of lens control instructed by a lens controller surely correspond to the contents of the lens control performed by a lens driving device by automatically adjusting the voltage level of an analog control signal so that the reference voltage of the control signal adequately corresponds to the reference value of a digital signal with respect to a lens driving device by which the analog control signal is inputted from the lens controller, the inputted control signal is A/D-converted to the digital signal, and the lens con trol is performed. SOLUTION: In this lens driving device, a CPU 58 connects a switch circuit 50 to a voltage VREFC generating a center voltage so that the output value of an A/D converter 66 becomes the center value of the digital signal when the center voltage of the control signal is inputted from a zoom demand 26, and the input and output characteristic of a voltage converting circuit 54 is adjusted by automatically controlling the digital potentiometer U3 of an offset circuit 56 so that the output value of the converter 66 becomes the center value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device, and more particularly to a lens driving device for controlling driving of a lens such as a focus lens or a zoom lens based on a control signal from a lens controller.

[0002]

2. Description of the Related Art Conventionally, there is a lens device used for a television camera or the like in which a lens driving device for driving a focus lens or a zoom lens by a motor is mounted or mounted. A lens controller (for example, a focus demand or a zoom demand) operated by a cameraman or the like is connected to the lens driving device, and a motor of the lens driving device is controlled by a control signal transmitted from the lens controller to drive the focus lens or the zoom lens. It is supposed to be.

In recent years, microcomputers have been mounted on lens driving devices, and microcomputers often perform complicated lens control.

[0004]

As described above, in a lens driving device equipped with a microcomputer as described above, since lens control is performed by digital processing, the lens controller transmits an analog control signal. (When an operation amount of the lens controller is detected by an analog circuit such as a potentiometer, an analog control signal is transmitted from the lens controller.)
The control signal is converted into a digital signal by an A / D converter.

In this case, it is necessary to match the contents of the lens control instructed by the lens controller with the contents of the lens control performed by the lens driving device. Therefore, the reference voltage of the analog control signal and the digital signal When a reference value is set and a reference voltage control signal is input from the lens controller, the A / D converter converts the reference voltage control signal into a reference value digital signal.

For example, when controlling the speed of a lens, the lens controller outputs an analog control signal indicating the moving direction and the moving speed of the lens, and usually instructs the center voltage of the voltage change range of the control signal to stop the lens. Voltage. On the other hand, the lens driving device recognizes the center value of the output value change range of the A / D converter as a value for controlling the lens to a stop state. Therefore, when the control signal of the reference voltage is input from the lens controller, the center voltage of the control signal and the center value of the output value of the A / D converter are used as the reference voltage of the control signal and the reference value of the digital signal, respectively. In this case, this control signal is converted into a digital signal of a reference value by A /
D-convert. Thus, when the lens controller has instructed to stop the lens, the lens can be stopped appropriately.

However, even if an A / D converter and other peripheral circuits are designed so as to obtain such A / D conversion characteristics, the linearity (linearity) which is the conversion characteristic of the A / D converter is actually obtained. ), Variations in parameters of each element of the peripheral circuit, and problems with temperature characteristics, it is difficult to accurately associate the reference value of the digital signal with the reference voltage of the control signal. For this reason, in the above-described example, there is a case in which, although the lens controller instructs to stop the lens, the lens does not actually stop but continues moving at a very low speed. is there.

Therefore, conventionally, an offset circuit using a variable resistor is provided so that the voltage level of the control signal can be adjusted before the control signal from the lens controller is input to the A / D converter. Although there is an adjustment that allows the reference voltage and the reference value of the digital signal to correspond appropriately, such an offset circuit requires time and effort such as manual adjustment. There was a problem that could not be readjusted. Further, there is a problem that the offset adjustment cannot be performed while the photographing is being performed, even if the above-described problem is confirmed during the photographing.

The present invention has been made in view of such circumstances, and a lens drive for inputting an analog control signal from a lens controller and A / D converting the input control signal into a digital signal to perform lens control. In the apparatus, by automatically adjusting the voltage level of the analog control signal and appropriately associating the reference voltage of the control signal with the reference value of the digital signal, the contents of the lens control instructed by the lens controller and the lens driving device It is an object of the present invention to provide a lens driving device that reliably prevents a problem that the contents of the lens control performed by the camera do not match.

[0010]

According to the present invention, in order to achieve the above object, an analog control signal is received from a lens controller, and the voltage of the received control signal is converted into a digital signal by an A / D converter. A lens driving device that drives a lens based on the value of the digital signal, wherein a voltage of the control signal is converted by a predetermined voltage conversion characteristic,
Voltage conversion means for inputting the converted control signal to the A / D converter; and a digital signal output from the A / D conversion means when a predetermined reference voltage is input to the voltage conversion means. Control means for adjusting a voltage conversion characteristic of the voltage conversion means so that the value coincides with a predetermined reference value.

A reference voltage generating means for generating the reference voltage; and a signal input to the voltage converting means, a reference voltage signal output from the reference voltage generating means or a control signal output from the lens controller. Switching means for switching the voltage conversion characteristic of the voltage conversion means by inputting a signal of the reference voltage to the voltage conversion means by the switching means.

According to the present invention, when a control signal of a reference voltage is input from the lens controller, an output value obtained by converting the reference voltage by the A / D converter matches the reference value of the digital signal. Since the voltage level of the control signal is automatically adjusted, the reference voltage of the control signal and the reference value of the digital signal can be easily and accurately associated with each other. It is possible to reliably prevent a problem in which the contents of the lens control performed by the driving device do not match.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a lens driving device according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing an embodiment of a television camera to which a lens driving device according to the present invention is applied. As shown in FIG. 1, the television camera 10 includes a lens unit 12 and a camera unit 14, and is supported by a camera platform 18 on a pedestal dolly 16. The head 18 has two operation rods 2
2 and 23 are extended, and a zoom demand 26 for operating a zoom speed is attached near the grip 24 of the operation rod 22. On the other hand, a focus demand 28 for operating a focus is attached to an end of the operation rod 23.

The zoom demand 26 is a thumb ring 3
A speed control signal for performing a zoom operation to the wide angle side or the telephoto side in accordance with the rotation direction and the rotation amount of the zoom lens 4 is output to the lens unit 12 via the cable 30. The lens unit 12 controls the speed of the zoom lens based on the speed control signal to drive the zoom lens.
The details of the control of the zoom lens will be described later.

On the other hand, the focus demand 28 transmits a position control signal for instructing a moving position of the focus lens in accordance with a rotation operation amount of the focus ring 28A to the cable 3.
1 to the lens unit 12. The lens unit 12
The focus lens is moved to a commanded position based on the position control signal. The cameraman adjusts the focus by rotating the focus ring 28A of the focus demand 28 with the right hand while looking at the captured image reflected on the bee finder 32, and performs the zoom adjustment by operating the thumb ring 34 of the zoom demand 26 with the left hand. Do.

FIG. 2 is a circuit diagram showing an embodiment of a lens driving device in the lens section 12. As shown in FIG.
FIG. 2 is a diagram showing only a lens driving circuit of a zoom lens, and a driving circuit of another lens such as a focus lens is omitted. As shown in the figure, the lens driving device includes a switch circuit 50, a buffer circuit 52, a voltage conversion circuit 54, an offset circuit 56, a CPU 58, an amplifier 60, a drive motor 62, and a zoom lens 64.

A speed control signal (hereinafter, simply referred to as a control signal) corresponding to the rotational position of the thumb ring 34 is input from the zoom demand 26 to the switch circuit 50. This control signal is an analog signal having a change range of 2.5 V to 7.5 V. When the thumb ring 34 is not operated, a voltage of 5 V for instructing stop of the zoom lens is input. Instruct to stop this zoom lens 5
The voltage of V is in a voltage change range of the control signal (2.5 V to 7.5).
V), which is the reference voltage of the control signal.

The switch circuit 50 is connected to the pin P of the CPU 58.
The switch SW1 is connected to the zoom demand 26 and the reference voltage VR of 5 V by a command signal output from
Switch to EFC side. This switching control will be described later, but during normal lens drive control, the switch SW
1 is connected to a zoom demand 26 and a zoom demand 2
The control signal inputted from 6 is inputted to the buffer circuit 52.

The buffer circuit 52 includes an operational amplifier U1 and a resistor R1 (2M) connected to the + input terminal of the operational amplifier U1.
Ω) and a reference voltage VREFC of 5V,
The control signal output from the switch circuit 50 is input to the + input terminal of the operational amplifier U1. The buffer circuit 52 outputs the control signal input to the + input terminal of the operational amplifier U1 from the output terminal of the operational amplifier U1 as it is, and inputs the control signal to the next voltage conversion circuit 54.

The voltage conversion circuit 54 includes an operational amplifier U2,
The reference voltage VREFC of 5 V connected to the + input terminal of the operational amplifier U2, the voltage VDC of 1.66 V, and the resistor R5 (3
0 kΩ), a resistor R6 (20 kΩ), and an operational amplifier U2.
Input resistance R2 (30 kΩ) connected to the-input terminal of
And a feedback resistor R4 (20 kΩ) connected between the − input terminal and the output terminal of the operational amplifier U2. The resistors R5 and R6 are connected to the reference voltage VREFC and the voltage VD.
C is connected in series, and the resistors R5 and R6 divide the voltage between the reference voltage VREFC and the voltage VDC to apply a voltage of 3 V to the + input terminal of the operational amplifier U2. .

The voltage conversion circuit 54 thus configured
Is a change range of the control signal input to the input resistor R2.
This circuit converts a voltage of 5 V to 7.5 V into a voltage of an input voltage range of 0 V to 3.33 V of an A / D converter 66, which will be described later, and converts the voltage of the control signal input to the input resistor R2 to the input voltage Vin. And the operational amplifier U2 with respect to this input voltage Vin.
Is the output voltage Vout, the input / output characteristics (voltage conversion characteristics) of the voltage conversion circuit 54 are expressed by the following equation (1).

Vout = 5-2 / 3 × Vin (V) (1) FIG. 3 is a graph showing Expression (1). As shown in FIG. 3, the input voltage Vin is lower than the lower limit voltage 2.5 V of the control signal.
, The output voltage Vout becomes the upper limit voltage 3.33V of the A / D converter 66, and when the input voltage Vin is the upper limit voltage 7.5V of the speed control signal, the output voltage Vout becomes the lower limit voltage 0V of the A / D converter. Becomes Further, when the input voltage Vin is the reference voltage (center voltage) of the control signal of 5 V, the output voltage Vout also becomes the center voltage 1.66 V of the input voltage range of the A / D converter 66 from 0 V to 3.33 V.

The control signal thus input to the voltage conversion circuit 54 is supplied to the control signal by the voltage conversion circuit 54 from 0V to 3.33.
After being converted to a voltage signal of V, the CPU 58
Input to terminal 0. A predetermined voltage is applied from the offset circuit 56 to the negative input terminal of the operational amplifier U2. As will be described later in detail, the straight line indicating the input / output characteristics of the voltage conversion circuit 54 shown in FIG. 3 is shifted up and down by the rise and fall of the applied voltage.

The control signal input to the AN0 terminal of the CPU 58 is then transmitted to an A / D converter 66 mounted on the CPU 58.
Is converted into a 16-bit digital signal, for example. The A / D converter 66 is mounted for the CPU 58 to recognize the control signal as a digital value.
Of course, it may be provided separately from the CPU 58. The case where the A / D converter 66 converts the control signal into a 16-bit digital value will be described.
Converts the voltage from 0 V to 3.33 V of the control signal voltage-converted by the voltage conversion circuit 54 as shown in FIG. 4 into a value from 0000H to FFFFH represented by a hexadecimal number. Ideally, the reference voltage (center voltage) of the speed control signal is 1.66 V (zoom demand 2).
Reference voltage (center voltage) of the control signal input from 6-5V
Is converted to 0 by the voltage conversion circuit 54).
Central value of digital value from 000H to FFFFH 80
Convert to 00H. The CPU 58 uses the center value 8000H of the output value range 0000H to FFFFH as a reference value.

The CPU 58 sets the rotation direction and rotation speed of the drive motor 62 of the zoom lens 64 based on the digital value output from the A / D converter 66 in this manner. That is, the output value of the A / D converter 66 is the reference value 800
In the case of 0H, it is determined that the operation of the thumb ring 34 (see FIG. 1) of the zoom demand 26 is no operation, and the drive motor 6
2 is set to the stop state. And this reference value 8
When the output value of the A / D converter 66 is larger than the reference value 8000H, the rotation direction of the drive motor 62 is set to forward rotation when the output value is smaller than the reference value 8000H. The rotational speed of the drive motor 62 is set higher as the difference between the reference value and the reference value 8000H is larger.
It should be noted that the zoom demand 26 outputs 2.5V to 7.5.
Since the magnitude of the control signal voltage up to V and the voltage of the control signal from 0 V to 3.33 V input to the A / D converter 66 are inverted in the voltage conversion circuit 54 (see FIG. 3). If the zoom demand 26 outputs a voltage higher than the reference voltage 5V, the drive motor 62 rotates in the reverse direction, and if the zoom demand 26 outputs a voltage lower than the reference voltage 5V, the drive motor 62 rotates in the forward direction.

When the rotation direction and the rotation speed of the drive motor 62 are set as described above, the CPU 58 then sends a drive signal via the amplifier 60 to drive the drive motor 62 in the rotation direction and the rotation speed. Output to Thereby, the drive motor 62 is driven in the rotation direction and the rotation speed, and the zoom lens 64 moves in the direction and speed based on the operation of the thumb ring 34 of the zoom demand 26.

With the configuration described above, the zoom lens 6
4 is driven by a control signal from the zoom demand 26. By the way, the parameters of each element of each circuit and the conversion characteristics of the A / D converter 66 do not exactly match the theoretical ones. For this reason, even if the A / D converter 66 outputs the reference value 8000H when the reference voltage of 5 V is input from the zoom demand 26, it may not actually be possible even in the design stage. More). In such a case, there occurs a problem that the zoom lens 64 is in a moving state even when the thumb ring 34 of the zoom demand 26 is not operated. In order to prevent such a problem, an offset circuit 56 as shown in FIG. 2 is provided.

As shown in FIG. 2, the offset circuit 56
It is constituted by a digital potentiometer U3 composed of one chip. This digital potentiometer U3 is basically a digital variable resistor that can change the contact position of the slider by a pulse signal. The VH terminal (pin number 3) and the VL terminal (pin number 6) are the variable resistors. The VW terminal (pin number 5) corresponds to the terminal of the slider of the variable resistor. Note that a voltage of 5 V from the reference voltage VREFC is applied to the VH terminal, and the VL terminal is grounded.

Each time one pulse is input to the INC terminal (pin number 1), the slider is shifted to the VH terminal side or the VL terminal side by the unit opposing value, and the shift direction is UD. Switching is performed according to the signal level input to the terminal (pin number 2). That is, when a pulse is input to the ING terminal while an H level signal is input to the UD terminal, the slider moves to the VH terminal side, and the L level is input to the UD terminal.
When a pulse is input to the ING terminal while a level signal is being input, the slider moves to the VL terminal side.

The VCC terminal (pin No. 8) and the VSS terminal (pin No. 4) are power supply lines for driving the digital potentiometer U3. A voltage of 5 V from the power supply VCC is applied to the VCC terminal, and the VSS terminal is grounded. Is done. When an L-level signal is input to the CS terminal (pin number 7), the operation of potentiometer U3 is turned on, and when an H-level signal is input, the operation of potentiometer U3 is turned off.

FIG. 5 shows the digital potentiometer U
3 is an equivalent circuit showing the internal configuration of the third embodiment. As shown in the figure, a VH terminal (pin number 3) and a VL terminal (pin number 6)
A resistor body in which a plurality of resistors RS having the same resistance value are connected is provided. Then, the FETs 70 and 7 are placed between the resistors RS.
., And each point between the resistor RS and the VW terminal (pin number 5) is connected via the drain and the source of the FET 70. The gate of the FET 70 is connected to a processing unit 72 described later.

On the other hand, an INC terminal (pin number 1) and a UD terminal (pin number 2) are connected to a processing unit 7 having a counter function.
2 is connected. When an H level signal is input from the UD terminal, the processing unit 72 increments an internal counter by one each time one pulse is input from the INC terminal,
When an L-level signal is input from the UD terminal, the counter is decremented by one each time one pulse is input from the INC terminal.

The processing section 72 outputs an H-level signal to the gate of the FET 70 previously associated with the value of the counter, and makes the drain-source of the FET 70 conductive. An L-level signal is output to the gates of the other FETs 70 to make the drain and source non-conductive. As a result, the VW terminal (pin number 5)
The position connected to the resistor between the H terminal and the VL terminal is set. In addition, the FET 70 has a V.sub.
The values from the minimum value to the maximum value of the counter value are associated in the order of reaching the H terminal. For example, when the FET 70 at a predetermined position is in a conductive state, an H level signal is input from the UD terminal, When one pulse is input from the INC terminal and the counter increases by 1, the FET 70 at that position
The FET 70 shifted by one to the VH terminal side becomes conductive. An L level signal is input from the UD terminal, and IN
When one pulse is input from the C terminal and the counter is decremented by 1, the FET 70 shifted by one to the VL terminal side becomes conductive.

Thus, the digital potentiometer U3
Has a configuration in which a slider (VW terminal) is shifted up and down on a resistor between a VH terminal and a VL terminal by a pulse input to an INC terminal. The processing unit 7
2 is to record the counter value in the EEPROM 74, and every time the counter value is changed, the EEPROM 7
The value recorded in 4 is also updated. Thus, even when the power of the digital potentiometer U3 is turned off, the final counter value, that is, the contact position of the slider is stored, and the next time the power is turned on, the slider returns to the original contact position. (The position when the power is turned off).

As shown in FIG. 2, the VW terminal corresponding to the slider of the digital potentiometer U3 configured as described above is connected to the voltage conversion circuit 5 via a resistor R3 (2 MΩ).
4 is connected to the-input terminal of the operational amplifier U2. on the other hand,
The INC terminal and the UD terminal of the digital potentiometer U3 for shifting the position of the slider are connected to the pins P12 and P11 of the CPU 58, respectively. A CS terminal (pin number 7) for turning on / off the operation of the potentiometer U3 is connected to a pin P10 of the CPU 58.

Next, the operation of the offset circuit 56 configured as described above will be described. First, the VW terminal (terminal of the slider) of the digital potentiometer U3 is connected to the potential of the + input terminal of the operational amplifier U2 of the voltage conversion circuit 54. If the potentials are set to the same potential, no current flows between the VW terminal and the − input terminal of the operational amplifier U2, and the input / output characteristics of the voltage conversion circuit 54 shown in FIG. .

With this state as a reference state, when an H-level signal is input from the pin P11 of the CPU 58 to the UD terminal of the digital potentiometer U3 and a pulse is input from the pin P12 to the INC terminal of the digital potentiometer U3, the digital potentiometer U3 Slider is VH
The potential shifts to the terminal side, and the potential of the VW terminal increases. When the potential of the VW terminal rises, a current flows from the VW terminal to the minus input terminal of the operational amplifier U2 via the resistor R2, so that the output voltage of the voltage conversion circuit 54 decreases as compared with the case of the reference state. Become. That is, the straight line of the equation (1) showing the input / output characteristics of FIG. 3 shifts downward. Accordingly, the output value of the A / D converter 66 also decreases accordingly. For example,
When the output value of the A / D converter 66 becomes larger than the reference value 8000H when a reference voltage of 5 V is input from the zoom demand 26, the CPU 58 outputs an H level signal from the pin P11 to the UD of the digital potentiometer U3.
The output value of the A / D converter 66 can be adjusted to the reference value by inputting a predetermined number of pulses from the pin P12 to the INC terminal of the digital potentiometer U3.

On the other hand, in the reference state, the CPU 58
UD of digital potentiometer U3 from pin P11 of
When an L-level signal is input to the terminal and a pulse is input from the pin P12 to the INC terminal of the digital potentiometer U3, the slider of the digital potentiometer U3
Shift to the L terminal side, and the potential of the VW terminal drops. VW
When the potential of the terminal drops, a current flows from the negative input terminal of the operational amplifier U2 to the VW terminal via the resistor R2, and as a result, the output voltage of the voltage conversion circuit 54 increases more than in the reference state. . That is, the straight line of the equation (1) showing the input / output characteristics of FIG. 3 shifts upward. Accordingly, the output value of the A / D converter 66 increases accordingly. For example, when a reference voltage of 5 V is input from the zoom demand 26, the output value of the A / D converter 66 becomes the reference value 8000H.
When the CPU 58 becomes smaller than the pin P11,
To input the L level signal to the UD terminal of the digital potentiometer U3 and input a predetermined number of pulses from the pin P12 to the INC terminal of the digital potentiometer U3, thereby adjusting the output value of the A / D converter 66 to the reference value. Can be.

Next, the reference voltage of the zoom demand 26 and A
CPU for associating output value of / D converter 66 with reference value
The procedure of the offset process 58 will be described with reference to the flowchart of FIG. First, when performing the offset process, the CPU 58 outputs a command signal from the pin P17 to the switch circuit 50, and switches the connection of the switch SW1 to the reference voltage VREFC of 5 V (step S10). 5
As described above, the voltage of V is the reference voltage (center voltage) of the control signal input from the zoom demand 26. In this manner, the connection of the switch SW1 is changed to the reference voltage VREF of 5V.
By switching to C, the virtual zoom demand 26
Is set to a state where the reference voltage is input from.

Then, the 5 V voltage input from the reference voltage VREFC is input to the A / D converter 66 of the CPU 58 via the buffer circuit 52 and the voltage conversion circuit 54, and the A / D converter 66 When the digital value is converted to the reference value,
It is determined whether it is 0H (step S12). At this time, if the reference value is 8000H, the switch SW1 of the switch circuit 50 is connected to the zoom demand 26, and the offset processing ends (step S14).

On the other hand, if the digital value output from the A / D converter 66 does not match the reference value, it is next determined whether the digital value is greater than the reference value (step S).
16). If it is determined to be larger, the pin P1
1 outputs an H level signal to the UD terminal of the digital potentiometer U3, and outputs one pulse from the pin P12 to the INC terminal of the digital potentiometer U3 to increase the voltage of the VW terminal (step S18).
As a result, the voltage output from the voltage conversion circuit 54 shifts to a lower direction, and the output value of the A / D converter 66 decreases. Then, the output value of the A / D converter 66 is gradually reduced by repeatedly executing the processing from the above step 12, and the digital value output from the A / D converter 66 by the processing of step S12 is changed to the reference value. If it is determined that the value has become equal to 8000H, the switch SW1 of the switch circuit 50 is connected to the zoom demand 26, and the offset processing ends (step S14).

If it is determined in step S16 that the digital value output from the A / D converter 66 is smaller than the reference value, an L-level signal is output from the pin P11 to the UD terminal of the digital potentiometer U3 as described above. At the same time, one pulse is output from the pin P12 to the INC terminal of the digital potentiometer U3 to lower the voltage of the VW terminal (step S20). As a result, the voltage output from the voltage conversion circuit 54 shifts to a higher direction, and the output value of the A / D converter 66 increases. Then, by repeatedly executing the processing from step 12, the output value of the A / D converter 66 is gradually increased, and the digital value output from the A / D converter 66 in the processing of step S12 is changed to the reference value. If it is determined that the value has become equal to 8000H, the switch SW1 of the switch circuit 50 is connected to the zoom demand 26, and the offset processing ends (step S14).

By executing the offset processing as described above, when the reference voltage indicating the stop of the zoom lens 64 is input from the zoom demand 26, the A / D converter 6
From 6, the reference value is output. This allows
The CPU 58 obtains the reference value from the A / D converter 66, and can appropriately stop the zoom lens 64 when the thumb ring 34 of the zoom demand 26 is not operated.

The offset processing may be performed once after the power of the lens driving device is turned on and before the lens driving control is started, or executed when the user turns on the switch. You may do so. Further, since the time required for the offset processing is extremely short, the offset processing may be performed at predetermined time intervals while the lens drive control is being performed. If the offset processing is performed at predetermined time intervals while the lens drive control is being performed, it is possible to always maintain a highly accurate offset state.

In the above embodiment, the switch circuit 50 outputs the reference voltage VREF from the zoom demand 26.
After switching the connection to C, 5 V from the reference voltage VREFC
The offset processing is executed by inputting the reference voltage to the subsequent circuit. However, the present invention is not limited to this. For example, the switch circuit 50 is not provided, and the zoom demand 26 is operated without operating the thumb ring 34 of the zoom demand 26. By inputting a reference voltage and turning on a predetermined switch by a user, the offset processing may be performed by the reference voltage input from the zoom demand 26.

In the above-described embodiment, the case where the present invention is applied to the lens driving device that drives the zoom lens based on the control signal input from the zoom demand 26 has been described. However, the present invention is not limited to this. The present invention can be applied to a lens driving device that generally converts an analog control signal input from a lens controller into a digital signal by an A / D converter and controls the speed or the position of the lens based on the digital signal. it can. For example, the focus lens is the focus demand 28 (see FIG. 1).
By operating the focus ring 28A, the position is controlled based on the position control signal input from the focus demand 28. In this case, the reference voltage of the focus demand 28 and the reference By performing the process of associating with the value,
The position specified by the focus demand 28 and the position where the focus lens is actually set can be accurately matched.

[0047]

As described above, according to the lens driving apparatus of the present invention, when a reference voltage control signal is input from the lens controller, the reference voltage is converted by the A / D converter. Because the voltage level of the control signal is automatically adjusted so that the output value matches the reference value of the digital signal, the reference voltage of the control signal can be easily and accurately associated with the reference value of the digital signal. It is possible to reliably prevent a problem in which the content of the lens control instructed by the lens controller and the content of the lens control executed by the lens driving device do not match. Thus, for example, when controlling the zoom lens by speed control, even though the control signal of the reference voltage for instructing the stop of the zoom lens is transmitted from the zoom demand,
A problem that the zoom lens does not stop because the output value of the A / D converter is different from the reference value is prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a television camera to which a lens driving device according to the present invention is applied.

FIG. 2 is a circuit configuration diagram showing an embodiment of a lens driving device.

FIG. 3 is a diagram illustrating input / output characteristics of a voltage conversion circuit.

FIG. 4 is a diagram illustrating conversion characteristics of an A / D converter.

FIG. 5 is an equivalent circuit diagram showing an internal configuration of the digital potentiometer.

FIG. 6 is a flowchart illustrating a procedure of an offset process;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... TV camera 12 ... Lens part 14 ... Camera part 26 ... Zoom demand 28 ... Focus demand 50 ... Switch circuit 52 ... Buffer circuit 54 ... Voltage conversion circuit 56 ... Offset circuit 58 ... CPU 60 ... Amplifier 62 ... Drive motor 64 ... Zoom Lens 66 A / D converter

Claims (3)

[Claims] 1. A lens driving device that receives an analog control signal from a lens controller, converts a voltage of the received control signal into a digital signal by an A / D converter, and drives a lens based on the value of the digital signal. In the device, voltage conversion means for converting the voltage of the control signal according to predetermined voltage conversion characteristics, and inputting the converted control signal to the A / D converter; and a predetermined reference voltage being input to the voltage conversion means. And control means for adjusting the voltage conversion characteristic of the voltage conversion means so that the value of the digital signal output from the A / D conversion means coincides with a predetermined reference value. Lens driving device. 2. A reference voltage generating means for generating the reference voltage, and a signal input to the voltage converting means, a reference voltage signal output from the reference voltage generating means or a control signal output from the lens controller. Switching means for switching the voltage conversion characteristic of the voltage conversion means after the switching means inputs the signal of the reference voltage to the voltage conversion means. The lens driving device according to claim 1. 3. The lens driving device according to claim 1, wherein the lens controller is a focus demand for driving a focus lens or a zoom demand for driving a zoom lens.