JP2000047083A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the temperature of a lens system without providing a dedicated sensor and to change driving torque in accordance with various temperature conditions by providing a driving torque changing means for changing the driving torque of a lens position driving means based on the detected temperature of the lens system. SOLUTION: The temperature of the lens system 1 is detected based on output voltage from a Hall element 6 at the fixed position of a diaphragm 2, which is detected by an output voltage detection means. Next, the driving torque optimum to drive a focusing motor 10 is obtained by a CPU 17 having a table showing the driving torque corresponding to the detected temperature of the lens system 1 under the temperature condition of the detected temperature based on the table. Then, it is outputted as a TS signal to a motor driving torque setting circuit 16. The circuit 16 sets the driving torque for driving the motor 10 in accordance with the TS signal. Thus, the image pickup device is miniaturized and the cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a silver halide film camera, an electronic still camera, and a video camera, and more particularly to an image pickup apparatus having a function of changing a torque of a lens position driving unit.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration of a video camera which is a conventional imaging device. In FIG. 2, reference numeral 1 denotes a lens system for condensing the subject image, reference numeral 2 denotes an aperture for controlling the amount of light of the received subject image, and reference numeral 3 denotes a device which converts the subject image received via the lens system 1 into electric charges, and generates a charge signal. The image sensor 4 for outputting to the image processor 4 converts the charge signal input by the image sensor 3 into a video signal (VS signal), and the image processor 5 for outputting the signal is provided on the diaphragm 2 and the diaphragm 2 is rotated.
Rotor 6 that opens and closes the magnet rotor 6
And a Hall element that converts the conversion of the magnetic field due to the rotation of the magnet rotor 5 into a voltage and outputs it as a signal to the amplifier 7. The Hall element 7 amplifies the signal input from the Hall element 6, Amplifier input to D converter, 8
Is an A / D converter that converts the signal amplified by the amplifier 7 into a digital signal and outputs it as a Hall element output voltage signal (HS signal); 9 is a focus lens; and 10 is a lens position drive that drives the focus lens 9. A focus motor having means, 11 a temperature sensor installed in close proximity to the lens system 1 to detect the temperature of the lens system 1, 12 an aperture drive circuit, 13 an aperture drive coil, 15 a motor drive circuit, 16 a lens A drive torque setting circuit 27 having drive torque changing means for changing the drive torque of the focus motor 10 based on the temperature of the system 1 is a CPU.

The CPU 27 controls the aperture driving circuit 12 and the motor based on the VS signal input from the video processing unit 4, the HS signal input from the A / D converter 8, and the temperature of the lens system 1 detected by the temperature sensor 11. An aperture drive control signal (SD signal) and a lens position drive control signal (LS signal) are supplied to the drive circuit 15 and the motor drive torque setting circuit 16, respectively.
And a motor drive torque control signal (TS signal).

Hereinafter, the operation of the conventional image pickup apparatus having a dedicated temperature sensor, particularly, the operation of controlling the aperture, detecting the aperture value, and changing the driving torque of the focus motor 10 due to the temperature change of the lens system 1 will be described. .

[0005] The optical image incident from the lens system 1 is formed on the image sensor 3 and then converted into a VS signal in the video processing unit 4 and input to the CPU 27. The CPU 27 detects the level of the VS signal input from the video processing unit 4 to determine whether the amount of light of the subject received by the image sensor 3 is an appropriate amount, and opens and closes the aperture 2 so that the VS signal is at an optimal level. Then, the light amount is controlled. That is, the CPU 27 sends the SD signal to the aperture drive circuit 12 so that the aperture 2 opens when the level of the VS signal is low, and sends the SD signal to the aperture drive circuit 12 so that the aperture 2 closes when the level of the VS signal is high. send. The aperture drive circuit 12 receives the SD input from the CPU 27.
The magnet rotor 5 is driven to open and close the aperture 2 by controlling the current flowing through the aperture drive coil 9 in accordance with the signal.

The opening / closing amount of the aperture 2, that is, the aperture value, is
Is detected based on the position information of the magnet rotor 5 that drives the motor. The change in the magnetic field due to the rotation of the magnet rotor 5 is converted into a voltage by the Hall element 6 and converted into a signal as an amplifier 7.
Is input to After being amplified by the amplifier 7, the signal is input to the A / D converter 8, converted into a digital signal, and input to the CPU 27 as an HS signal. CPU2
Reference numeral 7 denotes output voltage detecting means for detecting the output voltage of the Hall element 6 from the HS signal, detects the output voltage of the Hall element 6 from the HS signal, and further detects the output of the aperture 2 from the output voltage of the Hall element 6. Find the value. The aperture value is used as the aperture control and various other control data in the imaging apparatus.

Next, an operation for changing the driving torque of the focus motor 10 due to a change in the temperature of the lens system 1 in the conventional image pickup apparatus will be described.

In the case of a video camera provided with an autofocus control means, when performing autofocus, the
U27 outputs an appropriate LS signal to the motor drive circuit 15, and by controlling the focus motor 10, the focus lens 9 moves to an appropriate position. Here, there are various temperature conditions in which the imaging device is used, and under a high temperature condition, the driving torque of the focus motor 10 decreases.
To drive the focus motor 10 under high temperature conditions,
A drive torque that is higher than the drive torque required to drive the focus motor 10 at room temperature is required. Further, under a low temperature condition, the viscosity of the oil or the like of the lens system 1 becomes high, and the driving torque of the focus motor 10 becomes necessary at room temperature. Therefore, in order to drive the focus motor 10 under various temperature conditions, the temperature of the lens system 1 is detected using the temperature sensor 11. Then, the CPU 27 generates a table (not shown) representing a driving torque corresponding to the detected temperature.
Based on the table, an optimum drive torque for driving the focus motor 10 under the temperature condition of the detected temperature is obtained, and is output to the motor drive torque setting circuit 16 as a TS signal. Motor drive torque setting circuit 16
Sets the drive torque for driving the focus motor 10 according to the TS signal.

[0009]

As described above, the conventional imaging apparatus is provided with a dedicated temperature sensor for detecting the temperature of the lens system in order to optimize the driving torque of the motor according to the temperature condition. Equipment, the equipment becomes large,
There was a problem that the cost was high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has no special sensor.
It is an object of the present invention to provide an imaging apparatus capable of detecting a temperature of a lens system and changing a driving torque of a lens position driving unit according to various temperature conditions.

[0011]

According to a first aspect of the present invention, there is provided an imaging apparatus for controlling an amount of light mounted in a lens system, a device for controlling the aperture, and A magnet rotor interlocked with the opening and closing operation, a hall element for converting a change in magnetic field due to rotation of the magnet rotor into a voltage, an output voltage detecting means for detecting an output voltage of the hall element, and an output voltage detecting means. Temperature detection means for detecting the temperature of the lens system based on the detected output voltage of the Hall element at the fixed position of the diaphragm, lens position driving means for driving a lens in the lens system in the optical axis direction, and the temperature detection A driving torque changing means for changing a driving torque of the lens position driving means based on the temperature of the lens system detected by the means. Than it is.

[0012]

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a video camera which is an image pickup apparatus according to Embodiment 1 of the present invention. In FIG. 1, the same reference numerals in FIG. 2 denote the same or corresponding parts, reference numeral 14 denotes an aperture fixing circuit, and 17 denotes a CPU. Unlike the conventional CPU 27, the CPU 17 has a temperature detecting means for detecting the temperature of the lens system 1 based on the output voltage of the Hall element 6.

Hereinafter, the operation of the imaging apparatus according to the first embodiment configured as described above, in particular, aperture control, detection of the aperture value, and changing the driving torque of the lens position driving means due to the temperature change of the lens system 1 will be described. The operation will be described.

The optical image incident from the lens system 1 is formed on the image pickup device 3 and then converted into a VS signal in the video processing unit 4 and input to the CPU 17. The CPU 17 detects the level of the VS signal input from the video processing unit 4 to determine whether or not the amount of light of the subject received by the image sensor 3 is appropriate, and opens and closes the aperture 2 so that the VS signal is at an optimal level. Then, the light amount is controlled. That is, the CPU 17 sends the SD signal to the aperture driving circuit 12 so that the aperture 2 opens when the level of the VS signal is low, and sends the SD signal to the aperture driving circuit 12 so that the aperture 2 closes when the level of the VS signal is high. send.
The aperture drive circuit 12 drives the magnet rotor 5 to open and close the aperture 2 by controlling the current flowing through the aperture drive coil 9 in accordance with the SD signal input from the CPU 17.

The opening / closing amount of the aperture 2, that is, the aperture value, is
Is detected based on the position information of the magnet rotor 5 that drives the motor. The change in the magnetic field due to the rotation of the magnet rotor 5 is converted into a voltage by the Hall element 6 and converted into a signal as an amplifier 7.
Is input to After the signal is amplified by the amplifier 7, the signal is input to the A / D converter 8, converted into a digital signal, and input to the CPU 17 as an HS signal. CPU1
Reference numeral 7 denotes output voltage detecting means for detecting the output voltage of the Hall element 6 from the HS signal, detects the output voltage of the Hall element 6 from the HS signal, and further detects the output of the aperture 2 from the output voltage of the Hall element 6. Find the value. The aperture value is used as the aperture control and various other control data in the imaging apparatus.

Next, an operation of changing the driving torque of the focus motor 10 due to a change in the temperature of the lens system 1 in the imaging apparatus according to the present embodiment will be described.

In the imaging apparatus according to the present embodiment, the temperature of the lens system 1 is determined based on the output voltage of the Hall element 6 at the fixed position of the diaphragm 2 detected by the output voltage detecting means, without using a temperature sensor dedicated to temperature detection. Detect temperature.

First, the CPU 17 controls the aperture fixing circuit 14 so that the aperture value of the aperture 2 becomes a fixed value (for example, a fully opened state of the aperture 2 is an example of a fixed position of the aperture 2). Send a signal (SS signal).

The aperture fixing circuit 14 drives the magnet rotor 5 by controlling the current flowing through the aperture driving coil 13 in accordance with the SS signal input from the CPU 17, and drives the aperture 2 to a fixed position.

The temperature characteristics of the Hall element 6 will be described using the output voltage of the Hall element 6. The output voltage of the Hall element 6 is represented by the following (Equation 1).

VH = BIc / (ent) (Equation 1) where VH is the output voltage of the Hall element 6, B is the magnetic flux density, Ic is the current flowing through the Hall element 6, e is the charge amount of the carrier, n is the carrier concentration, and t is the thickness of the Hall element 6. When the Hall element 6 is driven at a constant current, the output voltage VH changes due to a change in carrier concentration with temperature. That is, when the Hall element 6 is driven at a constant current, the temperature can be detected from the output voltage of the Hall element 6 by fixing terms other than the carrier concentration. When the Hall element 6 is driven at a constant voltage, the output voltage VH changes as the charge amount of the carrier changes with temperature. That is, when the Hall element 6 is driven at a constant voltage, it is possible to detect the temperature from the output voltage of the Hall element 6 by fixing terms other than the charge amount of the carrier. In the imaging device according to the first embodiment, the Hall element 6
Is located close to the lens system 1, the temperature of the lens system 1 is detected by using the output voltage of the Hall element 6 at the fixed position of the diaphragm 2 by using the above-mentioned temperature characteristics of the Hall element 6. It is possible.

The change in the magnetic field due to the rotation of the magnet rotor 5 when the diaphragm 2 is driven to the fixed position is converted into a voltage by the Hall element 6 and output to the amplifier 7 as a signal. The signal is amplified by the amplifier 7 and then input to the A / D converter 8 to be converted into a digital signal, which is input to the CPU 17 as an HS signal. C
The PU 17 receives the HS signal from the A / D converter 8 and detects the output voltage of the Hall element 6 from the HS signal by the output voltage detecting means. Further, the CPU 17 detects the temperature of the lens system 1 with reference to a table (not shown) for determining the temperature of the lens system 1 from the output voltage of the Hall element 6 at the fixed position of the diaphragm 2 prepared in advance. .

The CPU 17 has a table (not shown) representing a driving torque corresponding to the detected temperature of the lens system 1, and drives the focus motor 10 under the temperature condition of the detected temperature based on the table. The optimum driving torque is obtained and output to the motor driving torque setting circuit 16 as a TS signal.

The motor drive torque setting circuit 16 sets a drive torque for driving the focus motor 10 according to the TS signal.

In order to detect the temperature of the lens system 1, the stop 2
Is moved to the fixed position, the light amount of the image sensor temporarily deviates from the normal exposure amount optimal for photographing. Therefore, the operation of moving the diaphragm 2 to the fixed position is performed during a period in which there is no trouble in photographing. For example, in the case of a video movie that handles a moving image, the aperture 2 is moved to a fixed position at the moment when the power is turned on and an image is output, at the moment when switching from playback to the camera recording mode, or when the operation mode is during playback. What should I do? Needless to say, these periods may vary depending on the type of the imaging device.

As described above, in the first embodiment, in the imaging apparatus including the Hall element 6 that converts a change in the magnetic field due to the rotation of the magnet rotor 5 into a voltage, the output voltage for detecting the output voltage of the Hall element 6 Detecting means; temperature detecting means for detecting the temperature of the lens system 1 based on the output voltage of the Hall element 6 at the fixed position of the diaphragm 2 detected by the output voltage detecting means; A lens position driving unit that drives the lens position, and a driving torque changing unit that changes the driving torque of the lens position driving unit based on the temperature of the lens system detected by the temperature detecting unit. The optimum drive for driving the focus motor 12 under various temperature conditions by detecting the temperature of the lens system 1 without providing a temperature sensor dedicated for detection. To torquing, it is possible to change the torque of the lens position driving means, it is possible to reduce the size and cost reduction of the imaging device.

[0027]

As described above, according to the present invention (claim 1), a diaphragm mounted in the lens system for controlling the amount of light, a device for controlling the diaphragm, and a magnet interlocked with the opening / closing operation of the diaphragm. In an imaging apparatus including a rotor and a Hall element that converts a change in a magnetic field due to rotation of the magnet rotor into a voltage, an output voltage detection unit that detects an output voltage of the Hall element, and an output voltage detection unit that detects an output voltage of the Hall element. Temperature detection means for detecting the temperature of the lens system based on the output voltage of the Hall element at the fixed position of the diaphragm, lens position driving means for driving a lens in the lens system in the optical axis direction, and the temperature detection means A driving torque changing means for changing a driving torque of the lens position driving means based on the detected temperature of the lens system. Detecting the temperature of the lens system without providing a temperature sensor dedicated to detection, a variety of temperature conditions,
The torque of the lens position driving means can be changed,
This has the effect of reducing the size and cost of the imaging device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an imaging device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an imaging device according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens system 2 Aperture 3 Image sensor 4 Image processor 5 Magnet rotor 6 Hall element 7 Amplifier 8 A / D converter 9 Focus lens 10 Focus motor 11 Temperature sensor 12 Aperture drive circuit 13 Aperture drive coil 14 Aperture fixed circuit 15 Motor drive Circuit 16 Motor drive torque setting circuit 17 CPU 27 CPU VS video signal HS Hall element output voltage signal SS aperture fixed control signal SD aperture drive control signal LS lens position drive control signal TS motor drive torque control signal

Claims (1)

[Claims] 1. A diaphragm mounted in a lens system for controlling the amount of light, a device for controlling the diaphragm, a magnet rotor interlocked with the opening and closing operation of the diaphragm, and converting a magnetic field change caused by rotation of the magnet rotor into a voltage. An imaging device comprising a Hall element for converting, based on an output voltage detecting means for detecting an output voltage of the Hall element, based on an output voltage of the Hall element at a fixed position of the diaphragm detected by the output voltage detecting means. Temperature detecting means for detecting the temperature of the lens system; lens position driving means for driving a lens in the lens system in the optical axis direction; and lens position driving means based on the temperature of the lens system detected by the temperature detecting means. An imaging apparatus comprising: driving torque changing means for changing driving torque.