JP3038255B2 - Camera aperture control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aperture control device for a camera such as a video camera and a still video camera.
The present invention relates to an aperture control device for a camera that detects an aperture value using a ball element.

[0002]

2. Description of the Related Art An aperture control device in which a hall element is provided in an iris motor for driving an aperture and an aperture value is detected by an output voltage of the hall element corresponding to the degree of opening of the aperture is, for example, an integrated type. Video camera VM-C1
It is publicly known as described in (Hitachi) Service Technical Data, Chapter 2, page 13. By the way, since the output signal of this hall element has a very large variation in the signal amount and the DC voltage offset, the range of the aperture value used for the control is limited in consideration of these adjustment variations.

[0003]

Therefore, there has been a problem that not only an accurate aperture value cannot be obtained, but also that the aperture value cannot be controlled in a small aperture state. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aperture control apparatus for a camera capable of suppressing an error in aperture value detection due to a temperature change of a hall element.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a DC bias current supplied to a hole element for detecting a diaphragm amount by giving a temperature characteristic to the DC bias current. The configuration is such that the sensitivity of the magnetic field detection of the control element is changed, thereby suppressing an error in the detection of the aperture value due to a temperature change.

[0005]

Since the output signal of the Hall element is proportional to the DC bias current applied thereto and the magnetic field applied thereto, the DC bias current supplied to the Hall element is controlled by the temperature so as to negate the temperature characteristics of the Hall element itself. By providing the characteristic, it is possible to suppress an error in detecting an aperture value due to a temperature change without causing a malfunction.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is an explanatory diagram showing a configuration of an aperture control device of, for example, a video camera according to one embodiment of the present invention. In FIG. 1, 1 is a lens, 2 is an aperture, 3 is an image sensor, 4 is a signal processing circuit, 5 is an image sensor drive circuit, 6 is an iris drive circuit, 7 is an iris detection circuit, 8 is an iris motor,
9 is a hole element, 10 is an amplifier, 11 is an A / D converter circuit, 12 is a microcomputer (microcomputer), 13 is an EEPROM (electrically erasable programmable read only memory), 14, 15, and
Reference numerals 16 and 17 are resistors, 18 is a constant current source, and 19 and 20 are voltage sources.

Light passing through the lens 1 and the aperture 2 is incident on the light receiving surface of the image sensor 3 and is photoelectrically converted by the image sensor 3. The output signal of the image sensor 3 is sent to the signal processing circuit 4, subjected to appropriate processing such as amplification by the signal processing circuit 4, and then input to the iris detection circuit 7.
In the iris detection circuit 7, the output of the signal processing circuit 4 is subjected to detection processing, and a signal corresponding to the level of the detected signal is output to the iris drive circuit 6. The iris drive circuit 6 drives the drive coil 24 of the iris motor 9 by the output of the iris detection circuit 7,
The aperture of the stop 2 is controlled in accordance with the received light intensity.

The Hall element 9 is disposed inside the iris motor 8, and the Hall element 9 converts the magnetic field generated in the iris motor 8 into a voltage and detects and outputs the voltage. A voltage corresponding to the rotation position of the iris motor 8, that is, the amount of aperture of the aperture 2, is output to the amplifier 10. Here, the bias current input terminal 26 of the hall element 9 is connected to the voltage source 20, and the bias current output terminal 25 of the hall element 9 is connected to the constant current source 18. Further, one output terminal 27 of the hall element 9 is connected to the amplifier 1 via the resistor 14.
The other output terminal 28 of the Hall element 9 is connected to the inverting input (minus input) of the amplifier 10 via the resistor 15. The inverting input of the amplifier 10 is connected to the voltage source 19 via the resistor 17, and the resistor 16 is connected between the output of the amplifier 10 and the inverting input. Therefore, the output voltage of the Hall element 9 is controlled by an amplifier (operational amplifier).
Amplified by the amplifier 10 with a predetermined amplification factor determined by the input side and the feedback side impedance of the A / D,
It is input to the D conversion circuit 11. The A / D conversion circuit 11 performs analog-to-digital conversion of the output (aperture voltage value) of the amplifier 10 and sends the digitized aperture voltage value to the microcomputer 12.

In this embodiment, the constant current source 18 comprises a voltage source 30, a resistor 31, and a transistor 32. The input of the constant current source 18 is connected to the collector of the transistor 32. The voltage source 30 is connected to the base, and the emitter of the transistor 32 is connected to the resistor 31.
Is connected to the earth via And the resistor 31
In addition, by making the transistor 32 have a predetermined temperature characteristic, the bias current flowing through the hall element 9 is increased as the temperature rises, thereby canceling the temperature characteristic of the hall element 9. It is configured in.

In this embodiment, the ROM in the microcomputer 12 or the EEPROM 13 read / written by the microcomputer 12 has an aperture voltage characteristic (standard aperture voltage) corresponding to an average aperture value of the hall element. Characteristics), that is, the diaphragm voltage values corresponding to the respective diaphragm values from the diaphragm open to the diaphragm close as shown by a characteristic curve S in FIG. 2 are stored in advance. Also, EEPROM
Reference numeral 13 denotes two or more aperture voltages (for example, a voltage Va at a point a in FIG. 2) at the time of adjusting the pre-shipment of the camera or turning on the power to the camera, including at least when the aperture is open and when the aperture is closed. (data including the voltage Vb at point b). The microcomputer 12 refers to the standard aperture voltage characteristic stored in advance and the aperture voltage stored at the time of adjustment before shipment or at the time of turning on the power by using a previously created arithmetic program, and the amplifier 1
The digitized aperture voltage value from 0 is calculated as the current aperture value as described later. The microcomputer 10 appropriately controls the signal processing circuit 4 and the image pickup device driving circuit 5 according to the obtained current aperture value.

As described above, in this embodiment, the image pickup device 3
Is amplified by the signal processing circuit 4, and the amplified signal is detected by the iris detection circuit 7, and the iris drive circuit 6 drives the iris motor 8 according to the level of the detected signal to stop the diaphragm 2. To work. The detection of the aperture value is performed by converting a magnetic field generated when the iris motor 8 is driven into a voltage by the hall element 9. At this time, the bias current flowing through the ball element 9 is increased as the temperature rises, thereby canceling out the temperature characteristics of the ball element 9 and suppressing an error in diaphragm value detection due to a temperature change. I have. Further, after the output voltage of the Hall element 9 is amplified by the amplifier circuit 10, it is converted into a digital signal by the A / D converter circuit 11,
Thereafter, an aperture voltage characteristic (characteristic curve S in FIG. 2) corresponding to a predetermined average aperture value of the hall element,
From the aperture voltages (for example, points a and b in FIG. 2) corresponding to the hall element characteristics of the individual cameras obtained when the aperture obtained at the time of adjustment before shipment or when the power is turned on and the camera is open or closed differs depending on each camera. 2 is point A in FIG. 3 and point b in FIG. 2 is point B in FIG.
The microcomputer 12 performs data conversion by a calculation method which becomes a point, and the microcomputer 12 always calculates a correct aperture value regardless of the characteristic variation of the Hall element 9. That is, specifically, when the aperture voltage is V, the inverse function of the characteristic curve S is f (V), and the symbol shown in FIG. 2 is used to represent the aperture value when the aperture voltage is V, the aperture value becomes f ((V−Vb) · (Vo−Vc) / (Va−Vb) + Vc). By doing so, regardless of the temperature change and the variation in the characteristics of the Hall element,
A correct aperture value can always be obtained, and the accuracy of signal processing control and image sensor drive control can be improved.

Next, another embodiment of the present invention will be described with reference to FIG. The figure shows the above-mentioned ROM or EEPROM.
Using the aperture voltage characteristics corresponding to the average aperture value of the hall element stored in the OM 13, the aperture is open and closed.
4 shows a flowchart when the microcomputer 12 calculates the aperture value from the aperture voltage of the current. In this embodiment, in the above embodiment shown in FIG. 1, the temperature characteristic compensation by the bias current flowing through the hall element 9 is set to overcorrection, so that the output signal of the hall element 9 is increased as the temperature increases. When the diaphragm detects a diaphragm voltage representing an open state more than the open state, the voltage is used as a new open state diaphragm voltage, and when the diaphragm detects a diaphragm voltage representing a more closed state than the closed state, the voltage is detected. Is set as the aperture voltage at the time of a new close.

FIG. 4A shows a process at the time of adjustment before shipment of the camera. At the time of adjustment before shipment, the aperture is opened and the Hall element output voltage Va at this time is measured.
This Va is stored in the EEPROM 13. FIG. 4B shows a process at the time of normal photographing, and is performed in step ST.
At 1, the aperture is closed and the Hall element output voltage Vb at this time is measured when the power is turned on.
The data is stored in the EPROM 13 and the process proceeds to step ST2. In step ST2, the microcomputer 12 calculates the current aperture value from the aperture voltage characteristics corresponding to the average aperture value of the hall element stored in advance and the above-described Va and Vb by the above-described calculation method. The process is performed, and the process proceeds to step ST3. In step ST3, it is determined whether or not the Hall element output voltage Vaa indicating that the aperture is more open than when the aperture is open is detected. If YES, a process of changing Vaa to Va is performed in step ST4, and the process proceeds to step ST5. Proceed to step ST5. Step S
At T5, it is determined whether or not the Hall element output voltage Vbb indicating that the aperture is more closed than when the aperture is closed is detected.
If YES, a process of setting Vbb to Vb is performed in step ST6, and the process returns to step ST2. If NO, the process immediately returns to step ST2. In this embodiment, in this way, the aperture value of the aperture is always updated even if the temperature of the apparatus rises after the power of the camera is turned on. Errors can be further suppressed. Note that the initial value of the aperture voltage is set to off during adjustment before shipment of the camera.
By storing only the aperture voltage at the time of opening, and automatically measuring the aperture voltage at the time of closing the power when the camera is turned on, the measurement at the time of turning on the power can be reduced. Further, in this embodiment, the temperature characteristic compensation of the hall element 9 is overcorrected, so that the temperature characteristic is less affected by the temperature characteristic compensation than in the embodiment of FIG. 1, and the effect of suppressing the error in the aperture value detection is large.

[0014]

As described above, according to the present invention, there is an effect that an error in aperture value detection due to a change in the temperature of the hall element can be suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an aperture control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing aperture voltage characteristics.

FIG. 3 is an explanatory diagram showing aperture voltage characteristics.

FIG. 4 is an explanatory diagram showing an example of a processing flow for calculating an aperture value according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens 2 Aperture 3 Image sensor 4 Signal processing circuit 5 Image sensor drive circuit 6 Iris drive circuit 7 Iris detector circuit 8 Iris motor 9 Hall element 10 Amplifier 11 A / D conversion circuit 12 Microcomputer 13 EEPROM 14, 15, 16 , 17 resistor 18 constant current source 19,20 voltage source

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takuya Imade 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Video Media Research Laboratory, Hitachi, Ltd. (72) Tomoyuki Kurashige 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Address Hitachi Image Information System Co., Ltd. (72) Inventor Hiroyuki Tarumi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi Image Information System Co., Ltd. (56) References JP-A-3-144546 (JP, A) JP-A-3-144426 (JP, A) JP-A-59-233319 (JP, A) JP-A-3-84527 (JP, A) JP-A-63-204237 (JP, A) JP-A-60-57827 (JP) JP-A-60-203390 (JP, A) JP-A-2-287446 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03B 7/10 G03B 7/091 H04N 5/238 G03B 7/095

Claims (5)

(57) [Claims] An iris motor for controlling an aperture of a lens, a hall element provided inside the iris motor for detecting an aperture value of the lens, and a bias current supplied to the hall element. in throttle control system of a camera and a bias current supply means, said Ho - to compensate for the temperature characteristics of the diaphragm value detection circuit by providing the temperature characteristics to the bias current supplied to the Le element, the ho - Le The bias current supplied to the device
So that the output signal of the Hall element increases
An aperture control device for a camera, wherein the correction is performed . 2. An iris motor for controlling an aperture of a lens.
And the iris motor to detect the aperture value of the lens.
A ball element provided therein, and a bias voltage applied to the ball element.
Current supply means for supplying current and digital signal
Calculate the aperture value from the converted output signal of the Hall element
Calculation means for calculating the average aperture value of the hall element.
The aperture voltage characteristics for the
In addition, at least when the aperture is open and closed
Storage voltage for each camera, and
Pre-stored aperture voltage characteristics and recorded for each camera
At least the squeezed aperture is open and closed.
The camera calculates the aperture value from the
In the iris control device, the iris is further opened than the open while the camera is operating.
When the diaphragm voltage indicating open is detected, the voltage is
In addition, the aperture value is set as the aperture voltage when the aperture is open.
Aperture control device for a camera, wherein 3. An iris motor for controlling an aperture of a lens.
And the iris motor to detect the aperture value of the lens.
A ball element provided therein, and a bias voltage applied to the ball element.
Current supply means for supplying current and digital signal
Calculate the aperture value from the converted output signal of the Hall element
Calculation means for calculating the average aperture value of the hall element.
The aperture voltage characteristics for the
In addition, at least when the aperture is open and closed
Storage voltage for each camera, and
Pre-stored aperture voltage characteristics and recorded for each camera
At least the squeezed aperture is open and closed.
The camera calculates the aperture value from the
In the iris control device, the iris is further closed than the close while the camera is operating.
After detecting the aperture voltage indicating the close,
The aperture value is set as the aperture voltage when the aperture is closed.
Aperture control device for a camera, wherein 4. The method according to claim 2, wherein
-Provide bias characteristics to temperature characteristics for the bias current supplied to the
To compensate for the temperature characteristics of the aperture value detection circuit.
An aperture control device for a camera. 5. An iris motor for controlling an aperture of a lens.
And the iris motor to detect the aperture value of the lens.
A ball element provided therein, and a bias voltage applied to the ball element.
Current supply means for supplying current and digital signal
Calculate the aperture value from the converted output signal of the Hall element
Calculation means for calculating the average aperture value of the hall element.
The aperture voltage characteristics for the
In addition, at least when the aperture is open and closed
Of the aperture voltage in the storage means
Remember, the previously stored diaphragm voltage characteristics and
When at least the aperture stored for each camera is open
And the aperture voltage at the time of closing, the calculating means calculates the aperture value.
In the camera aperture control device, the aperture voltage when the aperture is open is adjusted when adjusting the camera.
And the aperture voltage when the aperture is closed is
Measure each time the camera is powered on, and measure when the power is turned on.
The diaphragm voltage when the diaphragm is closed is stored in the storage means.
When it is different from the aperture voltage at the time of closing, or
The aperture voltage when the aperture is closed is stored in the storage means.
If not, the voltage measured at power-on is
The camera is characterized in that it is set to an aperture voltage of
A diaphragm control device.