JPH02111930A - Driving circuit for diaphragm - Google Patents

Abstract

PURPOSE:To have enough driving force and to obtain an inexpensive diaphragm device driving circuit with a simple constitution by providing first power supply circuits which supply power to a first shape memory alloy in response to a first selecting signal, and second power supply circuits which supply power to a second shape memory alloy in response to a second selecting signal. CONSTITUTION:When a light receiving value of a light receiver 26 which receives light of an object does not reach a standard value, a comparing and selecting circuit 28 outputs the first selecting signal. The first power supply circuits 30, 32 and 34 supply power to the first shape memory alloy 21a, it is heated and its temperature rises. As a result, shrinkage force arises when alloy returns to its original shape to open the diaphragm. On the other hand, when the light receiving value of the light receiver 26 exceeds the standard value, the comparing and selecting circuit 28 outputs a second selecting signal; moreover, the second power supply circuits 31, 33 and 35 supply power to the second shape memory alloy 21b. In this case, shrinkage force arises in the second shape memory alloy 21b to close the diaphragm. Therefore, an electric diaphragm driving circuit whose driving force is relatively large can be obtained as an inexpensive device with a simple constitution.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a drive circuit for an aperture device provided in an optical device such as a television camera or a camera. The device is an optical 1fi device such as a camera.
The aperture is controlled according to the brightness of the subject so that the amount of light received by D is constant, and it has been widely known to use electromagnetic force for this drive.

Figure 7 is a simplified front view of this type of electric diaphragm quick-acting device.
1 is an aperture device, 42 is an aperture blade, and 43 is a quick-acting lever. The aperture blade 42 is opened and closed by an interlocking mechanism (not shown) as the lever 43 turns, thereby changing the aperture diameter.

Reference numeral 44 denotes a drive coil formed into an arcuate ring, to which power is supplied via a lead wire (not shown), and one end of the drive lever 43 described above is fixed to this coil 44.

A magnet 45 has a similar shape and has a larger surface area than the drive coil 44, and as shown in the figure, both ends thereof are magnetized to N and S.

FIG. 8 is a schematic side view of the electric aperture drive device described above.

Although not shown in FIG. 7, 46 is a yoke made of a magnetic plate that forms a magnetic circuit together with the magnet 45.

The yoke 46 and the magnet 45 have the same shape, are arranged parallel to each other at a constant interval, and each is fixed to a fixed part (not shown). It's decorated.

It should be noted that the optical lens system can be arbitrarily placed in the optical path of this electric diaphragm drive device as needed.

In the above manual electric diaphragm drive device, a magnetic field is formed between the magnet 45 and the yoke 46, so the coil 4
When a current flows through 4, due to the relationship between the magnetic field, current, and force,
This coil 44 generates an electromagnetic force in a direction perpendicular to the magnetic field,
If the direction of the current is reversed, the direction of the magnetic force ','f1 will also be reversed.

FIG. 9 is a circuit configuration diagram for driving the above-mentioned electric aperture drive device.

In this figure, 47 is an input terminal for a light reception signal. This light reception signal is an output signal of a light receiving element that receives light that has passed through the aperture device 41, and is obtained by photoelectrically converting the subject light.

48 is a comparator, inputting the input voltage which is the light reception signal from the input terminal 47 to one side, inputting the reference voltage of the basic voltage source 49 to the other side, and comparing the input voltage and the base*a pressure;
Depending on the result, the transistors 52 or 53 for the subsequent switching operation are turned on.

In other words, the input pressure is the basis ifl! ? When the ff pressure is not reached, a High' voltage is output and the transistor 52
I will send you 4 letters.

As a result, due to the 111 Vcc of the power supply terminal 50,
The current flows through the terminal 50, the transistor 52, the drive coil 44,
The direction of the current flowing through the resistor 55 and the terminal 51 and the driving coil 1/1 is in the direction of the arrow shown in the figure.

On the other hand, the input terminal of comparator 48 is 1'+'! ?
'Low when the pressure exceeds a': Outputs the pressure, 1-
Due to the conduction of the transistor 53, a current flows through the g-shaped coil 44 in the direction opposite to the arrow shown in the figure.

Furthermore, when the input voltage is approximately equal to the reference voltage, the comparator 48 has a very small output voltage, so both the 1-transistors 52 and 53 are not turned on, and no current flows through the driving coil 44.

From the above, until the light reception signal reaches a predetermined basic value, current flows through the drive coil 44 in the direction shown in the figure, so a torque is generated in the drive coil 44 in the direction of the arrow in FIG. 7, and the drive lever 43 turns. to move the aperture blades 42 in the direction of opening.

When the received light signal exceeds a predetermined reference value, a current flows through the drive coil 44 in the opposite direction to the direction of the arrow shown in the figure, so a torque is generated in the drive coil 44 in the direction of the arrow in FIG. 7, and the drive lever 43 rotates in the opposite direction to the direction shown in the figure to move the aperture blades 42 in the direction of closing.

Due to this operation of the diaphragm, the received light signal is adjusted to a predetermined 4&,
(When the train is on duty at the station, the current flowing through the one fat moving coil 4.1 becomes low, the rotation of the drive lever 43 is stopped, and the aperture device 41 is held at a predetermined diameter.

``Problem to be Solved by the Invention'' The torque generated by the electromagnetic force of the electric diaphragm drive device described above is small and remains the same over time, so it is not sufficient as a driving force for the diaphragm.

If you want to increase the drive torque, drive coils 4 and 1
, it is unavoidable that the magnet 45 and the like become larger and more complex. In addition, the current configuration is complicated, and in addition to the parts described above, there are also parts such as a power supply member to the driving coil 44 and a yoke 46.
It requires many parts such as a mounting member for the magnet 45,
Furthermore, there is a problem in that assembly of these parts requires a lot of time and effort, which increases production costs.

The present invention was developed in view of the above-mentioned problems, and aims to develop a diaphragm device having sufficient force and to develop a drive circuit for driving this diaphragm device.

"Means for Solving the Problems" In order to solve the above problems, the present invention provides a first invention in which the aperture of the lens is adjusted according to the brightness of the subject so that the amount of light received by an optical device such as a camera is constant. In the aperture device that controls the aperture, the aperture is opened by supplying power to the first shape memory alloy,
an electric mechanism that closes the diaphragm by supplying power to the second shape memory alloy, and a light receiver that detects subject light that has passed through the diaphragm;
a comparison and selection circuit that outputs a first selection signal when the light reception value of the light receiver is lower than the reference value, and outputs a second selection signal when the light reception value is higher than the reference value; 1 a first power feeding circuit that feeds power to the shape memory alloy;
The present invention proposes a drive circuit for an aperture device, which is characterized in that it includes a second power supply circuit that supplies power to a second shape memory alloy in response to a selection signal.

As a second invention, the aperture device according to the first invention is configured to include a detector for detecting environmental temperature and adjust the power feeding levels of the first power feeding circuit and the second power feeding circuit according to the output of the detector. We propose a drive circuit for this purpose.

As a third invention, an intermediate band of a constant width is provided in the reference value of the comparison and selection circuit, and when the light reception value of the light receiver is within the intermediate band, the first power supply circuit and the second power supply circuit supply power. A driving circuit for the aperture device according to the first aspect of the invention is proposed, which has a configuration in which no output is provided.

As a fourth invention, the first and second power supply circuits include a first power supply circuit,
A driving circuit for an aperture device is proposed, which is characterized by including an impedance converter such as a transformer that supplies power to a second shape memory alloy.

"Function" When the light receiving value of the light receiver that receives the subject light does not reach the reference value, the comparison and selection circuit outputs the first selection signal and selects the first selection signal.
A power supply circuit supplies power to the first shape memory alloy.

As a result, the first shape memory alloy generates heat and its temperature rises, and as the first shape memory alloy returns to its shape, a contractile force is generated to open the aperture.

On the other hand, when the light reception value of the light receiver exceeds the reference value, contrary to the above, the comparison selection circuit outputs the second selection signal, and the second power supply circuit supplies power to the second shape memory alloy.

In this case, a contraction force is generated in the second shape memory alloy, causing the aperture to close.

"Example" Next, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a simplified front view of the aperture mechanism 10, Fig. 2 is a simplified rear view of the aperture mechanism, Fig. 3 is a simplified side view of the aperture mechanism viewed from below, and Fig. 4 is a view from the right side. It is a simplified side view of the same aperture mechanism.

In these figures, 11 is an annular fixed substrate, 12 is an aperture device having aperture blades 13, and the outer case of this aperture device 12 is fixed to the fixed substrate 11.

Reference numeral 14 denotes a drive lever, and this lever 14 is configured to operate the aperture blades 13 via an interlocking member (not shown) to change the aperture to be calibrated.

Reference numeral 15 denotes a connecting pin fixed to the drive lever 14, and this pin 15 is inserted into a notched groove 11a formed on the circumferential surface of the fixed base plate 11.
It penetrates through and further fits into a bifurcated tongue piece 16a formed protruding from one end of a movable ring 16 provided on the back surface of the fixed substrate 11.

The movable ring 16 is an annular plate, and the above-mentioned bifurcated tongue piece 16a
It is movably pivoted to the fixed substrate 11 by a connecting pin 17 at a symmetrical position.

Reference numeral 18 and 19 denote fastening pins fixed to the fixed substrate 11, which fasten one ends of a pair of shape memory alloy wires 21a and 21b, which will be described later, on the back side of the fixed μ plate 11.

A fixing pin 20 is fixed to the movable ring 16, and fixes a pair of shape memory alloy wires 21a and 21b.

That is, as can be seen from FIG. 2, the retaining pins 18 and 20
The first shape memory alloy wire 21a is fixed between the fixing pins 19 and 20, and the second shape memory alloy wire 21b is formed between the fixing pins 19 and 20.

Note that the shape memory alloy wires 21a and 21b may be integrated, or may be formed separately and independently.

Note that each of the fixing pins 18, 19, and 20 is provided with a lead wire for supplying power to the shape memory alloy wires 21a and 21b.

Reference numeral 22 denotes an insulating collar for electrically connecting the fixing pins 18 and 19 to the fixed substrate 11.

The aperture mechanism 10 configured as described above can be used as a 7-cut unit by supplying power and heating to the shape memory alloy wires 21a and 21b.

In other words, as is well known, when shape memory alloys are heated,
Since it is an alloy that reverts to a pre-memorized shape depending on the temperature, if power is supplied via the fixing pins 18 and 20 as in this embodiment, the first shape memory alloy wire 21a will be shaped by heat generation. The temperature rises and it returns to its shape according to that temperature.

As a result, the retaining pins 18 and 20 are attracted to each other, so that the movable ring 16 pivots slightly counterclockwise about the connecting pin 17 as a fulcrum, and its bifurcated tongue piece 16a moves in the direction of the arrow shown.

From this, the connecting pin 15 fitted into the forked tongue piece 16a
The drive lever 14 is rotated through the aperture blades 13 to open the aperture blades 13.

On the other hand, when power is supplied through the fixing pins 19 and 20, the second shape memory alloy wire 21b generates heat and rises in temperature, and an attractive force acts between the fixing pins 19 and 20 due to the contraction force of the shape.

As a result, the movable ring 16 moves clockwise (opposite to the above).
The drive lever 1 rotates in the opposite direction of the arrow in Figure 2).
4 operates in the direction of closing the aperture blades 13.

Note that when current is flowing through either one of the shape memory alloy wires 21a and 21b, tension is applied to the other shape memory alloy wire 21a and 21b, causing it to expand, but no current is flowing through this part. Therefore, the force required for elongation is extremely small.

Further, in this example, a commercially available Ti-Ni alloy shape memory alloy wire is used, and an example of its performance is that the wire diameter is φ0.15 m/m.

The resistance value is 43Ω/cm, the absorption capacity is 83%, the maximum practical load is 300g, and the operating current is 400mA.

FIG. 5 is a block diagram showing a circuit configuration for controlling the aperture mechanism 10 described above.

In this figure, 24 is a front lens, 25 is a rear lens, and the diaphragm mechanism 10 equipped with the shape memory alloy wires 21a and 21b described above is provided between these lenses.

26 is a light receiver consisting of an image light receiving element such as a CCD that receives incident light from the subject; 27 is a signal processing circuit;
In step 7, a composite signal for video and playback is created by manually inputting the signal from the light receiver 26, and various other processing is also performed, such as signal for only the center of the screen and correction for the 11-degree high angle portion.

A comparison circuit 28 compares the light reception value of the light reception signal passed through the signal processing circuit 27 with a reference value and outputs a 1 determination signal.

That is, if the light reception value of the light reception signal has not reached the standard value, the comparison circuit 28 determines that the subject is dark and outputs a Low signal, and if the light reception value of the light reception signal has fallen below the reference value, the comparison circuit 28 determines that the subject is dark. It determines that the light is bright and outputs a High signal.

In addition, an intermediate A IF with a certain width is provided for the above reference value, and if the received light value of the received light signal is within this intermediate band, it is assumed that the received light value is within the tolerance value and a High signal SZa is output. Then, it is sent as an oscillation stop signal to first and second oscillation circuits 30 and 31, which will be described later.

29 is an inverter which outputs a Low signal when the High signal from the comparison circuit 28 is input, and outputs a High signal when the LOW signal is input.

3o is the first oscillation circuit, which receives ■(ig) from the inverter 29.
Input the h signal to start oscillation, and input the Low signal to stop oscillation.

Reference numeral 31 denotes a second oscillation circuit having the same configuration as the first oscillation circuit 30, which starts oscillation by inputting a High signal from the comparison circuit 28, and stops oscillation by inputting a Low signal.

Reference numerals 32 and 33 denote first and second amplifier circuits for amplifying the oscillation outputs of the first and second oscillation circuits 30 and 31, respectively.

34 and 35 are first and second transformers for impedance conversion, which lower the output impedance of each transformer and supply the necessary current to the shape memory alloy wires 21a and 21b described above.

One end of the output coil of the first transformer 34 is connected to the stop pin 18 of the diaphragm mechanism 1o via a lead wire 23a, and the other end is connected to one end of the output coil of the second transformer 35, and the stop of the diaphragm mechanism 10 Common lead wire 23 to pin 20
It is connected via c.

Further, the other end of the output coil of the second transformer 35 is connected to the fixing pin 19 of the diaphragm 10 via a lead wire 23b.

Therefore, the first oscillation circuit 30, the first amplifier circuit 32, and the first transformer constitute a first power supply circuit, and the first
A configuration in which power is supplied to the first shape memory alloy wire 218 through the first transformer 34 by the oscillation of the oscillation circuit 30,
Further, a second power supply circuit is configured by the second oscillation circuit 31, the second amplifier circuit 33, and the second transformer 35, and the oscillation of the second oscillation circuit 31 supplies power to the second shape memory alloy wire 21b through the second transformer 35. The composition is as follows.

Note that the shape memory alloy wires 21a and 21b have a low resistance value, so if they are used as a transistor load to supply power, a large voltage will be applied to the transistor, which may cause the transistor to generate heat or waste power. Although a problem occurs, the above-described impedance converter consisting of the first transformer 34 and the second transformer 35 solves this problem.

36 is a temperature sensor that detects the environmental temperature.

The detection signal of this temperature sensor 36 is supplied to the first and second amplification circuits 32.33, and the amplification factors of these amplification circuits 32.33 are changed according to the detected temperature, and the power supply heat generation of the shape memory alloy wires 21a, 21b is performed. This is done so that the temperature remains constant.

The activation circuit of the aperture mechanism 10 configured as described above operates as follows.

First, the subject light is the front lens 24 and the aperture 4m4WLO.

The light passes through the optical path of the rear lens 25, enters the receiving light 26, and is converted into light.

This photoelectrically converted signal undergoes various correction processes in the signal processing circuit 27 and is sent to the comparison circuit 2B as a light reception signal.

The comparison circuit 28 outputs a Low signal to the inverter 29 when the light reception value of the light reception signal does not reach a reference value having an intermediate band, that is, when it is determined that the subject is dark.

The inverter 29 inverts the Low signal to make it High (
: symbol, and the first oscillation circuit 30 to which this equal symbol is input starts oscillation.

That is, the first power supply circuit operates, and supplies power to the first shape memory alloy wire 21a of the aperture mechanism 10.

As a result, as described above, the first shape memory alloy wire 21a generates an attractive force with the fixing pin 18, 20 due to the contraction force, so that the rotation of the movable ring 16 causes the aperture blade 13 to move in the opening direction.

Thereafter, the incident object light increases due to the opening operation of the aperture blades 13, and the received light input to the comparator circuit 28 (the received light value of No. 3 increases), so that the received light value of the received light signal falls into the intermediate band of the reference value. When it gradually approaches and finally falls within the intermediate band of this reference value, the ratio diaphragm circuit 28 outputs a High signal S21, and the first oscillation, ?L30, stops oscillating.

As a result, the current in the first shape memory alloy wire 21a becomes zero and the operation of the aperture blades 13 is stopped, so that the incident subject light is adjusted to a predetermined light amount.

On the other hand, in the comparison circuit 28, when the light reception value of the light reception signal exceeds the reference value having an intermediate band, that is, when it is determined that it is bright, the comparison circuit 28 outputs a High signal, and the second oscillation circuit 31 The signal I'5 is started.

In other words, the second power supply circuit operates and the aperture iso [
Ten second shape memory alloy wires 21b are powered.

At this time, the drive lever 14 operates in the direction of closing the aperture blades.

Then, when the amount of incident light from the subject decreases due to the closing operation of the aperture blades 13, the light receiving value of the light receiving signal enters the intermediate band of the reference value in the comparator circuit 28, and a High signal 5211 is generated.
Since the second oscillation circuit 31 outputs , the second oscillation circuit 31 stops oscillating, and as a result, the operation of the aperture blades 13 is stopped and the amount of incident light is adjusted to a predetermined amount.

Note that the oscillation unit 40 shown by the dotted line block in FIG. 5 is provided with a first oscillation circuit 30 and a second oscillation circuit 31;
As shown in FIG. 6, a common oscillation circuit 37, a first switching circuit 38 provided in place of the first oscillation circuit 30. A second switching circuit 39 may be provided in place of the second oscillation circuit 31, and the output signal of the comparison circuit 28 may cause one of the switching circuits to pass four times to output oscillation.

"Effects of the Invention" As described above, the diaphragm device of the present invention drives the diaphragm by using the contraction force accompanying shape recovery of the shape memory alloy, and furthermore, this drive circuit is capable of controlling the amount of light incident on the subject. The comparison and selection circuit selects the first power supply circuit and the second power supply circuit so that the power supply voltage is constant.
The configuration is such that aperture control is performed by selectively operating one of the power supply circuits.

Therefore, I! An electric diaphragm driving circuit with relatively large power can be provided as a low-cost device with a simple structure.

In addition, the power supply circuit can temperature compensate and supply power so that the heating temperature of the shape memory alloy remains constant regardless of changes in the environmental temperature, so the driving force is constant and stable aperture control can be performed.

Furthermore, in the L-Kang 2-function circuit, an intermediate band with a certain width can be provided directly in the comparison and selection circuit, so the opening and closing of the diaphragm does not go too far, and unstable control is eliminated. Mechanical adjustments and electrical circuit adjustments become easier.

Furthermore, since power is supplied to the shape memory alloy using an impedance converter such as a transformer, the drive circuit does not waste power.

[Brief explanation of drawings]

Figure 1 is a simplified front view of the wringer 4 showing an example of a one-point travel;
The figure is a simplified rear view of the same diaphragm +l'l, Figure 3 is a simplified side view of the diaphragm mechanism similar to the above as seen from below, and Figure 4 is a simplified screen view of the diaphragm mechanism similar to the above as seen from the right side. FIG. 5 is a block diagram showing the circuit configuration for driving the aperture mechanism, and FIG. 6 is a block diagram showing an embodiment in which the first oscillation circuit and the second oscillation circuit shown in FIG. 5 are used as a common oscillation circuit. Diagram: Fig. 7 is a simplified front view of an electric diaphragm device showing a conventional example, Fig. 8 is a simplified side view seen from the right side of Fig. 7, and Fig. 9 is a drive of an electric diaphragm device a shown in a conventional example. FIG. 10... Aperture mechanism 12... Aperture 'JA'; a 14... Drive lever 16... Movable ring 21a... First shape memory alloy wire I 21b...
- First shape memory alloy wire 26... Light receiver 28... Ratio/Membrane circuit 3o... First oscillation circuit 31... Second oscillation circuit 34... First transformer 35 ...Second transformer

Claims (4)

[Claims] (1) In an aperture device that controls the aperture of a lens according to the brightness of the subject so that the amount of light received by an optical device such as a camera is constant, the aperture is opened by supplying power to the first shape memory alloy, and the aperture is opened to the second shape memory alloy. An electric mechanism that closes the diaphragm by supplying power to the shape memory alloy, a light receiver that detects the subject light that has passed through the diaphragm, and a first
a comparison selection circuit that outputs a selection signal and a second selection signal when the received light value is higher than a reference value; a first power supply circuit that supplies power to the first shape memory alloy in response to the first selection signal; 1. A drive circuit for an aperture device, comprising: a second power supply circuit that supplies power to a second shape memory alloy in response to a second selection signal. (2) Claim (1) characterized in that the device is equipped with a detector for detecting the environmental temperature and adjusts the power supply level of the first power supply circuit and the second power supply circuit according to the output of the detector. ) Drive circuit for the aperture device described. (3) An intermediate band of a certain width is provided in the reference value of the comparison and selection circuit, and when the light reception value of the light receiver is within the intermediate band,
2. The drive circuit for an aperture device according to claim 1, wherein the first power supply circuit and the second power supply circuit do not output power. (4) A drive circuit for an aperture device, wherein the first and second power supply circuits include an impedance converter such as a transformer that supplies power to the first and second shape memory alloys.