JPH0560302B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to an imaging device that captures an image of a subject;
In particular, the present invention relates to an imaging device that is capable of recording still images and is equipped with a viewfinder section that displays photoelectric conversion output.

<Background of the invention> In recent years, CCD,
2. Description of the Related Art Electronic cameras are being actively developed that use solid-state imaging devices such as BBDs to convert still images of objects into electrical signals and record them on recording media such as magnetic sheets.

In such electronic cameras as well, it is desired to use an electronic viewfinder that has been conventionally used in video cameras for taking moving pictures. This is because the electronic viewfinder displays the output signal of the light receiving section for photoelectric conversion, so the user can clearly see what kind of image is actually being recorded. On the other hand, such confirmation is not possible with optical viewfinders.

Furthermore, since the electronic viewfinder must operate continuously during still image photography, it is desirable that the aperture means operate as a so-called auto iris. In order to photograph fast-moving subjects, a shutter is required to control the exposure time.
In order to provide an electronic viewfinder in this way, two complicated mechanisms, a shutter and an auto iris, are required. Compared to conventional video cameras, which were only equipped with an auto iris, this inevitably makes them more complicated and larger.

<Object of the Invention> In view of the above-mentioned points, it is an object of the present invention to provide an image pickup apparatus equipped with an electronic viewfinder that can be constructed simply and compactly by using an aperture means that has both an auto iris function and a shutter function.

<Description of Embodiment> FIG. 1 is a schematic block diagram of an imaging apparatus of this embodiment. In the figure, 201 is an optical system, 202 is an aperture means, 203 is a CCD as a light receiving section, 204
2 is a signal processing circuit; 205 is a recording signal processing circuit;
06 is NTSC decoder, 207 is amplifier, 208
209 is a magnetic head, 210 is a magnetic sheet, and 211 is a motor.

Image light from the subject is imaged onto the CCD 203 via the optical system 201 and the aperture means 202.
Electric signals corresponding to the subject image obtained by the CCD 203 are converted into R, G, and B color signals by a signal processing circuit 204. The output of the signal processing circuit 204 is sent to the recording signal processing circuit 205 and the NTSC decoder 20.
6 is input. The NTSC decoder 206 converts each color signal into an NTSC standard television signal.
Electronic viewfinder 20 via amplifier 207
8 so that the user can see it. Further, the recording signal processing circuit 205 converts each color signal into a recording signal,
For example, FM modulation is performed and the recording signal is amplified, and the amplified recording signal is supplied to a magnetic head 209 and recorded on a magnetic sheet 210 which is rotationally driven by a motor 211. The detailed operation of each circuit is already well known and will therefore be omitted.

Next, the mechanism of the throttle means 202 shown in FIG. 1 will be explained with reference to the exploded perspective view shown in FIG. 2.

In the figure, 1 is a substrate made of non-magnetic material;
2 is a permanent magnet magnetized in the vertical direction in the drawing, 3
5 is an opening for irradiating light from a subject onto a photoelectric conversion type light receiving unit such as a CCD, BBD, or image pickup tube (not shown); 5 is a convex portion provided on the substrate 1; 4a to 4e;
is a pin provided on the convex portion 5, 6 is a rotor formed of a printed circuit board, 7a to 7e are pins on the rotor 6, 8 and 9 are lead wires taken out from the top surface of the rotor 6 in the figure, 10 and 11 1 is a lead wire taken out from the lower surface of the rotor 6 in the drawing, 12 is an opening similar to 3, and 13 is an aperture blade, of which five blades are used, but four are omitted from the drawing for ease of understanding. 13a is a long hole provided in the aperture blade, 13b is a hole provided in the aperture blade, 14 is a yoke arranged at a predetermined distance from the rotor 6, 14a is an opening similar to 3,
15a to 15e are holes into which pins 7a to 7e are inserted, 16a to 16e are holes into which pins 4a to 4e are inserted, and 17 is a yoke, which has an opening similar to 14a although it is hidden in the drawing. .

The four permanent magnets 2 and the yokes 14 and 17 form a magnetic circuit, and the rotor 6 is arranged between the permanent magnets 2 and the yokes 14, and the coils 6a and 6b on the rotor 6
The rotor 6 rotates by passing a current through. The rotor 6 is rotatably attached to the convex portion 5 through the opening 12, and the aperture blade 13 is attached to the elongated hole 13.
Since the rotor 6 rotates, the aperture blades 13 rotate around the pin 4e and control the opening area of the aperture 12.

FIG. 3 is a plan view of the rotor 6. 6a is a drive coil formed of a conductor on the substrate of the rotor 6, and both ends of the coil 6a are connected to lead wires 8 and 9. A coil 6b having the same shape is also formed on the back surface of the rotor 6, and is called a braking coil. Braking coil 6
Both ends of b are connected to lead wires 10 and 11. The drive coil 6a and the brake coil 6b are placed in a magnetic field formed by the permanent magnet 2.

Below, the operation of the diaphragm device will be explained separately for the case where it operates as an auto iris when shooting a moving image and when viewing with an electronic viewfinder, and the case where it operates as a shutter when releasing the shutter for shooting a still image.

[When operating as auto iris]

When the drive coil 6a is energized by a drive circuit, which will be described later, a current flows in the magnetic field of the permanent magnet 2, so that a force is generated in the direction according to Fleming's left-hand rule. Since the permanent magnets 2 are magnetized so that adjacent magnets have opposite polarities in the vertical direction in FIG. . The direction of rotation can be controlled by the direction of the current flowing through the drive coil 6a. As the rotor 6 rotates, the braking coil 6b moves in the magnetic field of the permanent magnet 2, and a voltage is generated between the lead wires 10 and 11.

In this embodiment, when a negative voltage is applied to the positive lead wire 8 to the lead wire 9 of the drive coil 6a, the aperture closes.
At that time, the lead wire 11 of the braking coil 6b is connected to the positive
The structure is such that a negative voltage is generated.

[When operating as a shutter]

In this case, the drive coil 6a and the brake coil 6b are connected in series or in parallel, operate together as drive coils, and work together to open and close the aperture blades. Since both coils can be used, the aperture blades can be operated at high speed with less power consumption.

FIGS. 4a and 4b are circuit diagrams showing connection switching between the drive coil 6a and the brake coil 6b. Figure 4a
4 shows an embodiment in which a drive coil 6a and a brake coil 6b are connected in parallel during shutter operation, and FIG. 4b shows an embodiment in which a drive coil 6a and a brake coil 6b are connected in series.

In the figure, 21 to 24 and 21' to 24' indicate relay switches, which are connected to terminal a during video shooting and viewing with the electronic viewfinder, and are connected to terminal b when the release switch is pressed for still image shooting. It will be done. 25, 25' are auto iris drive circuits, and 26, 26' are shutter drive circuits.

In Fig. 4a, switches 21, 22, 23, 2
When 4 is connected to the contact a side, the auto iris control circuit 25 energizes the drive coil 6a. The detection signal from the braking coil 6b is fed back to the control circuit 25, and the aperture value is controlled while keeping the aperture open. And switch 21, 22, 2
3 and 24 are connected to the contact b side, the coil 6
a and 6b are connected in parallel and controlled by a shutter drive circuit 26.

In FIG. 4b, when a moving image is photographed and viewed using an electronic viewfinder, the control is performed in exactly the same manner as in FIG. 4a. At the time of release for still image photography, the coils 6a and 6b are connected in series and controlled by a shutter drive circuit 26'. In this example, a reed relay is used as the switch, but a switching operation using a transistor may also be used.

As mentioned above, when operating as a lens shutter, the driving coil 6a and the braking coil 6b work together, so the magnetic field produced by the permanent magnet 2 can be effectively used.
Compared to opening and closing the aperture blades using only the drive coil 6a, higher speeds can be achieved with less electric power.

FIG. 5 is a detailed circuit diagram of the auto iris drive circuit and shutter drive circuit shown in FIGS. 4a and 4b.

FIG. 6 is an operation timing chart of each part of FIG. 5 when photographing a still image.

In the figure, A is a half-open shutter drive circuit, and B is an auto-iris drive circuit. In this circuit, the drive current for opening the shutter is a constant current and is supplied directly from the battery. 31,3 in the figure
2 is a positive and negative power supply battery, 41 is a constant voltage circuit, OP1
is an operational amplifier constituting an amplifier, and 4 is a light receiving element (for example, an SPC (silicon photocell)), which is connected between both input terminals of the operational amplifier OP1 and placed behind the diaphragm aperture 3. 42 and 43 are voltage dividing resistors that provide the level of the non-inverting input terminal of the operational amplifier OP1, and TR1 has the base of the operational amplifier OP1.
The transistor connected to the output of OP1,
TR2 is a transistor whose base and collector are short-circuited and functions as a diode, and TR3 is a transistor whose base is connected to the base of the transistor TR2. SW2 is a drive mode changeover switch for the aperture means, and when the aperture means 202 is switched toward the terminal, the aperture means 202 functions as an auto iris, and when it is switched toward the terminal, it becomes a half-open shutter, and still images are taken.

In FIG. 5, when shooting a moving image, the switch SW2 is connected to the terminal side and the aperture operates as an auto iris. When photographing a still image, the diaphragm operates in auto iris mode while observing the subject, operates in shutter mode with the release operation, and returns to auto iris mode again after still image photography is completed.

The operation of the aperture means in each operation mode will be explained in detail below.

[Circuit operation as auto iris]

Operational amplifiers OP3, OP4, and OP5 are connected in parallel with positive and negative power supplies 31 and 32 connected in series.
The inverting input of the operational amplifier OP3 is grounded via a resistor 71, and the non-inverting input is connected to its output, serving as a voltage follower. A non-inverting input of operational amplifier OP4 is connected to a movable terminal 73a of variable resistor 73, and fixed terminals 73b and 73c of variable resistor 73 are connected to the anode and ground point of positive power supply 31, respectively. The inverting input of the operational amplifier OP4 is connected via a resistor 72 to the output of the operational amplifier OP3, whose output is connected to the drive coil 6 of the aperture.
a to ground, and at the same time is feedback connected to its inverting input via a resistor 74. Drive coil 6a
As described above, when a negative voltage is applied from the output of the operational amplifier OP4, the diaphragm is closed, and when a positive voltage is applied, the diaphragm is opened. The non-inverting input terminal of the operational amplifier OP5 is connected to the non-inverting input terminal of the operational amplifier OP4 via the damping coil 6b of the diaphragm, and the inverting input terminal thereof is connected to the non-inverting input terminal of the operational amplifier OP4 via a resistor 75. At the same time, it is connected to its output via a resistor 76. Further operational amplifier
The output of OP5 is connected to operational amplifier OP4 via resistor 77.
connected to the inverting input of A negative electromotive force is generated in the braking coil 6b when the aperture is about to close, and a positive electromotive force is generated when the aperture is about to open.

The effect will be explained below. When a power switch MSW (not shown) is turned on, a voltage proportional to the intensity of light incident on the light receiving element 4 through the aperture 3 of the aperture is generated at the output of the operational amplifier OP3. The positive power supply 3 where the intensity of the incident light is high and the output voltage of the operational amplifier OP3 is taken from the variable terminal 73a of the variable resistor 73.
If the potential is higher than the non-inverting input potential of operational amplifier OP4, which is a voltage division value of is closed in an attempt to weaken the amount of light incident on the light receiving element 4. At this time, when the diaphragm moves in the closing direction, the electromotive force generated in the braking coil 6b as described above is applied to the non-inverting input of the operational amplifier OP5. Operational amplifier OP5 non-inverts and amplifies this.
A negative voltage is generated at the output of OP4. This negative voltage is applied to the inverting input of operational amplifier OP4 via resistor 77, and operational amplifier OP4 inverts this negative voltage and outputs it as a positive voltage component. The voltage appearing at the output of operational amplifier OP4 during movement of the aperture is the sum of the negative voltage provided by the outputs of operational difference amplifiers OP1 and OP3 and the positive voltage provided by operational amplifier OP5. The electromotive force generated in the braking coil 6b reduces the driving voltage of the driving coil 6a, thereby suppressing the movement of the aperture. The resistance value of resistors 75 and 76 is R7
5, R76, the non-inverting amplification gain of the operational amplifier OP5 is 1+R76/R75.

Contrary to what has been described above, when the output voltage of the operational amplifier OP3 is lower than the variable terminal 73a of the variable resistor 73, that is, the non-inverting input of the operational amplifier OP4, the output voltage is inverted by the operational amplifier OP4 and input to the operational amplifier OP4.
A positive voltage generated at the output of 4 is applied to the drive coil 6a to try to open the aperture. As the aperture opens, a positive electromotive force is generated in the braking coil 6b, which is non-invertingly amplified by the operational amplifier OP5 and then applied to the operational amplifier OP4.
The output voltage of the drive coil 6a, that is, the drive voltage of the drive coil 6a, is reduced to slow down the movement of the aperture. This is the same as closing the aperture.

As described above, the amount of light incident on the light-receiving element 4 can always be kept constant by reducing the aperture area of the aperture when the intensity of the incident light is high, and increasing the aperture area of the aperture when the intensity of the incident light is low. Of course, even if the external light changes over time after the light intensity incident on the light receiving element 4 has settled down to a predetermined value, the amount of light incident on the light receiving element 4 will change by changing the aperture value accordingly. You can avoid it.

[Circuit operation as a shutter]

In the circuit A of FIG. 5, TR4 to TR9 are a group of switching transistors that control energization to the coil 9 of the motor, and the base of the transistor TR5 is connected to the output terminal OS of the timer TM1 via a resistor.
The bases of TR7 and TR9 are connected to the output terminal CS of the timer TM2 via a resistor. OP
2 is an operational amplifier constituting a constant current circuit, 65 is a resistor for detecting the shutter opening current value, 63 and 64
is a voltage dividing resistor and a variable resistor that provide the level of the non-inverting input terminal of the operational amplifier OP2, and by adjusting 64, the motor coils 6a, 6
The current value when opening b can be adjusted. The inverting input terminal of the operational amplifier OP2 is connected to the collector of the transistor TR6.

Further, OS is a shutter open signal, and CS is a shutter close signal. When the shutter opening signal OS is output, the switching transistor is activated by this signal.
TR5 turns on. Also at this time, the shutter close signal
Since CS is at the low level L, switching transistors TR4, TR6, TR7 and TR
9 is off and TR8 is on. Therefore, the coils 6a and 6b of the motor are energized from the battery 31 through the switching transistors TR8 and TR5 in the direction of the arrow OD, and the opening movement of the shutter starts as described above. At this time, since the voltage of the current detection resistor 65 is fed back to the inverting input of the operational amplifier OP2, the coils 6a and 6b
The current flowing to the current is maintained constant. As the opening movement of the shutter progresses and the aperture 3 of the aperture shown in Fig. 1 is formed, the aperture 3 allows the SPC for photometry to be
4, a current proportional to the amount of incident light flows to the collector of transistor TR1: Due to the action of transistor TR2, a current equal to this collector current flows to the collector of transistor TR3,
This current charges the time-fixing capacitor 45.

Also, when the shutter close signal CS is generated, this signal causes the switching transistor TR to
4. TR7 and TR9 are turned on. When switching transistor TR7 is turned on, switching transistor TR8 is turned off. Further, when the switching transistor TR4 is turned on, the switching transistor TR6 is turned on. Therefore, the coils 6a and 6b of the motor are energized in the direction of the arrow CD through the switching transistors TR6 and TR9, and the closing movement of the shutter begins.

Next, the still image shooting operation will be explained in detail.

Before the release, SW1 is open, SW2 is connected to the terminal side, and the aperture operates as an auto iris. In this state, release switch 1
When the switch SW1 closes with the release operation of 00, a trigger signal is input to the timer TM3 via the differentiating circuit D3. Then, the output of the timer TM3 becomes level H, the shutter closing signal CS is outputted via the OR gate 107, and the diaphragm performs a closing operation. The timer TM3 maintains the level H by the resistor 101 and the capacitor 102 for the time required for the aperture to close completely, and then becomes the level L.
When the output level of TM3 is inverted, flip-flop FF1 is set, and the Q output of FF1 is input to one input terminal of NAND gate 104. A synchronizing signal VD instructing the imaging light receiving section to start image accumulation is input to the other input terminal. Therefore, the output of the NAND gate 104 changes from level H to level L in synchronization with the first synchronizing signal VD after the aperture is closed, and the output of timer TM4 is set to level H. Further, the accumulated video signal is transferred and read out in synchronization with the VD after the shutter is closed. The output of timer TM4 becomes the shutter opening signal CO to open the aperture and set flip-flop FF2, and the output of FF2 becomes the shutter opening signal CO.
Switch the connection of SW2 from terminal to terminal. Therefore, approximately at the same time as the opening of the aperture starts, the photometric capacitor 45 starts to accumulate charges corresponding to the amount of light passing through the aperture.

When the accumulated charge of the capacitor 45 reaches a predetermined amount, the output of the timer TM4 becomes level L, and the output of the shutter opening signal OS is stopped. At the same time, when the output of timer TM4 is inverted, the differential waveform output from differentiator circuit D4 triggers timer TM5, the output of TM5 becomes high level, and a shutter close signal is outputted via OR gate 107.

Timer TM5 has resistor 105 and capacitor 106
After the level H is maintained for the time required for the diaphragm to close completely, the level becomes L. With the above operations, still image shooting is completed. When the output of TM5 becomes level L, FF2 is reset via the monostable multivibrator OSM, and the Q output of FF2 connects the switch SW2 from the terminal to the side, returning to the auto iris mode.

In this way, in this example, CCD, BBD,
Since photometry is started in synchronization with an image accumulation start signal of a light receiving section such as an image pickup tube, and moreover, photometry is started almost at the same time as the opening operation of the aperture means is started, so extremely accurate photometry values can be obtained.

And when using an electronic viewfinder,
Since the transition from the auto iris mode to the shutter mode and the transition from the shutter mode to the auto iris mode can be quickly performed, still image photography can be performed without giving a sense of discomfort to the photographer.

In addition, in order to avoid the complexity of the drawing, the fourth
Switches 21-24, 21'- shown in Figures a and b
24' is omitted.

Furthermore, although this embodiment is an embodiment in which video shooting is also possible, the present invention also encompasses an imaging device that only has a still image shooting function.

Further, in this embodiment, a CCD is used for the light receiving section, but the present invention is not limited to this, and it is of course possible to use other solid-state image pickup devices, image pickup tubes, or the like.

[Explanation of effects]

As described above, according to the present invention, it is possible to use the aperture means as both an auto iris and a shutter, so even when a viewfinder means for displaying the output signal of the light receiving section is provided, the viewfinder means can be used with a simple mechanism. The means can be displayed appropriately according to the subject brightness, and the exposure time can be controlled by the shutter when still images are taken.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of the imaging device of this embodiment, FIG. 2 is an exploded perspective view showing one embodiment of the aperture means, FIG. 3 is a plan view of the rotor 6, and FIGS. 4a and 4b are drive coils. 6a, a circuit diagram showing connection switching of the braking coil 6b, FIG. 5 is a detailed circuit diagram of the aperture drive circuit,
FIG. 6 is an operation timing diagram of each part in FIG. 5. In the figure, 202 is an aperture means, 203 is a CCD as a light receiving section, 208 is an electronic viewfinder as a viewfinder section, 25, 25' is an auto iris drive circuit as a first drive control means, 2
6 and 26' are shutter drive circuits as second drive control means, 100 is a release switch as release means, and SW2 is a changeover switch as switching means.

Claims (1)

[Scope of Claims] 1. A light-receiving section that extracts a subject image as an electrical signal, an aperture means that regulates the amount of exposure of the light-receiving section, first and second drive means that drive the aperture means, and the first drive means. The aperture means is driven by the aperture means, and the second drive means acts in a braking direction on the first drive means, and the aperture value is set to the value of the object image while the aperture means is maintained in an open state. Aperture drive control means for video shooting that performs continuous variable control according to brightness, wherein both the first drive means and the second drive means act in the driving direction of the aperture, and the exposure time of the aperture means is controlled. a still image photographing aperture drive means having a faster response speed than the video photographing aperture drive control means, which performs corresponding opening control and closing control; a release means for instructing still image photography; and displaying an output signal of the light receiving section. an electric viewfinder means; a switching means for switching the aperture means controlled by the moving image photographing aperture drive control means to control by the still image photographing aperture drive control means in response to a release operation of the release means; An imaging device characterized by: