JPS61144633A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain an image pickup device provided with a light shielding means having no possibility for failure by providing bent parts which are warped in the directions opposite from each other to avoid the collision of two sheets of shutter vanes to the positions where the shutter vanes are liable to collide against each other when driven. CONSTITUTION:The shutter vanes S3, S4 are respectively fixed to the shafts of the 1st and 2nd motors 17, 117. The shutter vanes S3, S4 are formed to a semi-disk shape and are provided with the bent parts S3a, S4a warped in the directions opposite from each other on the side parts thereof. The shutter vanes are formed into the shape provided with the bent parts S3a, S4a warped toward the outside to the sides S1a, S2a of two sheets of the convensional shutter vanes S1, S2 facing each other. The bent parts S3a, S4a contact slidingly with each other when the two shutter vanes S3, S4 rotate relatively in the stage of starting or stopping the shutter but said parts are warped to the outside and therefore there is no more possibility of the collision and therefore the failure of the shutter vanes S3, S4 is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an imaging device for imaging a subject, and particularly to an imaging device equipped with a light shielding means for shielding image light.

[Prior art]

Conventionally, two shutter blades that rotate at the same speed in the same direction and have a light-blocking part and a light-transmitting part are provided, and the exposure time is controlled by controlling the opening degree of the part where the light-transmitting part of the two shutter blades overlaps. An imaging device equipped with a so-called rotary shutter is known.

FIG. 1 shows an exploded perspective view of the rotary shutter. In the figure, 30 is an imaging unit such as a CCD z 8 M film, 31 is a drive motor, and 32 is a shaft of the Fi motor 31, which is provided with a groove 328. 33 and 34 are shutter blades made of thin plates, each having a semicircular shape. The shutter blade 33 is fixed to the shaft 32, and rotates in the direction of the arrow in the figure when the motor 31 is energized. 35 is an opening adjustment shaft provided with a through hole 35a;
It is rotatably attached to the shaft 32. Further, it is fixed to the shutter blade 34 at one end 35c.

35b is a cam groove. 36 is a slider and the through hole 3
6a, it is rotatably attached to the opening adjustment shaft 35. Bottle 3T is installed on slider 36.

The cam groove 35 extends in the inner diameter direction of the through hole 36a.
It enters the groove 32a via b. 3B is a control board with hole 38
a, 38b to move along the guide shaft 40. The pin 39 is fixed to the control plate 38 and enters a groove 36b on the outer periphery of the slider 36.

Next, the operation will be explained.

When the motor 31 is energized, the shutter blade 33 fixed to the shaft 32 rotates in the direction of the arrow in the figure. The rotation of the motor is transmitted to the opening adjustment shaft 35 via the groove 32a1 pin 3T and the cam groove 35b, and the shutter blade 34 rotates in the direction of the arrow in the figure.

Then, when the control board 38 is moved to the right in the figure, the pin 3
9. The pin 37 moves to the right in the figure through the groove 36b, and the shutter blade 34 moves to the right through the cam groove 35b and the groove 328.
3, the opening angle becomes smaller and the shutter time becomes shorter. Also, the control board 38
When the shutter blade 34 is moved to the left in the figure, the shutter blade 34 rotates clockwise relative to the shutter blade 33 (in the direction of the arrow in the figure) by an operation opposite to that described above, and the opening degree becomes larger and the shutter time becomes longer. In this way, the exposure time is controlled.

As described above, the conventional rotary shutter has disadvantages in that it requires a large number of cams and other mechanical parts, which increases the number of parts and makes it mechanically complex. This is also related to the above point, but there is no mechanical play in these mechanical parts.
Due to wear and tear, there were some issues with accuracy, reliability, longevity, etc.

A shutter as shown in FIG. 2 has been proposed to eliminate these drawbacks.

In the figure, 2 is a light emitting element, 4 is a light receiving element, and 20 is a CC
Solid-state image pickup devices such as D and BBD, and shutter blades i7 and 117 are the first shutter blades i7 and 117 for rotating blades Sl and S2, respectively. This is the second motor. Motor 17, 11
7 shaft and shutter blade S1. S2 are each fixed, and their rotation centers are coaxial. Both shutter blades S1 and S2 are attached parallel to each other with a slight interval between them. The second motors 17 and 117 cause relative rotation. Now, when the first and second motors 17, 117 are energized, the shutter blade S
1. S2 rotates in the direction of the arrow in the figure, and the exposure time of the image sensor 20 is controlled by the angle formed by the side S18 and the side S2a. Then, the exposure time is measured by the light emitting element 21 and the light receiving element 22 arranged with the shutter blades Sl and S2 in between.

However, in this shutter, since the two shutter blades Sl and S2 are formed in the shape of a semicircular plate, when controlling their rotational phase, the two shutter blades Sl and
, S2 comrade is that side Sta.

There was a drawback that the Sza portions collided with each other and were easily damaged. [Purpose] This invention aims to eliminate such conventional drawbacks, and provides an image light shielding means that is free from damage. The purpose is to provide an imaging device.

〔Example〕

FIG. 3 shows an embodiment of the invention.

In the figure, the same symbols as @Qff indicate the same parts.

S3. S4 is a shutter blade, which is fixed to the shafts of the first and second motors 17 and 117, respectively. This shutter blade S3. S4 is formed into a semi-disc shape, and its sides are bent in opposite directions!
S3a and S4a are provided. Just like the conventional two shutter blades facing each other St, 5217) Side S
It has a shape in which bent portions S3a and S4a which are bent outward are provided at portions la and S2a, respectively.

With this configuration, when the shutter is activated,
Two shutter blades when stopped 33. When S4 rotates relatively, the above bending t%s3a.

Even if the shutter blades S4a may come into sliding contact with each other, since those portions are curved outward, there is no risk of collision, and therefore the shutter blades S3. There will be no chance of S4 being damaged.

Next, a driving circuit for driving the rotary shutter shown in FIG. 3 will be explained with reference to FIG. 4. The figure shows the circuit diagram.

A series circuit of a resistor 1 and a light emitting element 2 such as an LID, a series circuit of a resistor 3 and a light receiving element 4, a series circuit of a resistor 5.6, a comparator 7, a capacitor 12 and a constant current source 11 are connected in parallel with the power supply E.
A series circuit of operational amplifiers 13 and 16 and a parallel circuit of operational amplifiers 13 and 16 are connected. The inverting input terminal of comparator 7 is resistor 5.6
is connected to the connection point P2, and its non-inverting input terminal is connected to the resistor 3
and the connection point P of the light receiving element 4. Comparator 7
The output of is connected to the base of the transistor 100 via a series circuit of a capacitor 8 and a resistor 9. transistor 1
The emitter of 0 is connected to the anode of the power source E, the collector is connected to the connection point between the capacitor 12 and the constant current source 11, and is also connected to the non-inverting input of the operational amplifier 13. Operational amplifier 1
3 has its output and inverted input connected directly, and functions as a buffer. The output of operational amplifier 13 is connected to the non-inverting input of operational amplifier 16 via analog switch 14 . A capacitor 15 is connected between the non-inverting input of the operational amplifier 16 and the cathode of the power source E. The operational amplifier 16 has its inverting input and output connected directly, and also functions as a buffer. Operational amplifier 16
The output of is connected to the cathode of the power source E via the first motor 17. The circuits 107 to 117 are connected to the comparator 10.
Except for the fact that the inverting input of T and P1 are connected, and the non-inverting input and P2 are connected, the circuit configurations are completely the same, except that parts 7 to 17 and numbers in the 100s are attached, so a description thereof will be omitted. The analog switches 14, 114 have their control terminals 14a
When 11148 is at a high level, it is in a conductive state, and when it is at a low level, it is in a non-conductive state. While the analog switches 14 and 114 are conductive, the output 1a of the operational amplifiers 13 and 113 is sampled to the capacitors 15 and 115, and the analog switches 1
While the capacitors 15 and 114 are in a non-conducting state, the charge (that is, the voltage) at the time of sampling is held in the capacitors 15 and 115, and is outputted at low impedance via the buffers 16 and 116.

i.e. 14, 15, 16 and 114, 115, 11
6 forms sample and hold circuits A and A'. Note that the control electrodes 14 and 11 of the analog switches 14 and 114
4 is directly connected and inputs the vertical synchronization signal 18.

As described above, between the light emitting element 2 and the light receiving element 40, there are semicircular shutter blades S3. attached to the shafts of the motors 1T and 117, respectively. S4 is placed, and the exposure time is measured based on the output of the light receiving element 4.

That is, the light from the light emitting element 2 is S3. While the current does not reach the light receiving element 4 because it is blocked by S4, no current flows through the light receiving element 4, and the voltage at point P1 is approximately equal to the power supply voltage. When the shutter blade S3 changes from blocking the light emitting element 2 and light receiving element 4 to passing light at time T1 due to the rotation of the motor, the light from the light emitting element 2 reaches the light receiving element 4 and the light receiving element 4 becomes conductive. In this state, the potential of Pl drops to near zero. Furthermore, when the motor rotates and the light from the light emitting element 2 is blocked again by the shutter blade S4 at time T2, the light does not reach the light receiving element 4 and becomes a non-conducting state P
The voltage of l rises almost to the power supply voltage. This state continues until the motor rotates and the light changes from the state where it is blocked by the blade S3 to the state where it is not blocked at time T'1. FIG. 5(a) shows the change in the potential of Pl over time.

Assuming that the resistance values of the resistors 5 and 6 are equal, the potential at the 82 points is approximately 1/2 of the power supply voltage.

As is clear from FIG. 5(a), at time T1, when the potential of Pl changes from the power supply voltage to almost zero volts, that is, when the light receiving element 4 is irradiated with light, the height relationship with the 82 point is reversed, and the voltage of the comparator T changes. The output changes from high level to low level. At this time, a base current flows to the transistor 10 through the series circuit of the capacitor 8 and the resistor 9, and the transistor 10 is turned on. By turning on the t transistor 100, both ends of the capacitor 12 are short-circuited, and the capacitor 12 is discharged. The base current flows through the transistor 10 only while the capacitor 8 is being charged by the resistor 9. Therefore, if this charging time constant is kept short enough, the transistor 10 will be turned on temporarily, short-circuiting the capacitor 12, discharging its charge, and then turned off again. Then, the capacitor 12 is charged by the constant current source 11. Here, the voltage vc(t) between the terminals of the capacitor 12 at time t is V
C(t)' I X (t-T, )/C,2+11
1 Madashi■0. : The current value C1 of the constant current source 11, : The capacitance of the capacitor 12. Therefore, the terminal voltage v*5(t) of the non-inverting input terminal of the operational amplifier 13 is Vcc: the voltage #i. Since the operational amplifier 13 has a buffer structure with its inverting input and output directly connected (voltage 7 lower), the output voltage of the operational amplifier is the same as the non-inverting input voltage. That is, it is calculated using equation (2). This is shown in FIG. 5(b).

When the vertical synchronization signal 18 arrives, the sample and hold circuit A
is activated, samples the output voltage of the operational amplifier 13 when the vertical synchronization signal arrives, and after that time, the sampled voltage is held at the output of the sample and hold circuit A, and the motor 1 is
7t-drive. If the arrival time of the vertical synchronization signal is ``■'', then the voltage of equation (2) at ``■'' is held. Time T
, the subsequent output voltage Vm of the sample-and-hold circuit A can be expressed as follows.

When the phase of the shutter blade S3 is delayed from the correct state, that is, when the time T1 is delayed from the synchronization signal arrival time TI and takes the value of (TI+ΔT, ), the sample and hold voltage VA'i! , can be expressed as follows.

When the motor is in the correct state, the motor is driven at a higher voltage to advance the phase and return to the correct phase.

If the phase of the shutter blade S3 is ahead of the correct phase, the motor is driven at a voltage lower than that of the correct phase for the exact opposite reason to the above to delay the phase and return to the correct phase.

Note that at time T, the output of the comparator 7 is inverted from low level to high level, but at this time, the capacitor 8,
No base current flows to the transistor 10 through the resistor 9. Therefore, since the transistor 10 remains off, there is no effect on the charging of the capacitor 12, as shown in FIG. 5(b).

As described above, the rotational phase of the shutter blade S3 can be controlled to always maintain a constant relationship with respect to the vertical synchronization signal.

Next, consider the circuit in the lower half of FIG. 4 consisting of circuits 107 to 117. This part is different from the upper half in that Pl is connected to the inverting input of the comparator 117, and P2 is connected to the non-inverting input of the comparator 117. In other words, the connection relationship between the inverting and non-inverting inputs of the comparator 17 is reversed.

Therefore, the output of the humpator 107 changes from high level to low level at time T when the potential at 11 points changes from approximately Ov to approximately Vcc. At this time, the transistor 110 is temporarily turned on to short-circuit both ends of the capacitor 112, and then the capacitor 112 is charged by the constant current circuit 111 in the same manner as the upper half circuit. The voltage v1 applied to the output of the sample and hold circuit is , and the rotational phase of the shutter blade S4 can be controlled to have a certain constant relationship with respect to the vertical synchronization signal. still,
The output change characteristics of the operational amplifier 113 are shown in FIG. 5(e), and the vertical synchronizing signal is shown in FIG. 5(d).

If the same motors 17 and 117 are used, the sample and hold voltages must be equal when the phase is properly controlled, so Vmu = Vchi
(6) That is, by changing the current value of the constant current source 11 or 111, the relationship between T and T, that is, the exposure time T
, -TI can be controlled.

In this way, an electric motor is attached to each of the two blades, and their rotational phases are controlled independently. By adopting such a configuration, the number of mechanical parts can be greatly reduced and the mechanical structure can be made extremely simple.

Furthermore, since the actual opening < m light time) is detected without any mechanical contact and feedback control is performed based on this, accuracy and reliability deteriorate due to play and wear that existed in conventional devices. There is no need to worry about this at all, and since there is no contact, the reduction in life caused by looseness and wear can be greatly reduced.

Incidentally, FIG. 6 shows an example of a constant current circuit with variable constant current value.

In the figure, 21 is a power supply with a voltage of 1, 22 is an operational amplifier,
23 is a transistor, and 24 is a variable resistor.

When the voltage ■1 is applied to the non-inverting input terminal of the operational amplifier 2, the inverting input terminal also has the same potential. In other words, since the voltage between the terminals of the resistor 24 is always maintained at ■1, the current value flowing through the variable resistor 24 is 1 to 1, assuming the resistance value R4. Let it be expressed as,
A current equal to the value (1) flows through the collector of the transistor 23 regardless of the load impedance.

Therefore, when the circuit shown in FIG. 5 is used for the constant current circuit 111 shown in FIG. 4, by varying the resistance value of the variable resistor 24, an arbitrary opening degree, that is, an arbitrary exposure time can be obtained.

Although this embodiment has been described using an example of an imaging device using a solid-state imaging device, it is of course applicable to a camera using a silver halide film.

〔effect〕

As explained above, according to the present invention, bent portions that are curved in opposite directions to avoid collision are provided in the portions where two shutter blades are likely to collide with each other when driven, so that damage to the shutter blades can be avoided. Accordingly, it is possible to obtain an imaging device equipped with a light shielding means that is free from the risk of shading.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view of a conventional rotary shutter, Fig. 2 is a perspective view showing another conventional example, Fig. 3 is a perspective view of an embodiment of the present invention, and Fig. 4 is an exploded perspective view of the rotary shutter of Fig. 3. Control circuit diagram, Figure 5 is 4v! Signal waveform diagram of each part of J,
FIG. 6 is a circuit diagram showing an example of a constant current circuit. 2... Light emitting element 4... Light receiving element S3. S4... Shutter blade S3a, S4a
...Bend portion 7.107...Funparator 11.111...Constant current source 13.16, 113, 116...Operation amplifier 1
4.114...Analog switch 17.117
...Motor 18...Vertical synchronization signal

Claims (1)

[Claims] An image capturing means for capturing an image of a subject; a light shielding means consisting of two shutter blades each having a bent portion curved in opposite directions on the side thereof for blocking image light to the image capturing means; An imaging device that has two drive means that drive two shutter blades, respectively, and an exposure time control means that controls the drive phase of these two drive means.