JPS635743B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the field of high speed rotary shutter devices.

(Prior Art) In order to record high-speed moving objects on photographic film without blur, there is a strong demand for the development of a shutter with a shutter speed of 1/1000 seconds or more. It is possible to obtain a shutter speed of 1/1000 or more with a sector shutter that rotates continuously at high speed, but it is difficult to obtain a shutter speed of 1/1000 or more seconds with a shutter that records one sheet at a time. It is. This is because the sector blend and its drive mechanism have inertia, and the motor itself also has inertia, making it impossible to instantaneously obtain the desired rotational speed. Also, even if the opening part of the sector reaches the desired speed, it must be slowed down and stopped, so the rotation angle until it opens is increased and the rotation angle until it stops is decreased. It is difficult. Therefore, a method has been adopted in which the opening part of the sector is accelerated from 180° in front of the film aperture, and when it reaches the film aperture, it is decelerated, rotated another 180°, and then stopped to complete one operation. has been done.

FIG. 6A is a diagram showing a conventional sector in which the film portion is opened by traveling 180 degrees, and one cycle is completed by traveling another 180 degrees. Figure 6B
is a graph showing driving characteristics. Sector s having an opening angle that fully opens the film aperture F
When the opening angle portion is at the dotted line position, it is accelerated clockwise from x and rotated 180 degrees to expose the film aperture F at y. After this exposure is performed, the lens is then rotated further 180 degrees while being decelerated, reaches the initial position z, and is brought to a standstill, completing the sixth photographing session. The angular velocity of sector s is obtained by differentiating the curve shown in FIG. 6B. At the beginning of the run, the speed is extremely slow, but it is gradually accelerated, and when it reaches the aperture portion y, it reaches the maximum angular speed, and is gradually decelerated to complete one cycle.

Generally speaking, the slope of the curve at time y
It is preferable that dω/dt be large and that the slope in z be small. However, it is difficult to create ideal conditions within a limited rotation angle.

(Problem to be solved by the invention) Having an opening angle that fully opens the film aperture,
If you try to configure a shutter system that can obtain a shutter speed of 1/1000 to 1/2000 seconds, the acceleration/deceleration method described above will not be able to obtain a sufficient sector speed, or you will have to make an unreasonable stop. A problem occurs.

(Means for Solving the Problems) In view of the above-mentioned circumstances, the present invention accelerates the sector by rotating it from an angle of 180° or more in front of the film aperture, and then rotating the sector at an angle of 180° or more from the film aperture. It is configured to rotate at a deceleration speed of 180 degrees or more, and then reverse and return to the initial position after stopping.

(Embodiment) FIG. 1 is an explanatory diagram for explaining driving of a sector device according to the present invention. In the present invention, as shown in FIG. 1A, the opening portion of the sector s is rotated from a position a at an angle α of 180° or more relative to the film aperture F. If the opening degree of sector s is θ, this angle α cannot exceed 2π−θ. It is accelerated from point a to the aperture center b, and from point b it is further decelerated while increasing the angle β.
It rotates and then stops for a moment. This β also cannot exceed (2π−θ). Next, it is rotated counterclockwise from position c, and d
It is returned to the position (d=a) and one photographing cycle is completed.

FIG. 1B is a diagram showing this operating characteristic. Sector s is accelerated from point a, which is α (=3π/2) before aperture F, and reaches point b. Since the acceleration time is π/2 longer than the case explained in Fig. 1, if the conditions such as inertia and acceleration are the same, the acceleration dω/dt at point b is less than the velocity at point y in Fig. 1 A. growing. sector s reaches point b,
When the film aperture F is fully opened, the speed is gradually reduced until it reaches point c. c.
The angular velocity dω/dt at the point becomes zero. This means that the sector has been temporarily stopped. Subsequently, it is rotated in the opposite direction and reaches point d, completing one imaging cycle.

According to such a sector device, the aperture portion b
Sufficient acceleration can be obtained at the point, and deceleration can be achieved without difficulty, making it possible to return to the next starting position.

Next, the drive device for the control sector will be explained.

FIG. 2 is a block diagram showing an example of the configuration of a control circuit for driving a sector shutter, and FIG. 3 is an operational characteristic diagram for explaining the operation of the circuit.

A pair of photocoupler PC ₁ is used to detect the position angle of sector s and form a control timing signal.
A PC ₂ is provided in association with sector s. Photocoupler PC ₁ is a photocoupler for detecting the state in which sector s has reached the position where aperture F is fully opened, and PC ₂ detects the state in which an open angle exists at point a shown in Fig. 1A. It is a photocoupler for

The sector s is adapted to be driven by a print motor M of low inertia. The motor has low inertia and can rotate in forward and reverse directions, and the steady rotation speed can be controlled by voltage. The timing generation circuit 1 is configured to receive a signal instructing the start of imaging and the signals from the photocouplers PC ₁ and PC ₂ described above, and the timing generation circuit 1 receives the next signal in accordance with the order of these inputs. The acceleration signal generation circuit 2, deceleration signal generation circuit 3, and inverted signal generation circuit 4 connected to each stage are sequentially driven to generate an acceleration signal V _A and a deceleration signal.
V _B and an inverted signal V _C are generated sequentially. These outputs are summed by a summing amplifier 5 and applied to a motor control circuit 6 to form a motor drive voltage and applied to the motor M.

Next, the operation of the control circuit will be explained in detail with reference to the time chart of FIG. 3.

When a start signal is applied to the timing generation circuit 1 when the sector opening is at the start position a indicated by the dotted line in FIG. The accelerating voltage is applied to the motor control circuit 6 and the motor M. This voltage gradually accelerates the sector s, and when it reaches point b shown in FIG. 1A, the photocoupler PC ₁ generates an output. The timing generation circuit 1 stops the operation of the acceleration signal generation circuit 2 and activates the deceleration signal generation circuit 3 according to the trailing edge of the output of PC ₁ . The output of the deceleration signal generating circuit 3 is converted into a decreasing voltage by the summing amplifier 5 and applied to the motor control circuit 6, and a gradually decreasing decelerating voltage is applied to the motor M. After decelerating for a predetermined period, the inversion signal generation circuit 4 is activated to generate an inversion signal. This signal causes the motor M to reverse from position c shown in Figure 1A and slowly move in direction d.The opening angle portion is d (=a).
When the position is reached, photocoupler PC ₂ outputs an output,
This output causes the reversal signal to stop, and the motor M to stop as well. As shown in FIG. 3, PC ₂ sends out an output three times during one operation, and the timing generation circuit sets the trailing edge of the third output as the point of stop.

FIG. 4 is a graph showing the relationship between motor control voltage and motor speed in comparison with a conventional device. Fourth
Figure A is a graph showing the relationship between motor speed and control voltage for 180° acceleration and 180° deceleration shown in Figure 6A.
Even if voltage V is instantaneously applied, the motor will speed up according to its own startup characteristics, and will not stop instantaneously even if it accelerates 180 degrees and the voltage becomes zero. FIG. 4B is a diagram showing the relationship between control voltage and motor speed in the case of the sector device according to the present invention described in detail above. 1st
The accelerating voltage V _A is applied only in the a→b interval (π<ω<2π−θ) shown in FIG. Since this section is substantially longer than in the conventional method, the motor can be smoothly increased to a predetermined rotational speed. In the section b→c, the voltage gradually decreases, and the motor rotates by β (π<β<2π−θ) while being decelerated, and the speed becomes zero. Subsequently, an inversion voltage (-V _C ) is applied to return it to the position d (=a), that is, the starting position.

FIG. 5 is a graph showing the mode of deceleration voltage.
As shown in Figure 5A, the control voltage is instantly changed from V _A.
When V _B =0, the effect of deceleration is large. However, in general, during deceleration, a force acts in the opposite direction to the acceleration direction, so a sudden voltage change will give an impactful force to the motor and mechanical system. As a result, mechanical noise is generated, and there is a possibility that the device cannot withstand repeated use.

FIG. 5B is a graph showing the aspect of the control voltage explained in FIG. 4B. Such a control voltage can be obtained by providing an integrating circuit using an operational amplifier in the deceleration signal generating circuit 3 shown in FIG. This uniform acceleration deceleration largely eliminates the motor and mechanical problems described in connection with FIG. 5A. However, even with this control method, a rather large change in acceleration can be seen at the shoulder section where the transition from V _A to V _B occurs. Although it is possible to operate the mechanical system without difficulty using this control method, it is also possible to use a deceleration voltage as shown in FIG. 5C. By providing a function generator in the deceleration signal generation circuit, a voltage change that approximates an ideal deceleration curve is given by a broken line. In this way, damage and noise caused by impact on the motor and mechanical system are completely eliminated.

Such voltage control can also be applied to control of the reversal voltage, but there is no need to take such consideration since the speed is decelerated and stopped for a while before being reversed. However, it is effective when shortening the inversion time.

(Effects) As described above in detail, according to the present invention, a high shutter speed can be easily achieved with a rotary shutter. Various modifications can be made to the embodiments described in detail above within the scope of the present invention. The scope of the present invention extends to all of the claims, including any modifications thereof.

[Brief explanation of the drawing]

1A and 1B are explanatory diagrams for explaining the driving of a sector device according to the present invention, FIG. 2 is a block diagram showing an embodiment of a control circuit for implementing the present invention, and FIG. is a graph for explaining the above circuit operation. Figures 4A and 4B are graphs showing the relationship between the voltage applied to the motor and the rotational speed of the motor, and Figures 5A, 5B, and 5C are the deceleration voltages applied to the motor. This is a graph for explaining the types of. FIGS. 6A and 6B are a schematic diagram and a running characteristic diagram for explaining the running of a conventional sector. s...Sector, F...Film aperture, 1
... Timing generation circuit, 2 ... Acceleration signal generation circuit, 3 ... Deceleration signal generation circuit, 4 ... Inversion signal generation circuit, 5 ... Summing amplifier, 6 ... Motor control circuit, M ... Motor.

Claims (1)

[Claims] 1. A sector having an opening angle θ that fully opens the film aperture, a motor coupled to rotate this sector in forward and reverse directions, and generating a signal when the sector opening portion is at the film aperture position. a first sector position detector, the sector is located at a position below the film aperture position α(π<α<2π−
a second sector position detector that generates a signal when the sector is located at a position separated by θ), and a timing signal for acceleration, deceleration and reversal in response to signals and start signals from the first and second sector position detectors. an acceleration voltage generation circuit that accelerates the motor using the start signal;
a deceleration voltage generation circuit that decelerates the motor using the first sector position detector signal; and an angle β (π<β<2π−θ) from the time when the first sector position detection signal is generated.
a reversing voltage generation circuit that generates a reversing voltage that reverses the motor after decelerating the motor and stops the reversing voltage according to the second sector position detector signal generated when the sector returns to the starting position; and a motor control circuit that supplies the motor to the motor.