JPS6231834A - Shutter control device - Google Patents

Abstract

PURPOSE:To speed sup shutter driving by increasing the speed of a motor for rotating the shutter to the constant acceleration of the first half and executing the speed decreasing to the constant acceleration for the last half. CONSTITUTION:When the shutter 1 has four notches, the opening and closing change- over angle is 45 deg.. When for the first half of a total driving time ta, an allowable maximum electric current Imax flows at a direct current motor 2, and for the last half, -Imax flows, the shutter is changed over in the shortest time. The shortest time ta is correctly calculated from the specifications of the motor 2 and the inertia efficiency of the shutter 1, and the prescribed square wave signal is generated 4 by a shutter opening and closing command 5. The signal is amplified 3 and drives the motor 2. For two paris of light emitting/pohotodetecting devices to sandwich the shutter 1, the penetration-hole passing light quantity is increased in one side and decreased in other side by the rotation of the disk. When the polarity of the output signal of one side photodetecting device is reversely rotated and added by an operational amplifier 10, the voltage signal to oscillate in the positive and negative is obtained with the stop position as the center and returned to an amplifier 3. When the shutter comes to the stop position, the square wave signal comes to b '0', the input of the amplifier 3 comes to be the position deviation signal only and the shutter stops correctly.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a shutter control device, and in particular, it is required to set the exposure time with minute resolution and high precision, such as the shutter of a reduction projection exposure device. The present invention relates to a shutter control device suitable for use in high temperature environments and in extremely high temperature ambient conditions.

[Background of the invention]

The shutter of a reduction projection exposure system is required to set the exposure time with minute resolution and high precision, and because it is used under extremely high temperatures caused by the illumination light source, the shutter is rotated by a stepping motor or DC motor. A simple configuration is used.

One way to improve the throughput of a reduction projection exposure apparatus is to shorten the exposure time. This requires a high-speed shutter.

As a measure to increase the speed of the shutter, conventional measures have been taken to increase its inertia by considering the shape and material of the shutter, as seen in the reference document ``Mechanism and control in steppers: text of the 1985 Spring Conference of the Japan Society of Precision Machinery Society Symposium by Yu Takahashi''. Measures have been taken to reduce the size of the

However, in order to achieve even higher speeds, it is necessary to use a DC motor, which is more suitable for higher speeds, as the drive motor, and to control it to maximize its performance.

Additionally, due to the structure of the shutter, equipment and parts necessary for control, such as a DC motor, a speedometer generator to detect speed, and a pulse encoder to detect rotation angle, become obstacles that obstruct the optical path.

It must be simplified and omitted as much as possible.

[Purpose of the invention]

An object of the present invention is to provide a shutter control device that increases the speed of the shutter.

[Summary of the invention]

The features of the present invention include a shutter provided with a light passing section and a light blocking section along the circumference, a motor rotating the shutter so as to selectively switch the light passing section and the light blocking section to light flux positions, and During the first half of the period from when one of the light passing section and the light blocking section is switched to the light flux position until the other is switched, the motor is accelerated at a constant rate, and during the second half, the motor is accelerated at a constant rate. and means for controlling the rotation of the motor so as to decelerate the motor at a uniform rate.

[Embodiments of the invention]

FIG. 1 is a diagram showing an embodiment of the present invention. Figure 1 shows a disc-shaped shutter. Figure 1 shows an example where the shutter has four notches, or light passage parts, along its circumference. The circle indicated by the dotted line in 11 is the cross section of the light beam. The figure shows the case where the shutter blocks light. When the shutter rotates by the angle θ shown in the figure, the notch comes to the position of the light beam, so the shutter becomes open.

1' is a side view of the shutter, showing that it is driven by a DC motor 2. 3 is an amplifier that drives the DC motor 2.

4 is a square wave signal generator, the output of which is input to the amplifier 3; Reference numeral 5 indicates a shutter opening/closing command signal, which is input to the square wave signal generator 4. 6 is a current detector, which uses a resistor in this example. Since a voltage proportional to the current of the DC motor 2 is obtained between both ends of this resistor, this voltage is fed back to the input of the amplifier 3. 7 is a hole provided in the shutter, and 2 holes are provided at the positions corresponding to the closed and open positions.
They are provided one by one. 8 is a light emitter, 9 is a light receiver, and two pairs are provided with a shutter 1' in between.

Reference numeral 10 denotes an operational amplifier, which functions to reverse the polarity of the output signal from one of the two light receivers and apply it to the amplifier 3.

FIG. 2 is a diagram for explaining the present invention in detail. When the shutter 1 has four notches as in this example, the rotation angle from close to open and from open to close is 45 degrees.

The first half of the total time ta for driving this 45 degrees is accelerated with the maximum acceleration allowed for the DC motor 2, and the second half is
If 2 is also decelerated at the maximum acceleration, 4 will be achieved in the shortest time.
A rotation of 5 degrees is performed. The relationship between the speed of the DC motor 2, the current, and the time t at this time is shown in FIGS. 2(a) and 2(b).

Figure 2 (a) shows that the speed of the DC motor 2 is 1/1/2 of the first half.
2 is accelerated at the maximum acceleration allowed by the DC motor 2 to reach Nmax, and the latter half is decelerated at the same maximum acceleration to return to O.

Figure 2 (b) shows that during the first half period, the DC motor 2
Flow the instantaneous maximum current I m &
2, indicating that the same <I-a, l must flow in the opposite direction.

The shortest driving time ta can be accurately known in advance from the specifications of the DC motor 2, the inertia rate of the shutter 1, and the like. The square wave signal generator 4 is configured to generate a positive square wave during the first period of ta/2 and a negative square wave during the subsequent period of t&/2 when receiving the shutter opening/closing command signal 5. This output waveform is shown in FIG. 2(c).

This square wave signal becomes the command value for the current control loop composed of the amplifier 3, the DC motor 2, and the current detector 6, so the DC motor current is controlled to be similar to this square wave signal. In the end, the shutter 1 is driven as expected. Since the hole provided in the shutter 1 is provided at the end point position, it does not affect the operation during the rotation from the start point to near the end point.

FIG. 3 is a diagram for explaining the principle of end point position detection. FIG. 3(a) is a diagram showing a pair of holes provided in the shutter 1. Straight line 7' is the stop position of shutter 1. As shown in the figure, the pair of holes are provided so as to be out of phase with each other about the stop position.

Two pairs of light emitters and light receivers are provided with the shutter 1 in between, and the amount of light passing through the hole is as shown in Fig. 3(b), where A is the amount of light passing through the hole A. B is the amount of light passing through hole B. In other words, when the disc deviates from the closed or open state, the amount of light passing through one hole increases and the amount of light passing through the other hole decreases.

Each photoreceiver generates a voltage proportional to the amount of light, and when the polarity of the output signal of one photoreceiver (in the example shown in the figure, side B) is reversed by the operational amplifier 10 and summed, the output signal is centered around the stop position. Since a voltage signal that swings positive and negative is obtained, this is fed back to the amplifier 3. This is shown in FIG. 3(c).

When shutter 1 reaches the stop position, square wave signal 1
The signal from the signal generator 4 becomes O, and the only input to the amplifier 3 is the position deviation signal from the two receivers, which positions the shutter 1 so that it is switched to the correct position and stopped. Control takes place.

FIG. 4(a) shows the relationship between the rotation angle θ of the shutter 1 and time t. This is a function obtained by integrating FIG. 2(a) over time t. FIG. 4(b) shows the relationship between the amount of light S passing through the shutter 1 and θ, with (a) showing the relationship from closed to open, and (b) showing the relationship from open to closed. This is a function obtained from the geometrical relationship between the light flux and the shutter 1 that blocks it.

FIGS. 4(a) and (b) show t1→θ, →S1 as shown in the figure.
By reading the light amount Sl at each time t1 in the order of
is required. FIG. 4(c) is a diagram showing the relationship between S and t from the time when the shutter 1 starts to be opened until it is closed, obtained in this manner.

(a) and (b) in FIG. 4(c) are the periods during which the shutter 1 is being driven, (a) corresponds to close → open, and (b) corresponds to open → close. (C) is a period in which the lens is stopped in the open state, and the length of the exposure time is set by adjusting the length of this period by adding or subtracting ta.

Exposure time is defined as the time from the time when the amount of light falls below 50% to the time when it cuts off to 50% at the fall, but as is clear from the figure, it cannot be shorter than tz+tz, so the shutter To speed up the tx
+t! This is achieved by reducing the time required for closing to opening and opening to closing.

Note that, according to the embodiments of the present invention, a compact shutter control device can be obtained that does not require instruments or parts that obstruct the optical path, such as a speedometer generator or a pulse encoder.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to maximize the capacity of the motor and increase the speed of shutter drive.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a shutter control device showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operating principle of the embodiment of the present invention,
FIG. 3 is a diagram explaining the principle of detecting the end point position, and FIG. 4 is a diagram showing the relationship between the rotation angle θ, the amount of light S passing through the shutter, and the time t. 1, 1'...Shutter, 2...DC motor, 3
... Amplifier, 4... Square wave signal generator, 5... Shutter opening/closing command signal, 6... Current detector, 7...
Stop position detection hole, 7'... Stop position, 8... Emitter, 9... Light receiver, 10... Operational amplifier, 11...
・Cross section of the beam of light.

Claims (1)

[Scope of Claims] 1. A shutter provided with a light passing part and a light blocking part along the circumference, and a motor rotating the shutter so as to selectively switch the light passing part and the light blocking part to light flux positions. Then, during the first half of the period from when one of the light passing section and the light blocking section is switched to the light flux position until the other is switched, the motor is accelerated at a uniform rate, and during the second half. In the shutter control device, the shutter control device includes means for controlling the rotation of the motor so as to decelerate the motor at a constant acceleration. 2. A shutter provided with a light passing part and a light blocking part along the circumference; a motor rotating the shutter so as to selectively switch the light passing part and the light blocking part to the light flux position; During the first half of the period from when one of the light passing section and the light blocking section is switched to when the other is switched, the motor is accelerated at a constant rate, and during the second half, the motor is accelerated at a constant rate. The correcting means includes means for controlling rotation of the motor so as to decelerate in an accelerated manner, and means for correcting a shift in the switching stop position of the shutter, and the correcting means is configured such that each of the light passing section and the light blocking section is adjusted to the position of the light flux. When properly switched and stopped, the first and second optical signals are generated that are substantially equal to each other, but when the light beam deviates from the position, the first optical signal increases and the second optical signal increases. is configured to decrease, and is configured to perform switching stop position control for the light flux position of each of the light passing section and the light blocking section based on the first and second optical signals. Shutter control device.