JPH0736079A - Pulse drive shutter - Google Patents

Abstract

PURPOSE:To normally control the action of a shutter motor even when heavy load is driven or a shutter time is long by selecting the cycle of a shutter based on the outputted result of a voltage detection means and pulse-driving a shutter. CONSTITUTION:Before the shutter is driven, a battery check action is conducted. When the heavy load such as a red-eye lamp is driven or the length of the shutter time becomes equal to or over some degree, the cycle of the driving pulse of the shutter 14 outputted to a shutter driver 13 from a CPU 12 becomes longer in a sequence that a stepping motor is driven, so that the driving cycle of the shutter driving pulse also becomes long. Thus, the stable control is conducted by reducing the angular velocity of the stepping motor and increasing the torque thereof based on the property of the stepping motor that the torque is increased when the angular velocity is reduced in order to compensate the reduction of the torque of a stepping motor caused by the lowering of a power source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera shutter, and more particularly to a pulse drive shutter.

[0002]

2. Description of the Related Art A conventional camera shutter has a phase output such that a coil for electromagnetically driving the shutter does not perform an opening / closing operation before driving the shutter so that a malfunction does not occur during an opening / closing sequence of the shutter. I checked the battery voltage after turning on the power for a certain time. The battery voltage obtained by the battery check operation is compared with a predetermined voltage, and the photographing operation is allowed, warned, or prohibited according to the result.

[0003]

However, when a heavy load such as a lamp for preventing the so-called red-eye phenomenon (hereinafter referred to as a red-eye lamp) is operated after checking the battery, the battery is exhausted and the load is released. The battery voltage may not recover to the voltage immediately after the battery check after the shutter open / close sequence is started. Further, when the shutter time is longer than a certain length, the battery may be exhausted because the step motor and the electromagnet for mechanical locking are driven during the shutter opening / closing sequence. In either case, the torque of the shutter motor is reduced, which is not preferable because it may cause an abnormal exposure or malfunction during the shutter sequence.

An object of the present invention is to perform control so that the operation of the shutter motor does not become abnormal even when a heavy load such as a red-eye lamp is driven, or when the shutter time exceeds a certain length. There is something to do.

[0005]

In order to solve the above problems, in a camera shutter according to the present invention, a battery built in the camera, a voltage detecting means for detecting the voltage of the battery, and the battery are provided. A shutter that operates as a power source and a shutter driving unit that selectively pulse-drives the shutter at a first cycle or a second cycle that is longer than the first cycle based on the output result of the voltage detection unit are provided.

Further, the battery built in the camera, the voltage detecting means for detecting the voltage of the battery, the load operated by the battery as a power source, the photographing lens, and the output result of the voltage detecting means And a photographing lens driving means for outputting a driving signal for selectively driving the photographing lens to a focus position before or after driving the load.

[0007]

[Operation] The battery check operation is performed prior to the driving of the shutter. If a heavy load such as a red-eye lamp is subsequently driven, or if the shutter time is longer than a certain length, increase the shutter open or close time during the shutter sequence longer than usual, and To compensate for the lack of torque.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an overview of a camera according to an embodiment. A lens barrel 3 having a taking lens 2 is provided on the front surface of the camera body 1 so as to be movable back and forth. In addition, the finder 4 and the projection unit 5
a, a light-receiving section 5b, and a strobe 6 are provided, and further, a red-eye lamp 7 is provided to alleviate the red-eye phenomenon at the time of stroboscopic photography. The release switch 8 is on the top surface of the camera body 1.
A flash mode switch 9 is provided, and the release switch 8 performs a photographing operation according to the states of the switch S1 and the switch S2 which are turned on in two steps by pressing.
Each time the strobe mode switch 9 is pressed, the flash inhibition mode, the automatic flash mode, and the forced flash mode can be cycled to be selected.

FIG. 2 shows a circuit diagram of this camera. Battery 1
0 supplies power to each circuit of the camera. Regulator 1
1 is an arithmetic circuit (hereinafter, CPU) that controls the entire camera operation.
A stable voltage is supplied to (12). The CPU 12 detects an inter-terminal voltage of the battery 10 and compares the minimum operating voltage Vc at which exposure is possible with an analog / digital (hereinafter referred to as A / D) converter 12a, and a read-only holding program and data.・ Memory (hereinafter R
OM) 12b, random access memory (hereinafter referred to as RAM) used for operations and temporary storage
12c are built in. Further, a shutter driver 13 is connected to the CPU 12 and outputs three signals, a signal φ0 allowing the operation of a step motor built in the shutter 14 and signals φ1 and φ2 for controlling the phase.
4 are driven according to their signals. Further CPU1
2 is a transistor 15 for causing the red-eye lamp 7 to emit light
To control. A release switch 8 and a strobe mode switch 9 are connected as input terminals of the CPU 12, and the well-known distance measuring circuit, photometric circuit, strobe control circuit, film sensitivity detecting circuit, etc., which are not shown, are also controlled by the CPU 12.

FIGS. 3 and 4 are time charts of the exposure control sequence when the flash of this camera is not lit and when the flash is lit. First, the sequence when the flash does not emit light in FIG. 3 will be described. The strobe does not emit light when the subject brightness reaches a certain level or higher (for example, Ev> = 6) in the strobe light emission prohibition mode or the automatic light emission mode, and the red-eye lamp 7 is not driven. When the photographer presses the release switch 8 and the switch S1 is turned on, C
The PU 12 energizes the shutter driver 13 to the coil forming the step motor built in the shutter 14 for a predetermined time in order to confirm whether or not the subsequent sequence can be performed normally (FIGS. 3a-b). Since this energization is performed so as to be in the same phase as the phase (mechanical stable position) at which the previous shutter operation has ended, the shutter 14 does not open or close. Here, the voltage of the battery 10 is equal to or higher than Vc, and the subsequent sequence is normally performed. Subsequently, the CPU 12 causes the distance measuring circuit to perform distance measurement, and calculates the distance to the subject based on the output thereof. Further, the photometric circuit is caused to perform photometry, and the brightness of the subject is calculated based on the output.

Next, the operation of the shutter 14 is started (see FIG.
e). In operating the shutter 14, the CPU 12 firstly causes the shutter driver 13 to set a mechanical initial position.
On the other hand, a pulse for driving the shutter 14 in the closing direction is output. When the initial position of the shutter 14 comes out (FIG. 3f), the next step is to open the shutter. The shooting lens is driven to the in-focus position according to the subject distance while the shutter is open (Fig. 3g-
h) When the opening operation is performed again to reach the exposure aperture determined by the subject brightness and the film sensitivity, the opening operation is stopped and the film is exposed (FIGS. 3i-j). When the exposure of the film is completed, the CPU 12 outputs a closing signal of the shutter 14 to the shutter driver 13 and returns it to the initial position (Fig. 3l). When the shutter 14 returns to the initial position, the shutter 14 release signal is output this time, and the shutter 14 is driven to a mechanically stable position (FIG. 3m). This is the end of the shutter drive sequence when the strobe is not emitting light.

Next, the shutter drive sequence when strobe light is emitted will be described with reference to FIG. When the photographer presses the release switch 8 to turn on the switch S1, the CPU 12
Energizes the shutter driver 13 to the coil forming the step motor built in the shutter 14 for a predetermined time (FIGS. 4a-b). Here, the voltage of the battery 10 is equal to or higher than Vc, and the subsequent sequence is normally performed. Subsequently, the distance to the subject and the brightness are calculated in the same manner as when the strobe is not lit. At this time, if the forced flash mode is selected by the flash mode switch 9 or if the automatic flash mode is selected and the brightness of the subject (for example, Ev <6) is low, the flash fires during the exposure operation. Before that, the CPU 12 turns on the transistor 15 to turn on the red-eye lamp 7 (see FIG. 4).
c). Since a large current is required to turn on the red-eye lamp 7 and the red-eye lamp 7 is driven directly from the battery 10, the voltage of the battery 10 gradually decreases, and even if the transistor 15 is turned off to turn off the red-eye lamp 7, the voltage before the battery check is reached. Does not recover (Fig. 4d).

Next, the operation of the shutter 14 is started. The operation is the same as that in the case where the strobe is not emitting light in FIG. 3, but in each sequence of ef-g and kl-m of FIG. 4 in which the step motor is driven, the CPU 12 to the shutter driver 13
The period of the drive pulse of the shutter 14 output to the above is longer (3/2 times in this example), so that the drive period of the shutter drive pulse, that is, φ1 and φ2 is also longer. This compensates for the decrease in the torque of the step motor due to the decrease in the power supply, and is based on the property of the step motor that the torque increases when the angular speed decreases, and is because the angular speed of the step motor is decreased to increase the torque for stable control. is there. The shutter is driven by a drive pulse of a normal cycle during the periods h-i and j-k. This is because a known shutter sector (not shown) opens during this period, which does not affect the exposure amount. There are two reasons that the torque to open the sector is relatively light. Although not shown, strobe light emission is performed at an appropriate timing between h and j in FIG. 4, which is determined by the subject distance and the aperture value of the taking lens. This is the end of the shutter drive sequence for strobe light emission.

As another embodiment of the present invention, as shown in FIG. 5, when the shutter speed (FIG. 5i-j) is longer than a predetermined time, it is impossible to prevent the voltage Ve from decreasing while the shutter is open. It is also conceivable to lengthen the cycle of the drive pulse of the shutter during the closing operation of the shutter (Fig. 5k-l-m).

Further, as shown in FIG. 6 as another embodiment of the present invention, when a heavy load such as the red-eye lamp 7 is driven, photographing is performed by the DC motor 16 during the opening / closing sequence of the shutter which causes a relatively heavy load. Driving the lens 2 to the in-focus position (Fig. 6g-h) drives the red-eye lamp 7 (Fig. 6c-).
It may be performed prior to d).

[0016]

According to the structure of the present invention, the shutter drive current is reduced on the basis of the result of the battery check, and the drive cycle of the shutter drive pulse is lengthened accordingly, so that the shutter result is not affected. There is an effect of compensating for the decrease in the torque of the shutter motor during the driving of, and preventing the malfunction.

[Brief description of drawings]

FIG. 1 is a schematic view of a camera according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a camera according to an embodiment of the present invention.

FIG. 3 is a time chart of a shutter drive sequence when the flash is not emitted according to the present invention.

FIG. 4 is a time chart of a shutter drive sequence during flash light emission according to the present invention.

FIG. 5 is a time chart of a shutter driving sequence according to another embodiment of the present invention.

FIG. 6 is a time chart of a shutter drive sequence according to another embodiment of the present invention.

[Explanation of symbols]

 10 Battery 12a Voltage Detection Means (A / D Converter) 14 Shutter 13 Shutter Driver 12 CPU

Claims (2)

[Claims] 1. A battery built in a camera, a voltage detecting means for detecting a voltage of the battery, a shutter operated by using the battery as a power source, and a shutter for operating the shutter based on an output result of the voltage detecting means. And a shutter drive unit that selectively pulse-drives at a second period longer than the period. 2. A battery built in a camera, a voltage detecting means for detecting a voltage of the battery, a load operated by using the battery as a power source, a photographing lens, and the output result of the voltage detecting means. A pulse driving shutter, comprising: a photographing lens driving unit that outputs a driving signal for selectively driving the photographing lens to a focus position before or after driving the load.