JPH0241012B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a film feeding device for a camera.

In the camera, the film is fed by the motor rotating at full speed, and at the same time, the perforation of the film is electrically detected and counted at a fixed position, and when this count reaches a certain value, the motor is stopped. A film feeding device for feeding one screen is known from Japanese Patent Application Laid-open No. 121524/1984. However, in this film feeding device, the motor rotates at full speed to feed the film, and the motor is stopped when the number of film perflation counts reaches a certain value, so the number of film perflation counts remains constant. Even if the stop command is issued when the perforation is reached, the motor continues to rotate by inertia, and film slip occurs for the amount of film feed corresponding to a certain number of perforations, which deteriorates the accuracy of the film stop position.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a film feeding device which eliminates these drawbacks and reduces the film movement speed before reaching the film stop position to reduce the amount of film slip and improve the accuracy of the film stop position. shall be.

The present invention will be described below by way of examples with reference to the drawings.

FIG. 1 shows a general example of a film feeding device in a camera, and this example will be explained first. 1 in the diagram
is a perflation detection circuit, which includes a light emitting diode LED, a photodiode PD, and an operational amplifier.
It is composed of _OP1 , _OP2 , variable resistor _VR1 , and resistors _R1 to _R4 . 2 is a shutter drive circuit, which is composed of a photometric element CDS, a capacitor C ₁ , a trigger switch SW ₁ , a variable resistor VR ₂ , an operational amplifier OP ₃ and a shutter magnet SMg. 3
is a counter and control circuit, and counter CNT,
RS flip-flop FF ₁ , capacitors C ₂ , C ₃ ,
It is composed of a diode D ₁ , resistors R ₅ and R ₆ , and an OR circuit OR ₁ . Reference numeral 4 denotes a motor control and brake circuit, which is composed of buffers A ₁ and A ₂ , resistors R ₇ and R ₈ , and transistors Tr ₁ and Tr ₂ . M is a film drive motor, which is connected to, for example, a film take-up spool. F is a film, and Vb is a power supply voltage.

Now, when the power is turned on, the capacitor C ₂ , the resistor
A pulse is generated in the initial reset circuit consisting of R ₅ and diode D ₁ , which passes through OR circuit OR ₁ to reset flip-flop FF ₁ . Therefore, transistor Tr ₁ is turned on and transistor Tr ₂ is turned on.
is turned off, and motor M remains stopped. When the release switch is turned on, the shutter drive circuit 2
When the shutter operation is completed, flip-flop _FF1 is set. In other words, when the mechanical release is performed and trigger switch SW ₁ opens,
Capacitor _C1 is charged through photometric element CDS. At this time, the output of the operational amplifier _OP3 is at a low level and the shutter magnet SMg is operating. When the charging voltage of the capacitor _C1 reaches the voltage set by the variable resistor _VR2 , the output of the operational amplifier _OP3 is inverted to a high level and the shutter magnet SMg is turned off. The output of the operational amplifier _OP3 is differentiated by a differentiating circuit consisting of a capacitor _C3 and a resistor _R6 , and becomes the set input of the flip-flop _FF1 , _which is set when the shutter operation ends at the rising edge of the output of the operational amplifier _OP3 . . Therefore, the transistor Tr ₁ is turned off, the transistor Tr ₂ is turned on, the motor M rotates, and the film F is fed. At the same time, the inverted output of the flip-flop _FF1 , which is the clear input, of the counter CNT is canceled and becomes active. The light emitting diode LED and photodiode PD detect the perflation of the film F being fed at a fixed position, and this detection signal is output as a perflation signal via operational amplifiers OP ₁ and OP ₂ to the counter CNT. is counted. For example, if the film F is full size and perforations are perforated at a rate of 8 per frame, the counter CNT outputs an output signal when it counts 8 perforations. This output signal passes through OR circuit _OR1 to reset flip-flop _FF1 . Therefore, the transistor Tr ₂ is turned off and the power supply to the motor M is stopped, and at the same time the transistor Tr ₁ is turned on and the power supply to the motor M is stopped.
The brake is applied to advance the film F by one screen.

In this film feeding device, the motor M rotates at full speed after the shutter operation ends until the perflation detection circuit 1 detects 8 perflations corresponding to one screen, so a stop command is issued after the 8 perflations are detected. Even if the power supply to the motor M is stopped and the brake is applied, the motor M rotates due to inertia, and the accuracy of the stopping position of the film F deteriorates.

Therefore, the present invention aims to improve the accuracy of the film stop position by reducing the film moving speed by cutting off or limiting the power supplied to the motor before the film reaches the stop position.

FIG. 2 shows an embodiment of the invention. In this embodiment, a chopper 5 consisting of an AND circuit AND 1 , a NAND circuit _{NAND 1} and an oscillator OSC is provided between a flip-flop FF ₁ and buffers A ₁ and A ₂ in the film feeding apparatus shown in FIG. nand circuit
NAND ₁ receives the 2nd and 3rd bit outputs (outputs of "2" and "4" digits) from the counter CNT, and also receives a pulse from the oscillator OSC, and after the shutter operation is completed, the contents of the counter CNT become 6. The output of the NAND circuit NAND ₁ remains at a high level until the output of the flip-flop FF ₁ becomes an AND circuit.
The signal is sent to buffers A ₁ and A ₂ through AND ₁ , and motor M rotates at full speed. From the time when the content of the counter CNT reaches 6 until it reaches 8, the pulse from the oscillator OSC is inverted by the NAND circuit NAND ₁ , and the output of the flip-flop FF ₁ is intermittent by the AND circuit AND ₁ , so that the motor M is choppered. The running speed of the film F is controlled to decrease. When the running speed of the film F has decreased sufficiently and the contents of the counter CNT reach 8, the flip-flop FF ₁ is reversed, the transistor Tr ₂ is turned off, and the power supply to the motor M is stopped, and at the same time, the transistor Tr ₁ is turned on. Then, an electromagnetic brake is applied to the motor M, and the film F is accurately stopped.

FIG. 3 shows another embodiment of the invention. In this embodiment, a temporary stop circuit 6 consisting of AND circuits AND ₂ and AND ₃ and a monostable circuit MM is provided between the flip-flop FF ₁ and the buffers A ₁ and A ₂ in the film feeding device shown in FIG. be. and circuit
The _{1st, 2nd,} and 3rd bit outputs (outputs of digits "1", "2", and "4") from the counter CNT are input to AND 2, and the flip-flop FF is input until the counter CNT reaches 7 after the shutter operation is completed. The output of ₁ is sent to buffers A ₁ and A _{2 through AND circuit AND 3 ,} and motor M rotates at full speed. When the counter CNT reaches 7, the output of the AND circuit AND ₂ becomes high level, the rising edge triggers the monostable circuit MM, the inverted output of the monostable circuit MM becomes low level, and the output of the flip-flop FF ₁ becomes the AND circuit. circuit
AND ₃ will cut it off. Therefore, the brake is applied to the motor M at the same time as the power supply to the motor M is stopped. The inverted output of the monostable circuit MM is a counter
Before CNT reaches 8, it returns to a high level and the AND circuit _AND3 turns on, supplying power to the motor M again.
When the counter CNT reaches 8, the power supply to the motor M is stopped and a brake is applied to the motor M, but at this time the speed of the motor M is at the slow part when restarting, and the film F is stopped accurately. .

As described above, according to the present invention, in the film feeding method in which the film is fed by a motor, the perforation of the film is counted, and the motor is controlled based on the counted number, the counted number is determined by the time when the film stops. a decelerating means for decelerating the moving speed of the film by applying a brake to the motor during a period when a predetermined number is reached before the desired position; and stopping the motor when the count number reaches a predetermined number. Since the present invention is provided with a stopping means for stopping the film, the amount of film slip can be reduced and the accuracy of the film stopping position can be increased.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional film feeding device, and FIGS. 2 and 3 are circuit diagrams showing each embodiment of the present invention. 5... Chiyotsupa, 6... Temporary stop circuit.

Claims (1)

[Claims] 1. In a film feeding device that feeds the film by a motor and counts the perforation of the film, and controls the motor based on the counted number, the counted number is predetermined before the position where the film is to be stopped. a deceleration means for decelerating the moving speed of the film by applying a brake to the motor during a period in which the count reaches a predetermined number; and a stop for stopping the motor and stopping the film when the count reaches a predetermined number. 1. A film feeding device comprising: means.