JPH083601B2 - Perforation counting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a perforation counting device that can be used as an automatic film feeder or the like.

[Conventional technology]

Most of recent compact cameras have a built-in motor for feeding a film, and the driving force of the motor is used to feed the film. In such an automatic feeder, in order to transfer the film more accurately,
It is known that the movement length of a film is detected by counting the number of passing perforations.

Among such perforation counting devices, the one that photoelectrically detects the passage of the perforation is provided with a light emitting part and a light receiving part so that the perforation is sandwiched from both sides, and when the film is fed, the light receiving part passes through the perforation. This is done by photoelectrically detecting the number of light pulses incident on. An LED or the like that irradiates a light beam having a wavelength that the film does not sensitize, such as an infrared light beam, is generally used in the light emitting unit, and an optical semiconductor element such as a phototransistor or a photodiode is used in the light receiving unit.

Further, a pulse counter is used to count the photoelectric signals output as pulses from the light receiving unit,
Since the perforation traverses the optical path of the light beam from the light projecting unit, a photoelectric signal from the light receiving unit (hereinafter referred to as J signal)
Is not a rectangular wave, but becomes a rectangular shape like a Sin wave that gradually increases and then gradually decreases. In order to enable the pulse counter to count pulses having such a rectangle, it is necessary to shape the waveform of the J signal into a shape close to a rectangular wave.

Therefore, the perforation counting device is provided with a waveform shaping section, and the waveform shaping section uses a reference voltage generating circuit and a comparator. The reference voltage generating circuit generates a reference voltage that is substantially intermediate between the peak value and the bottom value of the J signal and inputs the reference voltage to the comparator, and the J signal is input to the other input terminal of the comparator. The reference voltage is set when the cartridge is loaded into the camera and the automatic feeding of the film is started, and is held at a constant value until the photographing is finished and the cartridge is taken out.

[Problems to be solved by the invention]

However, in the above device, the perforation may not be detected or may be erroneously detected as described below. That is, when the motor is used for a long time using a power battery that has been depleted to some extent, the voltage of the power battery may temporarily drop, and for example, 5V at the beginning may become about 3V. Since the power supply battery that supplies power to the motor also supplies power to the above-mentioned LED, optical semiconductor element, and comparator, the waveform of the J signal also changes when the voltage of the power supply battery drops. Then, since the comparator compares the J signal having the changed waveform with the reference voltage set before the change of the waveform as described above, the comparator makes an erroneous detection.

Also, when the reference voltage is set within a fixed time at the start of the automatic film feeding, when the perforation does not pass within this fixed time, for example, the light receiving part is narrowed by the narrow part of the film leader part. When the light beam is continuously emitted to the, the peak value and the bottom value are read as the same value. Since the reference voltage in this case is set to this peak value, a pulse signal may be output depending on the influence of noise without inputting a signal by the comparator.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and is capable of reliably counting the number of perforations that have passed, even if the power supply battery has some voltage fluctuations. The purpose is to provide.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a method in which a perforation detection unit that photoelectrically detects the passage of perforations and generates a photoelectric signal during the transfer of a film and a counting unit that counts the number of perforations that have been detected in this way. A photoelectric reference signal from the perforation detection means, which has the same periodicity as the photoelectric signal and which generates a reference voltage which vibrates with an amplitude different from the photoelectric signal; It is newly equipped with a pulse generating means for generating a pulse signal in comparison with a reference voltage.

[Action]

According to the above configuration, when a photoelectric signal is generated by the perforation detection means, this photoelectric signal has the same periodicity as this photoelectric signal, and a vibration reference voltage that vibrates with an amplitude different from that of the photoelectric signal, Since the pulse signal is generated by the pulse generation means by discriminating the magnitude of the voltage, the photoelectric signal from the perforation detection means can be accurately shaped into a pulse.
Therefore, even if there is some voltage fluctuation in the power supply battery,
It is possible to reliably count the number of perforations that have passed through the counting means.

〔Example〕

In FIG. 3 showing the camera using the present invention as seen from the back side of the camera body 1, the film 3 pulled out from the cartridge 2 is wound up by the take-up spool 4 or is taken from the take-up spool 4. It is rewound to 2. Such film feeding is performed by driving a motor 29 (FIG. 1) provided in the take-up spool 4. A phototransistor 8 is provided on the upper side of the film feeding path 6 formed in the camera body 1, that is, in a portion where the perforation 3a of the film 3 runs. Against this phototransistor 8,
An LED 11 is provided on the back cover 9 side by hollowing out the pressure plate 10. The LED 11 irradiates the phototransistor 8 with infrared light having a wavelength that is not exposed to the film 3. LED11
Power transmission pins 12 and 13 for supplying power to the LED 11 are provided on the upper part of the. When the back cover 9 is closed, the power transmission pins 12 and 13 come into contact with the contacts 12a and 13a on the camera body side, and power is supplied to the LED 11 from the power supply battery built in the camera body 1.

FIG. 1 shows the outline of an electric circuit of the perforation counting device of the present invention. Then, FIG. 2 is a diagram showing voltage signals obtained from the connection points A, B, and C of this electric circuit. The light beam emitted from LED11 is
When the film 3 is transferred, the phototransistor 8 intermittently receives light at each passage of the perforations 3a. The operational amplifier 20 is connected to the connection point A between the phototransistor 8 and the resistor 16.
+ Input terminal of is connected.

The signal at this connection point A (hereinafter referred to as the A signal) is
Since it is a photoelectric signal due to the movement of the perforation 3a between the LED 11 and the phototransistor 8, it has a waveform close to a Sin wave as shown in FIG. The output of the operational amplifier 20 passes through the diode 21 and the −
It is fed back to the side input terminal and forms a non-inverting amplifier circuit. The output signal of the operational amplifier 20 is transmitted to the RC type integrating circuit formed by the resistor 22 and the capacitor 23. A resistor 24 is connected in parallel with the capacitor 23.

The voltage signal of the same phase as the A signal output from the operational amplifier 20 and the diode 21 slowly charges the capacitor 23 through the resistor 22 in the process of increasing the level, and decreases in the process of decreasing the level. Since the electric charge stored in the capacitor 23 is gradually discharged through the resistor 24, a voltage waveform represented as a B signal in FIG. 2 appears at the connection point B.

A comparator 25 is provided on the output side of the B signal whose amplitude has been lowered in this way. The comparator 25 inputs the B signal to the-side input terminal and the A signal to the + side input terminal. Then, the comparator 25 discriminates the magnitude of the A signal from the B signal input as the reference voltage. The signal output from the comparator 25 controls ON / OFF of the transistor 26. The signal obtained at the collector side of this transistor 26 is shown in FIG. 2 as the C signal. The C signal is an “L” signal when the A signal is larger than the B signal input to the comparator 25, and is “H” when the A signal is smaller than the B signal.
It is a signal. A counter 27 is provided on the output side of the C signal as described later, and counts the "H" signal.

The counter 27 is inputted as a C signal count signal,
This count value is sequentially sent to the CPU 28 from the output terminal. The CPU 28 monitors the count value from the counter 27 and controls the execution of the program based on this. As one of the executions of this program, for example, there is control of the motor 29 for film feeding, and the CPU 28 sends the motor 29 to the driver 30.
The motor 29 is operated by outputting the operation and stop commands. The electric circuit is powered by the dry battery 14.

Next, with respect to the operation of the present invention having the above configuration,
Description will be given along the flow of signals in the circuit diagram of the drawing.

When the cartridge 2 is loaded into the camera and the back cover is closed, the power transmission pins 12 and 13 provided on the back cover 9 side are connected to the contacts 12a and 13a provided on the camera body 1 side. When the LED 11 provided on the case back side is powered in this way,
Light emission starts. When the film 3 is pulled out from the cartridge 2 and transferred according to the program of the CPU 28, the LED 11
The light beam emitted from is intermittently received by the phototransistor 8. Therefore, the A signal extracted from the phototransistor 8 has a waveform shown by A in FIG. This A signal is input to the + side input terminal of the operational amplifier 20 and also to the + side input terminal of the comparator 25.

The voltage rising portion of the signal having the same phase as the A signal output from the operational amplifier 20 and the diode 21 and having a waveform almost similar to the Sin wave gradually increases as the electric charge passing through the resistor 22 slowly charges the capacitor 23. As the input signal of the resistor 22 reaches the peak value, the voltage at the capacitor 23 also saturates and reaches the peak value. As the input voltage of the resistor 22 drops, the electric charge charged in the capacitor 23 is gradually discharged to form a slow voltage drop curve like the B signal shown in FIG.

In this way, the amplitude of the signal B is reduced in phase with that of the signal A.
The signal is input to the negative input terminal of the comparator 25. Therefore, the comparator 25 sets A before the amplitude is reduced.
A comparison will be made between the signal and the B signal after its amplitude has been reduced. The output signal compared by the comparator 25 is a voltage as shown in FIG.
Outputs a rectangular wave of "H" level. The above B
When the power supply voltage drops, the signal responds to the voltage drop along with the A signal, and these A and B signals always cross twice during one cycle, so the comparator 25 ensures that a rectangular pulse is generated. Can be generated.

The signal indicating the passage of the perforation shaped into the rectangular wave as described above is accurately counted by the counter 27. The count output from the counter 27 is input to the CPU 28,
According to the programmed contents, a signal for instructing the motor 30 to start and stop the motor 29 is output to drive the motor 29.
Is operated to feed the film 3.

〔The invention's effect〕

According to the above configuration, when the photoelectric signal is generated by the perforation detection means, the photoelectric signal and the vibration reference voltage which has periodicity due to the photoelectric signal and vibrates with an amplitude different from that of the photoelectric signal, The pulse generation means discriminates the magnitude of the voltage to generate a pulse signal. In this way, the reference voltage is changed according to the input signal, so malfunctions due to fluctuations in power supply voltage and the effects of noise are eliminated, and the signal from the perforation detection means can be accurately shaped into pulses, and the number of perforations that pass can be reduced. It is possible to count reliably.

[Brief description of drawings]

FIG. 1 shows an outline of an electric circuit diagram of the perforation counting device of the present invention. FIG. 2 shows the waveform at each connection point of the circuit using the present invention. FIG. 3 is a rear view of a camera using the present invention. 4 ...... Take-up spool 8 ...... Phototransistor 11 ...... LED 12, 13 ...... Power transmission pin 12a, 13a ...... Contact 20 ...... Operational amplifier 25 ...... Comparator 29 ...... Motor.

Continued Front Page (56) References Open 59-95330 (JP, U) Open 61-182527 (JP, U) Open 50-98717 (JP, U)

Claims (1)

[Claims] 1. A perforation counting device for counting the number of perforations that pass through when a film is transferred by driving a motor built in a camera, the power being supplied from a power source for driving the motor. At the time of film transfer, the perforation detection means for photoelectrically detecting the passage of the perforation to generate a photoelectric signal, and the photoelectric signal from the perforation detection means, having the same periodicity as the photoelectric signal, and the photoelectric signal Is a vibration reference voltage generating means for generating a reference voltage oscillating with different amplitudes, and a pulse generating means for generating a substantially rectangular pulse signal by comparing the level of the photoelectric signal from the perforation detecting means with the reference voltage, A counter that counts the signals from this pulse generator. And a perforation counting device.