JPH0127407B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is an electric shutter camera that has a display device for displaying shutter speed, aperture value, power supply voltage, etc. This invention relates to a device for stopping the operation of the display device when the values become the same, and notifying the photographer of insufficient battery voltage.

(Prior art and its problems) Conventionally, in electric shutter cameras, when the voltage of the battery that serves as the power source decreases, the electric shutter circuit loses its performance, and therefore, as a method to notify the photographer of the decrease in battery voltage. There is a method of stopping the battery check lamp etc. from turning on when the battery check button is pressed. but,
For cameras that display information such as shutter speed and aperture value using a light-emitting diode in the viewfinder, it is easy to forget to check the battery voltage using a battery check.
If the exposure check shows the shutter speed or aperture value in the viewfinder, the user may decide that the battery capacity is still sufficient and turn off the shutter.

However, display in the viewfinder using a light emitting diode or the like is often possible even under voltage conditions where the battery voltage is so low that the circuit performance cannot be achieved. For example, when using a 6V silver oxide battery as a power source, assuming that the voltage at which the shutter circuit can demonstrate its performance is 4V, the battery check threshold must be set at approximately 4.2V, whereas the light emitting diode inside the The lighting of
2V to 3V is sufficient, and even if the battery reaches about 3V, the LED display will be displayed in the window window, and if you turn off the shutter under these conditions, the shutter control will be inaccurate.

Therefore, as a preventive measure against such erroneous operations, a battery check function may be added to the display device.

However, it is not enough to simply add a battery check function. The following conditions must also be considered. Typically, the display device is visible within the viewfinder. After looking at the display state of the display device, the photographer operates the release to drive the shutter, and after the shutter operation is completed, takes his eyes off the viewfinder. In this case, since the photographer will inevitably be able to see the display device in the viewfinder both when checking the exposure and when operating the shutter, the battery check display must be the same both when checking the exposure and when operating the shutter. .

(Means for Solving the Problems) In view of the above-mentioned circumstances, the present invention uses a comparator to control the display control circuit that regulates the operation of the display circuit depending on the presence or absence of a power supply voltage higher than a specified value. During operation, a comparison voltage is applied to the comparator via the release switch, and when the exposure check is operated, the current to the shutter magnet is cut off, and the internal resistance of the battery is reduced by the current flowing to the magnet during the release operation. A comparison voltage is applied to the comparator through a load circuit that generates a voltage equivalent to the voltage drop in the power supply voltage caused by When the values become the same, the operation of the display circuit is stopped.

(Example) The present invention will be described below with reference to the drawings.

The figure is a circuit diagram showing an embodiment of the device of the present invention, including a manual shutter section, various adjustments, an information input section for the sensitivity value of the film used, an adjusted aperture value, a constant voltage circuit attached to the circuit, and others, especially the present invention. Parts that are less relevant to the device are omitted. For convenience of explanation, a case will be described here in which the apparatus of the present invention is installed in conjunction with a circuit for displaying a shutter speed determined by an electronic shutter circuit with aperture priority.

In the figure, E is the battery, Ri is the internal resistance of the battery,
SW ₁ is an exposure check switch, SW ₂ is a power switch that closes by winding up, SW ₃ is a release switch,
SW ₄ is a battery check switch, SW ₅ is a memory switch, and SW ₆ is a trigger switch, which are configured to selectively close the battery according to the intended operation. Also, film sensitivity, aperture information voltage ASA,
A closed loop consisting of the photodetector P/D, the log diode D ₁ , the operational amplifier A ₁ , and the amplifier A ₂ is a so-called photometric circuit. _Q1 is a logarithmic expansion transistor, and the time-limiting capacitor _C2 is charged with the collector current of the next stage transistor _Q3 .
A ₃ is a time-limited switching circuit, which is a transistor
_Q3 inverts the output of the circuit _A3 , and the collector current of the next stage transistor _Q8 drives the shutter trailing curtain hold magnet _Mg1 .

On the other hand, a transistor Q ₉ whose base is connected to the output point A of the photometric circuit, and an operational amplifier in the next stage
_A4 is configured to obtain a voltage output that corresponds to the shutter speed. Transistors _Q14 and _Q28 are semiconductor switches, and have a symmetrical circuit configuration so as to switch between shutter speed display and battery voltage capacity display.

A ₇ is an LED driver for display, Q ₃₀ is
This is a switching transistor to cut the current of the LED. A ₅ is a comparator that detects the power supply voltage. When the power supply voltage generated at the Q point becomes low, the transistor Q ₂₃ in the subsequent stage becomes non-conductive, and the base current of the transistor Q ₃₀ whose base is connected to the emitter voltage point S is increased. The display is turned off and the display is turned off. A ₆ is an operational amplifier for creating a display signal corresponding to the power supply voltage, and its output voltage is connected to the input terminal of the display circuit (LED and LED driver A ₇ ) via a transistor Q ₂₈ that constitutes a semiconductor switch. In addition, in the circuit of the present invention, the positive side of the power supply is common, but the negative side is different for each operation of battery check, exposure check, and release, so that G ₃ , G ₂ , and G ₁ are connected to the switch SW _{4 .} , SW ₁ , and to the negative side of the battery via SW ₂ and SW ₃ . In addition, the illustrated circuit elements are necessary for proper circuit operation.

Next, the operation of the apparatus of the present invention having such a configuration will be explained.

First, when you intend to check the battery, select and close switch SW ₄ . The operation of each point in the illustrated circuit due to this operation will be explained in sequence.

The potential at point R (intersection of r ₄ and r ₃ ) is the positive bus line.
Since the base-emitter voltage V _BE of the transistor Q ₂₂ is lower than V _CC , the transistor Q ₂₂
and another transistor that receives this voltage
Q ₂₉ becomes conductive and transistor Q ₂₄
The transistor _Q25 becomes conductive while the transistor Q25 is non-conductive, and as a result, the potential of the bus _G1 becomes the collector-emitter voltage _VCE of the transistor _Q25 .

Since transistor Q ₂₉ is conducting, transistor Q ₂₈ is conducting.

Since the potential at point W is also high, point G also has a high potential, and as a result, transistor Q ₆ is conductive, transistors Q ₇ and Q ₈ are both non-conductive, and magnet Mg ₁ for holding the shutter rear curtain is not driven. .

Since the potential at point W is high, transistor Q15
conducts.

Amplifier which is the output terminal of the shooting information output circuit
The transistor Q14 forming a semiconductor switch connecting the output terminal of _A4 and the input terminal of the LED driver _A7 of the display circuit is made non-conductive.

As mentioned in the above sections, the voltage appearing at point M, which is the input terminal of the display circuit, is
A divided voltage of ₆ , which corresponds to the power supply voltage.

If the supply voltage is higher than the predetermined value by this comparator _A5 , the transistor
Q ₂₃ becomes conductive, the S point becomes high potential, so-called battery check clamp LED ₁ outside the window lights up, transistor Q ₃₀ becomes conductive, and the display element inside the window
The LED lights up at the position corresponding to the power supply voltage.

Then, when the power supply voltage becomes low, the battery check clamp LED ₁ goes out, and the display inside the viewfinder also goes out.

Note that this circuit has a function that disables the shutter magnet during a battery check, so the current that flows through the shutter magnet is passed through resistor _r7 , which is almost the same as when releasing the shutter. Current is extracted from the battery to create the conditions for circuit operation.

Next time you intend to check the exposure, press the switch.
Selectively close SW ₁ . At this time, the power supply voltage is applied between V _CC and _G2 . The potential of the negative bus G ₁ is higher by the base-emitter voltage V _BE of the diode Q ₁₆ and the transistor Q ₁₇ . That is, approximately 2V _BE is higher than the negative bus line _G2 , and this low voltage is applied to the circuit between V _CC and _G1 .

Therefore, first, the point K, that is, the base of the transistor Q ₅ is higher than the negative bus G ₂ by the base-emitter voltage V _BE , and the transistor Q ₅ becomes conductive, making the transistor Q ₇ non-conductive, and the transistor Q ₈ in the next stage becomes conductive. Keep in non-conducting state. Therefore, no current flows through the shutter magnet.

Since the bus _G3 is at a high level, the potential at the R points is almost the same as the bus _VCC , so the transistor _Q29 is non-conducting, and as a result, the W point is at a low level.

Therefore, transistor Q ₂₈ is non-conductive, transistors Q ₆ and Q ₁₅ are non-conductive, and transistor Q ₁₅ is non-conductive, so transistor Q ₁₄ is non-conductive.
is conductive.

Since the transistor _Q14 is in a conductive state, the voltage appearing at the M point corresponds to the output of the operational amplifier _A4 , that is, the shutter speed.

Regarding the detection of the power supply voltage by comparator _A5 , since the shutter magnet current decreases due to the operation described in the above section, G ₂ -V _CC is detected in the vicinity where the internal resistance of the battery is not so large that it can be used sufficiently. The voltage across the shutter magnet is higher by the drop caused by this internal resistance than when current is flowing through the shutter magnet. However, as mentioned above, since the bus _G1 is higher than the bus _G2 by the base-emitter voltage of the diode _Q16 and the transistor _Q17 , it is necessary to set the base-emitter voltage to correspond to the drop. Therefore, the same voltage is applied between G ₁ and V _CC as at the time of release.

When the power supply voltage (V _CC -G ₁ ) is higher than a predetermined value, transistor Q ₂₃ becomes conductive and transistor Q ₃₀ also becomes conductive, resulting in an LED display within the viewfinder.

Also, since the bus line G ₃ is at a high level, it goes without saying that the battery check clamp LED ₁ outside the winder does not light up.

When the power supply voltage becomes low, the transistor _Q23 becomes non-conductive, so the transistor _Q30 also becomes non-conductive, and the display in the viewfinder disappears.

When performing a release operation, switch SW ₂ is closed by winding the film, and then switch SW ₃ is closed by pressing the release button.

As a result, the next circuit operation is performed.

Transistor Q ₁₈ changes the voltage on bus G ₂ to bus
The voltage is only slightly higher than that of _G1 .

Since the bus G ₁ is the lowest level, the diode
Since Q ₁₆ is non-conducting, transistor Q ₅ is also non-conducting, and switch SW ₄ is open, bus G ₃ is at a high level, so the R point voltage is high and transistor Q ₂₉ is non-conducting. In other words, when the transistor _Q6 is non-conducting, the shutter magnet
Current is flowing through Mg ₁ .

Since transistor Q ₂₉ is non-conducting, transistors Q ₂₈ and Q ₁₅ are both non-conducting, so the voltage appearing at point M is a voltage corresponding to the output of operational amplifier A ₄ , that is, the shutter speed. The shutter speed is displayed in the viewfinder even when the shutter is released.

When the power supply voltage is detected by the comparator A5, the transistor Q23 is made non-conductive depending on the magnitude of the constant voltage applied to one end of the comparator A5 and (V _CC -G1)×r6/(r5+r6), that is, the transistor Q30 is controlled. , displaying or erasing the display in the viewfinder.

In addition, when examining the voltage at which the display disappears, that is, the internal resistance of the battery, the battery is, for example, a 6.3V silver oxide battery.
The performance maintenance voltage of the circuit is 4.0V, the built-in constant voltage is 2.6V applied to the non-inverting input terminal of comparator A5, the resistance of the shutter magnet is 330Ω, and the resistance r7 is
240Ω, and the current consumption of the circuit excluding the current flowing through shutter magnet Mg1 or resistor r7 and battery check clamp LED1 is 7mA.
Assume that the voltage between V _CC and G1 at which the display disappears is 4.3V.

In this state, first, the internal resistance of the battery when the display disappears when the release is released is the same as the internal resistance of the battery when the display disappears when the release is released.
4.3V/330Ω=13mA flows through Mg1 as well. Therefore, the total current is 7mA + 13 = 20mA, so the internal resistance of the battery is Rir = [(6.3-4.3)/20] x 10 ³ = 100Ω Next, the internal resistance of the battery when the display disappears during exposure check Rich seek.

During the exposure check, the total current of the circuit is 7 mA, but the voltage applied between V _CC - G1 is 1.3 V higher than the battery terminal voltage (diode Q16, transistor Q1
7) is low, so the battery voltage when the display disappears is 4.3 + 1.3 = 5.6V. Therefore,
The internal resistance Rich is Rich = (6.3-5.6)/0.007 = 100Ω.

(Effects) As described above, the present invention stops the operation of the display device when the internal resistance of the battery reaches the same value both during the exposure check and during the release operation, so the use of the power supply battery during the shooting operation is avoided. It is easy to visually check whether it is possible or not, and it can have extremely practical effects.

[Brief explanation of drawings]

The drawing is a circuit diagram showing an embodiment of the device of the present invention. r ₁ - r ₁₃ ...Resistance, A - V ... Specified position on the circuit, A ₁ - _{A 7} ... Various amplifiers, Ri ... Internal resistance of battery, Mg ₁ ... Shutter magnet, G ₁ ... _G3 ...
...Minus side bus of the circuit, V _CC ...Positive side bus of the circuit, Vref... Constant voltage source, LED ₁ ... Display element outside the battery check finder, LED...
Display element inside the viewfinder.

Claims (1)

[Claims] 1. In an electric shutter mechanism having a display circuit that displays information such as shutter speed, aperture value, or power supply voltage, a display control circuit that regulates the operation of the display circuit depending on the presence or absence of a power supply voltage higher than a specified value; A comparator that controls this display control circuit, a release switch that applies a comparison voltage to the comparator when the release is operated, a cutoff circuit that cuts off current to the shutter magnet when the exposure check is operated, and a release switch that applies a comparison voltage to the comparator when the release is operated. a load circuit that generates a voltage equivalent to the voltage drop in the power supply voltage caused by the internal resistance of the battery when current flows to the magnet during operation, and the comparator connected in parallel with the release switch via this load circuit. and an exposure check switch that applies a comparison voltage to the display circuit, and the operation of the display circuit is stopped when the internal resistance of the power supply battery reaches the same value during both the exposure check operation and the release operation. A display device in a featured electric shutter mechanism.