JPS61159119A - Flash actinometer - Google Patents

Abstract

PURPOSE:To perform resetting operation corresponding to next flash light emission after light measurement by providing a switching means which alternates an initial state and a light measurable state every time a flash light emission signal is inputted. CONSTITUTION:When flash light is detected by a photodetecting element 2, an NPN transistor (TR)4 turns on and a PNP TR9 and an NPN TR10 also turn on at the same time, so that a light emitting diode 14 illuminates. Then, the output of a D.FF16 is inverted into a low-level signal, an analog switch 20 turns on, and the output of a D.FF15 is still at a high level, so analog switches 18 and 19 turn on and flash light is incident on a photodetecting ele ment 21, so that a capacitor 22 begins to be charged with a photocurrent. When the 1st flash light emission is completed, the switches 18 and 19 are turned off through the FFs 15 and 16 and the charging of the capacitor 22 is completed, so that the light measuring operation is finished. The 2nd flash light detection is carried out in the same process; the output of the FF16 goes up to the high level and the switch 20 turns on to discharge the energy accumulated in the capacitor 22.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an improvement in a flash light meter that measures the amount of flash light emitted from a flash light emitting device.

(Background of the Invention) This type of flash light meter is generally referred to as an incident light type 7-meter meter, and is used when it is desired to know in advance the amount of flash light on the subject.

An example of such a flashlight meter and its usage will be briefly explained with reference to FIG. Flashlight meter 1.

When a known differential circuit detects a light emitting signal emitted from a flash light emitting device 3 placed at a place where the subject is located and attached to a camera 2, a light metering circuit (not shown) operates in synchronization with the light emitting signal to emit a flash light. Photometry begins, and the obtained photometry information is digitally displayed on the display section 1a.

By the way, such a flash light meter 1 has a configuration in which once the − times of photometry is completed, the light meter cannot be measured again unless the reset button 71b provided on the side surface of the flash light meter 1 is reset. Tonatsu [there. Therefore, in order to carry out such work, two people are required: one who presses the test firing button (not shown) on the flashlight emitting device 3, and the other who presses the reset button 1b of the flashlight meter 1, which greatly reduces work efficiency. It was bad.

Also, if you are doing it manually, you will not be able to measure the light again unless you press the test flash button, walk up to the flash meter 1, and press the reset button 1b to reset the flash meter 1. .

This causes inconveniences such as increased working time.

(Purpose of the invention) The object of the present invention is to solve the above-mentioned problems.

It is an object of the present invention to provide a flashlight meter capable of improving work efficiency.

(Features of the Invention) In order to achieve the above object, the present invention provides a switching means that alternately switches between an initial state and a photometry enabled state each time a signal indicating flash light emission by a flash light emitting device is input. , the reset operation is performed in response to the next flash light emission after photometry.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 shows an embodiment of the present invention.

1 is a resistor connected in series to a light receiving element (phototransistor) 2 for detecting flash light; 3 is a variable resistor for canceling external light connected to the base of an NPN transistor 4;
5 to 8 are resistors, 9 is PNP) transistor, 10 is p
N) transistors, 11 to 13 are resistors, 14 is a light emitting diode, 15.16 is D with preset/clear function
Flip 70 knob, 17 is a resistor, 18.19° 20 is an analog switch, 21 is a light receiving element (photodiode) for photometry, 22 is an integrating capacitor, 23 is a high input impedance operational amplifier, 24 is a variable resistor, and resistor 25 In addition, the operational amplifier 2S is arranged to be used as a non-inverting copper booster. 26 is a capacitor for high frequency cutting, 2
7 is a protection resistor, 28 is an external reset terminal, 29 is an external terminal for forcibly presetting the D flip-flop 15, A is an output terminal, and +V and -V are power supplies.

Next, the operation will be explained using the time chart shown in FIG. First, the base voltage of the NPN transistor 4 is adjusted using the variable resistor 3 so that the NPN transistor 4 will not be turned on due to the incidence of external light on the light receiving element 2. When NPN) transistor 4 turns on, PNP) transistor 9 and NPN)
Each transistor 10 turns on and the light emitting diode 14
is turned on, and by varying the resistance value of the variable resistor 3 so that the light emitting diode 14 is turned off, external light can be canceled. After completing the above adjustments,
Press the test flash button on the flash device (not shown),
- Cause the second flash to be emitted.

When the flash light is detected by the light receiving element 2, the NPN transistor 4 is turned on (see FIG. 2 (al)).

At the same time, PNP) transistor 9. NPN) transistor 1
0 is also turned on and the light emitting diode 14 lights up. In addition, N
PN) Before transistor 4 is turned on, high level signals are output from each output terminal ζ of D7 lip 70 and gate 15.16 (see Fig. 2 (C) and (d)).
All analog switches 18 to 20 are on (Fig. 2 (61)
(f)), and at this time, the charging voltage of the capacitor 22 is set to "Ov". PNP as mentioned above)
? When transistor 9 and NPN transistor 1° are turned on, a rising pulse is input to the clock input terminal CP of D7 rig 70, so the output of its output terminal Q is inverted from a high level to a low level signal (see Fig. 2). (d)), the analog switch 20 is turned off (see Figure 2(f)), and the output of the D7 lip 70 (output terminal) remains at high level (see Figure 2(C)). Therefore, analog switches 18 and 19 remain on (second
(see 61), therefore, the light receiving element 21 for photometry
When a flash light is incident on the capacitor 22, a photocurrent generated by the flash light flows into the capacitor 22, and the amount of flash light at that time becomes a voltage and the capacitor 22 starts to be charged. Note that if a high level signal is input to the external terminal 211 during photometry, the photometry operation can be stopped without waiting for the end of one light emission. Also,
Although it is sufficient to have either one of the analog switches 18 and 19, two are used in this embodiment for safety.

When the first flash is finished, D flip 70 knobs 1
Since a rising pulse is input to the clock input terminal CP of the D flip-flop 16, the input terminal DK of the D flip-flop 16 is input to the output terminal Q of the D flip-flop 16 at that time. Therefore, a low level signal (see FIG. 2(C)) is output from the output terminal Q. As a result, the analog switches 18 and 19 are turned off (see +61 in FIG. 2), and charging of the capacitor 22 is completed, that is, photometry is completed. After the photometry is finished, the analog switches 18 to 20 are off (see tel (f) in Figure 2), so the charging voltage of the capacitor 22 is maintained as it is.
It is input to the non-inverting input terminal of the operational amplifier 23. Here, let the resistance values of the variable resistor 24 and the resistor 25 be R, , R□.

The operational amplifier 23 is (charging voltage of capacitor 22 x Rta
/nts). The voltage obtained in this manner may be read as is with a voltmeter, but when taking photographs, it is preferable to perform a known apex calculation. Therefore, a logarithmic compression circuit (not shown) is arranged next to the output terminal 1000, and the output voltage of the output terminal 1000 (operational amplifier 23) is sent to the logarithmic compression circuit, and the film sensitivity Sv is calculated. Find this aperture value and display it on the display (this will be convenient).

After reading the photometric information obtained in the above manner, press the test flash button on the flashlight emitting device again to fire the second flash (see Figure 2 (al). When a flash of light is detected, the NPN transistor 4°10 and the PNP transistor 9 are turned on as described above, and a rising pulse is input to the clock input terminal CP of the D7 flip-flop 16, so that the aD flip-flop 16 is turned on.
The output of the output terminal Q becomes the signal of the output terminal (second
In the figure (see dl), the analog switch 20 is turned on and the energy charged in the capacitor 22 is discharged. When the second light emission is completed, the output from the output terminal Q of the D free lag flop 15 becomes a high level signal (see Fig. 2 (C)), and the analog switches 18 and 19 are turned on, and the initial state is Return to If setting the initial state by emitting a second flash is less efficient, inputting a high level signal to the external 9 set terminal 29 clears the D flip-flops 15 and 16, and similarly becomes the initial state.

According to this embodiment, since the configuration is such that the initial state is reached by detecting the next flash light after photometry, the person who presses the test flash button on the flash light emitting device and the reset button on the flash light meter There is no need for two people to do the work (
Furthermore, when the flashlight is used manually, there is no need to go back and forth between the flashlight emitting device and the flashlight quantity needle, which improves work efficiency, making it extremely convenient to use.

(Correspondence between the invention and the embodiments) In this embodiment, the -1, D flip-flop 15°16 corresponds to the switching means of the present invention.

(Modification) In this example, a flash light is used as a signal indicating flash light emission, but the signal is not limited to this, and a signal synchronized with flash light emission may be used, or a signal emitted in synchronization with flash light emission. Other light may also be used.

(Effects of the Invention) As explained above, according to the present invention, a switching means is provided which alternately switches between an initial state and a photometry enabled state each time a signal indicating flash light emission by a flash light emitting device is input. Since the reset operation is performed in response to the next flash emission after photometry, work efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a time chart of each circuit shown in FIG. 1, and FIG. 3 is a diagram explaining how to use a general flashlight meter. 2... Light receiving element, 4... NPN transistor, 1
4...Light emitting diode, 15.16...D clip 70 knobs, 18-20...analog switch, 21.
... Light receiving element, 22... Capacitor, 23... Operational amplifier.

Claims (1)

[Claims] 1. A flash light meter that measures the amount of flash light emitted from a flash light emitting device is provided with a switching means that alternately switches between an initial state and a photometry enabled state each time a signal indicating flash light emission by the flash light emitting device is input. A flashlight meter characterized by: