JPS60220322A - Stroboscope device - Google Patents

Abstract

PURPOSE:To obtain a stroboscope device where light emission is controlled correctly even if device is used for photographing as a short distance with a high- sensitive film, by varying the quantity of charging of a main capacitor, which supplies a discharging current to a flash tube, in accordance with one of film sensitivity, distance, and exposure information at least. CONSTITUTION:When a switch 1 is turned on in accordance with turning-on of a power switch of a camera, a capacitor 3 is charged to a prescribed voltage, and simultaneously, a transistor TR4 is turned on. Then, an oscillating circuit 5 is operated, and a main capacitor 6 and a capacitor 7 are charged in prescribed relations to each other. A voltage dividing resistance 10 consisting of resistances 11-13 is connected in parallel with the capacitor 7, and terminals 15-17 are provided in accordance with voltage dividing points, and values of resistances connected in series are larger in the order of terminals 15-17 in accordance with a film sensitivity value. A changeover switch 20 is turned in accordance with the set operation of the film sensitivity to select prescribed one of terminals 15-17, and for example, the switch 20 is connected to the terminal 15 if the film sensitivity is ASA1000.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a strobe device that controls the charging voltage of a main capacitor for causing a flash discharge tube to emit light.

[Prior art]

A strobe device is used to provide artificial lighting to a subject.
Various types have been put into practical use so far. Among them,
Auto-adjustable strobes integrate the amount of light reflected from the subject from the moment the strobe light starts illuminating, and cut off the strobe light when this integrated value reaches a predetermined value, making it easy to operate. It is widely used because it is easy to obtain proper exposure.

These automatic light control strobes come in series control type and parallel control type, depending on their dimming method, but the series control type is superior in terms of power saving and has recently become mainstream. In this series-controlled automatic light control strobe, in order to control the flash discharge tube to stop emitting light, the discharge path of the flash discharge tube is cut off when the reflected light from the subject reaches a predetermined integral value. However, the timing of this cutoff tends to be slightly delayed. As a result, more illumination than is appropriate is given to the subject, and the photograph is taken with an exposure meter.

The above disadvantages occur to a degree that cannot be ignored, especially when photographing at close range. In other words, during close-range shooting, the timing at which the strobe stops firing approaches the timing at which the strobe starts firing, but the flash characteristics of the strobe have an extremely rapid rise region. If the timing of the light emission stopping operation is delayed in the rising region or near the peak point of light emission, the ratio of the excessive amount of illumination light to the appropriate illumination light amount will increase. As a result, the exposure will definitely be too automatic, and there will also be many cases where the exposure exceeds the latitude of the film and becomes incorrectly exposed.

Furthermore, the above-mentioned phenomenon may also occur when the film sensitivity of the film used increases. In other words, when the film sensitivity was low, the timing of the strobe light emission stop operation was at the point when the strobe light emission peak had passed, but as the film sensitivity became higher, the stop operation timing was advanced, and the light emission characteristics changed. It may enter a region with a rapid rise. Therefore, even in such a case, for the same reason as mentioned above,
It will be overexposed.

Furthermore, when performing daytime synchronized photography in which the strobe fires while taking into account outside light, for example, when the level of outside light is low and the strobe light output is kept low in response, the flash stops. The timing of the operation is still set in a region where the light emitting characteristics suddenly rise, and there is a drawback that the ratio of illumination light from the strobe becomes larger than a predetermined ratio.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and provides a strobe device that can properly control light emission even when used for close-up photography or using a high-sensitivity film. The purpose is to

[Structure of the invention]

In order to achieve the above object, in the present invention, the amount of charge of the main capacitor that supplies discharge current to the flash tube is
It is configured to be variable in accordance with at least one of film sensitivity information, distance information, and exposure information.

[Explanation of Examples]

In FIG. 1 showing an embodiment of the present invention, for example, when the power switch of a camera is turned on, a switch 1
When turned on, since the oscillation stop transistor 2 is turned off in the initial state, the capacitor 3 is charged to a predetermined voltage and the transistor 4 is turned on at the same time. As a result, the oscillation circuit 5 is activated, and the main capacitor 6
and capacitor 7 are charged in a predetermined relationship with each other. Capacitor 7 has a resistor 11~ in parallel with it.
A voltage dividing resistor 10 consisting of 13 is connected, and terminals 15 to 17 are provided corresponding to each voltage dividing point. In the order of terminals 15, 16, and 17, the values of the resistors connected in series increase in accordance with the film sensitivity value. The switching switch 20 is rotated in conjunction with the film sensitivity setting operation, and selects a predetermined one of the terminals 15 to I7. For example, when the film sensitivity is ASA ] 00, terminal 17. In the case of ASA400, terminal 16.
In the case of 85A100O, it is connected to terminal 15.

As the capacitor 7 is charged, the terminals 15-
17, different voltages are generated, and these voltages also gradually increase. Then, the voltage of terminal I6 is Vref
, a signal voltage is generated at the output terminal of the comparator 21, which turns on the oscillation stop transistor 2.
be done. Therefore, the capacitor 3 is rapidly discharged and the Hess potential of the transistor 4 is lowered, so that the 0FFL oscillation of the transistor 4 is stopped. Therefore, charging to the main capacitor 6 is stopped at that point.

When the shirt release is performed thereafter, the X contact 23 is momentarily turned on and the trigger circuit 24 is operated, so that the flash discharge tube 25 emits light by the electric energy stored in the main capacitor 6. Note that at this point, the capacitor 7 is also discharged, so the signal voltage of the comparator 21 disappears, and the oscillation stop transistor 2 is turned off.

At the same time that the flash discharge tube 25 emits light and illuminates the subject, the dimming circuit 26 operates. This dimmer circuit 26 integrates the reflected light from the subject, and when a predetermined integral value is detected, it turns off the thyristor 27 connected in series to the discharge path of the flash discharge tube 25. Light emission is controlled to stop.

In the above operation, the film sensitivity setting is ASAlo
If oO, the changeover switch 20 is connected to the terminal 15. Since the voltage available from terminal 15 is always lower than the voltage available from terminal 16, it reaches Vref earlier than terminal 16 reaches Vref. Therefore, A
In the case of SA 1000, charging of the main capacitor 6 is also stopped early, and its charging voltage is also lowered. In this way, as the charging voltage of the main capacitor 6 becomes lower, the peak emission intensity of the flash discharge tube 25 also becomes lower, as shown in FIG.

Figure 3 shows the luminescence characteristics A with the peak luminescence intensity increased at the same shooting distance (short distance) and the same film sensitivity.
1 and 2 show the luminescence characteristics B with a lower peak luminescence intensity. These characteristics A and B each have t so as to give the same amount of illumination light to the subject.
Although cutoff control is performed at times 1 and t2, the light emission is actually stopped at times tl' and t2', which are delayed by Δt, respectively. Therefore, characteristic A is 30. 3 for characteristic B
The extra light emission indicated by 1 will be added. However, as is clear from the figure, characteristic B has a low peak emission intensity.
, the amount of extra light emitted is smaller. Furthermore, in characteristic B, the light emission is controlled to stop at a gentle portion of the light emission characteristic, and this control becomes easier, so the synergistic effect of these effects further optimizes the light emission control.

From the above, as in the embodiment shown in FIG. 1, when the film sensitivity of the film used becomes high and the timing of the strobe light emission stop approaches the region where the light emission characteristics suddenly rise or near the peak light emission, By lowering the charging voltage of the main capacitor 6 in accordance with the film sensitivity, excessive illumination light can be significantly reduced.

Also, the timing of the strobe light emission stop approaching the region where the light emission characteristics suddenly rise or the light emission peak approaches is not only due to the film sensitivity becoming higher, but also due to the shooting distance becoming shorter. be. In order to deal with this, the changeover switch 20 in FIG. All you have to do is connect it to a predetermined terminal inside.

Furthermore, in the case of daytime synchronized photography in which the amount of external light and the amount of strobe light are taken at a predetermined ratio, the external light level is low;
In order to deal with the fact that the strobe light emission stop timing is earlier, the charging voltage of the main capacitor 6 may be lowered in accordance with the output of the light receiving element that measures external light.

In the above embodiment, in order to obtain a charging stop signal for the main capacitor 6, a voltage dividing resistor 1 consisting of resistors 11 to 13 is used.
0 is used, but it can be replaced with a variable resistor, or the terminal voltage of the main capacitor 6 can be detected by multiple comparators each having a different darkness value, and film sensitivity information, distance information, A predetermined one may be selected from the plurality of comparators in accordance with the exposure information G, and the oscillation stop transistor 2 may be controlled thereby.

〔Effect of the invention〕

As mentioned above, in the past, when taking pictures using a strobe, in situations where the strobe stopped firing early, overexposed pictures tended to be taken due to excessive lighting. According to the invention, such excessive illumination is almost eliminated, and it becomes possible to take pictures under appropriate illumination depending on the situation. Further, according to the present invention, since the main capacitor is not charged more than necessary, it is also effective in terms of power saving. In addition, the charging voltage can be controlled without increasing the number of main capacitors, so
The configuration of the control means also does not become complicated.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 is a characteristic diagram showing the correlation between the charging voltage of the main capacitor and the peak emission intensity of the strobe. Figure 3 shows when the strobe emits light 1 (Figure 1) 2... Transistor for stopping oscillation 4... Transistor 5... Oscillation circuit 6... Main capacitor 10... Voltage dividing resistor 20... Switching Switch 21...Comparator 25...Flash discharge tube 26...Dimmer circuit.

Claims (3)

[Claims] (1) In a strobe device that charges a main capacitor with an oscillation current from an oscillation circuit and causes a flash discharge tube to emit light with a discharge current from the main capacitor, at least one of film sensitivity information, distance information, and exposure information is provided.
A strobe device according to the invention, further comprising a control means for controlling the charging voltage of the main capacitor. (2) The strobe device according to claim 1, further comprising a dimming means for stopping light emission of the flash discharge tube. (3) The strobe device according to claim 1, wherein the control means controls the charging voltage of the main capacitor by controlling the oscillation operation of the oscillation circuit to stop.