JPH08278538A - Flash photographing device - Google Patents

Abstract

PURPOSE: To provide a flash photographing device capable of preventing light emission from being stopped because a discharging current does not flow when a switching element connected to a discharge tube in series is turned on after it is turned off. CONSTITUTION: This device is provided with a discharge tube 22 for flash photographing; a main capacitor 3 supplying light emitting energy to the discharge tube 22; the switching element 24 connected to the discharge tube 22 in series; a trigger means consisting of a trigger transformer 5 impressing trigger energy on the discharge tube 22, a trigger capacitor 6, an SCR 8, a resistance 7 and a resistance 9; a detecting means consisting of a photodiode 33 detecting the light emitting output of the discharge tube 22, a resistance 34 and a comparator 51; and a driving circuit consisting of 1st and 2nd pulse generators 36 and 38 cyclically driving the switching element 24 and the trigger means, the photodiode 33, the resistance 34 and an AND gate 37. In the device, the operation of the trigger means is inhibited when the detecting means detects that the light emitting output is equal to or above a 1st specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to flash control of a flash photographing device, and more particularly to so-called flat light emission control which enables full-speed synchronized photographing of a focal plane shutter.

[0002]

2. Description of the Related Art A conventional method for controlling flat light emission is, as described in JP-A-55-129327, apply a trigger to a flashlight discharge tube at the start of light emission and turn on a switching element for flashlight current control. When the light of the flash discharge tube is detected and the light output becomes higher than a predetermined value, the switching element is turned off, and when the light output becomes lower than the predetermined value, the switching element is turned on and these operations are repeated. By means of this, or alternatively, the switching element is continuously turned on and off by an oscillator to stabilize the peak value of flat light emission. The reason why the trigger is not applied in conjunction with the switching element is to prevent waste of trigger energy and to prevent the influence of noise when the light of the flash discharge tube is measured by the photometry circuit of the camera.

[0003]

In the above-mentioned conventional control method, it has been premised that the discharge tube is always ionized when the switching element is turned off and then turned on again, and the discharge current flows when the switching element is turned on. . Therefore, in particular, when the peak value is low, that is, the discharge current is low, and the operation of the discharge tube is unstable, the switching element is turned off at the initial stage of light emission, and when it is turned on, the discharge current does not flow and the light emission is stopped. It was

The present invention has been made in order to solve such a conventional problem, and when a switching element is turned off and then turned on, a discharge current does not flow and light emission can be prevented from stopping. The purpose is to provide.

[0005]

[Means and Action for Solving the Problems] The structure for realizing the object of the invention according to the present application is as described in claim 1.
A discharge tube for flash photography, a main capacitor for supplying emission energy to the discharge tube, a switching element connected in series to the discharge tube, trigger means for applying trigger energy to the discharge tube, and the discharge tube And a drive means for periodically driving the switching element and the trigger means, and the operation of the trigger means when the light emission output by the detection means is a first predetermined value or more. Is prohibited.

According to this structure, the light emission output of the discharge tube is detected after the switching element is turned on, and when the current does not flow and the light emission output is below a predetermined value, the trigger circuit is operated to trigger the discharge tube. The above problem is solved by applying a trigger voltage to the electrodes to start the discharge and continue the discharge.

As a specific configuration for achieving the object of the invention according to the present application, as described in claim 2, the drive circuit for periodically driving the trigger means has a photodetection means, and the discharge tube The second light output of which is higher than the first predetermined light output of
The switching element is turned off when the predetermined value of is reached, and the switching element is turned on when the optical output drops to a third predetermined value that is lower than the second predetermined value and higher than the first predetermined value. It is a composition.

According to this structure, for example, even when the discharge cannot be continued when the IGBT is turned on, the discharge tube can be triggered again to restart the discharge.

Further, as a concrete configuration for realizing the object of the invention according to the present application, as described in claim 3, the detecting means has a first comparator, and the light detecting means has a second comparator.
And the inputs of the two comparators are connected to a connection point between a light receiving element for detecting the light emission output of the discharge tube and a resistor connected in series with the light receiving element.

According to this structure, since the light receiving element of the light detecting means provided in the driving means and the light receiving element provided in the detecting means can be formed by the same element, the circuit structure can be simplified.

Further, as a concrete constitution for realizing the object of the invention according to the present application, as described in claim 4, the driving means generates the first pulse in response to the light emission start pulse. A pulse generator and a second pulse generator that responds to the light emission start pulse and generates a second pulse after a predetermined time delay from the start pulse, and includes the switching element in response to the first pulse. It is turned on to drive the trigger means in response to the second pulse.

According to this structure, the switching element connected in series to the discharge tube is turned on by the first pulse in response to the light emission start pulse from the first pulse generator, and the second pulse having the delay characteristic is turned on. Since the second pulse from the generator drives the trigger means with a delay after the switching element is turned on, the discharge of the discharge tube can be reliably started. When the switching element is off when the trigger means is driven, the discharge current is blocked by the switching element, so that discharge of the discharge tube may not be started.

[0013]

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, 1 is a power supply circuit including a power supply battery for charging a main capacitor 3 which will be described later, 2 is a backflow prevention diode, and the main capacitor 3 is charged from the power supply circuit 1 via the diode 2. . 3 is a flash discharge tube 22
It is the main capacitor that gives the luminescence energy to. Reference numeral 4 denotes a current limiting coil, one end of which is connected to the anode of the main capacitor 3 and the other end of which is connected to the anode of the discharge tube 22.

Reference numeral 5 is a trigger transformer, 6 is a trigger capacitor, and 8 is an SCR for discharging the energy of the trigger capacitor 6 through the primary winding of the trigger transformer 5. Reference numeral 9 is a gate resistance of the SCR 8. Reference numeral 7 is a resistor for charging the trigger capacitor 6, one end of which is the anode of the main capacitor 3 and the other end of which is the S
It is connected to the CR anode. 10 is the SCR8
One end is connected to the gate of the
3 is a resistor connected to the collector. Reference numeral 13 is an NPN transistor, the emitter of which is connected to the cathode of the main capacitor 3, the collector of which is connected to one end of the resistor 10 and the base of which is connected to the output of a comparator 51 described later via the resistor 41.

Reference numeral 12 is a base resistance of the transistor 13. Reference numeral 11 is a resistor, one end of which is connected to the cathode of the SCR 8 and the other end of which is connected to the cathode of the main capacitor 3. 14
Is a capacitor, one end of which is connected to the anode of the SCR 8 and the other end of which is connected to the anode of a diode 15 described later. Reference numeral 15 is a diode, the cathode of which is connected to the cathode of the main capacitor 3. 16 is a diode,
The anode is connected to one end of the resistor 17, and the cathode is connected to one end of the capacitor 14.

Reference numeral 20 denotes an NPN transistor, the base of which is connected to the cathode of the main capacitor 3 via the resistor 18. The emitter is the anode of the diode 15,
The collector is connected to the cathode of the discharge tube 22 via the resistor 21. Reference numeral 19 is a resistor having one end connected to the base of the transistor 20 and the other end connected to the emitter of the transistor 20. Reference numeral 22 denotes a discharge tube, which converts the energy stored in the main capacitor 3 into light. The cathode of the discharge tube 22 is connected to the anode of the diode 23, and the anode is connected to one end of the coil 4.

24 is an IGBT as a switching element
(Gate insulated bipolar transistor)
The collector is connected to the cathode of the diode 23 and the cathode of the SCR 8, and the emitter is connected to the cathode of the main capacitor 3. Reference numeral 26 is a diode whose cathode is connected to one end of the coil 4 and whose anode is connected to the collector of the IGBT 24. 27 and 28 are resistors connected in series, and the connection point is connected to the gate of the IGBT 24.

Reference numeral 29 denotes a PNP transistor, the collector of which is connected to one end of the resistor 27, the emitter of which is connected to the positive electrode of the voltage source 32 and the base of which is connected to one end of the resistor 30.
An NPN transistor 31 has a collector connected to one end of the resistor 30, an emitter connected to the cathode of the main capacitor 3, and a base connected to one end of the resistor 39. 32 is a voltage source, and the positive electrode is connected to the IGBT 2 via the transistor 29.
A drive voltage is applied to the gate of No. 4, and the negative electrode is connected to the cathode of the main capacitor 3. The voltage source supplies power to the AND gate 37, the comparators 35 and 51, and the pulse generators 36 and 38 via a power supply line (not shown), and also supplies power to a reference voltage generation circuit (not shown) of the comparators 35 and 51. are doing.

Reference numeral 33 denotes a photodiode as a light receiving element, which is arranged to directly receive the light of the discharge tube 22. The cathode of the photodiode 33 is connected to the plus electrode of the voltage source 32, and the anode is connected to one end of the resistor 34. 35 is the first with hysteresis
Of the reference voltage V _ref1 to the plus input,
Negative inputs are connected to the connection points of the photodiode 33 and the resistor 34, respectively. The comparator 35 is configured to output a low level voltage when the negative input exceeds the reference voltage and output a positive voltage when the negative input drops from the reference voltage to a voltage lower than a predetermined voltage.

Reference numeral 36 denotes a first pulse generating circuit which, when a pulse is applied to the input, outputs a predetermined time width (for example, 1).
0 ms) pulse is output. 37 is an AND gate as an AND circuit, one input of which is the comparator 3
5, the other input is connected to the output of the pulse generator 36, and the output is connected to one end of the resistor 39. Reference numeral 38 denotes a second pulse generator having a delay characteristic, and when a positive pulse is applied to the input regardless of the output state, a delay is applied to the output for a predetermined time (for example, several microseconds), and the switching cycle of the IGBT 24 ( Generally, a pulse having a predetermined time (for example, several hundreds of microseconds) longer than about 30 microseconds and shorter than the pulse time width of the first pulse generator is output. The output pulse is a resistance 4
It is transmitted to the gate of the SCR 8 via 0 and 10.

Reference numeral 51 denotes a second comparator, which is connected to the negative input of the reference voltage V _ref2 and to the positive input of the connection point between the photodiode 33 and the resistor 34, respectively.
The comparator 35 is configured to output a high level voltage when the plus input exceeds the reference voltage. The output of the comparator is connected to the gate of the transistor 13 via the resistor 41.

The operation of FIG. 1 will be described in detail below.

It is assumed that the main capacitor 3 is charged by the power supply circuit 1. When a light emission start pulse is applied to the input of the first pulse generator 36, a positive pulse is generated at the output of the generator 36. Further, since the photodiode 33 is not irradiated with light from the discharge tube, the output of the comparator 35 is a high level voltage. Therefore, when the output of the pulse generator 36 becomes high level, the output of the AND gate 37 also becomes high level, and the second delay characteristic
Is transmitted to the input of the pulse generator 38 of
Is transmitted to the base of the transistor 31 via. The transistor 31 is turned on because the base current is supplied, and the on-state causes the base current of the transistor 29 to flow through the resistor 30, so that the transistor 29 is turned on and the voltage of the voltage source 32 is generated at the collector. The partial pressure of the voltage resistors 27 and 28 is applied to the gate of the IGBT 24, and the IGBT 24 is turned on.

On the other hand, due to the high level voltage applied to the input of the second pulse generator 38, the pulse width is about 300 μsec after about 3 μsec after the voltage is applied to the output of the pulse generator 38. A pulse is generated. The pulse is resistance 4
It is applied to the gate of SCR8 via 0 and 10, and as described above, the IGBT24 is already turned on.
8 is turned on, and the electric charge accumulated in the trigger capacitor 6 is discharged through the SCR 8, the IGBT 24, and the primary winding of the trigger transformer 5, and a high frequency high voltage is generated in the secondary winding of the trigger transformer 5, causing a discharge tube. The discharge tube 22 is ionized by being applied to the trigger electrode of the
Is turned on, the electric charge of the main capacitor 3 is discharged through the coil 4, the discharge tube 22, the diode 23, and the IGBT 24 to start light emission. When the SCR 8 is turned on, the voltage of the capacitor 14 is applied to the cathode of the discharge tube 22 via the transistor 20. Therefore, the discharge tube 2
A voltage that is about twice the voltage of the main capacitor 3 is applied between the anode and the cathode of the second capacitor 2 to assist the ionization of the discharge tube 22. In the transistor 20, when the SCR 8 is turned on, the electric charge of the capacitor 14 is discharged through the resistor 18 and the base of the transistor 20, and the transistor 20 is turned on.

Next, the light emission output of the discharge tube 22 is received by the photodiode 33, and a voltage corresponding to the output light is generated across the resistor 34. When the voltage of the resistor 34 exceeds the reference voltage V _ref1 , the output of the comparator 35 shifts to the low level. AND gate 37 depending on the low level
Output shifts to the low level, the transistor 31 is turned off, and accordingly the transistor 29 is turned off and the IGB is turned off.
Since the gate of T24 becomes low level, the IGBT24
The current that was flowing through is cut off. The energy accumulated in the coil 4 by the cutoff is discharged as a current through the discharge tube 22, the diode 23, and the diode 26. At this time, the cathode of the diode 23 becomes higher than the main capacitor voltage by the amount of the forward voltage drop of the diode 26. This voltage causes the trigger capacitor 6 to be rapidly charged via the resistor 17, the diode 16 and the primary winding of the trigger transformer 5. In addition, the capacitor 14
Is rapidly charged through the resistor 17, the diode 16 and the diode 15.

On the other hand, the output of the second comparator 51 is at the low level when the discharge tube 22 is not generating an optical output, the transistor 13 is in the OFF state, and the output from the pulse generator 38 is as described above. Voltage is resistance 40 and 10
Is transmitted to the SCR 8 via. When the discharge tube 22 starts to emit light, the reference voltage V _ref2 of the second comparator 51 is set lower than the voltage lower than the reference voltage V _ref1 of the first comparator 35 by a predetermined voltage.
1 is inverted before the first comparator 35 and outputs a high level. The high level output causes the transistor 13
Is turned on and the output voltage of the pulse generator 38 is SC
It is prohibited to be transmitted to the gate of R8.

Next, when the light output of the discharge tube 22 decreases, that is, the negative input of the comparator 35 drops, and the negative input drops from the reference voltage V _ref1 to a voltage lower by a predetermined voltage, the output of the comparator 35 becomes a high level, as described above. To I
A voltage is applied to the gate of the IGBT 24 and the IGBT 24 turns on. At this time, the discharge tube 22 is normally the coil 4 described above.
Since the current is flowing or is in the ionized state, the electric charge of the main capacitor 3 starts to discharge through the discharge tube 22 again.

As described above, when the output of the AND gate 37 becomes high level, the pulse generator 3 after a predetermined delay time elapses.
A pulse is generated from the output of 8. However, when the discharge is started and the transistor 13 is turned on as described above, the output pulse is prohibited by the transistor 13 and is not transmitted to the gate of the SCR8, and the SCR8 is not turned on. Therefore, the trigger voltage is not applied to the discharge tube 22. After that, the above-described operation is repeated and the light emission output is stabilized at a predetermined value. After that (usually about 10 milliseconds), when a low output is generated from the pulse generator, the output of the AND gate 37 becomes low level, the IGBT 24 is turned off, and the issuing is stopped.

Next, the pulse generator 36 is driven as described above, the IGBT 24 is turned on, and the pulse generator 3 is turned on.
8 is driven and the trigger circuit is driven to start light emission, and after the predetermined light output and the IGBT 24 are turned off, the light emission output is reduced and the output of the comparator 35 becomes high level and IG
The BT24 turns on. Generally, the discharge tube is not stable in the initial stage of discharge, especially when the discharge current is small. Therefore, if the current of the discharge tube 22 does not flow here, the potential of the light output detecting resistor 34 drops below the reference voltage of the comparator 51, and the output of the comparator 51 becomes low level, so the transistor 13 is off and the IGBT 2
After 4 turns on, the output from the pulse generator 38 is applied to the gate of the SCR 8 and the SCR 8 turns on. Since the trigger capacitor 6 and the capacitor 14 are already charged by this turning on as described above, the trigger voltage is applied to the trigger electrode of the discharge tube 22 and the negative voltage of the capacitor 14 is applied to the cathode of the discharge tube 22. Therefore, the discharge of the discharge tube 22 is started. The subsequent operation is the same as described above. [Correspondence between the Invention and the Embodiment] The trigger transformer 5, the trigger capacitor 6, the SCR 8, the resistor 7 in the above embodiment,
The circuit composed of the resistor 9 forms a trigger means for applying trigger energy to the discharge tube of the present invention.
Further, the circuit composed of the photodiode 33, the resistor 34, and the comparator 51 forms a detection means for detecting the light emission output of the discharge tube of the present invention. Further, the first pulse generator 36, the second pulse generator 38, the photodiode 3
The circuit composed of 3, the resistor 34, the comparator 35, and the AND gate 37 forms a drive circuit for periodically driving the switching element and the trigger means of the present invention.
Further, the photodiode 33, the resistor 34, and the comparator 35 provided in the drive circuit form the photodetector of the present invention.

The above is the correspondence between each configuration of the embodiments and each configuration of the present invention, but the present invention is not limited to the configurations of these embodiments, and the functions shown in the claims or It goes without saying that any structure may be used as long as the functions of the structure of the embodiment can be achieved.

Further, the present invention may be combined with each of the above embodiments or their technical elements as required.

In addition, the present invention may be applied to a device in which all or part of the configuration of the claims or the embodiments forms one device or is combined with another device. May be an element that constitutes the.

The present invention also relates to various types of cameras such as single-lens reflex cameras, lens shutter cameras, video cameras,
Further, the present invention can be applied to optical devices other than cameras and other devices, devices applied to those cameras and optical devices and other devices, and elements constituting these devices.

[0035]

As described above, according to the first and second aspects of the present invention, the discharge of the discharge tube is started once, and the IGBT is repeatedly turned on and off to control the light emission. In the control method, even when the discharge cannot be continued when the IGBT is turned on, the discharge tube can be triggered again to restart the discharge, and the discharge can be prevented from stopping.

According to the invention described in claim 3, the light receiving element of the light detecting means provided in the driving means and the light receiving element provided in the detecting means can be formed by the same element, so that the circuit configuration is simplified. be able to.

Further, according to the invention described in claim 4, the switching element connected in series to the discharge tube is turned on by the first pulse in response to the light emission start pulse from the first pulse generator, and the delay characteristic is obtained. With the second pulse from the second pulse generator having the following, the trigger means is driven with a delay after the switching element is turned on, so that the discharge tube can be surely started to discharge. When the switching element is off when the trigger means is driven, the discharge current is blocked by the switching element, so that discharge of the discharge tube may not be started.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

[Explanation of symbols]

1 Power Supply Circuit 2, 15, 16, 23, 26 Diode 3 Main Capacitor 4 Current Limiting Coil 5 Trigger Transformer 6 Trigger Capacitor 7, 9, 10, 11, 11, 12, 17, 18, 19, 21,
27, 28, 30, 34, 39, 40, 41 Resistance 8 SCR 13, 20, 31 NPN transistor 14 Capacitor 22 Discharge tube 24 IGBT 29 PNP transistor 32 Voltage source 33 Photodiode 35, 51 Comparator 36 Pulse generation circuit 37 AND gate 38 pulse generator

Claims (4)

[Claims] 1. A discharge tube for flash photography, a main capacitor for supplying emission energy to the discharge tube, a switching element connected in series to the discharge tube, and trigger means for applying trigger energy to the discharge tube. And a detection means for detecting the light emission output of the discharge tube and a driving means for periodically driving the switching element and the trigger means. When the light emission output by the detection means is a first predetermined value or more, A flash photographing apparatus, wherein the operation of the trigger means is prohibited. 2. A drive circuit for periodically driving the trigger means has a light detecting means, and when the light emission output of the discharge tube reaches a second predetermined value higher than the first predetermined light output, 2. The switching element is turned off, and the switching element is turned on when the light output drops to a third predetermined value lower than the second predetermined value and higher than the first predetermined value. The flash photography device described. 3. The detecting means has a first comparator, and the light detecting means has a second comparator, which is connected in series with a light receiving element for detecting the light emission output of the discharge tube and the light receiving element. The flash photographing apparatus according to claim 3, wherein the inputs of the two comparators are connected to a connection point with a resistor. 4. The first pulse generator which generates a first pulse in response to a light emission start pulse, and the second pulse which is delayed by a predetermined time from the start pulse in response to the light emission start pulse. And a second pulse generator for generating a pulse, which turns on the switching element in response to the first pulse and drives the trigger means in response to the second pulse. First,
2. The flash photography device according to any one of 2 and 3.