JPH045971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strobe light emission control device for a camera, and more particularly to a strobe light emission control device for a camera suitable for use in daytime synchronized photography, backlight photography, and the like.

As is well known, a photometric photodetector is installed at the bottom of the mirror box of a single-lens reflex camera, and this photodetector measures the light reflected from the photographic film surface to determine the amount of light emitted by the strobe. Control,
Various so-called TTL autostroboscopic devices have been proposed in the past. This TT-auto strobe device has the great advantage of being able to perform strobe photography with any aperture of the photographic lens without complicated exposure calculations or manual operations. A common control method is to close the camera shutter as soon as the reflected light from the strobe reaches the appropriate exposure.
Although the main part of the subject is properly exposed by the strobe light, the surrounding background etc. are underexposed or overexposed, which is a drawback.

In view of the above-mentioned points, an object of the present invention is to provide a first light-receiving element that measures the main part of the object, and a second light-receiving element that measures almost the entire part or other than the main part of the object. While performing exposure control based on the memorized photometric output of the element, it is determined from the memorized light output of both light receiving elements whether the subject brightness of the main part is lower than the surrounding subject brightness, and if it is low,
An object of the present invention is to provide a strobe light emission control device for a camera, which controls a strobe light emission so that the light amount of the main part becomes an appropriate light amount based on a non-memory photometric output of a first light receiving element.

According to the present invention, even in daytime synchronized photography, backlight photography, etc., areas other than the main parts of the subject are exposed to appropriate levels of natural light, etc., and the main parts of the subject receive light that is insufficient in natural light. Since the light is supplemented by the strobe light and exposed to an appropriate level, there is no risk of overexposure or underexposure over the entire screen.

Hereinafter, the present invention will be explained based on an illustrated embodiment.

FIG. 1 shows a photometry system of a camera strobe light emission control device according to the present invention. Inside a camera body 1, which is a single-lens reflex camera, a movable reflective mirror 2 for observation is supported by a holding frame 3 and rotatably disposed. This movable reflective mirror 2
is formed of a semi-transparent mirror, and a part of the subject light that passes through the photographic lens 4 and enters the camera is reflected by the surface of the mirror 2, and is reflected by the focusing glass 5.
The image of the subject is determined above. This object image is observed through a finder eyepiece 6 and a pentagonal Datzha prism 7. Also, mirror 2
A part of the subject light transmitted through the through hole 3 of the holding frame 3
a, and is incident on an auxiliary reflection plate 9 which is rotatably arranged coaxially with the mirror 2 and is positioned so as to hang down just in front of the focal plane shutter 8. The auxiliary reflecting plate 9 has a diffusing surface having substantially the same reflectance as the emulsion surface of the photographic film 11, and light incident on the same surface is diffusely reflected forward again. This diffusely reflected light is
The light enters a light receiving element substrate 12 disposed at the bottom of the mirror box through a condenser lens group 13. The condensing lens group 13 serves as an imaging lens that substantially recombines the subject image formed on the auxiliary reflection plate 9 onto the light receiving element substrate 12. Since the auxiliary reflection plate 9 is arranged near the film 11 so as to be almost parallel to the film 11, during photographing, the reflected light based on the subject image on the film surface enters the light receiving element substrate 12 through the condensing lens group 13. Then, the subject image is re-imaged on the same substrate 12 in substantially the same state.

In FIG. 1, the reference numeral 2A indicates the position when the movable reflection mirror 2 is lifted out of the photographing optical path.
Reference numeral 9A indicates the position of the auxiliary reflector 9 that has been flipped up in conjunction with the upward movement of the mirror 2, and reference numeral 14 indicates a strobe that is detachably attached to the camera body 1.

As shown in FIG. 2, the light-receiving element substrate 12 is formed of a horizontally long rectangular plate, and its surface has a substantially square-shaped light-receiving section 12a for partial photometry in the center. , an inverted concave-shaped light receiving section 12b for average photometry is provided around the light receiving section 12a. The partial photometering hole 12a measures the main part of the subject image formed on the substrate 12, and the average photometering photometer 12b measures the peripheral part of the subject image. I'm starting to do that. That is, the light receiving section 12a serves as a first light receiving element that measures the main part of the subject, and the light receiving part 12b serves as a second light receiving element that measures the light of other than the main part of the subject. Also,
A portion of the light receiving element substrate 12 below the light receiving section 12a is a non-light receiving region 12c where no light receiving section is provided.
It is becoming. This non-light-receiving area 12c is provided to eliminate the influence of specularly reflected light from the sky in the subject field.

In the photometry system of the strobe light emission control device of this embodiment, the light receiving section 12a for partial photometry and the light receiving section 12b for average photometry are provided on the same substrate 12; Of course, the light receiving elements for average photometry may be arranged separately. However, in this case, the light receiving element for average photometry is generally arranged so as to photometer almost the entire subject image.

Next, an electric circuit of the strobe light emission control device of the present invention in which the partial photometry light receiving section 12a and the average photometry light receiving section 12b are connected will be described.

As shown in FIG. 3, the electric circuit of the strobe light emission control device includes a light receiving element PD ₁ for partial photometry (corresponding to the above-mentioned light receiving section 12a for partial photometry, hereinafter referred to as a light receiving element).
Write as PD ₁ . ) and a photodetector for average photometry
PD ₂ (corresponds to the above average photometry light receiving section 12b.Hereinafter,
It is written as photodetector PD ₂ . ) are arranged respectively.

The above photodetector PD ₁ for partial photometry is an operational amplifier.
It is connected in the forward direction between the inverting input terminal and the non-inverting input terminal of _A1 . The non-inverting input terminal of this operational amplifier A ₁ is connected to an integrating capacitor C ₁ for direct photometry, one end of which is grounded, and a reference voltage Vr ₁ is applied through a direct photometry start command switch SW ₁ . ing. Direct photometry start command switch SW ₁ above is X contact SW ₆
(See Figure 4) is formed by a normally closed switch that opens just before it closes, and from the moment it opens, the charge in the integrating capacitor C ₁ is discharged through the photodetector PD ₁ for partial photometry. The function is to directly measure the light reflected from the strobe light from the subject. Furthermore, the non-inverting input terminal of the operational amplifier _A1 is also connected to the non-inverting input terminal of the operational amplifier _A2 for impedance conversion. This operational amplifier _A2 has its inverting input terminal connected to its output terminal to form a voltage follower circuit, and serves as an impedance converter with an amplification factor of 1. The output terminal of this operational amplifier A ₂ is connected to the base of the transistor Q ₂ and the non-inverting input terminal of the automatic light emission control level determination comparator A ₁₁ , respectively.

The inverting input terminal of the operational amplifier _A1 is connected to the collector and base of an NPN logarithmic compression transistor _Q1 , respectively. The emitter of the logarithmic compression transistor _Q1 is connected to the output terminal of the operational amplifier _A1 . This logarithmic compression transistor Q ₁ has the role of converting the photocurrent i ₁ generated in the partial photometry photodetector PD ₁ into a logarithmic compression voltage by using the forward current-voltage characteristics of the PN junction. . In addition, the output end of operational amplifier A ₁ is connected to a constant current source through variable resistor VR ₁ for photometry level adjustment.
Connected to CS ₁ . This constant current source CS ₁ serves to cause a constant current I ₁ to flow through the photometric level adjustment variable resistor VR ₁ . Variable resistor for adjusting the photometry level above
VR ₁ has a movable contact terminal connected to transistor Q ₂
In order to consider that the photometric outputs of the partial photometry photodetector PD ₁ and the average photometry photodetector PD ₂ for a subject of the same brightness are equivalent, regardless of the light-receiving area, etc., the transistor
It serves to make the collector current flowing through Q ₂ k ₀ times the photocurrent i ₁ generated in the photodetector PD ₁ . That is, when the partial photometry photodetector PD ₁ and the average photometry photodetector PD ₂ measure a subject with the same luminance, and the photocurrents are i ₁ and i ₂ , respectively, k ₀ = i ₂ / i ₁
The variable resistor VR ₁ serves to amplify the photocurrent i ₁ generated in the photodetector PD ₁ by a factor of k ₀ determined and set in advance, and to flow the amplified photocurrent i 1 between the collector and emitter of the transistor Q ₂ .

The transistor Q ₂ is formed of an NPN type transistor, and its collector is formed of a PNP type transistor forming a current mirror circuit.
Q ₅ and Q ₆ are connected to the collector and base of transistor Q ₅ and the base of transistor Q ₆ , respectively. Operating voltage Vcc is applied to the emitters of transistors Q ₅ and Q ₆ , respectively, and the collector of transistor Q ₆ is
It is connected to the collector of transistor Q ₄ and to the collector and base of transistor Q ₇ , respectively. transistor
_Q7 is formed by a PNP type transistor,
The base and emitter of transistor _Q8 , which is also PNP type, are connected to form a current mirror circuit. Transistor Q ₇ ,
The operating voltage Vcc is applied to each emitter of _Q8 , and the collector of transistor _Q8 is connected to the collector and base of logarithmic compression transistor _Q9 , respectively.

On the other hand, the average photometry photodetector PD ₂ is connected in the forward direction between the inverting input terminal and the non-inverting input terminal of the operational amplifier A ₃ . A reference voltage Vr ₁ is applied to the non-inverting input terminal of this operational amplifier A ₃ .
In addition, the collector and base of the logarithmic compression transistor _Q3 are connected to the inverting input terminal of the operational amplifier.
The bases of a transistor _Q4 forming a current mirror circuit together with the logarithmic compression transistor _Q3 are connected to each other. The emitters of NPN transistors Q ₃ and Q ₄ are respectively connected to the output terminal of operational amplifier A ₃ . The output terminal of the operational amplifier A ₃ is connected to one end of the memory photometry command switch SW ₂ that stops the memory photometry by the average photometry photodetector PD ₂ , and is also connected to the emitter of the logarithmic compression transistor Q ₉ . There is.

The logarithmic compression transistor Q ₉ is formed of an NPN type transistor, and its base is connected to the non-inverting input terminal of an operational amplifier A ₆ whose inverting input terminal and output terminal are connected to form an impedance converter. There is. The output terminal of operational amplifier A ₆ is connected to the non-inverting input terminal of operational amplifier A ₇ through resistor R ₂ . The non-inverting input terminal of this operational amplifier _A7 is also connected to the output terminal of operational amplifier _A9 through a resistor _R4 . Also, op amp
The inverting input end of _A7 is connected to the other end of a resistor _R1 to which the reference voltage _Vr1 is applied, and is also connected to its output end through a resistor _R3 .
The resistance values of the resistors R ₁ to R ₄ are set to be equal to each other, and the operational amplifier A ₇ has the same resistance value as the resistors R ₁ to _{R 4 .}
In addition, a subtraction circuit is formed that subtracts the reference voltage Vr ₁ from the sum of the output voltage _{V 6 of} the operational amplifier A 6 and the output voltage V ₉ of the operational amplifier A ₉ and outputs the difference voltage V ₇ . The output terminal of this operational amplifier _A7 is connected to the other end of a strobe light emission amount storage capacitor _C4 , one end of which is grounded, through a strobe light emission amount storage command switch _SW4 . The light emission amount memory command switch SW ₄ is the movable reflection mirror 2
(See Figure 1) is a normally closed switch that opens just before the light rises, and the strobe light amount memory capacitor _C4 stores the amount of strobe light that is insufficient when exposed to natural light, etc., of the main part of the subject. It serves to store the amount of light emitted as a voltage value.

The other end of the strobe light emission amount storage capacitor _C4 is also connected to the non-inverting input end of an operational amplifier _A8 , whose inverting input end and output end are connected to form an impedance converter. and op amp
The output terminal of _A8 is an NPN type transistor.
Connected to the base of Q ₁₀ . transistor
The emitter of Q ₁₀ is grounded and the collector is
It is connected to one end of a variable resistor VR ₂ for setting film sensitivity, and is also connected to an inverting input terminal of a comparator A ₁₁ for determining an automatic light emission control level. The film sensitivity setting variable resistor VR ₂ has a reference voltage Vr ₁ applied to its other end, and
The resistance value thereof is changed in conjunction with a film sensitivity setting variable resistor VR ₃ to which a reference voltage Vr ₁ is similarly applied to the other end. Variable resistance VR ₃ above
One end is connected to the non-inverting input terminal of a comparator A ₁₀ for determining the shutter control level, and is also connected to the collector of a transistor Q ₁₂ which generates a voltage across its base in accordance with the film sensitivity. This transistor _Q12 is formed of an NPN type transistor, and its emitter is grounded and its base is connected to the base and collector of an NPN type transistor _Q11 , which forms a current mirror circuit with the same transistor _Q12 . . The emitter of the transistor _Q11 is grounded, and the collector is connected to a constant current source _CS2 through which a constant current _I2 flows, and is also connected to the non-inverting input terminal of the operational amplifier _A9 . The operational amplifier A ₉ has its inverting input connected to its output to form an impedance converter, and its output is connected to the non-inverting input of the operational amplifier A ₇ through the resistor R ₄ , as described above. ing.

As mentioned above, the memory photometry command switch SW ₂ has one end connected to the output terminal of the operational amplifier A ₃ and the other end connected to a capacitor C ₂ for storing subject brightness by average photometry, which is grounded at one end. connected to the end. This memory photometry command switch SW ₂
is formed by a normally closed switch that opens just before the movable reflection mirror 2 rises, and the subject brightness measured by average photometry at that point is stored in the memory capacitor C in the form of the output voltage V ₃ of the operational amplifier A ₃ . It serves as a memory for ₂ . The other end of the storage capacitor _C2 is connected to the inverting input end to the output end of the operational amplifier _A4 , which is used as an impedance converter.
is connected to the non-inverting input terminal of The output terminal of this operational amplifier A ₄ is a logarithmic expansion transistor Q ₁₄
It is connected to the Emitsuta. The logarithmic expansion transistor Q ₁₄ is formed of an NPN type transistor, and a reference voltage Vr ₁ is applied to its base, while its collector is connected to a shutter second time integration capacitor C ₃ whose one end is grounded. It is connected to the. Furthermore, a reference voltage Vr ₂ higher than the reference voltage Vr 1 is applied to the other end _of the shutter second time integration capacitor C ₃ through a shutter second time count command switch SW ₃ . The shutter second count command switch SW ₃ is formed of a normally closed switch that opens in synchronization with the start of travel of the front curtain of the focal plane shutter 8 when the movable reflection mirror 2 completes its ascent. From the start of the curtain run, the charge in the integrating capacitor C ₃ is discharged through the logarithmic expansion transistor Q ₁₄ , so that the capacitor C ₃
The function is to start counting the shutter seconds. The other end of this shutter second time integration capacitor _C3 is an operational amplifier whose inverting input end is connected to the output end, making it an impedance converter.
Connected to the non-inverting input of _A5 . The output terminal of this operational amplifier _A5 is connected to the inverting input terminal of the shutter control level determination comparator _A10 .

The output terminal of the shutter control level determination comparator _A10 is connected to the base of the electromagnet control transistor _Q13 through a resistor _R6 .
This electromagnet control transistor _Q13 is formed of a PNP transistor, and has a collector grounded through the trailing curtain locking electromagnet _Mg1 , and an operating voltage Vcc applied to its emitter. Further, the output terminal of the automatic light emission control level determination comparator A ₁₁ is connected to the automatic light emission control signal terminal provided on the camera body 1 through a resistor R ₅ .
Connected to _T1 .

As described above, the camera strobe light emission control device of the present invention is configured.

Next, a strobe electric circuit that cooperates with this strobe light emission control device will be explained. Incidentally, the electric circuit of this strobe itself is already known as an electric circuit of a strobe that is understood by the camera and capable of automatically controlling light emission.

As shown in Figure 4, the electric circuit of the strobe includes a power supply circuit VS ₁ that includes a DC-DC converter that is a well-known blocking oscillator, and the positive output terminal of the circuit VS ₁ is A positive operating voltage supply line E ₁ is led out from the terminal via a backflow prevention diode D ₁ . Furthermore, an operating voltage of approximately several hundred volts is supplied from the power supply circuit VS ₁ between the negative operating voltage supply lines E ₁ and E ₀ from the negative output terminal of the power supply circuit VS ₁ . . A main capacitor _C5 is connected between the two operating voltage supply lines _E1 and _E0 , and
A series circuit of voltage dividing resistors R ₇ and R ₈ is connected in parallel with the capacitor C ₅ . This voltage divider resistor R ₇ and R ₈
The connection point is connected to the cathode of the trigger thyristor SCR ₁ via the trigger capacitor C ₆ , and is also connected to the erroneous flash prevention switch SW located on the side of the camera body 1 through the connection contact (not shown). Connected to one end of ₅ . This erroneous flash prevention switch SW ₅ is formed of a normally closed switch that opens immediately after the trailing curtain of the focal plane shutter 8 starts running, and the other end is connected to one end of the X contact SW ₆ . . X contact SW ₆ is
As is well known, it is formed of a normally open switch that closes when the front curtain completes travel, and the other end is connected to the operating voltage supply line E ₀ of the strobe side through a connection contact (not shown). . In addition, the positive end of the main capacitor _C5 is connected to the anode of the trigger thyristor _SCR1 via series-connected resistors _R9 and _R10 .
It is connected to one end of the flash discharge tube F via a peak current limiting coil _L1 . A neon tube Ne ₁ for indicating completion of charging is connected between the connection point between the resistors R ₉ and R ₁₀ and the line E ₀ . The gate of the thyristor SCR ₁ is connected to the cathode via a resistor R ₁₁ and to the line E ₀ via a resistor R ₁₂ . In parallel with the above coil _L1 , there is a back electromotive voltage blocking diode D that prevents each element of the electric circuit from being destroyed by the back electromotive force generated in the coil _L1 when the main thyristor SCR ₂ is turned off. ₂ are connected. Further, the anode of the thyristor SCR ₁ is connected to one end of the primary coil of the trigger transformer L ₂ via a trigger capacitor C ₈ and to the line E ₀ via a trigger capacitor C ₇ .

One end of the secondary coil of the trigger transformer _L2 is connected to the trigger electrode of the flash discharge tube F, and the other ends of the primary and secondary coils of the transformer _L2 are commonly connected to the cathode of the thyristor _SCR1 . and is connected to the gate of the main thyristor SCR ₂ via a resistor R ₁₃ . The cathode of Methy Lister SCR ₂ is above line E ₀
A resistor _R14 and a capacitor _C10 are connected in parallel between the cathode and the gate. This parallel circuit of resistor R ₁₄ and capacitor C ₁₀ prevents the main thyristor SCR 2 from malfunctioning due to noise, and also prevents the main thyristor SCR ₂ from malfunctioning due to noise.
This is to apply a reverse bias between the gate and cathode when SCR ₂ is turned off. The anode of the main thyristor SCR ₂ is connected to the other end of the flash discharge tube F, and there is a resistor between it and the gate.
R ₁₅ is connected. Also, thyristor SCR ₂
The anode of is connected to the above line E ₀ through a resistor R ₁₆ as well as a commutation capacitor C ₉
connected to one end of the Commutation capacitor
The other end of C ₉ is connected to the cathode of diode D ₃ , whose anode is connected to the positive terminal of main capacitor C ₅ .
It is connected via a resistor R ₃₀ and is also connected to the line E ₀ via an arrester tube _AR .

The trigger electrode of the arrester tube A _R is connected to one end of the secondary coil of the trigger transformer _L3 . A diode D ₄ and a capacitor C ₁₁ are connected in series between the anode of _{the thyristor SCR 1 and} one end of the primary coil of the trigger transformer L ₃ .
The other end of the next coil is commonly connected to the above line _E0 via a diode _D5 . The anode of the trigger thyristor SCR ₃ is connected to the connection point between the diode D ₄ and the capacitor C ₁₁ .
The cathode of the thyristor SCR ₃ is connected to the connection point between the trigger transformer L ₃ and the diode D ₅ , that is, the anode of the diode D ₅ . Between the gate and cathode of the thyristor SCR ₃ there is a resistor R ₁₇
and a capacitor C ₁₂ are connected in parallel, and a resistor R ₁₈ is connected between the gate of the Cystar SCR ₃ and the above line E ₀ . The parallel circuit of the resistor R ₁₇ and capacitor C ₁₂ serves to prevent thyristor SCR ₃ from malfunctioning due to noise.

In addition, the anode of the above thyristor SCR ₁ has
One end of a capacitor C ₁₃ is connected, and the other end of the capacitor C ₁₃ is connected to the collector of a PNP transistor Q ₁₄ via a resistor R ₂₀ . The emitter of transistor Q ₁₄ is connected to the cathode of the above thyristor SCR ₃ through a resistor R ₁₉ ,
A resistor _R21 is connected between the emitter and the base. The base of the transistor Q ₁₄ is connected to the resistor R ₂₂
is connected to the drain of a junction type N-channel field effect transistor (hereinafter referred to as FET) _Q16 for current limiting. The source and gate of FETQ ₁₆ are connected to the automatic activation control signal terminal T ₂ connected to the camera side, and are also connected to the anode of the diode D ₆ . The cathode of the diode _D6 is connected to the collector of an NPN type light emission control level determination transistor _Q15 via a resistor _R25 . Transistor Q ₁₄ above
Integrating capacitor with one end connected to the collector of
The other end of the parallel circuit of C ₁₄ and discharge resistor R ₂₃ is a resistor.
It is connected to the base of the transistor _Q15 via _R24 , and is also connected to the emitter of the photometric light receiving element _PD3 , which is a phototransistor. The collector of photodetector PD ₃ is connected to the above line E ₀
It is connected to the.

The collector of the above transistor _Q15 is a resistor
Connected to the above line E ₀ via R ₂₆ . The emitter of transistor _Q15 is connected to the movable contact terminal of aperture value changeover switch _SW7 . The fixed terminal of the switch _SW7 is connected to the above transistor.
It is connected to each connection point of resistors R ₂₉ , R ₂₈ , and R ₂₇ connected in series between the collector of Q ₁₄ and the above line E ₀ , and is connected to the emitter of transistor Q ₁₅ by switching the above switch SW ₇ . The applied potential can be switched. Further, the collector of the transistor _Q14 is connected to the anode of a Zener diode _ZD1 for constant voltage generation, and the cathode of the diode _ZD1 is connected to the line _E0 . Also, a capacitor C ₁₅ is connected in parallel with the Zener diode ZD ₁ . The above Zener diode ZD ₁ and capacitor C ₁₅ are:
It forms the power supply section of an automatic flash control circuit for a strobe that uses the photodetector PD ₃ as a photometric element.

The automatic light emission control signal terminal _T2 is connected to the automatic light emission control signal terminal _T1 of the camera. Also, the above negative working voltage supply line
_E0 is connected to the power line that supplies the camera's operating voltage Vcc.

As described above, the electric circuit of the strobe that cooperates with the strobe light emission control device of the present invention is configured.

Next, the operation of the strobe light emission control device of the present invention shown in FIGS. 1 to 3 will be explained together with the operation of the strobe electric circuit shown in FIG. 4.

First, when the camera's shutter release button (not shown) is pressed, a power switch (not shown) is turned on, and operating voltage is supplied to the camera's electric circuit shown in Fig. 3, which activates the partial photometry photodetector PD ₁ . and the average photometry photodetector PD ₂ enter the light receiving state, and each of the photodetectors PD ₁ and PD ₂ starts memory photometry. That is, a part of the subject light that passes through the photographic lens 4 and enters the camera body 1 passes through the movable reflection mirror 2 and the through hole 3a of the holding frame 3, is further reflected by the auxiliary reflection plate 9, and is reflected by the auxiliary reflection plate 9. Photodetector PD ₁ , 1
2a, PD ₂ and 12b, this incident light causes each element PD ₁ and PD ₂ to enter a light receiving state, thereby generating photoelectrodes i ₁ and i ₂ in the same elements PD ₁ and PD ₂ , respectively. .

The photocurrent i ₁ generated in the photodetector PD ₁ is logarithmically compressed by the logarithm compression transistor Q ₁ and output as a logarithm compression voltage V ₁ to the output terminal of the operational amplifier A ₁ . Variable resistor VR ₁ for photometry level adjustment
Since a constant current _I1 is flowing through the constant current source _CS1 , the movable contact terminal of the variable resistor _VR1 takes a potential that is a constant potential difference with respect to the voltage _V1 .
Therefore, the collector of transistor Q ₂ has
A current k ₀ i ₁ that is k ₀ times the photocurrent i ₁ flows, and a current k ₀ i ₁ also flows through the collector of the transistor Q ₅ . Then,
Due to current mirror action, transistor Q ₆
A current k ₀ i ₁ also flows through the collector of .

On the other hand, the photocurrent i ₂ generated in the photodetector PD ₂
is logarithmically compressed by the logarithm compression transistor Q ₃ and output as a logarithm compression voltage V ₃ to the output terminal of the operational amplifier A ₃ . This voltage V ₃ is expressed as V ₃ =Vr ₁ −kT/qlni ₂ (1). However, k is Boltzmann's constant, T
is the absolute temperature, and q is the unit charge of the electron. Logarithmic compression transistor Q ₃ and transistor Q ₄ form a current mirror circuit, so the collector of transistor Q ₄ has
A current i ₂ flows.

Current k ₀ i ₁ flows in the collector of the transistor Q ₆ , and current i ₂ flows in the collector of transistor Q ₄ , so i ₃ flows in the collector of transistor Q ₇ .
A current of =i ₂ −k ₀ i ₁ flows. transistor Q ₇
When a current _i3 flows through the collector of the transistor
The same current i ₃ flows through the collector of Q ₈ , and this current i ₃
flows into the collector of the logarithmic compression transistor _Q9 . Now, the potential of the emitter of the transistor Q ₉ is the output voltage V ₃ of the operational amplifier A ₃ , so the base of the transistor Q ₉ is V ₆ = Vr ₁ −kT/qlni ₂ +kT/qln(i ₂ -k ₀ i ₁ ) = Vr ₁ +kT/qlni ₂ -k ₀ i ₁ /i ₂ ...(2) A voltage V ₆ is generated. This voltage V ₆ is applied to the non-inverting input of operational amplifier A ₆ and is
The same voltage V ₆ is output at the output end of A ₆ . Therefore, at the output terminal of the operational amplifier _A7 forming the subtraction circuit, if the output voltage of the operational amplifier _A9 is _V9 , then _V7 = _V9 + _V6 - _Vr1 = _V9 + kT/qlni2 _{- k0} i ₁ /i ₂ ...(3) A voltage V ₇ is output. The above voltage V ₉ can be approximately expressed as V ₉ =kT/qlnI ₂ /Is (4) because the constant current I ₂ flows through the collector of the transistor Q ₁₁ through the constant current source CS ₂ . . However, Is indicates the reverse saturation current of transistor _Q11 . Therefore, by substituting equation (4), the above equation (3) can be transformed into V ₇ =kT/qln(i ₂ −k ₀ i ₁ /i ₂・I ₂ /Is) ……(5) can do. This voltage _V7 is stored in the strobe light emission amount storage capacitor _C4 as a voltage representing the required light emission amount of the strobe, and is also applied to the non-inverting input terminal of the operational amplifier _A8 .
Operational amplifier _A8 converts this voltage _V7 into impedance, outputs it, and applies it to the base of transistor _Q10 . Now, if we select transistors Q ₁₀ and Q ₁₁ so that their characteristics are the same, that is,
Assuming that the reverse saturation currents Is of transistors _Q10 and _Q11 are the same, the collector current _i4 of transistor _Q10 satisfies the following relationship: _V7 = kT/ _qlni4 /Is...(6) . Therefore, by comparing the above equations (5) and (6), the following can be obtained: i ₄ =I ₂ (i ₂ −k ₀ i ₁ /i ₂ ) (7). However, the condition is that i ₂ ≧k ₀ i ₁ is satisfied. In this way, the collector current i ₄ of the transistor Q ₁₀ is equal to the photocurrent i ₁ due to partial memory photometry,
The inverting input terminal of the comparator A ₁₁ for automatic light emission control level judgment changes depending on the photocurrent i ₂ due to average memory photometry, and the product of the reference voltage Vr ₁ to the current i ₄ and the variable resistor VR ₂ for setting the film sensitivity is input to the inverting input terminal of the comparator A 11 for automatic light emission control level judgment. The voltage dropped by the amount is applied as the determination reference voltage.

Now, by using average memory metering, the appropriate exposure time for the background using natural light, etc. can be obtained as, for example, 1/8 second, and by using partial memory metering, the appropriate exposure time for the main part of the subject using natural light, etc. can be obtained. For example, suppose it is obtained as 1/2 second. That is,
A current i ₁ that satisfies the ratio of i ₂ : k ₀ i ₁ = 1/2: 1/8,
Assuming that i ₂ occurs in each photodetector PD ₁ and PD ₂ ,
When controlling based on the shutter 8 average memorized photometric output, the main part of the subject will be exposed to only k ₀ i ₁ /i ₂ = 1/4 of the appropriate exposure depending on natural light, etc. . Therefore, in such a case, when the shutter 8 is fully opened, the correct exposure will be determined.
It is sufficient to irradiate the subject with strobe light for an exposure of i ₂ −k ₀ i ₁ /i ₂ =3/4. For this purpose,
The determination reference voltage applied to the inverting input terminal of the automatic light emission control level determination comparator A ₁₁ may be lowered by _twice i ₂ −k ₀ i ₁ /i. In the device of the present invention, a variable resistor VR ₂ for setting film sensitivity is used.
By flowing the current i ₄ of the above equation (7) through
The determination reference voltage is _doubled by i ₂ −k ₀ i ₁ /i. Therefore, based on this judgment reference voltage,
Since the automatic light emission control level is determined, the main part of the subject will be properly exposed when exposed to natural light or the like and strobe light.

Also, a variable resistor that works with the variable resistor VR ₂ above.
A constant current I ₂ flows through VR ₃ , and a voltage drop from the reference voltage Vr ₁ equal to the product of the constant current I ₂ and the variable resistor VR ₃ is applied to the non-inverting input terminal of the comparator A ₁₀ for determining the shutter control level. This voltage is applied as a determination reference voltage. Because transistor Q ₁₁ and
QP ₁₂ forms a current mirror circuit,
This is because the same current I ₂ flowing through the collector of transistor Q ₁₁ flows through the collector of transistor Q ₁₂ .

On the other hand, the output voltage V ₃ of the operational amplifier A ₃ is also applied to the other end of the subject brightness storage capacitor C ₂ through the storage photometry command switch SW ₂ .
The voltage is stored in the capacitor _C2 as a voltage representing the subject brightness based on average memorized photometry. Further, this voltage V ₃ is applied to the non-inverting input terminal of the operational amplifier A ₄ , and the operational amplifier A ₃ outputs the same voltage V ₃ and applies it to the emitter of the logarithmic expansion transistor Q ₁₄ . As a result, the same current i ₂ as the photocurrent i ₂ flowing through the average photometry photodetector PD ₂ flows through the emitter of the logarithmic expansion transistor Q ₁₄ .

Next, when the shutter release mechanism is activated and the movable reflection mirror 2 is about to start rising, the storage photometry command switch SW ₂ is opened, and the light emission amount storage command switch SW ₄ is also opened. When the memory photometry command switch SW ₂ is released, the charging voltage of the subject brightness memory capacitor C ₂ is maintained at the voltage V ₃ representing the subject brightness at that time, and after this, the emitter of the transistor Q ₁₄ is The photocurrent i ₂ at that point continues to flow. Also,
When the flash output memory command switch SW ₄ is released, the charging voltage of the strobe flash output memory capacitor C ₄ is set to the voltage V ₇ that represents the amount of light required for the main part of the subject at that time. held,
After this, the collector current i ₄ of transistor Q ₁₀ is
The value will not change from that point. Therefore, the determination reference voltage to be applied to the inverting input terminal of the automatic light emission control level determination comparator _A11 is determined.

The movable reflective mirror 2 starts to rise, and when the rise is completed, the shutter second count command switch SW ₃ is opened in synchronization with the start of travel of the shutter front curtain. When this switch SW ₃ is opened, the shutter second time integration capacitor C ₃
flows current i ₂ between the collector and emitter of transistor Q ₁₄ to discharge its charge.
That is, capacitor _C3 discharges according to the charging voltage value of capacitor _C2 . Therefore, counting of the shutter seconds obtained by average memorized photometry is started.

Also, just before the front curtain runs and X contact SW ₆ closes, the direct photometry start command switch is activated.
SW ₁ is opened. When the switch SW ₁ is opened, the application of the reference voltage Vr ₁ to the other end of the integrating capacitor C ₁ for direct photometry is stopped, and the capacitor C ₁ transfers its charge to the photodetector PD ₁ for partial photometry. Through the photocurrent i begins to discharge as ₁ .

Moving on to Figure 4, when the X contact SW ₆ closes, if the shutter rear curtain has not started running at this point, both ends of the trigger capacitor C ₆ will
Switch SW ₅ - Contact SW ₆ - Resistor R ₁₂ - Thyristor - Shorted through the gate and cathode of SCR ₁ ,
Thyristor SCR ₁ for trigger is capacitor C ₆
Ignition occurs when the charged charge is discharged. When the trigger thyristor SCR ₁ fires, the charge in the capacitor C ₇ becomes the thyristor SCR ₁ −
It is discharged through the resistor R ₁₃ - the gate cathode of the thyristor SCR ₂ , and the main thyristor SCR ₂ becomes conductive. Also, at the same time, capacitor C ₈
Since the charged charge is also discharged through the primary coil of thyristor SCR ₁ - trigger transformer L ₂ ,
The flash discharge tube F is brought into an excited state by applying the high voltage generated in the secondary coil of the transformer _L2 to the trigger electrode. Therefore, the charge accumulated in the main capacitor _C5 is transferred to the coil _L1 - flash discharge tube F.
- A sudden discharge occurs through the thyristor SCR ₂ , and the flash discharge tube F starts flashing.

Also, the charge in the capacitor _C13 is discharged through the thyristor _SCR1 - resistors _R11 , _R12, etc.
Since the Zener diode ZD ₁ is reverse biased, a constant voltage is generated across the diode ZD ₁ . This constant voltage biases the transistors Q ₁₄ , Q ₁₅ , the light receiving element PD _3, etc., and the automatic light emission control circuit of the strobe comes into operation. but,
Now, since _the anode of the diode _D6 is at high level (hereinafter referred to as "H" level) through the automatic light emission control signal terminals _T1 and _T2 , even if the photocurrent is Even if the integrating capacitor C ₁₄ is charged to the specified voltage by , and the transistor Q ₁₅ is turned on, FETQ ₁₆
Transistor Q ₁₄ is never turned on through. In other words, the strobe is in a state where it is not automatically adjusted by its own automatic light emission control circuit.

Returning to FIG. 3, when the flash discharge tube F starts emitting light, the reflected light from the film surface increases, so the photocurrent i ₁ flowing through the partial photometry photodetector PD ₁ also increases, and the integrating capacitor C The charging voltage of ₁ decreases rapidly. Then, the output of the operational amplifier _A2 , which applies this voltage to the non-inverting input terminal, also decreases, and the potential at the non-inverting input terminal of the automatic light emission control level judgment comparator _A11 becomes lower than the potential at the inverting input terminal. However, the output of the comparator _A11 is inverted to low level (hereinafter referred to as "L" level).

Then, an "L" level signal is applied to _the gate and source of _the current limiting FETQ ₁₆ in _{FIG .} Current flows through the source, attracting _the base of transistor Q ₁₄ and turning it on.
When transistor Q ₁₄ turns on, current flows through resistor R ₁₈ - gate/cathode of thyristor SCR ₃ - resistor R ₁₉ , so the trigger thyristor
SCR ₃ fires. Then, since the charge in the capacitor C ₁₁ is discharged through the thyristor SCR ₃ and the primary coil of the trigger transformer L ₃ ,
A trigger pulse is generated in the secondary coil of transformer _L3 , and the arrester tube A _R is excited. For this reason,
The discharge of the main capacitor C ₅ now bypasses the arrester tube A _R , and the charge of the commutation capacitor C ₉ is discharged through the arrester tube A _R , so that the anode of the main thyristor SCR ₂
A reverse bias is applied between the cathodes and between the cathode and the gate, the thyristor SCR ₂ suddenly becomes non-conductive, and the flash discharge tube F stops emitting light.

Therefore, the flash discharge tube F emits a flash of light in an amount sufficient to satisfy the amount of light for the main part of the object, which is insufficient due to natural light, etc., and then stops emitting light.

On the other hand, the shutter seconds count command switch
From the moment SW ₃ is opened, the integrating capacitor
The charge in C ₃ continues to discharge constantly, and the voltage charged in the capacitor C ₃ gradually decreases. Comparator with this charging voltage applied
The output of _A5 also decreases, and finally the potential at the inverting input terminal of the shutter control level determination comparator _A10 becomes lower than the potential at the non-inverting input terminal. Therefore, the output of the comparator A ₁₀ is inverted to "H" level, the electromagnet control transistor Q ₁₃ is turned off, and the trailing curtain locking electromagnet Mg ₁ is demagnetized. When the electromagnet Mg ₁ is demagnetized, the shutter rear curtain moves, and the exposure of the subject image onto the photographic film surface is completed. Since the shutter time is controlled by the shutter time obtained by average memorized photometry, the entire subject is properly exposed. Furthermore, since the strobe light compensates for the insufficient exposure of the main part of the subject by natural light, etc., appropriate exposure is achieved as well.

Note that the above description of the operation of the strobe light emission control device of the present invention is an explanation of the operation when the exposure time due to natural light etc. is longer than the strobe tuning time and the brightness of the main part of the subject is lower than the surrounding brightness. However, if the exposure time due to natural light etc. is shorter than the strobe tuning time, the false flash prevention switch SW ₅ will open before the synchro contact SW ₆ closes.
The strobe does not fire. Therefore, photography is performed using only natural light or the like. Of course, it is also possible to provide a warning means to display this when the high-speed shutter is activated.
Furthermore, when the luminance of the main part of the subject is higher than the surrounding luminance, i ₂ ≦k ₀ i ₁ and current i ₄ does not flow, so the judgment level of comparator A ₁₁ becomes reference voltage Vr ₁ . , the moment the strobe fires, the output of comparator A ₁₁ becomes "L" level. Therefore, since the strobe stops emitting light immediately after emitting light, most photos are taken using natural light.

As described above, according to the present invention, the light-receiving element controls the exposure based on the memorized photometry output obtained from the light-receiving element that measures almost all or other than the main part of the object, and also measures the main part of the object. Based on the non-memory photometry output obtained from the camera, the flash is controlled to compensate for the lack of light intensity in the main part, making it an extremely convenient camera that eliminates the drawbacks of the conventional technology mentioned at the beginning of the specification. A strobe light emission control device can be provided.

In the above embodiment, the camera is a TTL direct metering camera using a focal plane shutter, but it goes without saying that the camera equipped with the strobe light emission control device of the present invention is not limited to this type of camera. . For example, when the device of the present invention is installed in a lens shutter camera,
Since the strobe light can be synchronously emitted even during high-speed shutter speeds, the range in which the device of the present invention can function can be further expanded.

Also, although the camera was an aperture-priority camera,
Since the apparatus of the present invention determines the overall exposure by memory metering, it can of course be applied to shutter speed priority cameras in almost the same way.

[Brief explanation of drawings]

FIG. 1 is a side view of a main part showing a photometry system of a strobe light emission control device for a camera showing an embodiment of the present invention;
FIG. 2 is an enlarged front view showing the light-receiving element board shown in FIG. FIG. 4 is a circuit diagram showing an example of an electric circuit of a strobe that cooperates with the strobe light emission control device of the camera shown in FIGS. 1 to 3 above. 12a... Light receiving section for partial photometry (first light receiving element), 12b... Light receiving section for average photometry (second light receiving element), A ₁ to _{A 9} ... operational amplifier, A ₁₀ ... for determining shutter control level Comparator (exposure control circuit), A ₁₁ ... Comparator for automatic flash control level judgment (strobe control circuit), C ₁ ... Integral capacitor for direct photometry (strobe control circuit), C ₂ ... Capacitor for storing subject brightness (exposure control circuit), C ₃ ... Shutter second time integration capacitor (exposure control circuit), C ₄ ... Strobe light emission amount storage capacitor (strobe control circuit),
PD ₁ ...Photodetector for partial photometry (first photodetector),
PD ₂ ...Photodetector for average photometry (second photodetector),
SW ₁ ... Direct photometry start command switch (strobe control circuit), SW ₂ ... Memory metering command switch (exposure control circuit), SW ₃ ... Shutter second count command switch (exposure control circuit), SW ₄ ... Light emission Amount memory command switch (strobe control circuit).

Claims (1)

[Scope of Claims] 1. A first light-receiving element that measures the main part of the object, a second light-receiving element that measures almost the entire object or other than the main part, and a photometry output from the second light-receiving element. an exposure control circuit that controls exposure based on the stored photometric output of the first storage circuit, and a photometric output of the first light-receiving element and a second A second memory circuit stores a signal of the difference between the photometric output of the photodetector and the photometric output of the first photodetector in response to the closing timing of the X contact that causes the strobe to emit light. an integrating circuit that integrates, and a control circuit that compares the output of this integrating circuit with the output of the second storage circuit, and outputs a light emission stop signal to the strobe when the integrated value reaches a value corresponding to the difference signal. A strobe light emission control device for a camera, comprising: and.