JPS59140429A - Camera used together with flash light emitting device - Google Patents

Abstract

PURPOSE:To simplify the constitution of a system, and also to raise the accuracy of a dimming control by combining a photodetector for an automatic focusing and a photodetector for a dimming control. CONSTITUTION:When a photodetecting operating circuit 3 is used for an automatic focusing, a difference of output voltages of differential amplifiers 113, 114, namely, a difference of infrared light quantities which are made incident to a photodetector 103 and 110 is detected by an output of a differential amplifier 115, and a focusing operation is executed by a driving means 4. In a flash photographing state, the potential of gates 102, 104, 109 and 111 becomes a high level, the photodetector 103 and 110, and potential wells 101, 105 and 108, 112 are reduced to a non-conducting state, also the potential of a gate 106 becomes a low level, and the photodetector 103 and 110, and a potential well 107 are reduced to a conducting state. Accordingly, a reflected light by an object to be photographed of a flash light emission is made incident to the photodetectors 103, 110, photoelectrically converted, added and accumulated to the potential well 107 as a charge, and when it exceeds voltage ER of a reference voltage source 118, an output of a comparator 117 is varied to a high level, a light quantity controlling circuit is operated through a terminal 119 and the light emission is stopped instantaneously.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a camera used with a flash light emitting device,
In particular, it relates to a camera for use with a dimmable flashlight device and equipped with an automatic focusing device.

<Description of Prior Art> In recent years, cameras equipped with automatic focus adjustment devices have been developed and sold. Such adjustment devices include an active type that measures distance by projecting light onto a subject from the camera side and receives the reflected light, and a passive type that measures distance by receiving light from the subject.

Both require a light receiving device.

Nowadays, dimmable flash devices are the mainstream, and they stop emitting light by detecting the reflection of light from the subject.

In this way, when a light receiving device is also required for a flashlight emitting device, a light receiving device must be provided for each device independently.

<Object of the Invention> In view of the above-mentioned drawbacks, the present invention focuses on the fact that focus adjustment and flashlight emission are not performed at the same time during camera photography. It is an object of the present invention to provide a camera that can use a dual-purpose element and perform accurate light control.

Incidentally, the camera 2 may be configured integrally with the flashlight emitting device, or may be configured separately.

<Description of Embodiments> FIG. 1 is a control block diagram for automatic focus adjustment. In the figure, 1 is an infrared light emitting element, and 2 is an imaging plane 6 of the camera.
9 is an imaging optical system for subject light, 3 is a light receiving calculation circuit, and 4 is a focusing lens position driving means.

The infrared light emitted from the infrared light emitting element 1 is projected onto the subject via the optical system 2, and the reflected light from the subject is received by the light receiving calculation circuit 3 via the optical system again to obtain a focus state detection signal. Then, the driving means 4 is driven to perform focus adjustment. The lens position detection potentiometer outputs a voltage according to data based on the lens position, that is, the measured distance.

Note that in order to increase the sensitivity of receiving reflected infrared light from the subject, it is desirable to place an optical filter in front of the light receiving element that passes only light near the irradiated infrared light.

FIG. 2 is a detailed diagram of the light reception calculation circuit 3 of FIG. 1.

The light receiving elements 103 and 110 are connected to the potential wells 101 , 105 and 108 , 112 through the gates 102 , 104 and 109 , 111 , and to the potential well 107 through the gate 106 .
connected to. Botential wells 101 and 105
is connected to the inverting and non-inverting inputs of differential amplifier 1130. Potential wells 108 and 112 are also connected to the inverting and non-inverting inputs of differential amplifier 114. The output of the differential amplifier 113 is connected to the non-inverting input of the differential amplifier 115, and the output of the differential amplifier 114 is connected to the inverting input of the differential amplifier 115.The output of the differential amplifier 115 is connected to a focusing drive handshaft to drive it. Potential well 107 is comparator 1
17 non-inverting inputs. The inverting input of comparator 117 is connected to reference voltage source 118 and its output is connected to terminal 119.

The configuration of the light receiving circuit is as described above, and its operation will be explained below with reference to FIG. Third
During the distance measuring operation indicated by tl in the figure, the infrared light emitting element 1 turns off (high level) and off (low level) as shown in FIG. 3(a). Return. Also, the potentials of electrodes A and B at 102 and 109 are in phase with the infrared light emitting element as shown in Fig. 3(b), and the high level and low level are returned to <b. , B' potential is shown in Figure 3 (
As shown in c), the high level and low level are repeated in opposite phase to the infrared light emitting element. Further, the potential of the electrode C of the gate 1o6 is up to i, which is a high level. For these gates, when the electrode is at a high level, the light receiving element and the potential well are in a non-conducting state, 1 ft knee o -L
/ When in Hell, conduction occurs between the photodetector and the potential well. Then, from the above explanation, while the infrared light emitting element 1 is off, the gates 102 and 109 are at a low level, and the light receiving elements 103 and 110 and the potential well 1 are connected to each other.
O1 and H1O8 are electrically conductive, storing an amount of charge in the potential well in proportion to the intensity of external light, and as a result, a screw pressure proportional to the charge is generated in the both/kuyaru well.

Also, while the infrared light emitting element 1 is on, the gates 1o4 and 111
becomes low level, the light receiving elements 105 and 110 and the potential wells 105 and 112 conduct, and in the same way, a voltage is generated with an amount of electricity equal to [2] compared to [the intensity of external light and the intensity of infrared light]. do. Since the gate 106 is always at a high level, the potential well 107 of both the light receiving elements 103 and 110 is non-conductive, and no charge or voltage is generated.

As explained above, when the differential amplifier 113 takes the differential pressure between the potential wells 105 and 101, a voltage proportional to the intensity of the infrared light from the infrared light emitting element 1 incident on the light receiving element 103 is generated at the output.

Similarly, a voltage proportional to the intensity of the infrared light from the infrared light emitting element 1 incident on the light receiving element 110 is generated at the output of the differential amplifier 114. Differential amplifier 1 by differential amplifier 115
13 and 114, that is, a voltage proportional to the difference in the amount of infrared light incident on the light receiving elements 103 and 110 is generated at their outputs.

When the infrared light incident on the photodetector 105 is stronger than the infrared light incident on the photodetector 110, that is, when the output of the differential amplifier 115 is positive, the optical system focuses at a position closer to the subject, and the photodetector 103° external light is the light receiving element 110
In other words, if it is weaker than the infrared light incident on the differential amplifier 1
When the output of No. 15 is negative, the camera is configured to focus at a position farther from the subject.

When the output of the differential amplifier 115 is positive, the focusing driving means 4 is driven to focus on a position further away from the current position, and when the output of the differential amplifier 115 is negative, the driving means 4 is driven to focus at a position further away than the current position. The driving means 4 is driven to focus on a point, and when the output of the differential amplifier 115 is zero, the driving means 4 maintains the current focal position. In this way, the current state of focus is detected from the output of the differential amplifier 115, and the driving means 4 is operated to perform focusing, thereby maintaining the focused state.

Although it was not clearly shown in the explanation of the operation in Figure 2, just before the gate becomes low level and the light receiving element and the potential well become conductive, the voltage that was there is cleared, and after the gate becomes conductive again, the potential well becomes conductive. The time it takes for the amount of charge stored in the well to reach a steady state is sufficiently short compared to the blinking period, and when the gate becomes high level and the potential well becomes isolated, the amount of charge stored in the well is stored until just before that point. Since the charges are held as they are in the potential well, there is no potential fluctuation in the potential well.

Next, the operation during flash photography shown in period t2 in FIG. 3 will be explained with reference to the electric circuit diagram of the flash light emitting device shown in FIG.

At time T1 when autofocusing is completed and the flash photography mode is entered, the potential of the gates 102, 104, 109, 111 becomes high level as shown in FIGS. 110 and the potential wells 101, 105, 108, and 112 become non-conductive, and the potential of the gate 106 becomes low level, and the light receiving elements 103, 110 and the potential well 107 become conductive. Therefore, the added charges of the light receiving elements 103 and 110 are accumulated in the potential well 107.

Here, the flash light emitting device will be explained using FIG. In FIG. 4, 201 is a battery, which is connected to the low voltage input side of a DC-DC converter 202 that boosts the DC voltage. The high voltage side output of the DC-DC converter 202 is connected to the resistor 205 via the rectifier diode 203.
, a trigger capacitor 206 , a trigger transformer 207 , a trigger thyristor 208 , a resistor 209 216 , and a sub-nyristor 217 , which are connected to a known light amount control circuit 220 and a main capacitor 221 in a parallel circuit. The flash discharge tube 210 has a rectifier diode 203 and a main thyristor 2.
An anode and a cathode are connected between the trigger transformer 207 and the trigger electrode thereof is connected to the high voltage terminal of the trigger transformer 207 . A series circuit of a synchro switch 222 and a resistor 223 is connected between the anode of the battery 201 and the gate of the trigger thyristor 208. Further, the gate of the commutating Nyristor 217 is connected to a dimming control terminal P, which is directly connected to the output terminal 119 in FIG.

The configuration shown in FIG. 4 has been described above, and its operation will now be explained. When you turn on the power switch for the flashlight emitting device (not shown in the diagram), DC-DC! After the converter 202 operates to charge the trigger capacitor 206, commutating capacitor 213, capacitor 215, and main capacitor 221 to almost the same voltage with the polarity shown, the synchronizer switch 222 is turned on at time T2 in FIG. . Then, a gate current is supplied from the battery 201 to the trigger thyristor 208 via the synchronizer switch 222 and the resistor 223, the trigger thyristor 208 is turned on, and the known trigger circuit 204 is activated to ionize the flash discharge tube 210 and make it conductive. . Then, the anode of the main thyristor 216 becomes high voltage, commutation capacitor 213, resistor 214, capacitor 2
15 to the main thyristor 216,
The main thyristor 216 turns on and flash light emission begins.

The light reflected by the subject emitting flash light is reflected by the light receiving element 10 in FIG.
3.110, is photoelectrically converted, and is added and accumulated in the potential well 107 as a charge.

At time T3, the voltage attempts to exceed the voltage ffR of the reference voltage source 118. Then, at that moment, the inverting input voltage of the comparator 117 [R] is higher than the potential well 107 which is the non-inverting input.
3(f), the output of the display comparator 117 changes from low level to high level. This causes a gate current to flow through the terminal 119 to the sub-thyristor 217, turning the sub-thyristor 217 on. Then, a known light amount control circuit 220 is activated and the light emission is stopped instantaneously. After that, when the charge in the potential well 107 is cleared at time T4 in FIG. 6 by a clear signal not shown in between, as shown in FIG.
As shown in , the voltage of the potential well 107 becomes zero. Therefore, as shown in FIG. 3(f), the output voltage of the comparator 117 is set to a high level, and the charge of the color converter 107 is cleared, thereby removing the influence of non-flash light incident from the outside between times T1 and T2.

In this way, since dimming control is performed by the sum of the outputs of multiple light receiving elements for automatic focus adjustment, the sensitivity for dimming control increases and accurate control becomes possible. Become.

Furthermore, as already explained above, the light receiving elements 103°110
An optical filter is placed in front of the infrared light emitting device 10 to pass only light having a wavelength close to the emission wavelength material.

Therefore, the dimming of flash light emission is performed using only wavelength components in this vicinity. However, the wavelength Fi of the infrared light emitted from the infrared light emitting element 1 is very close to visible light, and as can be seen from the reflected light reception rate used in dimmable flash devices currently in practical use, the above-mentioned The presence of the optical filter does not adversely affect the dimming characteristics.

Furthermore, although this embodiment has been described as an example of an active type autofocus #A joint device, a passive type can also be applied if a plurality of light receiving elements are used. Also, the light receiving element is 2
Although an example in which one light receiving element is used is used, it is also possible to use three or more light receiving elements, and in that case, the sub light control may be performed using the sum of the outputs of at least two light receiving elements.

<Description of Effects> As explained above, according to the present invention, it is possible to use the light receiving element for automatic focus adjustment as well as the light receiving element for dimming control, which simplifies the system configuration. At the same time, it becomes possible to perform dimming control accurately.

[Brief explanation of drawings]

Fig. 1 is a schematic block diagram of an embodiment of an automatic focus adjustment device, Fig. 2 is a detailed circuit diagram of the light receiving calculation circuit shown in Fig. 1, Fig. 3 is an operation timing diagram of each part of Fig. 2, and Fig. 4 1 is an electrical circuit diagram of a flashlight emitting device used with the camera of this embodiment. In the figure, 1...infrared light emitting element 2...imaging optical system 3...light receiving calculation circuit 4...focus adjustment lens position driving means 9 are shown. Applicant Canon Co., Ltd.

Claims (1)

[Claims] Receives external light for automatic focus adjustment. Used with a flash light emitting device characterized in that a plurality of light receiving elements are used also as light receiving elements for performing dimming control of the flash light emitting device, and the dimming control is performed using the sum of the outputs of the plurality of light receiving elements. camera.