JPH02283174A - Electronic camera - Google Patents

Abstract

PURPOSE:To obtain proper exposure by setting a charge storage time to an image pickup element based on a reference data depending on object distance information and a strobe lighting characteristic of a prescribed light emission quantity. CONSTITUTION:A shutter speed as a function of object distance information resulting from the range finding by a range finding (AF) sensor 23 and a stored charge based on an object light onto a CCD image pickup element 6 depending on the strobe lighting characteristic is stored on a lookup table 25 in advance as a reference data. Then a data of the shutter speed on the table 25 from the object distance information and the stored charge is read with a system controller 8 while applying transmission and reception of the signal with the system controller 8. The read shutter speed is fed to the image pickup element 8 via a drive circuit 9 with the system controller 8 and the exposure of the image pickup element 6 is controlled as the element shutter to obtain proper exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic camera, and more particularly, to an electronic camera that obtains an appropriate E exposure based on subject distance information when photographing under strobe illumination.

[Prior Art] Conventionally, when photographing while irradiating strobe light, means for varying the amount of light emitted by the strobe based on subject distance information and thereby controlling the exposure of the camera have been developed, for example, by
An example thereof is disclosed in Japanese Patent No. 9-1204. This "electronic light emitting device that performs automatic exposure adjustment in conjunction with a camera" described in Japanese Patent Publication No. 49-1204 can be used in combination with a camera to measure the distance to the subject determined by the camera's aperture value and distance measuring mechanism. This relates to an electronic light emitting device in which exposure is automatically adjusted by changing the amount of emitted light.

In other words, a capacitor that is charged by a DC power source, a discharge tube that is ignited and emits light by a trigger pulse that is generated when a synchronizing contact installed on the camera is opened, and a voltage detection variable resistor of the capacitor that is attached and connected to the capacitor. A detection circuit that detects the voltage of the capacitor and changes the voltage to be detected by changing the voltage, and a detection signal generated by the detection circuit causes the six-conductor switching element to conduct and short-circuit the capacitor. When the capacitor is rapidly discharged and the voltage drops and reaches the detection point regulated by the voltage detection variable resistor described above, the semiconductor switching element becomes non-conductive, and the photoelectric sensor installed on the camera side. A variable resistor that is inserted and connected to an exposure adjustment circuit for daylight photography consisting of an element, a meter, a variable resistor, etc. and works in conjunction with the 1lllll distance mechanism, a variable resistor that changes in conjunction with the aperture, and a variable resistor that changes in conjunction with the 11I11 distance mechanism. A composite resistor consisting of variable resistors that
It consists of an electric circuit that is connected so that the detection circuit operates as the voltage detection variable resistor described above by an electric switch that is closed in conjunction with the depression of the shutter push button, and the shutter push button is pressed for photographing. As a result, the electric switch is first closed, and the capacitor is discharged by the detection circuit and the semiconductor switching circuit until the voltage is regulated by the resistance value of the composite resistor, and the voltage rapidly drops, and the shutter button is pressed. Further pressing the shutter activates the shutter and closes the synchro contact, causing the discharge tube to emit light with a predetermined amount of light, and photographing with proper exposure is automatically performed.

[Problems to be Solved by the Invention] However, the technical means described in Japanese Patent Publication No. 1204/1984, which varies the amount of light emitted from the strobe itself based on subject distance information and thereby controls the exposure of the camera, is not applicable to electronic cameras. When applied to a strobe, the color temperature of the emitted light changes depending on the amount of light emitted by the strobe. Therefore, a problem arises in that the so-called white balance (hereinafter abbreviated as F1WB), which is adjusted so that a white subject is reproduced as white, changes.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an electronic camera that does not require readjusting the night balance even if exposure is controlled based on subject distance information.

[Means for Solving the Problems] The electronic camera of the present invention includes at least object distance information;
The present invention is characterized by having means for setting the charge accumulation time to the imaging water T based on reference data determined by strobe light emission characteristics of a predetermined amount of light emission.

[Function] The reference data in this electronic camera is the charge accumulation time to the image sensor that provides the optimum exposure to the image sensor based on the subject distance information and the strobe light emission characteristics of the predetermined amount of light emission. Proper exposure can be obtained by regulating the shutter speed of the camera using the above reference data.

[Example] Hereinafter, the electronic camera of the present invention will be specifically described with reference to the drawings. First, before explaining the present invention in detail, the basic concept of the present invention will be explained below.

When photographing with a strobe light using an electronic camera, the present invention fixes the aperture in advance and reads out the electronic shutter speed from a lookup table based on subject distance information obtained by firing the strobe at full capacity, thereby determining the optimum exposure. That's what you're trying to get. That is, the distance measuring mechanism (hereinafter referred to as AF
The shutter speed as a function of the subject distance information measured by the camera (abbreviated as ) and the amount of accumulated charge based on the subject light on the image sensor determined from the strobe light emission curve is stored in advance as reference data on a lookup table. ing. Therefore, the shutter speed data on the lookup table is read out by the system controller based on the subject distance information and the accumulated charge amount while exchanging signals with the system controller. This read shutter speed is supplied by the system controller to the image pickup element f via the drive circuit, and if the exposure of the electronic camera is thereby controlled as an element shutter, proper exposure will be achieved.

FIG. 1 is a block system diagram of an electronic camera showing an embodiment of the present invention.

In Fig. 1, subject light entering from a photographic lens 1 passes through an aperture 2 having a preset aperture value, part of the light is reflected by a half mirror 3 and guided to an optical element 4, and the rest The light passes through the half mirror 3 and is exclusively directed to the CCD image pickup device 6 operated by the COD drive circuit 9. As the shutter mechanism, an element shutter of the CCD image sensor 6 is used.

The charge conversion output of the photometric element 4 is integrated and photometered by a photometric circuit 7, and the photometric output is input to a system control circuit (hereinafter abbreviated as system controller) 8 consisting of a microcomputer.

The system controller 8 has the above-mentioned photometric element, All + optical circuit 7
Information regarding the illuminance of the subject, that is, −III
Based on the light output, it is determined whether or not it is necessary to cause the strobe 21 to emit light. If it is not necessary to cause the strobe 21 to emit light, use the -II+ optical element 4. The shutter speed is set by the system controller 8 with aperture priority so that the exposure is properly determined by the photometry circuit 7. Further, if it is necessary to cause the strobe 21 to emit light, the system controller 8 sends out a light emission control signal to the light emission control circuit 22.
This causes the strobe 21 to emit light. In this case, the above-mentioned light emission control of the strobe 21 provides only the control timing, and as a strobe,
It emits full light or a predetermined amount of light, which will be described later, that is, it emits constant light. In addition, photoelectric Q is accumulated by the clock pulse from the system controller 8.

The output of the CCD imaging device 6, which performs drive control for transfer, is led to the process circuit 10 and processed into an image signal, and then
recording circuit] 1. The output of the recording circuit 11 is sent to recording 71.1 in synchronization with the timing pulse from the system controller 8.
2 is supplied with an image signal of the subject on a recording medium 13 such as a high-pressure disk.
2 is a head drive circuit 14 controlled by the system controller 8 in which the head is fed in the radial direction of the recording medium 13; 3 is a motor drive circuit 15 controlled by the system controller 8;
is rotated at a predetermined speed.

The electronic still camera configured in this manner is further provided with a mode changeover switch 17, which can be used to change modes such as recording and playback, and when in recording mode, to perform rapid shooting (continuous shooting). You can set whether the shooting mode is 111 mode or not. Further, a quick-shot frame number setting switch 18 and a display section 19 are provided, and switch 1
The number of continuous shooting frames and the date set in step 8 are displayed on the display section 19.

The object distance information obtained by the AF sensor 23 is supplied via the ΔIII distance process circuit 24 to a lookup table 25 formed of a memory element, and the table data is read out, thereby performing two-way communication with the system controller 8. Exposure control information such as shutter speed and time is required.

In this embodiment, which eliminates such a configuration of fixed aperture and fixed strobe light emission, the means for manually determining the shutter speed at which proper exposure can be obtained using only subject distance information is shown in Figures 2 to 4 below. explain.

FIG. 2 is a characteristic diagram showing changes in strobe light emission power with respect to time t when the strobe 21 shown in FIG. 1 is made to emit light. In the figure, the solid line ρ1 represents the case when the strobe is driven with a fully charged main capacitor and starts emitting light, that is, the case is fully emitted, and the dotted line g6 represents the case when the main capacitor (not shown) is charged by a predetermined amount. The cases in which light emission starts are shown in each case. When you start emitting light from this predetermined amount of charge, for example, if you want to take continuous shots of a series of golf swings or the form of a running person as two still images at fixed time intervals under strobe light, the first photo will be taken. The main capacitor starts with a fully charged state, but after the second capacitor, it is not always possible to start with a fully charged state depending on the time interval, and the main capacitor starts with a level lower than the fully charged state, that is, with a predetermined amount of charge. It turns out. Therefore, as can be seen from FIG. 2, the dotted line g, which starts emitting light after a predetermined amount of charging, has a lower light emitting power than the solid line g1, which indicates full light emission.

Now, if time [1] is the starting point of exposure capture into the image sensor 6 (see Figure 1), the exposure to the allotropic T-6 is the integral sum of the subject light with respect to the elapsed time from time t1, that is, the charge This is the accumulated amount. If such a change in the amount of charge accumulation with respect to time t is plotted, a characteristic line diagram such as the curve shown by the solid line J22 in FIG. 3 is obtained. The curve Ω2 shown in FIG. 3 is obtained when the subject distance is a constant value, but as the subject distance changes, the characteristic diagram naturally changes.

FIG. 4 is a characteristic diagram showing temporal changes in the amount of charge accumulation when the subject distance is changed. In the figure, if the curve g3 is the change over time in the amount of charge accumulated in the image sensor when the object distance is L meters, then when the object distance is doubled to 2L meters, the amount of light reflected from the object and reaching the image sensor will be ,
Since it is inversely proportional to the square of the subject distance, that is, -/4, a characteristic diagram shown by curve g4 in FIG. 4 is obtained.

In other words, in FIG. 4, if the amount of charge accumulated when the subject distance is 2L meters at arbitrary time t2 is Q, then the amount of charge accumulated when the subject distance is L meters is 4Q. Furthermore, when the subject distance becomes shorter than L meter, the characteristic curve moves upward in FIG. 4, resulting in a characteristic diagram such as curve g5, for example.

Therefore, the amount of charge accumulated by the subject light irradiated to the image sensor is an appropriate value Q. The time t becomes as follows. That is,
Appropriate exposure amount Q on the vertical axis. If p7 is a dotted line drawn from the point parallel to the horizontal axis, the amount of charge volume is the appropriate exposure amount Q. When the subject distance is L meters, the time becomes the intersection t3 of the dotted line p and the curve p3, but when the subject distance is 2L meters, the time becomes the intersection t4 of the dotted line g and the curve g4. In other words, by changing the exposure time, that is, the shutter speed, appropriate exposure for various subject distances can be obtained.

Therefore, by adding subject distance information to the strobe light emission curve, it is possible to determine the shutter speed for obtaining proper exposure. Therefore, if the above is stored in memory as a data conversion table and the subject distance information is entered manually from outside, the shutter speed can be uniquely determined by reading out the table data. It is possible to adjust the light at any time.

By the way, as mentioned above, when shooting a single shot, the strobe is shot at full power, but when shooting a quick shot, the strobe is usually charged to a predetermined amount, so two data tables for single shooting and quick shooting are stored in memory. If you have it, you will be able to handle both single shooting mode and continuous shooting mode. In other words, the strobe light emission curve in the case of charging a predetermined amount without fully charging is the same as the second one above.
Since the curve becomes like curve II6 shown in the figure, a data table can be developed accordingly.

Furthermore, if the gain of the circuit system of the process circuit 10 shown in FIG.
Since o can be obtained, the charge accumulation time can be adjusted by increasing the gain. Normally, the exposure time when the gain is increased is shorter than when the gain is not increased, so the lookup table is uniquely defined and the system controller provides information on whether to increase the gain or not. If this is done, the shutter speed can be changed in the subsequent processing process using the gain up information.

As described above, according to this embodiment, the amount of light emitted by the strobe is constant, that is, there is no need for a light emission control circuit for the strobe itself, so that the strobe light can be adjusted at low cost. Further, since only the object distance information is used and the Δ or 1 light information is not used, it becomes possible to create an all-in-one sequence.

[Effects of the Invention] As described above, conventionally, exposure was controlled by changing the amount of light emitted by the strobe, so controlling the exposure would change the strobe dimming time, resulting in W B h < not being constant. , the WB had to be readjusted, but according to the present invention, the strobe dimming time is constant, so exposure control can be performed without having to think about the WB, which is a remarkable effect.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of an electronic camera showing an embodiment of the present invention. FIG. 2 is a characteristic diagram showing changes in the strobe light emission power with respect to time t in FIG. 1, and FIGS. Figure 4 is a characteristic diagram showing the change in the amount of charge accumulated in the CCD image sensor over time t in Figure 1 above. Figure 3 shows the case where the subject distance is constant, and Figure 4 shows the case where the subject distance is varied. It is a line diagram which shows each case. 6... CCD image sensor (image sensor) 8.
・・・・・・・・・Cisco

Claims (1)

[Claims] (1) An electronic camera characterized by having means for setting a charge accumulation time in an image sensor based on reference data determined by at least subject distance information and strobe light emission characteristics of a predetermined amount of light emission.