JPH03154043A - Camera - Google Patents

Abstract

PURPOSE:To obtain the electronic flash light emission of an appropriate light quantity even if a diaphragm provided on a camera is a finite stage by controlling the flash time of a light emissing means in accordance with a distance to an object to be photographed, measured by a distance measuring means and a set diaphragm value, in a camera having an electronic flash light emitting means and a finite stage diaphragm. CONSTITUTION:When a distance to an object to be photographed is measured by a distance measuring circuit 12, an operator sets a diaphragm value by using a setting circuit 13. Also, in a control circuit 10, the diaphragm value is selected automatically in an electronic flash light emission mode, the electronic flash light emission quantity is calculated by using them, and the flash time for giving this light emission quantity is derived. Subsequently, this time is given to a light emission quantity control circuit 47, and also, a color temperature is determined, and in accordance with the color temperature, amplification degree data is read out of a RAM 11, and the gain of color balance setting circuits 25, 27 is adjusted. Also, in accordance with a selected diaphragm value and luminance from a photometric element 23, a shutter speed is determined, and when charging of a main capacitor 48 is completed, light is emitted only during the determined flash time by pushing a shutter release button.

Description

[Detailed Description of the Invention] Summary of the Invention In a camera equipped with a finite step aperture that adjusts the aperture value in multiple steps, the flash duration of a strobe is adjusted according to the set aperture value and the measured distance to the subject. do.

When the strobe flash time differs, the color temperature of the strobe light changes. In a camera equipped with a solid-state electronic imaging device, the flash duration of the strobe is determined according to the aperture value and the distance to the subject so that proper color balance adjustment is always performed under strobe light emission. Perform one-color balance adjustment according to the amount of light emitted.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera equipped with a strobe light emitting means.

Conventional technology and its problems Guide number Gn that practically represents the amount of strobe light emitted
is expressed as Gn-F-,77 using the effective F number (aperture value) and the distance g to the subject.

The guide number Gn is always constant since strobe light emission is usually caused by discharging charges charged to a constant voltage all at once. Since the distance g to the subject differs for each shot, the aperture value F is changed to satisfy the above equation. If the aperture provided in the camera can change the aperture value continuously, the above equation can be satisfied by changing the aperture value F. However, in a camera equipped with a finite step aperture, such as a turret aperture, in which the aperture value can only be set stepwise, it is not always possible to select an appropriate aperture value that satisfies the above equation. Therefore, it becomes impossible to obtain an appropriate amount of exposure when photographing with strobe light emission.

On the other hand, when the amount of light emitted by a strobe is adjusted by changing the flash duration, the following problem arises. Figure 5 shows
It shows the time change in the light emission intensity when all of the charge charged to a predetermined constant voltage is consumed for strobe light emission (this is called full light emission). On the other hand, Fig. 6 shows the luminescence intensity when the discharge time of the charge charged to the above-mentioned constant voltage is controlled so that the amount of light emitted per flash is 1/2 of the above-mentioned full light emission (this is called 172 light-emissions). It shows the change over time. Furthermore, FIG. 7 shows the emission spectrum of full emission and the emission spectrum of 1/2 emission.

While full-emission light has a reddish tinge, 1/2-emission light has a relatively large amount of short wavelength light, resulting in bluish light. The color temperature of the strobe light changes depending on the light emission time (flash time).

Still video cameras (electronic still cameras) and regular (movie) video cameras use CC as an imaging means.
A solid-state electronic imaging device such as D is used, and the video signal representing the subject image output from this solid-state electronic imaging device is sent to a recording medium such as a video disk or video tape after passing through a processing circuit such as color balance adjustment. recorded.

In conventional cameras, the color temperature during flash photography is fixed, and color balance is adjusted based on this color temperature. There is no problem with strobe devices that always fire only at full flash.

As mentioned above, when the flash duration is changed, the color temperature of the strobe flash differs, so if the color temperature is fixed, it is not possible to always adjust the color balance appropriately.

Summary of the Invention Purpose of the Invention The present invention provides a camera that can always emit strobe light with an appropriate amount of light even if the camera is equipped with a finite step aperture that can only change the aperture value in multiple steps. The purpose is to

Another object of the present invention is to provide a camera that can perform appropriate color balance adjustment even if the strobe flash time changes.

Structure and Effects of the Invention The first invention measures the distance to a subject in a camera equipped with a strobe light emitting means for projecting strobe light and a finite step aperture that adjusts the aperture value in a plurality of steps. 11
1 distance means, and means for controlling the flash duration of the strobe light emitting means according to the distance to the subject determined by the distance measuring means and the aperture value set in the finite step aperture. Features.

According to the first invention, the flash duration of the light emitting means is adjusted so that the amount of light emitted satisfies the above formula according to the measured distance to the subject and the set aperture value.
Even with a camera having a finite step diaphragm, such as a turret diaphragm, in which the aperture value can only be changed in steps, an appropriate amount of exposure can be obtained in strobe photography, and good photography can be achieved.

The second invention includes a strobe light emitting means for projecting strobe light, a means for adjusting the color balance of a color signal representing a subject image output from a solid-state electronic imaging device, and a distance measuring means for measuring the distance to the subject. , in a camera equipped with an aperture for controlling the amount of exposure, the amount of light emitted by the strobe light emitting means is determined according to the distance to the subject measured by the distance measuring means and the aperture value set in the aperture. and controlling the color balance adjustment means according to the determined light emission amount so that appropriate color balance adjustment is performed under strobe light emission of the light emission amount determined by the light emission amount determination means. It is characterized by having a means to do so.

According to the second invention, even if the color temperature of the strobe flash changes due to a change in the amount of light emitted per flash in a camera that controls the amount of light emitted from the strobe light, the color balance is adjusted appropriately accordingly, so that no data is recorded. The color tone of the color video signal is always adjusted to a constant value.

DESCRIPTION OF EMBODIMENTS An embodiment in which the present invention is applied to a still video camera will be described below.

FIG. 1 shows part of the electrical configuration of a still video camera.

The overall operation of the still video camera is controlled by the control device 10.
supervised by. This control device 10 is.

It consists of a CPU, memory, interface, etc.

The imaging optical system 20 includes an imaging lens system 21. for forming a subject image. It consists of a finite step diaphragm 22 and a shutter (as shown, the shutter can also be realized by an electronic shutter as described later). A photometric element 23 for measuring the illuminance of incident light is arranged in a part of the optical path of the optical system 20, and a signal representing the measured illuminance is input to the control device 10.

The diaphragm 22 is a so-called turret diaphragm, as its front view is shown in FIG. The diaphragm 22 includes a disk 22A, and the disk 22A has a hole 22A formed in the center thereof with internal teeth. A disk 22A is rotated around this hole 22A by a motor (not shown). Disk 22
A is provided with a plurality of openings 22B having a predetermined effective diameter around the hole 22A. The amount of incident light is limited by the size of these apertures 22B. The aperture 22 of this embodiment has four types of aperture values (for example, F2.8, F
4. F5.6.

F8) can be set. In the case of manual setting, the selected aperture 22B is positioned in accordance with the setting of the aperture value by the aperture value setting switch 13, and in accordance with the command from the control device 10 in the case of automatic setting, and is positioned at a position where the incident light passes. .

A solid-state imaging device 24 such as a CCD is arranged on the focal plane of the optical system 20, and this device has three primary colors, R
Outputs color signals for (red), G (green), and B (blue). The video data of the subject imaged on the imaging device 24 is read out as three-color video signals in synchronization with a synchronization signal given by the control device IO, and is read out as a three-color video signal by a preamplifier circuit (when shown), a variable gain amplification circuit ( color balance adjustment circuit)
25, 26, and 27, respectively, and input to the process matrix circuit 28. This circuit 28 generates a luminance signal Y and two color difference signals R-Y and B-Y, and these signals are then input to a recording signal processing circuit 29. This processing circuit 29 includes a line sequential circuit, a pre-emphasis circuit, an FM
The circuit 29 includes a modulation circuit 1 and a synthesis circuit, and an FM-modulated composite video signal is output from this circuit 29 and sent to a gate circuit 30 for recording control.

The still/video magnetic disk 31 is driven by a disk motor 3.
3 for a constant rotational speed, e.g. 3600r, p, s.

Rotationally driven. A magnetic head 32 for recording is in contact with this magnetic disk 31, and a phase detection pulse PG is applied to the core of the magnetic head 32 for each rotation of the magnetic disk 31.
A phase detector 35, which generates , is nearby. The magnetic head 32 is transported in the radial direction of the magnetic disk 31 by its transport mechanism and positioned on a predetermined track. Phase detection pulse PC is given to control device IO.

In the case of an electronic shutter system, the solid state electronic imaging device 24 has its signal charge accumulation time controlled by the controller 10. That is, the solid-state electronic imaging device 24
The shutter open time can be arbitrarily set by controlling the signal charge accumulation time in the light receiving section.

The still video camera is equipped with a power supply 1, which supplies operating voltage to each of the above-mentioned circuits including the control device 10.

Further, still video cameras include a strobe device to obtain an appropriate amount of exposure for indoor photography and other photography that requires auxiliary light. This strobe device is also driven by the power supply 1, but another power source may be used to supply the necessary power to the strobe device.

The strobe device includes a discharge tube (strobe) 48 and a discharge tube 4.
8 and a circuit for controlling the amount of light emitted per flash by the flash duration.

The voltage of the power supply 1 is boosted by the DC/DCC/type converter 41, and the main capacitor 43 is charged. capacitor 43
The charging voltage is detected by the voltage detection circuit 42 and notified to the control device 10. Due to this.

The control device 10 can know that charging of the main capacitor 43 is completed.

The DC/DCC/formula 41 also outputs a suitable voltage,
This charges the capacitor 50. capacitor 5
The charging voltage of 0 is supplied as the operating voltage of the control circuit 45.

The control circuit 45 drives the trigger circuit 4B in response to the strobe light emission command from the control circuit 10, and also provides the light emission amount control circuit 47 with a signal representing the timing of the start of the flash emission. 5CRI turns by driving the trigger circuit 46.
is turned on, and the charge stored in the main capacitor 43 is transferred to the discharge tube 4.
8, and strobe light emission begins.

In the light emission amount control circuit 47, a flash duration for controlling the amount of light emission is preset by a control device. The control circuit 47 measures the flash duration from the start of light emission.

When the flash time has elapsed, the control circuit 47 turns on SCR2. As a result, the charge on the main capacitor 43 is reduced to the resistor 49.
, 5CR2.

Since the SCR,1 is turned off, light emission from the discharge tube 48 is stopped. As described above, the amount of strobe light emitted by the strobe device is controlled by controlling the flash duration.

The control device 10 is equipped with RAM II. This R
AMII is for storing data for controlling the variable gain amplifier circuits 25 and 27 so that proper color balance adjustment is performed under the controlled light emission amount of the strobe device.

As described above, as the flash time of the strobe light emission becomes shorter, the strobe light emission becomes more bluish and the two-color temperature becomes higher. R.A.
As shown in FIG. 3, the MII includes data WBB and WB that control the color balance adjustment circuits 25 and 27 in accordance with the color temperature.
R is set.

RAM II also stores color temperature data (not shown) corresponding to the flash duration. Alternatively, the flash duration may be converted into color temperature according to the execution program of the control device 10. However, data WBB, corresponding to the flash duration,
WBR may also be stored. Color temperature of outdoor light 5
Based on the data WBB and WBR at 500K (assumed to be 1, 0) 1. A circuit 25 that adjusts the color signal R as the color temperature becomes higher (as the flash duration becomes shorter).
These data WBR and WBB are set so as to increase the amplification degree (data WBR) of the nine-color signal B and decrease the amplification degree (data WBB) of the circuit 27 that adjusts the nine-color signal B.

Color balance adjustment data WBR corresponding to a color temperature corresponding to a flash time corresponding to a light emission amount calculated by the control device 10 as described later (this flash time is given to the light emission amount control circuit 47 as described above); .

WBB is read from RAMII and applied to electronic volume circuit 14. The electronic volume circuit 14 outputs a voltage signal corresponding to the given data WBR, WBB, and the digital/analog (D/A) conversion circuit 15
Contains R and 15B. The D/A conversion circuit 15R converts the adjustment data WBR of the R signal into an analog signal.

The D/A conversion circuit 15B converts the B signal adjustment data WBB into an analog signal. The output analog signals of these D/A conversion circuits 15R and 15B are applied to variable gain amplifier circuits 25 and 27, respectively, so that the color balance of one color signal is adjusted.

FIG. 4 is a flowchart mainly showing the processing procedure of the control device IO regarding exposure control and strobe light emission.

The distance to the subject is measured by the distance measuring circuit 12 (step 51), and the aperture value set by the operator is input using the setting circuit 13. Alternatively, the control device 10 automatically selects the aperture value in the strobe light emission mode (step 52). Using these n1 determined distances and the set aperture value, the amount of strobe light emission is calculated according to the above formula, and the flash duration that provides this amount of light emission is derived. (Step 53). On the one hand, this flash duration is given to the light emission amount control circuit 47, and on the other hand, the color temperature is determined based on this flash time (or directly from the light emission amount).

Data WBR from RAMII according to this color temperature.

WBB is read out and the gains of the one-color balance setting circuits 25 and 27 are adjusted (step 54). On the other hand, the shutter speed is determined according to the selected aperture value and the brightness detected by the photometric element 23 (steps 81 and 82).

When the shirt release button is pressed after charging of the main capacitor 43 is completed, the strobe emits light for the determined flash duration and the shutter is opened for the time corresponding to the determined shutter speed. Then, exposure is performed (step 55). As a result, the video signal output from the solid-state electronic imaging device 24 passes through the previously adjusted color balance circuits 25 to 27, and a video signal having a hue matching the color temperature of the actual strobe light emission is recorded on the video floppy. (Step 5B)
.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the invention. FIG. 2 is a front view showing the aperture, and FIG. 3 shows an example of the contents stored in the RAM. FIG. 4 is a flowchart mainly showing the processing procedure of the control device regarding exposure control and strobe light emission. Figures 5 and 6 are graphs showing temporal changes in the light emission intensity of the strobe device. Figure 5 shows full flash, and Figure 6 shows 1.
/2 emission. FIG. 7 shows the emission spectrum of full emission and the emission spectrum of 1/2 emission. 10...Control device. 11...RAM. 12... Distance measurement circuit. 14...Electronic volume. 22...Aperture. 25-27...Variable gain amplifier circuit. 47... Light emission amount determination circuit. 48...discharge tube. Above Figure 2 F5.6 3rd cause

Claims (2)

[Claims] (1) In a camera equipped with a strobe light emitting unit that projects strobe light and a finite step aperture that adjusts the aperture value in multiple stages, a distance measuring unit that measures the distance to the subject and a distance that is measured by the distance measuring unit The camera is characterized by comprising means for controlling the flash duration of the strobe light emitting means in accordance with the distance to the subject and the aperture value set in the finite step aperture. (2) A strobe light emitting means for projecting strobe light, a means for adjusting the color balance of the color signal representing the subject image output from the solid-state electronic imaging device, a distance measuring means for measuring the distance to the subject, and an exposure amount. and a diaphragm for controlling the iris, the amount of light emitted by the strobe light emitting means is determined according to the distance to the subject measured by the distance measuring means and the aperture value set for the diaphragm. a determining means, and a strobe light having an amount of light determined by the light emitting amount determining means, so that appropriate color balance adjustment is performed.
A still video camera comprising: means for controlling the color balance adjustment means according to the determined amount of emitted light.