JPH06194726A - Camera and control method thereof - Google Patents

Abstract

PURPOSE:To prohibit the preliminary light emission at the time of daylight synchro photographing. CONSTITUTION:A distance from a main material to be photographed is measured by a distance measuring sensor 27. Circuits 15, 16, 17, 18, 19 are used to obtain an AV photometric value showing the mean brightness inside of a visual field and a SP photometric value for measuring the brightness of the main material to be photographed, and a difference of luminance between the main material to be photographed and the background is computed. In the case where a distance from the main material to be photographed is short and a computed difference of the luminance is,large, the daylight synchro photographing is performed. When the daylight synchro photographing is performed, since the surrounding of the main material to be photographed is bright and the red eye phenomenon is hard to be generated, preliminary light emission is prohibited.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a camera that uses a pre-emission light source by setting a pre-emission mode to perform pre-emission before shooting and a control method thereof.

[0002]

BACKGROUND ART Red-eye phenomenon often occurs when stroboscopic photography is performed when a subject is a human being. This red-eye phenomenon occurs when the pupil of the human eye opens and the blood vessels are imaged when it is dark.

For this reason, there is a camera in which pre-light emission is performed by using a light source such as a stroboscopic light emission device before photographing and the pupil of the eye is closed by the pre-light emission to prevent the red-eye phenomenon.

In the camera which prevents the red-eye phenomenon in this way, when the pre-light emission mode is set, the pre-light emission is always performed even when the pre-light emission is unnecessary, and the battery is wasted.

[0005]

DISCLOSURE OF THE INVENTION The present invention aims at performing pre-emission only when it is truly necessary.

According to the present invention, in a camera in which a pre-emission mode is set to perform pre-emission using a pre-emission light source, distance measuring means for measuring a distance to a main subject, a main subject and a background are measured. Based on the brightness difference measuring means for measuring the brightness difference, the distance to the main subject measured by the distance measuring means, and the brightness difference measured by the brightness difference measuring means, whether or not daytime synchronized photographing should be performed is determined. And a pre-light emission prohibiting means for prohibiting the pre-light emission by the pre-light emitting light source in response to the daytime synchronous photography determining means and the daytime synchronous photography determining means determining that the daytime synchronous photography should be performed. It is characterized by

In the camera control method of the present invention, the pre-light emission mode is set to measure the distance to the main subject in the camera that uses the pre-emission light source to perform the pre-emission before photographing, and the main subject and the background are measured. And measure the brightness difference between
Based on the measured distance to the main subject and the measured brightness difference, it is determined whether the daytime synchronized shooting should be performed. In response to the determination that the daytime synchronized shooting should be performed, the pre-light emission is performed. The feature is that pre-light emission by the light source is prohibited.

When the distance to the main subject is relatively short, the main subject is darker than the background, and the brightness difference between the main subject and the background is large, daytime synchronized photography is automatically performed.
The red-eye phenomenon is unlikely to occur even when the main subject is a human, when the surroundings of the main subject are bright, such as when the subject is backlit when the daytime synchronized shooting is performed.

According to the present invention, it is determined whether the daytime synchronized photographing should be performed, and when it is determined that the daytime synchronized photographing is performed, the pre-light emission by the pre-emission light source is prohibited. When the red-eye effect is unlikely to occur during daytime sync photography and pre-emission is unnecessary, pre-emission is prohibited, so it is possible to prevent battery waste and save power.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in which the present invention is applied to a digital still camera will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of a digital circuit of an embodiment of the present invention.
It is a block diagram which shows the electric constitution of a still camera.

The imaging optical system includes a diaphragm 2, an imaging lens 3,
And a CCD 4 as a solid-state electronic image sensor (image sensor). A mechanical shutter is provided if necessary, but generally the shutter function is achieved by an electronic shutter realized by the control of the CCD 4. The image pickup lens 3 forms a subject image on the CCD 4,
It is moved by the imaging lens driving device 25 controlled by the CPU 5 and positioned at the in-focus position.

The digital still camera is provided with a power switch 21 and a shutter release button 22, and a signal indicating the input of the power switch 21 and the depression of the shutter release button 22 is given to the CPU 5. Shutter release button 22 has a two-step stroke
This type is used for photometry and distance measurement in the first step of pressing, and the main shooting of the subject is performed in the second step of pressing.

The digital still camera includes a flash photographing setting switch 23 and a pre-flash setting switch 24, and a signal indicating that the switches 23 and 24 are pressed is given to the CPU 5. When the flash shooting setting switch 23 is pressed, flash shooting is performed using the flash light emitting device. By pressing the pre-flash setting switch 24, pre-flash is performed immediately before strobe flash (main flash) at the time of shooting, and the red-eye phenomenon is prevented. The pre-flash is the digital still
In the camera, the stroboscopic light emitting device is used, but the light source for pre-emission such as a light emitting diode may be provided to perform pre-emission without using the stroboscopic light emitting device.

The digital still camera is provided with a photometric sensor 26 for preliminary photometry, and photometric data is given to the CPU 5 and stored in a predetermined area of the memory 6. The CPU 5 controls at least one of the aperture value and the shutter speed on the basis of the photometric data obtained from the photometric sensor 26 so that the exposure amount to the CCD 4 falls within an appropriate range.

After the rough exposure amount adjustment based on such preliminary photometry, preliminary photographing is performed. By this preliminary photography, the photometric value is calculated and the precise exposure control is performed using the video signal obtained from the CCD 4. These high precision exposure controls will be described in detail later.

The digital still camera is provided with a distance measuring sensor 27 for distance measurement. Distance measuring data representing the distance to the object is given to the CPU 5 and stored in a predetermined area of the memory 6. . The CPU 5 is also a distance measuring sensor 27
The image pickup lens 3 is positioned at the in-focus position via the image pickup lens driving device 25 based on the distance measurement data from. CPU
5 further determines the amount of light emitted from the strobe device based on the distance to the subject and the aperture value, as will be described later.

The digital still camera is for indoor photography,
In addition, a strobe device is included so that an appropriate exposure amount can be obtained when auxiliary light is required. The digital still camera can be set to prohibit flash photography,
When the stroboscopic photography is prohibited, the stroboscopic photography is not performed, and when the stroboscopic photography is not prohibited, the strobe device is driven by the power supply 41.

The strobe device can perform pre-flashing before shooting, in addition to main flashing when shooting a subject. A pre-flash setting switch 24 is provided for pre-flash, but this digital still camera prohibits pre-flash during daytime sync photography.

Therefore, it is determined by the digital still camera whether daytime synchronization photography is performed.
This determination is made based on the distance to the object obtained by the distance measuring sensor 27 and the difference between the spot photometric value and the average photometric value obtained during precise exposure control. Controlled by the CPU 5 to perform daytime synchronized photography when the distance to the subject is relatively short, the background is brighter than the main subject, and the difference between the spot photometric value and the average photometric value is large (for example, 1.5 EV or more). .

The strobe device is a discharge tube (strobe) 45.
And a charging circuit 40 for charging the electric charge given to the discharge tube 45.
And a light emission quantity control circuit 30 for controlling the quantity of strobe light emission, and a stop circuit 46 for stopping the light emission of the discharge tube 45.

The voltage of the power supply 41 is boosted by the boosting circuit 42 and the main capacitor 43 is charged. The charging voltage of the main capacitor 43 is supplied to the CP via an appropriate voltage reducing circuit or voltage detecting circuit
It is detected by being applied to the A / D port of U5. This allows the CPU 5 to know that charging of the main capacitor 43 has been completed.

Since the CPU 5 can detect the charging voltage of the main capacitor 43, the charging voltage of the main capacitor 43 before the discharge tube 45 emits light and the main capacitor 43 after the discharge tube 45 emits light.
It is also possible to detect each of the charging voltage and the charging voltage and to calculate the amount of light emitted from the discharge tube 45 from the difference between these voltages.

The strobe light emission is performed by giving the strobe light emission command X ON to the trigger circuit 44. When the strobe light emission command X ON from the CPU 5 is given to the trigger circuit 44, the trigger circuit 44 is driven, the electric charge accumulated in the main capacitor 43 is discharged through the discharge tube 45, and strobe light emission starts.

The amount of strobe light emission is determined according to the distance to the subject. The CPU 5 creates emission light amount data. The emitted light amount control circuit 30 includes a D / A converter 31A
An electronic volume circuit (EVR) 31 including the above is included, and the light emission amount data output from the CPU 5 is EVR31.
Is converted to a voltage and output. Also stop circuit
A differential amplifier circuit 36 for providing a stop signal to 46 is included.

Further, the emitted light quantity control circuit 30 includes a reference power source 32.
And a capacitor 34 is included. The output voltage of the EVR 31 is given to the capacitor 34 via the resistor 33. A switch 35 for discharging the charge of the capacitor 34 is also provided. A reference power supply circuit is provided at the negative input terminal of the differential amplifier circuit 36.
The reference voltage output from 32 is applied, and the differential amplifier circuit 36
The terminal voltage of the capacitor 34 is applied to the positive input terminal of the.

The switch 35 is normally turned on, and CP
It is turned off when the flash emission command X of U5 is given. When the switch 35 is turned off, the EV
Charging of the capacitor 34 is started based on the voltage output from R31.

A voltage is output from the EVR31 and the switch 35
When is turned on, a predetermined charge is accumulated in the capacitor 34. When the terminal voltage of the capacitor 34 becomes equal to the reference voltage output from the reference power supply 32, a stop signal is output from the differential amplifier circuit 36 and is given to the stop circuit 46, so that the discharge tube 45 stops emitting light.

In the CCD 4, interlace photographing is performed by the substrate extraction pulse, the A field vertical transfer pulse, the B field vertical transfer pulse and the horizontal transfer pulse, and the A field and B field video signals (GRG) are obtained.
B color sequential signals) are alternately generated for each field period and sequentially read. The driving of the CCD 4 (imaging and reading of a video signal) is performed at least at the time of photographing, and for precision photometric processing and distance measuring processing prior thereto.

The image signals of the A field and the B field representing the subject image output from the CCD 4 are passed through a correlated double sampling circuit (CDS) 7 to a color separation circuit 8
Given to three primary colors, G (green), R (red) and B
It is separated into (blue) color signals.

The color signals G, R and B are given to a variable gain amplifier circuit (hereinafter referred to as GCA) 9. In Figure 1, GC
Although one block is shown as A9, GCA is actually provided for each of the R, G, and B signals. In the GCA 9, the gamma correction circuit is provided after correction of variations in light transmittance of the color filters provided in the CCD 4 between filters (hereinafter referred to as color filter variation correction) and white balance adjustment.
Given to 10. This is because the focusing control described later is performed with high accuracy. For the purpose of focusing control, at least color filter variation correction may be performed, but it is more preferable to perform white balance adjustment in addition to this.

The output color signals R, G, B of the GCA 9 are gradation-corrected by the gamma correction circuit 10 and input to the clamp and resampling circuit 11.

The clamp and resampling circuit 11 is
The three color signals R, G, B are clamped and re-converted into color sequential signals of GRGB ... Which match the color filter arrangement in the CCD 4. This color sequential signal is input to the gain control and blanking circuit 12. The gain control and blanking circuit 12 amplifies the color sequential signal to an appropriate level for recording and adds the blanking signal to it. The output signal of the gain control / blanking circuit 12 is applied to the A / D converter 14 to be digitally converted.

Before the main photographing, the precise photometric processing (exposure control) is performed as described above. The photometric processing is performed by utilizing the low frequency component of the video signal obtained from the CCD 4 by the preliminary photographing.

In order to take out the low frequency component of the video signal representing the image in the photometric area (described later) provided in the photographing area of the CCD 4 for the photometric processing, the Y _L synthesizing circuit 15,
A gate circuit 16, an integrating circuit 17, an amplifying circuit 18, and an A / D converter 19 are provided. The output data of the A / D converter 19 is given to the CPU 5.

The main photographing is performed after the photometric processing, the exposure control (control of the diaphragm and the shutter) based thereon, and the focusing control (positioning of the image pickup lens 3). CC by actual shooting
The video signals obtained from D4 are the above-mentioned circuits 7, 8, 9,
Input to A / D converter 14 via 10, 11 and 12
The data is converted into digital image data by the / D converter 14, processed by an image data processing circuit (not shown) such as Y / C separation and data compression, and then recorded on a recording medium such as a memory card. become.

The photometric processing (and exposure control based on it) prior to the main photographing will be described.

The photometric processing is performed by the Y _L combining circuit 15, as described above.
This is performed using the gate circuit 16, the integrating circuit 17, and the amplifying circuit 18. The Y _L synthesizing circuit 15 is supplied with the output color signals R, G, B of the GCA 9.

The CPU 3 outputs a window signal WIND for controlling the gate circuit 16 and a reset signal HLRST for resetting the integrating circuit 17. These signals WIND
The timing of HLRST will be described later.

The color signals R, G and B output from the GCA 9 are added by the Y _L synthesizing circuit 15 to generate a relatively low frequency luminance signal Y _L (hereinafter simply referred to as luminance signal Y _L ). The luminance signal Y _L passes through the gate circuit 16 while the window signal WIND is being applied in the required horizontal scanning period. The integrator circuit 17 has a reset signal HLRST.
Is reset when is given, and then the gate circuit 16
The luminance signal Y _L input from is integrated. The integrated signal of the integrator circuit 17 is amplified by the amplifier circuit 18 and then input to the A / D converter 14, which converts it into digital integrated data for photometry.

In the photometric processing of this embodiment, average photometry (hereinafter referred to as A
V metering) and spot metering (hereinafter referred to as SP metering) for measuring the brightness of the main subject in the field of view are performed. AV metering in A field, SP metering in B
Each is done in the field. SP metering is
This is useful when the brightness of the main subject and the background in the field of view are different, and it is necessary to set appropriate exposure conditions according to that.

Further, in this embodiment, the integration by the integration circuit 17 and the A / D conversion operation and the addition processing by the A / D converter 14 are alternately performed every horizontal scanning period.

FIG. 2 shows the AV photometric area and the SP photometric area set in the photographing area 50 of the CCD 4.
FIG. 3 is a time chart when AV photometry is performed,
FIG. 4 is a time chart when SP metering is performed.

The AV photometric area is basically set over almost the entire photographing area 50. In this embodiment, the AV photometric area is set for a period of 40 μs after the lapse of 16 μs from the trailing edge of the horizontal synchronizing signal HD (the start point of the horizontal scanning period) in the horizontal direction, and the 35th horizontal scanning in the vertical direction. 24th from the line
It is set up to the 6th horizontal scan line.

The SP photometric area is set as a small area at an arbitrary position within the photographing area 50. In this embodiment, the SP metering area is set at the center of the photographing area 50, and the horizontal direction is the 87th horizontal scanning line in the vertical direction during the period of 15 μs after 28.5 μs has elapsed from the fall of the horizontal synchronizing signal HD. From the 194th
It is set up to the second horizontal scan line.

The memory 6 attached to the CPU 5 is provided with a photometry area and a distance measurement area. The photometric area includes an AV photometric area data area and an SP photometric area data area.

When AV photometry is performed, integration is performed every other horizontal scanning line in the AV photometry area.
The above integration is performed every other horizontal scanning line for A / D conversion, reset and integration of the integration circuit, and data addition processing.

As shown in FIG. 3, in AV photometry, between the 34th horizontal scanning line and the 246th horizontal scanning line, the gate circuit 16 is provided with 16 μs after the fall of the horizontal synchronizing signal HD. A window signal WIND having a pulse width of 40 μs is applied. Then, the integration circuit 17 integrates the luminance signal Y _L and A of the integration signal in the horizontal scanning period subsequent to the horizontal scanning period in which this integration operation is performed.
/ D conversion, reset of integration circuit 17 and AV of memory 6
The addition of integrated data to the photometric area data area is alternately repeated for each horizontal scanning period.

When SP photometry is performed, the gate circuit 16 is provided between the 87th horizontal scanning line and the 194th horizontal scanning line as shown in FIG.
A window signal WIND having a pulse width of 15 μs, which rises 28.5 μs after the fall of the horizontal synchronizing signal HD, is applied.

Also in the SP photometry, the window signal WIND having a pulse width of 15 μs is given to the integrating circuit 17 and the luminance signal Y is obtained.
_When the integration of _L is performed, A of the integration signal is detected in the horizontal scanning period subsequent to the horizontal scanning period in which the integration operation is performed.
The / D conversion, the reset of the integrating circuit 17, and the addition of the integrated data to the SP photometric area data area of the memory 6 are performed.

When AV photometry is performed, the CPU 5 adds integrated data for one horizontal scanning line obtained on the basis of the window signal WIND having a pulse width of 40 μs in the AV photometry area data area for one field period by the procedure described later. Then, the AV photometric value is calculated.

When SP metering is performed, the CPU 5
The integrated data for one horizontal scanning line obtained based on the window signal WIND having a pulse width of 15 μs is added in the SP metering area data area for one field period by the procedure described later to calculate the SP metering value.

The brightness difference is detected from the AV photometric value and the SP photometric value thus obtained, and is used for the determination of the daytime synchronized photography.

In this digital still camera, focusing control is performed based on the distance measurement data from the distance measurement sensor 27. The lens driving device 25 is driven based on the distance information to the subject obtained from the distance measurement data, and is positioned at the in-focus position.

In general, when the image is out of focus and the image is blurred, the high frequency component contained in the video signal obtained from the CCD by photographing is small. When the image comes into focus, the high-frequency component of the video signal increases, and the high-frequency component contained in the video signal becomes maximum at the correctly focused position. Focusing control can also be performed based on such a fact.

In this case, a gate circuit for passing the output signal of the gain control and blanking circuit 12 for a certain period, a bandpass filter for extracting high frequency components, a detection circuit, an integration circuit and an amplification circuit are provided. Then, distance measurement data is calculated, and focusing control is performed based on this data.

FIG. 5 shows the aperture value F according to the distance to the subject.
No. and a guide number GNo. Showing the amount of light emitted from the strobe light emitting device. FIG. 6 is a table showing the correspondence between the guide number GNo., The light emission amount data EVR value and the output voltage of the EVR31. . Data of various tables shown in FIGS. 5 and 6 are stored in the memory of the CPU 5.

FIG. 7 is a flow chart showing the processing procedure of photographing.

When the power switch 21 is pushed down and the digital
When power is supplied to the still camera, it is monitored whether or not the shutter release button 22 has been pressed (step 61).

When the shutter release button 22 is depressed in the first step (YES in step 61), the distance measuring sensor
The distance to the subject is measured using 27 (step 6
2). The measured distance to the subject is stored in a predetermined storage area of the memory 6. Preliminary photometry using the photometric sensor 26 and precise photometry processing using the circuits 15, 16, 17, 18 and 19 are performed (step 63) to obtain EV photometric values and AV photometric values, respectively. These photometric values are stored in a predetermined storage area of the memory 6.

Subsequently, the lens driving device 25 is controlled so that the image pickup lens 3 is brought into the in-focus position based on the distance to the subject (step 64).

When the shutter release button 22 is pressed in the second step (YES in step 65), the photometric value (EV photometric value or AV photometric value) stored in the memory 6 is reached.
Based on this, it is determined whether or not stroboscopic photography should be performed (step 66). If the subject is not too dark (NO in step 66), the subject is photographed without firing the strobe (step 67). When the subject is dark (YES in step 66), the process shifts to flash photography.

In flash photography, the aperture value and guide number GNo. Shown in FIG. 4 are referred to, and the aperture value and guide number are determined according to the distance to the subject stored in the memory 6 respectively. Be (step
68). The aperture stop 2 is driven so that the aperture value becomes the determined aperture value (step 69). Further referring to FIG. 5, the EVR value is calculated from the determined guide number GNo. Further, the EV photometric value is subtracted from the AV photometric value, and the difference between these photometric values is detected (step 70).

Subsequently, it is judged whether or not the pre-light emission mode is set by the pre-light emission setting switch 24 (step 71).

If the pre-flash mode is set (YES in step 71), it is determined whether pre-flash is required.

When the subject is brighter than the background, the brightness difference between the background and the subject is large, and the subject is close to the subject, daytime synchronized photography using the strobe 45 is performed. In daytime synchronized photography, the subject's surroundings are bright, so the red-eye effect is unlikely to occur even if the subject is a human.

Therefore, based on the distance data representing the distance to the main subject stored in the memory 6 and the brightness difference detected in step 70, it is judged whether or not the daytime synchronized photographing is performed (step 72). ). When it is determined that the daytime sync photography is performed, the pre-flash is not performed and the waste of the battery 41 is prevented (step 72).
Then YES).

Subsequently, it is determined whether or not the red-eye phenomenon may occur. The red-eye phenomenon tends to occur when the eyes of the human eye are dark enough to open. Further, the smaller the angle between the subject and the strobe light emitting device and the subject and the imaging lens, in other words, the farther the subject is from, the more likely the red-eye phenomenon occurs.

Therefore, it is checked whether the subject brightness value is EV6 or less (step 73) and whether the distance to the subject is 1 m or more (step 74).

If the subject brightness value is EV6 or less (YES in step 73) and the distance to the subject is 1 m or more (YES in step 74), pre-light emission is performed (step 75). When daytime synchronized shooting is performed (YES in step 72), the subject brightness value is EV6 or more (NO in step 73), or the distance to the subject is 1
If it is equal to or less than m (NO in step 74), it is considered unlikely that the red-eye effect will occur. This prevents the battery from being wasted.

When photographing a subject, E5 is used as the light emission amount data from the CPU 5 based on the distance to the subject.
The VR value is determined and given to EVR31. As a result, strobe light is emitted (step 76), the shutter of the CCD 4 is controlled, and the subject is photographed (step 77).

The emitted light quantity data is given to the EVR 31, and is converted into an analog voltage value in the D / A converter 31A, and the stop circuit 46 is converted according to the magnitude of the analog voltage value.
Stops the flash firing (step 78).

When the photographing of the subject is completed, the video signal is read out from the CCD 4 (step 79), and the circuits 7, 8, 9,
Recording on the memory card is performed through steps 10, 11, 12 and 14 (step 80). Subsequently, the diaphragm 2 is returned to the home position (step 81).

When the shutter release button 22 is released (step 82), the digital still camera is in the initial state.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a digital still camera.

FIG. 2 shows a photometric area.

FIG. 3 is a time chart of AV photometric processing.

FIG. 4 is a time chart of SP photometric processing.

FIG. 5 shows a correspondence relationship between a distance to a subject, an aperture value, and a guide number.

FIG. 6 shows a correspondence relationship between a guide number and an EVR value.

FIG. 7 is a flowchart showing a procedure of a photographing process.

[Explanation of symbols]

5 CPU 15 Y _L synthesis circuit 16 Gate circuit 17 Integration circuit 18 Amplification circuit 19 A / D converter 23 Strobe setting switch 24 Pre-flash setting switch 27 Distance sensor 45 Strobe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location G03B 7/16 8102-2K 7/28 8102-2K (72) Inventor Hiroshi Shimatani Izumi, Asaka City, Saitama Prefecture 3-chome 11-46 Fuji Shashin Film Co., Ltd. (72) Inventor Izumi Miyake 3-chome 11-46 Izumi, Asaka City, Saitama Prefecture Fuji Shashin Film Co., Ltd.

Claims (2)

[Claims] 1. A camera for performing pre-emission before shooting using a pre-emission light source by setting a pre-emission mode, distance measuring means for measuring a distance to a main subject, and brightness difference between the main subject and background. It is determined whether or not daytime synchronized photography is to be performed based on the brightness difference measuring means for measuring the distance, the distance to the main subject measured by the distance measuring means, and the brightness difference measured by the brightness difference measuring means. A daytime synchro photographing determination means, and a pre-flashing prohibiting means for prohibiting pre-light emission by the pre-light emission source in response to the daytime synchro photographing determination means determining that the daytime synchro photographing should be performed, are provided. camera. 2. A camera that performs pre-emission before shooting using a pre-emission light source by setting a pre-emission mode, measures the distance to the main subject, and measures the brightness difference between the main subject and the background. Based on the measured distance to the main subject and the measured brightness difference, it is determined whether or not the daytime synchronized shooting should be performed. A camera control method that prohibits pre-emission by the light emission source.