JPH11331685A - Digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a diaphragm from being operated by means of the momentary change of luminance and to enable photometry stably by permitting the diaphragming value of the diaphragm to be larger than a present setting value when a state that the measured photometric value is larger than a stipulated value continues for a prescribed time at the time of monitoring a picked-up image. SOLUTION: When a main body power source is supplied, a mode becomes the monitoring one and the image of a subject is picked-up and displayed on a display part 122. CPU 121 checks the diaphragming value (F value) which is set at present in the monitoring mode. Moreover, it is judged whether the photometric value is larger than Ev 15. Then, the shutter speed of CCD 103 at the time of monitoring and the gain of an AGC amplifier 105 are calculated and set based on the photometric value which is obtained by executing photometry. When the state that the measured photometric value is larger than the first stipulated value (Ev 15) continues for the prescribed time, the diaphragming value of the diaphragm is made larger than the present setting value (diaphragming) so as to re-start photometry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera, and more particularly, to a digital camera having an aperture function.

[0002]

2. Description of the Related Art Recently, digital cameras capable of recording a captured image on a recording medium and displaying the captured image on a monitor have been put to practical use. Some of the digital cameras have a monitoring function of continuously displaying a captured image on a monitor as long as the power is turned on even in a case other than shooting.

[0003] As a method of performing AE control during monitoring, a quantization error of an electronic shutter is corrected by AGC or the like during monitoring, as in a "digital camera" described in Japanese Patent Application Laid-Open No. 10-84502. There is also known an aperture control apparatus that switches an aperture during monitoring based on an Ev diagram having hysteresis, such as an aperture control apparatus described in Japanese Patent Application Laid-Open No. 10-20358.

[0004]

However, in the "digital camera" described in Japanese Patent Laid-Open No. Hei 10-84502, smearing occurs when the CCD is irradiated with excessive light, and photometry is performed based on the luminance signal. In this case, there is a problem that the photometric accuracy deteriorates. In addition, Japanese Patent Application Laid-Open
In the “aperture control device” described in Japanese Patent No. 20358, the aperture change frequently occurs even if hunting does not occur unless hysteresis is increased for the aperture change.
In a system such as the "aperture control device" described in Japanese Patent Application Laid-Open No. 10-20358, there is a problem in that photographing is hindered by the time required for changing the aperture.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to provide a digital camera capable of performing stable photometry without operating the aperture due to a momentary change in luminance during monitoring.

[0006]

According to a first aspect of the present invention, there is provided a digital camera, comprising: an imaging unit that outputs a subject image input through an optical system as image data; A photometric unit that detects a photometric value based on a luminance signal and performs photometry; an aperture that limits the amount of light of the subject image input via the optical system; and an aperture value of the aperture based on the photometric value of the photometric unit. Aperture control means, and display means for displaying an image in accordance with the image data picked up by the image pickup means, and when monitoring the picked-up image on the display means, the photometric value measured If the state equal to or greater than the first specified value continues for a predetermined time,
The aperture value of the aperture is set to be larger than the current set value.

Further, a digital camera according to claim 2 is
2. The digital camera according to claim 1, further comprising: A when monitoring an image captured by the display means.
When the instruction to execute the F operation is detected, if the measured photometric value is equal to or less than the second specified value, the aperture value of the aperture is set to be smaller than the current set value.

The digital camera according to claim 3 is
2. The digital camera according to claim 1, further comprising: A when monitoring an image captured by the display means.
When an instruction to execute the F operation is detected, if the measured photometric value is equal to or more than a third specified value, the aperture value of the aperture is set to be larger than the current set value.

A digital camera according to claim 4 is
2. The digital camera according to claim 1, further comprising: A when monitoring an image captured by the display means.
When the instruction to execute the F operation is detected and the AF operation is executed, the aperture is opened.

A digital camera according to claim 5 is
In the digital camera according to the first aspect, during the change of the aperture value, the photometric operation is prohibited, the correction of the aperture change is performed by changing the shutter speed or the AGC, and then the photometry is restarted.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a digital camera according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a digital camera according to the present embodiment. In FIG. 1, reference numeral 100 denotes a digital camera. The digital camera 100 includes a lens system 101, a mechanical mechanism 102 including an aperture / filter unit, and the like.
CCD 103, CDS circuit 104, variable gain amplifier (A
GC amplifier) 105, A / D converter 106, IPP10
7, DCT108, coder 109, MCC110, D
RAM 111, PC card interface 112, CP
U121, display unit 122, operation unit 123, SG (control signal generation) unit 126, strobe device 127, battery 12
8, DC-DC converter 129, EEPROM 13
0, focus driver 131, pulse motor 132,
A zoom driver 133, a pulse motor 134, and a motor driver 135 are provided. A detachable PC card 150 is connected via the PC card interface 112.

The lens unit includes a mechanical mechanism 102 including a lens 101 system, an aperture and a filter section, and the mechanical shutter of the mechanical mechanism 102 performs simultaneous exposure of two fields. The lens system 101 is formed of, for example, a varifocal lens, and includes a focus lens system 101a and a zoom lens system 101b.

[0014] The aperture is turret-shaped,
By rotating the turret, F2.8, F5.6,
Four aperture values F9.5 and F16 can be set. The focus driver 131 drives the pulse motor 132 according to a control signal supplied from the CPU 121 to move the focus lens system 101a in the optical axis direction. The zoom driver 134 drives the pulse motor 132 according to a control signal supplied from the CPU 121 to move the zoom lens system 101b in the optical axis direction.
Further, the motor driver 135 drives the mechanical shutter of the mechanical mechanism 102 in accordance with the control signal supplied from the CPU 121, or sets the aperture value by rotating the turret-shaped aperture.

A CCD (Charge Coupled Device) 103 converts a subject image input via a lens unit into an electric signal (image data). The CDS (correlated double sampling) circuit 104 is a circuit for reducing noise in the CCD type image pickup device.

The AGC amplifier 105 corrects the level of the signal that has been correlated double-sampled by the CDS circuit 104. The gain of the AGC amplifier 105 is determined by the CPU 1
21 is set by using the data stored in the EEPROM 130 to set the setting data (control voltage) in the AGC amplifier 105 via a D / A converter built in the CPU 121. Further, the A / D converter 10
6 is a CCD 10 input via the AGC amplifier 105
3 to convert the analog image data into digital image data. That is, the output signal of the CCD 103 is the CDS
Via the circuit 104 and the AGC amplifier 105;
The D converter 105 converts the digital signal into a digital signal at an optimum sampling frequency (for example, an integer multiple of the subcarrier frequency of the NTSC signal).

The digital signal processor IPP
(Image Pre-Processor) 107, DCT (Discrete Cos)
ine Transform) 108 and coder (Huffman Enco
A der / Decoder) 109 performs various processing, correction, and data processing for image compression / decompression on the digital image data input from the A / D converter 106 by dividing the digital image data into color difference (Cb, Cr) and luminance (Y). Apply. The IPP (Image Pre-
The processor 107 integrates the luminance (Y) signal of the input image data to calculate an AE evaluation value, and
1 and the luminance (Y) of the input image data.
Calculates an AF evaluation value based on the high-frequency component of the signal
And outputs a video signal based on the color difference signal (Cb, Cr) and the luminance signal (Y).
Output to 2. The DCT 108 performs, for example, orthogonal transformation, which is a process of image compression / decompression based on JPEG, and JP
It performs Huffman encoding / decoding, etc., which is a process of image compression / decompression based on EG.

Further, an MCC (Memory Card Controlle)
An r) 110 temporarily stores the compressed image and records the image on the PC card 150 via the PC card interface 112 or reads the image from the PC card 150.

The CPU 121 uses a RAM (not shown) as a work area in accordance with a program stored in a ROM (not shown), and in accordance with an instruction from the operation unit 123 or an external operation instruction such as a remote controller (not shown). Controls all operations inside the camera. Specifically, the CPU 1
Reference numeral 21 controls an imaging operation, an automatic exposure (AE) operation, an automatic white balance (AWB) adjustment operation, an AF operation, an image recording operation, a reproduction operation, and the like. In the control of the AE operation, the CCD 103 is controlled based on the photometric value Ev measured.
The shutter speed and the aperture value of the aperture are set. More specifically, the CPU 121 controls the AE operation by:
A photometric value Ev is calculated based on the AE evaluation value obtained by integrating the luminance signal of the image data input from the IPP 107, and a corresponding appropriate shutter speed, aperture value, and the like are calculated.
Controlling the shutter speed of the CCD 103 and the motor driver 135 to set the aperture value of the aperture, etc., and set an appropriate exposure (AE).
I do.

A camera power source is a battery 128, for example, a NiCd, nickel hydrogen, lithium battery, or the like.
The signal is input to the C-DC converter 129 and supplied to the inside of the digital camera.

The display unit 122 is implemented by an LCD, an LED, an EL, or the like, and displays photographed digital image data, decompressed recorded image data, and the like. Operation unit 1
Reference numeral 23 includes a function selection key, a shutter release key (RL) for instructing recording of a captured image, and a key for externally performing various other settings. When the shutter release key (RL) is
1 is turned on to instruct execution of the AF operation. Also,
When the shutter release key (RL) is fully depressed, RL2 is turned on to instruct recording of an image. EEP
In the ROM 130, adjustment data and the like used when the CPU 121 controls the operation of the digital camera are written.

The digital camera 100 (CPU 1
21) a monitoring function (monitoring mode) for continuously displaying captured images on the display unit 122, and an image recording function (image recording mode) for recording image data obtained by imaging a subject on the PC card 150. And a reproduction function (reproduction mode) for displaying image data recorded on the PC card 150.

Next, the monitoring process (aperture process) will be described with reference to FIGS. FIG. 2 is a diagram showing an example of an Ev diagram used for the AE at the time of monitoring, FIG. 3 is a diagram showing an example of an Ev diagram used for the AE when the RL1 is turned on at the time of monitoring, and FIG. FIG. 5 is a diagram showing an example of an Ev diagram used for the AE at the time (when the RL2 is turned on at the time of monitoring), and FIG. 5 is a flowchart for explaining a process (aperture process) at the time of monitoring.

The Ev diagram generally shows a target exposure value Ev
(Aperture Value)
FIG. 6 is a diagram showing a combination of the exposure value Ev, the opening value AV, and the time value TV in these exposure adjustments: Ev = AV + TV. The luminance value Lv (Light Value) is a photometric value, and Ev = Lv for proper exposure. Here, 1 / T is equal to 2 raised to the power of TV, and FNo. Is 2 AV
There is a relationship that is equal to the power.

[Ev used for AE during monitoring]
Diagram] FIG. 2 is a diagram showing an example of an Ev diagram used for the AE at the time of monitoring. The characteristic data of the Ev diagram shown in FIG. 2 is converted into data and stored in a ROM (not shown) of the CPU 121. Is stored in Depending on the aperture value calculated from the photometric value Ev, F2.8 (open) or F2.8
5.6 is selected.

In FIG. 2, when Ev is in the range of 9 to 15, and when the aperture value F2.8 is selected, the shutter speed is changed in the range of 1/60 to 1/4000 seconds and photographing is performed. Is done. When the metering value Ev is in the range of 11 to 17, and the aperture F5.6 is selected, the shutter speed is changed in the range of 1/60 seconds to 1/4000 seconds, and shooting is performed.

The point at which the photometric value Ev increases and the aperture value changes from F2.8 to F5.6 is Ev = 15 and shutter speed = 1/4000 sec. That is, F
If Ev is 15 or more in 2.8, the time during which Ev is 15 or more is counted, and if the counted time is within a predetermined time, the shutter speed is reduced to a short time in order to lower the luminance. When shooting is performed with setting, and the counted time exceeds a predetermined time (for example, 1/400
If it is 0 second), the aperture is changed to F5.6 and the shutter speed is changed to 1/1000 second.

[Ev diagram used for AE during monitoring (RL1 on)] FIG. 3 shows an Ev diagram used for AE when RL1 is turned on during monitoring, and is shown in FIG. The characteristic data of the Ev diagram is converted into data and stored in a ROM (not shown) of the CPU 121. Depending on the aperture value calculated from the photometric value Ev, F
2.8 (open) or F5.6 is selected.

In FIG. 3, when the photometric value Ev is in the range of 9 to 15, and when the aperture value is F2.8, the shutter speed is in the range of 1/60 to 1/4000 seconds. Variable and photographed. Further, the photometric value Ev is 12-17.
When the aperture F5.6 is selected in the range, the shutter speed is changed in the range of 1/125 second to 1/4000 second, and the image is captured.

The point at which the photometric value Ev increases and the aperture value changes from F2.8 to F5.6 is Ev = 15, the shutter speed is 1/4000 second, the aperture value is F2.8, and the shutter speed is Even at 1/4000 second, the photometric value Ev is Ev15
If so, the aperture is changed to F5.6 and the shutter speed is changed to 1/1000 second. On the other hand, the point at which the luminance decreases and the aperture value is changed from F5.6 to F2.8 is that the aperture is F2.8 and the shutter speed is 1 even when the shutter speed is 1/125 second and Ev is 12 or less. / 500
Change to seconds.

[Ev Diagram Used for AE During Recording] FIG. 5 shows an Ev diagram used for AE during recording (when RL2 is turned on during monitoring). The characteristic data of the Ev diagram shown in FIG.
It is stored in the ROM (not shown) of U121. Depending on the aperture value calculated from the photometric value Ev, F2.8, F2.8
The shutter speed is determined by selecting from four values of 5.6, F9.5 and F16. At the time of this recording, a mechanical shutter is used. The mechanical shutter can be set within a range of 1 to 1/500 second.

[Processing at Monitoring (Aperture Processing)] Next, processing at the time of monitoring (aperture processing) will be described with reference to the flowchart shown in FIG. When the power of the main unit of the digital camera is turned on, it enters the monitoring mode,
The subject image is captured and displayed on the display unit 122. If the shutter release key (RL) is not pressed in the monitoring mode, the Ev of FIG.
A diagram is used.

In the monitoring mode, the CPU 121
Checks the currently set aperture value (F value),
It is determined whether or not the F value is set to F5.6 (step S1). If the F value is set to F5.6, the process proceeds to step S2, while the F value is set to F5.6. If not, the process moves to step S14.

In step S14, the photometric value Ev is set to Ev1.
It is determined whether or not the photometric value Ev is equal to or greater than Ev15. If the photometric value Ev is equal to or greater than Ev15, the process proceeds to step S2. If the photometric value Ev is equal to or greater than Ev15, the process proceeds to step S15. Is determined as a count, and it is determined whether or not a predetermined time has elapsed during which the photometric value Ev is equal to or greater than Ev15. The photometric value Ev is Ev15
If the predetermined time has not elapsed, the process proceeds to step S2. On the other hand, if the predetermined time has elapsed for the photometric value Ev to be equal to or greater than Ev15, the photometry is stopped (step S16). The F value is changed from F2.8 to F5.6.
And the shutter speed of the CCD 103 is shifted and set by the F value change (step S17). Thereafter, the photometry is restarted (step S18), and step S3 is performed.
Move to

In step S2, based on the photometric value Ev obtained by photometry, the CCD 103 during monitoring is used.
The shutter speed and the gain of the AGC amplifier 105 are calculated and set, and the process proceeds to step S3.

In the above-described processing, if the measured photometric value Ev is equal to or greater than the first specified value (Ev15) for a predetermined time during monitoring, the aperture value of the aperture is set to be smaller than the current set value. Since the photometry is restarted with a large aperture (the aperture is stopped down), that is, the aperture is not operated with a momentary change in luminance, so that stable photometry can be performed.

While the aperture is being changed, the photometric operation is prohibited.
When the metering is restarted, the aperture change is corrected by changing the shutter speed (the gain of the AGC amplifier 105 may be changed) and then restarted. Disturbance in photometry due to vignetting caused by driving of the diaphragm and fixed aperture can be prevented.

Subsequently, a shutter release key (RL)
A check is made. Shutter release key (RL)
It is checked whether the button has been pressed halfway (RL1 on) or fully pressed (RL2 on). In step S3, a check is performed to determine whether or not RL1 is on. If RL1 is not on, the process returns to step S1. On the other hand, if RL1 is on, step S4
Move to When RL1 is turned on during monitoring, the Ev diagram shown in FIG. 3 is used during AE control.

In step S4, the photometry value Ev is fixed (held), and photometry is stopped (step S5). Then,
The photometric value Ev is checked, and it is determined whether the photometric value Ev is equal to or less than Ev12 (step S6). When the photometric value Ev is equal to or less than Ev12, the current F value is F5.6.
Is set to F2.8, the F value is changed to F2.8 (step S7), and the process proceeds to step S8. On the other hand, if the photometric value Ev is not equal to or less than Ev12 in step S6, the process proceeds to step S19, and it is determined whether the photometric value Ev is equal to or greater than Ev15. If the photometric value Ev is equal to or greater than Ev15, the F value is changed to F5.6 if the current F value is set to F2.8 (step S).
7) Go to step 8. In step S8, an AF process is performed. The aperture is opened during AF.

In the above processing, when the execution of AF is instructed, if the photometric value Ev is brighter than the second specified value (Ev15), the aperture is stopped down without waiting for the specified time. In addition, appropriate photometry can be performed even in the case of high luminance. Also, when the execution of AF is instructed, the aperture is released when the photometric value Ev is darker than the third specified value (Ev12), so that appropriate photometry is possible even for a dark subject. .

When the AF is performed, the aperture is opened, so that the depth of field becomes shallow and the accuracy of distance measurement can be improved.

Subsequently, in step S9, it is checked whether or not RL2 is on. If RL2 is on, the process proceeds to step S10. When RL2 is turned on during monitoring, the Ev diagram shown in FIG. 4 is used during AE control. Step S
In step 10, the shutter speed of the mechanical shutter is calculated from the photometric value Ev, an image is captured at the calculated shutter speed of the mechanical shutter, and a recording process of storing the captured image in the PC card 150 is performed (step S10).

On the other hand, if RL2 is not turned on in step S9, the process moves to step S13 and RL1
It is determined whether or not is turned on. If RL1 is on, the process returns to step S9. If RL1 is not on, the process returns to step 12 to restart photometry and release the fixation (holding) of photometric value Ev. (Step S11), and returns to step S1.

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately changed without changing the gist of the invention.

[0045]

According to the digital camera of the present invention, an image pickup means for outputting a subject image input via an optical system as image data, and a photometry by detecting a photometric value based on a luminance signal of the image data. Metering means, an aperture for limiting the amount of light of the subject image input via the optical system, an aperture control means for setting the aperture value of the aperture based on the photometric value of the photometric means, and an image captured by the imaging means. Display means for displaying an image in accordance with the data, when monitoring the image picked up on the display means, if the photometric value measured is equal to or more than the first specified value for a predetermined time, Since the aperture value of the aperture is set to be larger than the current set value, it is possible to prevent the aperture from operating due to a momentary change in luminance during monitoring, and stable photometry can be performed.

According to the digital camera of the second aspect, in the digital camera of the first aspect, when monitoring the image photographed on the display means,
When the instruction to execute the AF operation is detected, if the measured photometric value is equal to or less than the second specified value, the aperture value of the aperture is set to be smaller than the current set value. Appropriate metering is possible when the subject becomes dark.

The digital camera according to claim 3 is
2. The digital camera according to claim 1, wherein, while monitoring an image photographed on the display means, if an instruction to execute an AF operation is further detected, the measured photometric value is equal to or greater than a third specified value. In the case of, the aperture value of the aperture is set to be larger than the current setting value, so that appropriate photometry can be performed when a high-luminance subject is obtained.

The digital camera according to claim 4 is
2. The digital camera according to claim 1, further comprising: detecting an instruction to execute an AF operation while monitoring an image photographed on the display unit;
Since the aperture is opened, the depth of field can be reduced, and the ranging accuracy can be improved.

The digital camera according to claim 5 is
In the digital camera according to the present invention, during the change of the aperture value, the photometric operation is prohibited, the correction of the aperture change is performed by changing the shutter speed or the AGC, and then the photometry is restarted. In addition, it is possible to prevent noise due to drive or power supply fluctuation due to aperture change and disturbance of photometry due to vignetting due to fixed aperture drive.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a digital camera according to an embodiment.

FIG. 2 is a diagram illustrating an example of an Ev diagram used for AE during monitoring.

FIG. 3 shows A when RL1 is turned on during monitoring.
It is a figure showing an example of an Ev diagram used for E.

FIG. 4 is a diagram illustrating an example of an Ev diagram used for AE during recording (when RL2 is turned on during monitoring).

FIG. 5 is a flowchart illustrating a process (aperture process) during monitoring.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Digital camera 101 Lens system 101 a Focus lens system 101 b Zoom lens system 102 Mechanical mechanism including autofocus 103 CCD (charge coupled device) 104 CDS (correlated double sampling) circuit 105 Variable gain amplifier (AGC amplifier) 106 A / D Converter 107 IPP (Image Pre-Processor) 108 DCT (Discrete Cosine Transform) 109 Coder (Huffman Encoder / Decoder) 110 MCC (Memory Card Controller) 111 RAM (Internal Memory) 112 PC Card Interface 121 CPU 122 Display Unit 123 Operation Unit 125 motor driver 126 SG unit 127 strobe 128 battery 129 DC-DC converter 130 EEPROM 131 focus driver 132 pulse motor 133 zoom driver 134 Sumota 135 motor driver 150 PC Card

Claims (5)

[Claims] An imaging unit that outputs a subject image input through an optical system as image data; a photometric unit that detects a photometric value based on a luminance signal of the image data and performs photometry; An aperture for limiting the amount of light of the subject image inputted by inputting the aperture; an aperture control unit for setting an aperture value of the aperture based on a photometric value of the photometric unit; and an image displayed according to image data captured by the imaging unit. And a monitor for monitoring the image picked up by the display when the photometric value obtained by the photometry is equal to or more than a first specified value for a predetermined time. A digital camera characterized in that the value is larger than a current set value. 2. The digital camera according to claim 1, wherein, while monitoring an image taken on said display means, if an instruction to execute an AF operation is further detected, the measured photometric value is used. A digital camera, wherein when the aperture value is equal to or less than a second prescribed value, the aperture value of the aperture is set smaller than a current setting value. 3. The digital camera according to claim 1, wherein, while monitoring an image taken on the display means, if an instruction to execute an AF operation is further detected, the measured photometric value is used. A digital camera, wherein, when the value is equal to or more than a third prescribed value, the aperture value of the aperture is set to be larger than a current setting value. 4. The digital camera according to claim 1, further comprising: detecting an instruction to execute an AF operation while monitoring an image photographed on said display means.
A digital camera, wherein the aperture is opened when an operation is performed. 5. The digital camera according to claim 1, wherein the metering operation is prohibited while the aperture value is being changed, and the change in the aperture is corrected by changing the shutter speed or the AGC, and thereafter, the metering is restarted. A digital camera.