JP2004023442A - Image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup device in which a short return time and low power consumption are made compatible by driving a CCD and its driving circuit slowly while it is not necessary to utilize the output of the CCD such as when charging a stroboscope, during a menu mode, when reproducing an image or in the case of writing onto a card. <P>SOLUTION: In the image pickup device having an imaging device 12 for picking up an image of an object, a DSP 14 for processing an output of the imaging device 12 into a luminance signal and a chrominance signal and a clock generator 17 for varying a driving frequency of the imaging device 12, the image pickup device has the clock generator 17 for lowering the driving frequency of the imaging device when charging for the stroboscope, during the menu mode, when reproducing the image or in the case of writing onto the card. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image pickup device built in, for example, a digital still camera, a portable videophone terminal device, or a notebook PC with a built-in camera.
[0002]
[Prior art]
2. Description of the Related Art In an electronic device such as a recent digital still camera that captures and reproduces an image, there is an operation state in which an imaging device is not used even when the device is turned on. In particular, in portable devices, there are various modes for suppressing power consumption of devices that are not used to prevent waste of power, and various proposals have been made for power saving.
As an example, the technology disclosed in Japanese Patent Application Laid-Open No. 2001-238189 is disclosed in Japanese Patent Application Laid-Open No. 2001-238189, in order to realize a power-saving operation most suitable for a user's usage mode while eliminating a user's operation burden. The voltage of the power supply that supplies power to each processing block is made variable based on the state of the power supply detected by the voltage detection circuit, and any one of a plurality of processing blocks is processed according to the detected state of the power supply. By controlling the operation of the device by changing the frequency of the clock signal supplied from the plurality of clock sources corresponding to the processing block, or by changing the voltage value supplied from the corresponding plurality of voltage sources. It is disclosed to perform power operation control.
The above-described conventional example is an example of an apparatus for saving power. In an imaging apparatus such as a digital camera using a CCD as an image sensor, the following will describe power saving in more detail.
In general, in a digital camera, the CCD is not used at the time of charging the strobe, at the time of the menu mode, at the time of reproducing the image, and at the time of writing the card. Therefore, the power saving pattern shown in FIG. Is set. In this power saving pattern, each combination of on / off of the CCD power supply, driving or off of the CCD driving circuit, on / off / standby of the CDS / AD power supply, and the effect of the power consumption and the recovery time based on the combination are displayed. Among them, what is particularly remarkable is that the CCD power supply is off and the CCD drive circuit off is excellent in power saving.
For example, when the CCD power supply, the CCD drive circuit, and the CDS / AD power supply are turned off during the flash charging, a sequence example from the start of the flash charging to the output of the monitor is as shown in FIG. In FIG. 7, when the flash charging is completed, a CCD drive circuit power control signal is generated, and a 3.3 V system voltage is applied to the CCD drive circuit. Next, a DC 15 V control voltage is generated, and then a DC -7.5 V control signal is generated, and the 15 V and -7.5 V system voltages are supplied to the CCD. Thus, power is turned on to the CCD.
[0003]
[Problems to be solved by the invention]
However, in the above case, when the video output is viewed, the CCD output signal is generated from the second field even if the power is supplied to the CCD, and after that, about three fields (fields 2, 3, and 4 in FIG. 7) are generated. It is time to stabilize the CCD, and normal exposure is performed from the fifth field. That is, when the CCD power supply is turned off during flash charging, it takes several fields for normal exposure. The data photoelectrically converted from the CCD by the photodiode is read out at the next VD and output as field 5 of the CCD output signal, and appears on the monitor output from the fifth field (field 5) of the CCD output signal. become.
As described above, if the CCD drive circuit is turned off by turning off the CCD power supply while the strobe is being charged, power is saved, but the time required to restart the CCD power supply and the CCD drive circuit and the time required to stabilize the CCD again are obtained. Time is taken as the return time. In order to shorten this, it is necessary to always turn on the CCD power supply, but the current consumption increases.
In addition, in the menu mode shown in FIG. 8, the image reproduction shown in FIG. 9, and the card writing shown in FIG. FIG. 8 shows a sequence example in the case where the CCD power supply is turned on and the CCD driving circuit is in standby in the menu mode, and FIG. 9 shows a sequence example in the case where the CCD power supply is turned on and the CCD driving circuit is in standby in reproducing the image. FIG. 10 shows an example of a sequence in a case where the CCD power supply is turned on and the CCD driving circuit is set to the standby mode when writing a card.
The present invention provides a short recovery time and low power consumption by slowly driving a CCD and its driving circuit when it is not necessary to use the CCD output, such as when charging a strobe, in a menu mode, when reproducing an image, or when writing a card. It is an object of the present invention to provide an imaging device that is compatible with both.
[0004]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an image pickup device for picking up an image of a subject, a signal processing unit for processing an output of the image pickup device into a luminance signal and a color signal, and a frequency variable unit for changing a drive frequency of the image pickup device. Wherein the strobe charging is controlled by the frequency variable means so as to lower the driving frequency of the image sensor.
According to the present invention, by slowly driving the image pickup device at the time of flash charging, it is possible to reduce power consumption due to driving, and to shorten the stabilization time and the restoring time of the image pickup device by driving.
According to the second aspect of the present invention, an image sensor that images a subject, a signal processing unit that processes an output of the image sensor into a luminance signal and a color signal, a frequency variable unit that changes a driving frequency of the image sensor, And controlling the driving frequency of the image sensor by the frequency variable means during image reproduction.
According to the present invention, by slowly driving the imaging device during image reproduction, power consumption due to driving can be reduced, and the driving device can reduce a recovery time such as a stabilization time of the imaging device.
[0005]
According to the third aspect of the present invention, the imaging device for imaging a subject, a signal processing unit for processing an output of the imaging device into a luminance signal and a color signal, and a frequency varying unit for varying a driving frequency of the imaging device are provided. An image pickup apparatus comprising: a control unit that controls a drive frequency of the image pickup device to be reduced by the frequency variable unit when writing a card.
According to the present invention, by slowly driving the image sensor at the time of card writing, it is possible to reduce power consumption due to driving and to shorten the stabilization time and the restoring time of the image sensor by driving.
Furthermore, according to the invention of claim 4, an image sensor for imaging a subject, signal processing means for processing the output of the image sensor into a luminance signal and a color signal, and frequency varying means for varying the driving frequency of the image sensor An imaging apparatus comprising: a control unit configured to control a driving frequency of the imaging device to be reduced by the frequency variable unit in a menu mode.
According to the present invention, by slowly driving the imaging device in the menu mode, it is possible to reduce power consumption due to driving, and to shorten the stabilization time and the restoring time of the imaging device by driving.
According to a fifth aspect of the present invention, the frequency variable unit controls the image pickup device by lowering a clock frequency of a clock generator in accordance with a command from a CPU in order to lower the drive frequency. .
In the above invention, the means for lowering the drive frequency of the image sensor can be based on means for lowering the clock frequency of the clock generator in accordance with a command from the CPU.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an example of a digital camera as a configuration example of an imaging apparatus. In FIG. 1, a lens system 10, an aperture / shutter system 11, a CCD 12 serving as an image sensor, a front end for performing signal processing are shown. 13, a DSP (Digital Signal Processor) 14 for performing image processing, and a CPU 15.
A TG (Timing Generator) 16 for driving the CCD 12, a clock generator (CLK) for generating a clock for the TG 16 to synchronize the system with the DSP 14, and for supplying a clock for peripheral functions such as a USB in addition to a system clock Generator; Clock Generator 17. Here, the clock generator 17 has a multiplexer inside, and is configured to be able to change the output frequency under the control of the CPU.
Further, in FIG. 1, an SDRAM 18 connected to the DSP 14 for reading / writing the A / D-converted raw data and signal-processed data of the CCD output, an LCD 19 for displaying images for monitoring and reproduction and various information, a memory card 20 , An EEPROM 21 for storing data such as adjustment values, an external ranging element 22 for AF, and an operation switch 23.
Further, the front end 13 includes a CDS circuit 131 for correlated double sampling for removing image noise, an AGC circuit 132 for gain adjustment and correction, and an A / D converter 133 for digital signal conversion. Has a JPEG coder and a video DA converter.
The CPU 15 has a function of performing calculations such as AF (autofocus), AE (auto iris), and white balance, a function of setting parameters for the front end 13 and the DSP 14, a function of processing an operation from a user, have. Further, the DSP 14 generates an evaluation value such as AF, AE, and white balance (in the case of AF, for example, an integrated value for each frequency component of an image), and the CPU 15 calculates the evaluation value.
[0007]
In the above configuration, the output signal of the CCD 12 is A / D-converted via the CDS circuit 131 and the AGC circuit 132, and stored in the SDRAM 18 as the CCD 12 is arranged. The still image processing from the CCD 12 usually reads out the CCD data from the SDRAM 18 to generate a luminance signal and a color signal, performs JPEG processing, and records it on the memory card 20. The data converted from the Raw data of the CCD 12 to the display RGB signal or the YUV signal is output from the video DA converter inside the DSP 14 and displayed on the LCD 19.
When displaying the subject distance or the like, the CPU 15 draws the image on the SDRAM 18 via the DSP 14 and superimposes the image signal on the DSP 14. Also, the AF receives 1 / L (reciprocal of the distance to the subject) output from an external distance measuring element in analog form at the AD port of the CPU 15 and drives the optical system according to the distance to the subject.
Here, when the output frequency of the CLK generator 17 is output at a low frequency under the control of the CPU 15 when the CCD 12 is turned on during the flash charging, a sequence example from the flash charging to the output of the monitor is shown in FIG. As shown. That is, during strobe charging (the "L" period of strobe charging in FIG. 2), the frame rate is reduced as shown by VD (1 fps) in FIG. 2 by lowering the output frequency of the CLK generator 17. . Then, when the flash charging is completed, the frame rate of the CLK generator 17 is returned to a normal frame rate of, for example, 30 fps.
[0008]
In this case, since the CCD power supply is always turned on, the voltages of the 15V system and the -7.5V system are always applied to the CCD 12, and the CCD driving circuit is always in a conductive state capable of driving the CCD 12. In this sequence, since the CCD 12 is driven at a low speed even during flash charging, electronic shutter control for obtaining an appropriate signal amount is also performed. As a result, after charging is completed, a stable output signal as shown in FIG. 2 can be obtained without spending time (frames 2, 3, and 4 of VD in FIG. 7) for stabilizing the CCD 12 as in the conventional example in FIG. Obtained immediately. Then, the monitor output of the LCD 19 appears at an early stage (frame 0 in FIG. 2) after the strobe charge.
As described above, when the CCD driving circuit is driven at a low speed by turning on the CCD 12 during charging of the strobe, power is supplied to the CCD 12 and the CCD driving circuit without increasing power consumption much compared to the conventional example of FIG. And the time for stabilizing the CCD 12 can be reduced.
[0009]
FIG. 3 shows a specific sequence at the time of image reproduction, FIG. 4 shows a specific sequence at the time of card writing, and FIG. 5 shows a specific sequence in the menu mode. This is the same as the sequence during strobe charging shown.
Thus, the frequency reduction by the clock transmitter 17 can reduce the time from the charging of the strobe, the menu mode, the image reproduction, and the end of writing to the card to the normal operation without increasing the power consumption so much.
[0010]
【The invention's effect】
As described in the above embodiments, according to the present invention, an image sensor for imaging a subject, signal processing means for processing an output of the image sensor into a luminance signal and a color signal, and a drive frequency of the image sensor are variable. In the imaging device having means for causing the flash device to charge the strobe, at the time of menu mode, at the time of image reproduction, or at the time of writing a card, by having a means for reducing the drive frequency of the image sensor, by slowly driving the image sensor, In addition to reducing the power consumption due to the driving, the driving can reduce the recovery time such as the stabilization time of the image sensor, and can achieve both the short recovery time and low power consumption.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of an imaging apparatus.
FIG. 2 is a timing chart during flash charging.
FIG. 3 is a timing chart at the time of image reproduction.
FIG. 4 is a timing chart when writing a card.
FIG. 5 is a timing chart in a menu mode.
FIG. 6 is a power saving pattern diagram of a CCD.
FIG. 7 is a timing chart at the time of flash charging.
FIG. 8 is a timing chart in a menu mode.
FIG. 9 is a timing chart during image reproduction.
FIG. 10 is a timing chart when writing a card.
[Explanation of symbols]
12 CCD
13 Front end 14 DSP
15 CPU
16 TG
17 Clock generator.

Claims (5)

An image pickup apparatus comprising: an image pickup element for picking up an image of a subject; signal processing means for processing an output of the image pickup element into a luminance signal and a color signal; and frequency variable means for changing a drive frequency of the image pickup element.
An image pickup apparatus, wherein the driving of the image pickup device is controlled to be reduced by the frequency variable means when the strobe is charged. An image pickup apparatus comprising: an image pickup element for picking up an image of a subject; signal processing means for processing an output of the image pickup element into a luminance signal and a color signal; and frequency variable means for changing a drive frequency of the image pickup element.
An image pickup apparatus, characterized in that at the time of image reproduction, control is performed by the frequency variable means so as to lower the drive frequency of the image pickup device. An image pickup apparatus comprising: an image pickup element for picking up an image of a subject; signal processing means for processing an output of the image pickup element into a luminance signal and a color signal; and frequency variable means for changing a drive frequency of the image pickup element.
An image pickup apparatus, wherein, at the time of writing to a card, the frequency variable means controls the drive frequency of the image pickup device to be reduced. An image pickup apparatus comprising: an image pickup element for picking up an image of a subject; signal processing means for processing an output of the image pickup element into a luminance signal and a color signal; and frequency variable means for changing a drive frequency of the image pickup element.
An imaging apparatus, wherein in a menu mode, the frequency variable unit controls the drive frequency of the image sensor to decrease. 5. The apparatus according to claim 1, wherein the frequency varying unit performs control by lowering a clock frequency of a clock generator in accordance with a command from a CPU in order to lower a driving frequency of the image sensor. 6. An imaging device according to item 1.

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