CN1925563A

CN1925563A - Digital camera, storage medium and image processing device

Info

Publication number: CN1925563A
Application number: CNA2006101261678A
Authority: CN
Inventors: 细田润
Original assignee: Casio Computer Co Ltd
Current assignee: Casio Computer Co Ltd
Priority date: 2005-08-31
Filing date: 2006-08-29
Publication date: 2007-03-07
Anticipated expiration: 2026-08-29
Also published as: KR100817978B1; TW200731783A; JP2007097125A; TWI317602B; KR20070026059A; JP4254805B2; CN100456807C

Abstract

The photo image data is temporarily stored in the image buffer after taking a photo, then the data is stored in the recording media, therefore making the continuous shooting possible in a shorter interval. The operating frequency of CPU which controls the digital camera is set in a first operating frequency when the image buffer is in use and a second operating frequency lower than the first frequency is set when the image buffer is idle. The image buffer is provided to store continuously shooting images even without a necessary content. The power consumption is reduced by switching the other action speed into a lower one which is still running when the image buffer is going to stop.

Description

Digital camera, storage medium, and image processing apparatus

Technical Field

The present invention relates to a digital camera that records an image obtained by shooting as image data, a storage medium that stores an operating frequency setting program, and an image processing apparatus.

Background

Conventionally, in a digital camera, image data acquired at the time of shooting is temporarily stored in a buffer memory, and if the image data temporarily stored in the buffer memory reaches a predetermined unit, a predetermined compression process is performed on each image data of the predetermined unit, and the image data is converted into image data (JPEG data) in JPEG format in the buffer memory, and the JPEG data is transferred to a recording medium such as a memory card and written. Then, the JPEG data temporarily stored in the buffer memory is deleted from the buffer memory or subjected to overwriting processing upon completion of transfer to the recording medium or writing processing.

Further, it is known that a so-called digital camera capable of performing quick shooting and continuous shooting can be used in which, when a sufficient free space is stored in the buffer memory, if at least temporary storage into the buffer memory is completed, converted JPEG data is not deleted, and transfer to the next shooting is possible, storage processing of image data into the buffer memory is preferentially performed, and priority of transfer and write processing to the recording medium is lowered than that, and thus, the next shooting can be performed at shorter time intervals.

However, it is known that the portable information processing terminal increases the operating frequency (driving frequency) of a cpu (central processing unit) or mpu (micro Processor unit) which is a central processing unit when the load is heavy, decreases the operating frequency when the load is light, and changes the operating frequency according to the load amount to reduce power consumption. In other words, it is known that the operation speed, which is the amount of processing that can be handled by a CPU or the like in a unit time, is increased when the amount of processing to be handled is large and decreased when the amount of processing to be handled is small, and the power consumption is reduced by changing the operating frequency according to the amount of processing to be handled in the unit time (see, for example, japanese patent application laid-open No. 2002-366252).

However, in a conventional digital camera, the operating frequency of a CPU or the like is generally fixed. Therefore, when the vehicle is operated, the operating frequency is often higher than necessary, and in such a state, a battery (secondary battery) as a power source is uselessly consumed, which hinders the battery life, i.e., the continuous operating time, from being lengthened. The operating frequency is also changed in the digital camera in consideration of the relevant facts. In this case, if the operating frequency of the CPU or the like is increased during shooting (when image data is fetched into the buffer memory), and the operating frequency of the CPU or the like is decreased in a shooting standby state in which a through (through) image is displayed, it is considered that wasteful consumption of the battery can be effectively suppressed.

However, as described above, the storage processing of the image data into the buffer memory is performed with priority, and the priority of the transfer and write processing to the recording medium is lower than that, and when the processing is performed, there is a period in which the transfer and write processing to the recording medium is continued after the imaging standby state in which the through image is displayed. At this time, if the operating frequency of the CPU is lowered, when the snapshot and the continuous shooting are to be continuously performed, the image data previously captured is sequentially stored in the image buffer, and the empty capacity of the image buffer is eventually exhausted, so that the next shooting cannot be immediately performed.

That is, in order to enable continuous shooting at a shorter time interval, when the waiting time until the next shooting is reduced by temporarily storing image data acquired at the time of shooting in a buffer memory and writing the image data to a recording medium such as a memory card, the operation of writing the image data from the buffer memory to the recording medium is performed in parallel with the next shooting while waiting after the end of the shooting operation. Therefore, as described above, if the operating frequency in the shooting standby state is lowered, the processing speed is lowered before the end of writing of image data to the recording medium. Therefore, if the image capturing is continuously performed, the previous images are sequentially accumulated in the buffer memory, and the next image capturing cannot be immediately performed.

Disclosure of Invention

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a digital camera capable of continuous shooting at short time intervals such as continuous snapshots and continuous shots while prolonging the battery life, an operating frequency setting program used for realizing the digital camera, and an image processing apparatus capable of prolonging the battery life and continuously recording image data at short time intervals.

In order to solve the above-mentioned problems, the invention 1 is a digital camera for temporarily storing image data obtained by image capturing in an image buffer and then recording the image data in a recording medium from the image buffer, the digital camera comprising: a processing device for reading out the image data temporarily stored in the image buffer from the image buffer, recording the image data on the recording medium, and controlling each part of the camera; a determination unit that determines a state of the image buffer; a setting unit that sets an operating frequency of the processing device to an operating frequency corresponding to the state of the image buffer determined by the determining unit; the processing device operates according to the operating frequency set by the setting means.

Further, in invention 2, the determination means determines whether or not the image buffer is used; the setting means sets the operating frequency of the processing device to a first operating frequency when it is determined by the determining means that the image buffer is being used, and sets the operating frequency of the processing device to a second operating frequency lower than the operating frequency when it is determined by the determining means that the image buffer is not being used.

Further, in invention 3, the determination means determines a state of a free capacity of the image buffer; the setting means sets the operating frequency of the processing device to an operating frequency corresponding to the state of the free capacity determined by the determining means.

Further, in invention 4, the determination means determines the state of the free capacity of the image buffer by determining whether or not the free capacity of the image buffer is equal to or greater than a predetermined threshold; the setting unit sets the operating frequency of the processing device to a first operating frequency when the determination unit determines that the free capacity of the image buffer is not equal to or greater than a predetermined threshold, and sets the operating frequency of the processing device to a second operating frequency lower than the first operating frequency when the determination unit determines that the free capacity of the image buffer is equal to or greater than the predetermined threshold.

Further, in invention 5, the determination means includes: threshold value storage means for storing the threshold value when the determination means determines the state of the free capacity of the image buffer; a threshold value changing unit that changes the threshold value stored in the threshold value storage unit; the setting means sets the operating frequency of the processing device to an operating frequency corresponding to the state of the free capacity determined by the determining means, based on the threshold value changed by the threshold value changing means.

Further, in invention 6, the digital camera has a remaining power amount detecting part that detects a remaining power amount of the power supply battery; the determination criterion changing means changes the determination criterion based on the remaining power of the power supply battery detected by the remaining power detecting means.

Further, the invention 7 is a storage medium storing an operating frequency setting program for operating a computer provided in a digital camera for recording image data obtained by shooting onto a recording medium, as a determination means for determining a state of an image buffer for temporarily storing the image data and a setting means; the setting means reads out the image data temporarily stored in the image buffer, records the image data on the recording medium, and sets an operating frequency of a processing device that controls each section of the camera to an operating frequency corresponding to the state of the image buffer determined by the determining means.

Further, the present invention is an image processing apparatus which stores image data temporarily in a first storage means and then stores the image data in a second storage means from the first storage means, the image processing apparatus comprising: a processing device for reading out the image data temporarily stored in the first storage means, recording the image data in the second storage means, and controlling each part of the device; a determination unit that determines a state of the first storage unit; a setting unit that sets an operating frequency of the processing device to an operating frequency corresponding to the state of the image buffer determined by the determining unit; the processing device operates according to the operating frequency set by the setting means.

As described above, in the invention 1, even when the operating speed of the apparatus is lowered to extend the battery life, the operating speed of the apparatus can be set to a speed suitable for the recording operation to the recording medium of the image data when the image data is recorded. Therefore, it is possible to continuously take images at short intervals while prolonging the battery life.

In addition, in the invention 2, the operating frequency is not lowered during the recording of the image data on the recording medium, and after the recording of the image data is completed, the operating frequency is lowered to an operating frequency corresponding to an operation which is parallel to the recording operation of the image data and is continued after the recording of the image data is completed. Therefore, it is possible to continuously take images at short intervals while prolonging the battery life.

In addition, in the

inventions

3 and 4, the operating frequency can be lowered during recording of image data within a range that does not hinder the subsequent image data recording operation. Therefore, it is possible to continuously take images at short intervals while prolonging the battery life.

In the invention 5, the frequency of lowering the operating frequency during recording of image data can be changed within a range that does not hinder the subsequent image data recording operation. Therefore, it is possible to continue shooting at short intervals while further prolonging the battery life.

Further, in the invention 6, the frequency of lowering the operating frequency during recording of image data can be changed to an effective frequency corresponding to the remaining power of the power supply battery, within a range that does not hinder the subsequent image data recording operation. Therefore, it is possible to continue shooting at short intervals while further prolonging the battery life.

Further, in the invention 8, even when the operating speed of the apparatus is lowered to extend the battery life, the operating speed of the apparatus can be set to a speed suitable for a recording operation to a recording medium of image data when recording image data. Therefore, it is possible to continuously take images at short intervals while prolonging the battery life.

Drawings

The drawings are briefly described as follows.

Fig. 1 is a block diagram of a digital camera common to embodiments of the present invention.

Fig. 2 is a block diagram showing a task configuration of a program stored in a flash memory of the digital camera.

Fig. 3 is a diagram showing the operation contents and the change of the operating frequency of the REC mode in embodiment 1.

Fig. 4 is a program flow diagram showing the frequency change processing of the CPU of the REC main task.

Fig. 5 is a program flow diagram showing the processing contents of the CPU of the REC management task executed in parallel with the REC main task.

Fig. 6 is a transition diagram showing a change in the storage state of data in the image buffer.

Fig. 7 is a program flow chart showing the frequency changing process of the CPU of the REC main task of embodiment 2.

Fig. 8 is a program flow diagram showing the processing contents of the CPU of the REC management task executed in parallel with the REC main task.

Description of the symbols

1-a digital camera; 2-a CPU; 8-CCD: 12-an image processing section; 13-SDRAM; 14-liquid crystal monitor (LCD); 15-external memory; 16-a flash memory; 17-a microcomputer; 18-key input section; 19-a battery; 20-power control circuit.

Detailed Description

(example 1)

An embodiment of the present invention is described below with reference to the drawings. Fig. 1 is a block diagram showing an electrical configuration outline of a digital camera 1 common to the respective embodiments having general functions such as AE (automatic exposure control), AWB (automatic white balance control), and AF (automatic focus control).

The digital camera 1 is mainly configured by a CPU2 that performs overall system control, and includes the following components. In the figure, a lens unit (block)3 is a component of a drive mechanism of an optical system including a telescopic zoom lens and a focus lens, and a motor driver 5 for controlling the drive of a motor 4 as a drive source is connected to a CPU2 via a bus 6. In response to a control signal from the CPU2, the motor driver 5 drives the motor 4 to control movement corresponding to a change in the zoom magnification of the optical system, repetitive operation from the camera body at the time of power switching, and storage operation into the camera body. Further, an arc tube for emitting the photographing auxiliary light and a flash circuit 7 including the drive circuit and the like are connected to the bus 6 as necessary.

The digital camera 1 includes a CCD8 as an image pickup device. The CCD8 is driven by the vertical and horizontal drivers 10 in accordance with a Timing signal generated by a Timing Generator (TG) 9 in accordance with an instruction from the CPU2, and outputs an analog image signal corresponding to an optical image of the subject imaged by the optical system to the analog signal processing section 11. The analog signal processing unit 11 includes a CDS circuit for removing noise included in the output signal of the CCD8 by correlated double sampling, and an a/D converter for converting the noise-removed image signal into a digital signal, and outputs the digital-converted image signal to the image processing unit 12.

The image processing unit 12 performs processing such as blanking clip (pedestal clamp) on the input image signal, converts the signal into a luminance (Y) signal and a color difference (UV) signal, and performs digital signal processing such as automatic white balance, contour enhancement, and pixel interpolation. The YUV data converted by the image processing unit 12 is sequentially stored in the SDRAM13, and in the Recording (REC) mode for image capturing, every 1 frame worth of data (image data) is stored, converted into a video signal, and sent to the liquid crystal monitor (LCD)14 with the backlight 14a to be displayed as a through image.

When the image pickup process is performed by pressing the shutter button, the image data (YUV data) temporarily stored in the SDRAM13 is compressed by the CPU2, and once stored in a buffer (hereinafter referred to as an image buffer) in the SDRAM13, the image data is finally recorded in the external memory 15 as an image file of a predetermined format. In the present embodiment, the external memory 15 is a memory card that is connected via a card interface, not shown, and is freely removable from the camera body. The image file recorded in the external memory 15 is read out by the CPU2 in accordance with a user's selection operation in the playback mode, expanded as YUV data in the SDRAM13, and displayed on the liquid crystal monitor (LCD) 14.

The flash memory 16 is a program memory and is also a built-in image memory, and the flash memory 16 secures a program area, an image storage area storing a captured image (compressed image data) in a state where the external memory 15 (memory card) is not mounted.

The program area stores a program and data for causing the CPU2 to control the entire camera, and particularly in the present embodiment, stores a program for causing the CPU2, which is the processing device of the present invention, to function as a determination means, a setting means, and data necessary for the operation described later. In the program area, setting data on various functions of the digital camera 1 that are automatically set are stored in accordance with a setting operation based on the user in addition to the above-described programs and data.

The CPU2 is connected to the microcomputer 17, and the microcomputer 17 is connected to a key input unit 18 and a power supply control circuit 20 for supplying electric power of a rechargeable battery 19 such as a nickel-metal hydride battery to the above-mentioned units. The key input unit 18 is constituted by unillustrated switches such as a power button, a shutter button for instructing shooting, a zoom operation button, and a mode switching button. The shutter button has a so-called half shutter function that enables a user to perform a 2-stage operation such as a half-pressed position for notifying forenotice of shooting and a full-pressed (pressed) position for instructing an actual shooting operation.

Then, the microcomputer 17 stably scans the operation states of the switches of the key input unit 18 and transmits an operation signal corresponding to the content based on the switch operation for use to the CPU 2. The power supply control circuit 20 is further controlled to stably detect the voltage of the battery 19, and the detection result is sent to the CPU 2.

Fig. 2 is a diagram showing a task configuration of a program stored in the program area of the flash memory 16, and the CPU2 controls each unit of the digital camera 1 by executing these tasks according to a predetermined operating frequency (driving frequency). The outline of each task is as follows.

The ROOT task (T1) is a task for initializing hardware, loading programs and data, and initializing software after power-on,

the KEY task (T2) is a task for acquiring KEY operations such as a shutter button and battery remaining power information from the microcomputer 17,

the REC main task (T3) is the main task of the REC mode,

the REC management task (T4) is a task of controlling the main action of the REC mode,

the DISP management task (T5) is a task of controlling display via the DISP driver (d1),

the FILE management task (T6) is a task of controlling access to the FILE system via the FILE driver (d2),

the IMAGE task (T7) is a task of controlling the CCD8 and processing IMAGE data from the CCD8,

the LENS task (T8) is a task of performing control of the LENS part 3,

the MEASURE task (T9) is a task of performing AE/AWB/AF processing.

The OS service T0 is an operating system that manages the entire system including memory management.

Next, the operation of the digital camera 1 configured as described above according to the present invention will be described. When the REC mode is set, the digital camera 1 performs the operation shown in fig. 3, and the life of the battery 19, that is, the continuous operating time is prolonged during the time, so as described later, the operating frequency of the CPU2, that is, the operating speed of the CPU2, which is the amount of processing that can be handled by the CPU2 per unit time, is appropriately changed.

That is, fig. 3 is a diagram showing the operation content of the digital camera 1 in the REC mode and the change in the operating frequency of the CPU 2. In the REC through state (1) for preparation for shooting after the setting of the REC mode, the digital camera 1 performs only display of the captured image and AE/AWB processing, and the amount of processing that the CPU2 should handle per unit time is small, and a large load is not generated in the CPU2, so the operating frequency of the CPU2 is a low operating frequency (in the present embodiment, f is 32 MHz). In the half-shutter state (2) in which the shutter key is half-pressed thereafter, determination of AE/AWB and AF processing are performed. Since this processing is to be performed in as short a time as possible, the operation speed of the CPU2 is increased by switching the operation frequency of the CPU2 to a high operation frequency (in this embodiment, f is 81 MHz). In the locked state (3) in which the shutter key is held in the half-pressed state, only the REC through display is performed in the fixed AE/AWB state, as in the REC through state (1), and therefore, the amount of processing to be handled by the CPU2 per unit time is small, and a high operation speed is not required, and therefore, the operating frequency of the CPU2 is a low operating frequency.

Then, if the shutter is fully pressed, the shooting process (4) is entered. Here, if there is a flash operation, flash emission processing, processing for converting the electric charge from the CCD8 into digital data by the analog signal processing section 11, processing for transferring digital data, and processing for converting RGB format data into YUV data and JPEG are performed. In this case, since the amount of processing to be handled by the CPU2 per unit time is increased, the processing speed is high, and a high-speed operating frequency at which the operating speed of the CPU2 is increased is selected.

The image data converted into JPEG format is then stored in an image buffer in the SDRAM13, and recording is started in an external memory (memory card) 15. In addition, in the use (5) of the buffer at this time, in parallel with this, the display processing of the captured image toward the REC through state (6) of the next shooting is performed. Then, regardless of the amount of processing that the CPU2 should handle per unit time, the operating frequency of the CPU2 is maintained at a high speed until the recording of the image data stored in the image buffer into the external memory (memory card) 15 is completed. Here, the half-press operation of the shutter release button is possible only in the REC through state, and the full-press operation of the shutter release button is possible only in the AE/AF lock state.

The above operation is realized by executing the REC main task (T3) and the REC management task (T4) shown in fig. 2 in accordance with the setting of the REC mode. The following describes specific processing contents of the CPU2 when each task is executed.

Fig. 4 is a program flowchart showing the operating frequency changing process of the CPU2 in the REC main task (T3). In the related processing, the CPU2 receives information from tasks other than the ROOT task (T1) at any time while starting the processing (step SA1), and determines the content if any information is received (step SA 2). Then, when receiving information indicating that the shutter button is half-pressed from the KEY task (T2), if the operating frequency of the user is low speed (32MHz) (YES in step SA 3), the operating frequency is switched to high speed (81MHz) (step SA4), and then half-processing execution information is transmitted to the REC management task (T4) (step SA5), whereas if the operating frequency of the user is low speed (32MHz) (NO in step SA 3), the operating frequency is not switched, and then half-processing execution information is immediately transmitted to the REC management task (T4) (step SA 5).

When receiving information indicating that the shutter button is fully pressed from the KEY task (T2), if the operating frequency of the user is low (32MHz) (YES in step SA 6), the user switches the operating frequency to high (81MHz) (step SA7), and then transmits shooting processing execution information to the REC management task (T4) (step SA 8). In contrast, if the own operating frequency is low speed (32MHz) (NO in step SA 6), the switching of the operating frequency is not performed, and photographing process execution information is immediately transmitted to the REC management task (T4) (step SA 8).

When receiving information indicating that the image buffer is empty (information indicating that recording of all image data stored in the image buffer to the external memory 15) from the REC main task (T3), the half processing (AF/AE) is not being executed, that is, only after transmitting the half processing execution information to the REC management task (T4) in step SA5, and only when not receiving the half processing execution information from the REC management task (T4) (NO in step SA 9), the operating frequency of the REC main task is switched to the low speed (32MHz) (step SA 10).

When the half-process execution information is received from the REC management task (T4), the image buffer is not being used, that is, when the shooting process execution information is transmitted to the REC management task (T4) in step SA8, the operating frequency of the device is switched to the low speed (32MHz) only when the information indicating that the image buffer is empty is not received from the REC management task (T4) (NO in step SA 11) (step SA 10). Thereafter, returning to step SA1, reception of information is awaited, and the process described is repeated.

Fig. 5 is a program flow chart showing the processing contents of the CPU2 of the REC management task (T4) executed in parallel (time-sharing) with the processing. In the case of the above processing, the CPU2 first initializes a count variable Nb indicating the number of buffers (step SB1), receives information from tasks other than the ROOT task (T1) as needed (step SB2), and determines the content of the received information (step SB 3).

Then, if the half-process execution information is received from the REC main task (T3), the half-process composed of the AE/AWB decision and the AF process is executed (step SB 4). Then, at the time of processing end, the half-processing end information is transmitted to the REC main task (T3) (step SB5), and the process returns to step SB2 to wait for the reception of the information.

Further, if the photographing process (photographing process execution) information is received from the REC main task (T3), an image buffer is obtained in the SDRAM13 (step SB6), and the count variable Nb is counted (step SB 7). After the photographing process is executed (step SB8), the JPEG recording process is instructed to the FILE management task (T6) (step SB9), and the process returns to step SB2 to wait for information to be received. The photographing process is a process before image data (JPEG data) converted into the JPEG format is stored in the image buffer, and the JPEG recording process is a process of recording the JPEG data stored in the image buffer in the external memory 15.

After receiving the information from the FILE management task (T6), when the content thereof is the information that the JPEG recording process is ended, an image buffer, that is, an image part of 1 is opened (step SB11), and after counting down the count variable Nb (step SB12), it is examined whether the count variable Nb is "0". Here, if the count variable Nb is "0" (YES in step SB 13), the image buffer is empty, so it is notified to the REC main task (T3) (step SB 14). That is, in this embodiment, even when the image data (JPEG data) is actually left in the image buffer, the image buffer is notified as empty at the time when the JPEG recording process is completed. Further, if the count variable Nb is not "0" (NO in step SB 13), it returns to step SB 2. The same process is then repeated.

In the above-described processing, after the REC main task (T3) transmits the photographing processing execution information to the REC management task (T4), the state until the REC management task (T4) receives the information indicating that the image buffer is empty is determined as the buffer being used, but the REC main task (T4) transmits the information indicating the image buffer at the time when the JPEG data starts to be stored in the image buffer to the REC main task (T3), and the REC main task (T3) may determine the state from the time when the JPEG data is stored in the image buffer to the time when the JPEG data is read out, as shown in fig. 3, as the buffer being used.

Fig. 6(1) to (5) are transition diagrams showing changes in the storage state of the data in the image buffer when continuous shooting (continuous shooting) is performed while repeating the above-described processing of fig. 4 and 5. In the figure, solid-line arrows indicate the storage area of JPEG data written to the external memory 15, and dotted-line arrows indicate the storage area of JPEG data written to the external memory 15 last time.

Here, in the present embodiment, in the REC mode, when JPEG data is present in the image buffer, that is, before the end of writing of JPEG data into the external memory 15, the operating frequency of the CPU2 is always set to high speed (81MHz), so that the operating speed of the CPU2 is high, and the data writing processing speed to the external memory 15 is high. Therefore, even if the image buffer does not have a capacity larger than necessary, a plurality of images (in the figure, the state of reaching the fourth image) can be continuously captured without interruption by using the image buffer.

After the JPEG data is written into the external memory 15, the operating frequency of the CPU2 is switched to a low speed (32 MHz). Therefore, the display processing of the captured image, which is the processing toward the REC through state in the next shot, is performed in parallel with the writing operation (recording operation) of the JPEG data shot before, and is continued even after the writing is completed, and when continuous shooting is not performed, the device operates at a low speed from the midway, so that power consumption can be reduced. Therefore, it is possible to continue shooting in a short time such as continuous snapshot or continuous shooting while extending the battery life.

(example 2)

Next, embodiment 2 of the present invention is explained. In the present embodiment, in the above-described digital camera 1, the CPU2 executes the REC main task (T3) and the REC management task (T4) having different contents from those of embodiment 1 in accordance with the setting of the REC mode, and the CPU2 functions as the determination means, the setting means, the threshold changing means, and the remaining power detecting means of the present invention. If a difference from embodiment 1 is described, in embodiment 1, the high-speed operation is performed without fail when the image buffer is used, that is, when JPEG data whose recording to the external memory 15 is not completed is slightly left in the image buffer, but in this embodiment, the operation frequency is switched between the high-speed operation and the low-speed operation in accordance with the amount of use (or the free capacity) in addition to the presence or absence of the use of the image buffer. The following describes specific processing contents of the CPU 2.

Fig. 7 is a program flowchart showing the frequency change processing of the CPU2 of the REC main task (T3). In the present embodiment, the CPU2 receives information from tasks other than the ROOT task (T1) at any time while starting processing (step SC1), and if any information is received, determines the content thereof (step SC 2).

Then, when receiving information indicating that the shutter button is half-pressed from the KEY task (T2), if the operating frequency of the user is low speed (32MHz) (YES in step SC 3), the operating frequency is switched to high speed (81MHz) (step SC4), and then half-processing execution information is transmitted to the REC management task (T4) (step SC5), and if the operating frequency of the user is not low speed (32MHz) (NO in step SC 3), half-processing execution information is immediately transmitted to the REC management task (T4) (step SC5) without switching the operating frequency.

When receiving information indicating that the shutter button is fully pressed from the KEY task (T2), if the operating frequency of the user is low (32MHz) (YES in step SC 3), the user switches the operating frequency to high (81MHz) (step SC7), and then transmits shooting processing execution information to the REC management task (T4) (step SC 8). On the contrary, if the own operating frequency is not the low speed (32MHz) (NO in step SC 6), the shooting process execution information is sent to the REC management task (T4) immediately without switching the operating frequency (step SC 8). Here, the same as in embodiment 1 is applied.

In the present embodiment, when the information of the buffer FULL is transmitted from the REC management task (T4), the operating frequency is switched to the high speed (81MHz) only when the operating frequency of the self is the low speed (32MHz) (YES in step SC 9) (step SC 10). The buffer FULL information is information indicating that the amount of use of the image buffer is large, and is transmitted when processing is urgently necessary.

When the imaging processing end information or the half processing (AF/AE) end information is transmitted from the REC management task (T4), if the current time is not the buffer FULL (the amount of used image buffer is large) state, that is, if the buffer EMPTY information indicating that the amount of used image buffer is small is received from the REC management task (T4), the operating frequency is switched to the low speed (32MHz) (step SC12) if the buffer FULL information is not received (NO in step SC 1).

Further, when the buffer EMPTY information is transmitted from the REC management task (T4), the half processing or the photographing processing is not being performed at this time (NO in step SC 13), and only when the operating frequency is high speed (81MHz) (YES in step SC 14), the operating frequency is switched to low speed (32MHz) (step SC 12). Thereafter, returning to step SC1, reception of the message is awaited, and the process described is repeated.

Fig. 8 is a program flow chart showing the processing contents of the CPU2 of the REC management task (T4) executed in parallel (time-sharing) with the processing. In the present embodiment, the CPU2 first initializes a variable Sb indicating the free capacity of the image buffer, and sets a variable Sth, which is a criterion for determining whether the amount of use of the image buffer is large or small, to a predetermined initial value Sth0 (step SD 1). Then, information from tasks other than the ROOT task (T1) is received as needed (step SD2), and the content of the received information is determined (step SD 3).

Then, if the half-process execution information is received from the REC main task (T3), the half-process composed of the decision of AE/AWB and the AF process is executed (step SD 4). Then, at the time of processing completion, the half-processing completion information is transmitted to the REC main task (T3) (step SD5), and the process returns to step SD2 to wait for the reception of the information.

Further, if the photographing processing (photographing processing execution) information is received from the REC main task (T3), an image buffer is obtained in the SDRAM13, and the spare capacity Sb is retrieved (step SD 6). Subsequently, when the shooting process is executed (step SD7), the execution of the JPEG recording process is instructed to the FILE management task (T6) (step SD8), and the shooting end information is transmitted to the REC main task (T3) (step SD 9). When the free capacity Sb at this time is smaller than the determination criterion Sth (YES in step SD 10), it is determined that the image buffer usage is large (the free capacity is small), and the buffer FULL information is transmitted to the REC main task (T3) (step SD 11). Accordingly, as described above, the operating frequency is switched to the high speed (81MHz) by the REC main task (T3). On the other hand, if the free capacity Sb is equal to or larger than the determination criterion Sth (NO in step SD 10), the process returns to step SD2 as it is, and waits for reception of information.

When the information is finally received from the FILE management task (T6) and the content thereof is JPEG recording end information, an image buffer, that is, an area of the 1-image part is opened, and the free space Sb is acquired at that time (step SD 12). If the free space Sb is equal to or larger than the decision criterion Sth (YES in step SD 13), it is judged that the free space of the image buffer is large (the amount of use is small), the buffer EMPTY information is transmitted to the REC main task (T3) (step SD14), and the process returns to step SD2 to wait for the reception of the information. Accordingly, as described above, the operating frequency is switched to the low speed (32MHz) by the REC main task (T3). On the other hand, if the free capacity Sb is smaller than the criterion Sth (NO in step SD 13), the process returns to step SD2 as it is, and waits for reception of information.

Through the processing described above, in the REC mode operation, the operation speed is switched to high speed or low speed in accordance with the amount of use of the image buffer to be switched therebetween, specifically, the free capacity of the image buffer determined by comparison with the determination criterion Sth.

In the REC management task (T4), when the battery remaining capacity detection information indicating that the battery remaining capacity information is acquired from the microcomputer 17 and transmitted periodically is received from the KEY task (T2), the remaining capacity of the battery 19 is confirmed, and the remaining rate Lb of the battery is acquired (step SD 15). Then, the determination criterion Sth is changed to a value obtained by multiplying the initial value Sth0 of the determination criterion by the remaining battery rate Lb (step SD 16). Then returns to step SD2 to await receipt of the message.

Accordingly, in the REC mode operation, the operation speed is switched to the high speed or the low speed in accordance with both the state of the free capacity of the image buffer and the change in the battery remaining capacity, that is, even if the actual free capacity of the image buffer is the same, the operation speed is easily switched to the low speed side when the battery is left to be small (the remaining rate Lb is low), and the operation speed is easily switched to the high speed side when the battery is sufficient (the remaining rate Lb is high).

As described above, in the present embodiment, in the REC mode operation, the operating frequency of the CPU2 is set to high speed (81MHz) in the state where the image buffer usage is large (the free capacity is small), and the operating frequency of the CPU2 is set to low speed (32MHz) in the state where the image buffer usage is small (the free capacity is large). That is, the JPEG data writing operation (recording operation) is performed at a high speed only when it is considered necessary to enable continuous shooting at short intervals, and is performed at a low speed in the other state. Therefore, the battery life can be further extended as compared with example 1.

As described above, when the battery is left small (the residual rate Lb is low), the operation speed can be easily switched to the low speed side, and when the battery is sufficient (the residual rate Lb is high), the operation speed can be easily switched to the high speed side. That is, when the operation speed is high from a state where the empty capacity of the image buffer is large and the operation speed is low, the empty capacity of the image buffer gradually decreases to shift to a state where the empty capacity of the image buffer is small, and when the operation speed is high, the later time becomes earlier when the remaining battery capacity is sufficient (remaining rate Lb is high), and conversely, when the remaining battery capacity is small (remaining rate Lb is low), the later time becomes later when the latter state becomes later. Therefore, in a situation where the remaining battery power is low, the period during which the operation speed is increased to a high speed is reduced, and the battery life can be further extended. When the battery is sufficient (the survival rate Lb is high), the data can be quickly written into the external memory 15.

Note that, in the present embodiment, the initial value Sth0 of the determination reference Sth for determining whether the amount of use of the image buffer is large or small is dynamically changed in accordance with the battery remaining capacity, but the determination reference Sth may be a fixed value. In this case, when the determination criterion Sth is set to a sufficiently large value, the same operation as in example 1 can be performed. On the other hand, when the determination criterion Sth is set to a sufficiently small value, the operating frequency starts to be high when the image buffer is full. That is, at the time when the image buffer becomes full and the next image capturing cannot be performed, the high-speed operation is switched, and therefore, at the other normal time, the low-speed operation in which power consumption is suppressed can be performed.

In the present embodiment, the operation speed is controlled to be high speed (81MHz) and low speed (32MHz) in accordance with the state of the free capacity of the image buffer determined at the stages of the buffer FULL and the buffer EMPTY, but the state of the free capacity of the image buffer may be controlled to be 3 stages or more, and the operation speed may be controlled to be 3 stages or more in accordance with the state. Note that, as for the determination criterion at this time, it may be a fixed value, unlike the present embodiment, which is dynamically changed in accordance with the remaining battery capacity.

The criterion Sth may be dynamically changed according to a condition other than the remaining battery capacity, for example, the size of an image recorded by continuous shooting, and when the criterion Sth is set to a fixed value, the user can set the criterion Sth to an arbitrary value as necessary.

In the above description, although the case where the present invention is applied to a digital camera has been described, if image data is processed, the image data is temporarily stored in an arbitrary image buffer (first storage means) and then recorded in another recording medium (second storage means), the same technique as that of the present invention can be applied to another image processing apparatus. In this case, when the image processing apparatus operates using the battery as a power source, it is possible to extend the battery life and to perform continuous processing at short intervals.

Claims

1. A digital camera for recording image data obtained by photographing in a recording medium,

the digital camera includes:

an image buffer that temporarily stores the image data;

a processing device for reading out the image data temporarily stored in the image buffer, recording the image data on the recording medium, and controlling each section of the camera;

a determination unit that determines a state of the image buffer; and

a setting unit that sets an operating frequency of the processing device to an operating frequency corresponding to the state of the image buffer determined by the determination unit;

the processing device operates according to the operating frequency set by the setting means.

2. The digital camera according to claim 1, wherein:

the determination means determines the presence or absence of the use of the image buffer,

the setting means sets the operating frequency of the processing device to a first operating frequency when it is determined by the determining means that the image buffer is being used, and sets the operating frequency of the processing device to a second operating frequency lower than the first operating frequency when it is determined by the determining means that the image buffer is not being used.

3. The digital camera according to claim 1, wherein:

the determination means determines a state of a free capacity of the image buffer;

the setting means sets the operating frequency of the processing device to an operating frequency corresponding to the state of the free capacity determined by the determining means.

4. The digital camera according to claim 3, wherein:

the determination means determines the state of the free capacity of the image buffer by determining whether the free capacity of the image buffer is equal to or greater than a given threshold,

the setting unit sets the operating frequency of the processing device to a first operating frequency when the determination unit determines that the free capacity of the image buffer is not equal to or greater than a predetermined threshold, and sets the operating frequency of the processing device to a second operating frequency lower than the first operating frequency when the determination unit determines that the free capacity of the image buffer is equal to or greater than the predetermined threshold.

5. The digital camera according to claim 4, wherein:

further comprising:

a threshold value storage unit that stores the threshold value when the determination unit determines the state of the free capacity of the image buffer; and

a threshold value changing unit that changes the threshold value stored in the threshold value storage unit,

the setting means sets the operating frequency of the processing device to an operating frequency corresponding to the state of the free capacity determined by the determining means, based on the threshold value changed by the threshold value changing means.

6. The digital camera according to claim 5, wherein:

has a remaining power detecting section for detecting a remaining power of the power supply battery,

the determination criterion changing means changes the determination criterion in accordance with the remaining power of the power supply battery detected by the remaining power detecting means.

7. A storage medium for storing a plurality of data items,

which stores an operating frequency setting program for causing a computer of a digital camera which records image data obtained by photographing into a recording medium to function as a determination means and a setting means,

wherein,

a determination section that determines a state of an image buffer that temporarily stores the image data,

and a setting unit that reads out the image data temporarily stored in the image buffer, records the image data on the recording medium, and sets an operating frequency of a processing device that controls each unit of the camera to an operating frequency corresponding to the state of the image buffer determined by the determination unit.

8. An image processing apparatus that stores image data from a first storage means to a second storage means after temporarily storing the image data in the first storage means, comprising:

a processing device that reads out the temporarily stored image data from the first storage means, records the image data in the second storage means, and controls each unit of the device;

a determination unit that determines a state of the first storage unit; and