JPH10150627A - Digital still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute the erasure of invalid data in a flash memory without having influence to photographing in a still video camera using the flash memory as a recording medium. SOLUTION: When a memory card incorporated with a flash memory is mounted in the ON state of a power source, the control (reclaim) of erasing invalid data generated in rewriting data within the flash memory is started. When a release button is operated before the finish of erasing control, (when S1 is turned ON), reclaim is suspended and after finishing photographing, reclaim is restarted to erase all the pieces of invalid data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital still camera, and more particularly to erasure control of invalid data in a digital still camera using a flash memory as a recording medium.

[0002]

2. Description of the Related Art In recent years, an optical image of a subject has been captured by an imaging lens,
An image is formed on a solid-state imaging device such as a CCD via an optical imaging system such as an aperture, and an electric image signal that is photoelectrically converted and output by the imaging device is converted into digital data and recorded in a semiconductor memory. Digital still cameras have been put to practical use.

As the semiconductor memory, a flash memory (flash EEPROM) can be used. In the flash memory, when rewriting data, new data is written in an empty sector while old data is left as it is, so that invalid data (old data) increases each time rewriting is performed. In particular, when an image is edited by inserting a memory card of a digital still camera into a card slot of a personal computer (hereinafter, referred to as a personal computer) using a card adapter or the like, a large amount of invalid data may be generated.

Therefore, in order to effectively use the capacity of the memory card and to record a specified number of images, it is necessary to erase invalid data to create a free area.
The following methods have been used to create an empty area. That is, when an effective data area (latest data area) and an invalid data area (old data area) are mixed in an erase unit (eg, erase unit 1) in a flash memory, only data in the effective data area is spared. While writing to the unit, the spare unit is referred to as the erasing unit 1, while all data of the original erasing unit is erased and used as a new spare unit.

[0005]

As described above, the control for erasing invalid data and creating a free area is generally performed when new data cannot be stored. When a flash memory is used as a storage medium, for example, when an image signal is to be recorded in the flash memory, it is executed only when it is determined that recording is not possible due to a lack of free space. .

However, when the erasing of invalid data is started as described above, the photographing cannot be performed until the end, and there is a possibility that the photographing opportunity may be missed. For example, if you remove a memory card with a built-in flash memory from the camera and perform editing on a personal computer, the amount of invalid data may increase significantly, and the memory card with the increased invalid data must be returned to the camera. When trying to shoot, it takes a long time to erase invalid data because many invalid data needs to be erased.
There was a possibility that an unexpected waiting might be forced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the control for creating a free space by erasing the invalid data can be performed without affecting the shooting operation as much as possible. It is an object of the present invention to improve the usability of a digital still camera while effectively utilizing the digital still camera.

[0008]

According to the present invention, a memory card having a built-in flash memory is detachably attached to a camera body, and converts an optical image of a subject into an electric image signal to convert the optical image into an electric image signal. In a digital still camera configured to record in a flash memory,
The control for erasing only invalid data generated at the time of data rewriting stored in the flash memory to create a free area is executed when the memory card is inserted into the camera body.

According to this configuration, for example, the storage content (data) of the memory card removed from the camera body is
If invalid data has been rewritten by a personal computer and the number of invalid data has increased, the invalid data will be erased immediately when the memory card is remounted in the camera body,
Recover the free space reduced by working on a personal computer before shooting. That is, invalid data is not erased only when it is determined that a newly photographed image signal cannot be stored, but invalid data is erased in advance before photographing.

The invalid data may be erased even when a memory card is inserted while the power of the camera body is not turned on. According to the second aspect of the present invention, there is provided a configuration in which the control for erasing only invalid data generated at the time of data rewriting and creating a free area stored in the flash memory is performed when a power switch of a camera body is operated. did.

According to this configuration, the invalid data is erased when the power of the camera body is turned on, so that the invalid data is erased when the memory card is inserted. Can be revived. In addition, if the configuration is such that the invalid data is deleted when the power of the camera body is turned off, the photographing does not have to be waited for by deleting the invalid data, and the invalid data generated in the power-on state is deleted each time. That is, if the memory card is not replaced, it is possible to start shooting without invalid data at the next power-on.

According to the third aspect of the present invention, the control of erasing only invalid data generated in data rewriting and creating a free area, which is stored in the flash memory, is performed immediately before recording an image signal in the flash memory. Is always executed. According to such a configuration, invalid data is always erased immediately before recording regardless of whether or not storage of a captured image signal is possible. Therefore, an empty area for recording a captured image signal is provided. , And invalid data can be deleted in advance.

According to the present invention, the control for erasing only invalid data generated in data rewriting and creating a free area stored in the flash memory is performed immediately after recording of an image signal in the flash memory. Configuration. According to this configuration, invalid data is erased immediately after recording, so that the erase control can be prevented from affecting the shooting, and the invalid data can be erased in advance to prepare for the next shooting. Therefore, it is possible to secure a free area necessary for recording.

According to the present invention, the control of erasing invalid data generated at the time of data rewriting and creating a free area, which is stored in the flash memory, is controlled by an electric image recorded in the flash memory. It is configured to be executed when the signal is erased. According to this configuration, when the unnecessary image signal is erased, the area of the image signal becomes an invalid data area. Therefore, the erasure of the invalid data area including the area where the image signal is recorded is performed. To secure a vacant area suitable for image deletion.

According to the present invention, the control for erasing only invalid data generated in the data rewriting and stored in the flash memory to create a free area is executed for a predetermined free area. The configuration was adopted. According to such a configuration, invalid data is not erased all at once, but is stopped when a minimum necessary free area is secured, thereby avoiding the erasure of invalid data from continuing for a long time.

According to a seventh aspect of the present invention, the predetermined empty area is set to a maximum image size. According to such a configuration, the invalid data is erased in order to create a free area of a maximum image size necessary and sufficient for recording the image signal. Therefore, while the image signal can be recorded, the waiting time due to the invalid data is minimized. Can be limited.

According to the present invention, when the control for erasing only invalid data generated in data rewriting and creating a free area stored in the flash memory is executed, the release operation is performed. When the empty area of the flash memory at that time is equal to or larger than a preset empty area, the control for creating the empty area is interrupted, and the photographing process is executed with priority.

According to this configuration, if there is an empty area in which a newly captured image signal can be recorded when the release operation is performed, the empty area is initially necessary and sufficient. To be executed preferentially,
Reduce the waiting time for shooting. According to a ninth aspect of the present invention, the control for creating the interrupted empty area is restarted after the recording of the image signal in the flash memory is completed.

According to this configuration, the erasure of the invalid data interrupted so that the photographing is prioritized is restarted after all the series of photographing operations are completed, and the invalid data remaining between the photographing operations is erased. In the invention according to claim 10, the control for creating the interrupted empty area is restarted before recording the image signal in the flash memory, and the recording of the image signal in the flash memory is completed after the control for creating the empty area is completed. Is performed.

According to such a configuration, the process from photographing to compression processing is preferentially terminated by interruption of invalid data erasure. However, final recording to the memory card is not performed, and compression processing and the like are completed and the flash memory is completed. The erasure of the invalid data is resumed in a state where only the recording remains, and the recording to the memory card is performed after all the erasure is completed. In the invention according to claim 11, stored in the flash memory,
The control for erasing only invalid data generated at the time of data rewriting and creating a free area is performed immediately before recording of an image signal to the flash memory by a predetermined free area, while the image signal to the flash memory is controlled. In this configuration, invalid data remaining immediately after the recording is completed is erased.

According to this configuration, when recording an image in the flash memory, if there is a sufficient free space for the image recording, the invalid data is not erased and the free space is insufficient. However, if there is enough free space for image recording, erasure is interrupted at that point, and erasure of invalid data remaining in the flash memory is performed after image recording to the flash memory is completed.

According to the twelfth aspect of the present invention, the total amount of invalid data generated in data rewriting, which is recorded in the flash memory, is stored. In this configuration, control is performed to erase only the invalid data to create a free area. According to such a configuration, even if the memory card is removed from the main body, the erasure is not performed unless invalid data increases during that time, and invalid data increases by rewriting data by a personal computer or the like while the memory card is removed. Erase only when

According to a thirteenth aspect of the present invention, a warning is issued when the total amount of invalid data recorded in the flash memory and generated when data is rewritten exceeds a predetermined amount. According to such a configuration, it is possible to confirm in advance that the total amount of invalid data is equal to or more than the predetermined amount, so that the necessity of deleting invalid data can be recognized in advance,
Erase is not performed carelessly.

[0024]

According to the first aspect of the present invention, when the memory card is inserted into the camera body, the invalid data is erased. The photographing can be performed after the image is secured. For example, it is possible to prevent the interruption of the photographing due to the start of the memory erasure control during the continuous photographing.

According to the second aspect of the present invention, the memory erasure control is performed when the power switch of the camera body is operated, so that the erasure of invalid data is started in the middle of photographing, and it is necessary to wait until the memory erasure control ends. There is an effect that it is possible to avoid disappearing. According to the third aspect of the invention, invalid data is always deleted immediately before recording regardless of whether a new image signal can be stored or not, so that an empty area for recording a captured image signal is secured. In addition to this, there is an effect that invalid data can be deleted in advance.

According to the fourth aspect of the invention, by deleting the invalid data immediately after the end of the recording, it is possible to prevent the deletion of the invalid data from hindering the photographing, and to delete the invalid data in advance. There is an effect that the user can go and prepare for the next shooting. According to the fifth aspect of the present invention, when an image signal is erased, a new image signal can be recorded as an empty area immediately after the erased image recording area becomes an invalid data area. There is an effect that shooting can be performed for the number of shots corresponding to the processing without erasing invalid data.

According to the present invention, the invalid data is erased only when there is no preset free area, and the invalid data is erased when the preset free area is secured. Thus, the time required for erasing invalid data can be minimized, and the effect on shooting can be sufficiently suppressed. According to the invention described in claim 7, the invalid data is erased so that a free area for the maximum image size can be secured.
Even when the free area is insufficient, there is an effect that a newly shot image signal can be recorded by erasing control with a minimum necessary time.

According to the eighth aspect of the present invention, when a release operation is performed during the erasure of invalid data, if the free area is equal to or more than a predetermined area, the erasing operation is interrupted and shooting can be immediately performed. There is an effect that even when the image data is insufficient, the erasure is interrupted at the stage when the minimum necessary free area is secured and the shooting can be started. Claim 9 or 10
According to the invention described above, the erasure of invalid data that has been interrupted to give priority to imaging is restarted under conditions that do not affect imaging, and there is an effect that erasing of invalid data in the flash memory can be performed early.

According to the eleventh aspect of the present invention, the recording of the captured image signal in the flash memory is performed with a short wait time by the minimum erasing control, and all the invalid data in the flash memory is transferred to the next time. This has the effect of erasing images as far as possible without taking over. According to the invention of claim 12, while the memory card is removed from the camera body, the invalid data is erased only when the invalid data area is increased due to rewriting by a personal computer or the like. Is limitedly performed at the time of request, and the effect on photographing can be avoided as much as possible.

According to the thirteenth aspect, by warning that the invalid data area is equal to or larger than the predetermined value,
There is an effect that it is possible to avoid inadvertently starting memory erasure.

[0031]

Embodiments of the present invention will be described below. FIG. 1 shows a hardware configuration of a digital still video camera according to the embodiment. In the figure, a light image of a subject obtained through an optical system composed of a focus lens 101, an aperture 102 and the like is formed on a light receiving surface of an image sensor such as a CCD 103. At this time, the focus lens 101 and the aperture 102 are driven by a focus drive circuit 104 and an aperture drive circuit 105, respectively.

Here, the CCD 103 constituting the image pickup device
Converts an optical image formed on the light receiving surface into a charge amount and outputs an analog image signal. The analog image signal output from the CCD 103 is subjected to noise reduction processing, gain adjustment, and the like in a pre-processing circuit 106. Then, after being converted into a digital image signal by the A / D converter 107, the digital image signal is input to the signal processing circuit 108, subjected to luminance processing, color processing, compression processing, etc., and then to the memory card 110 via the card controller 109. Be recorded.

The memory controller 111 temporarily records the digital image signal before processing in the frame memory 112, stores the processed digital image signal in the image storage memory 113, and stores the digital image signal stored in the image storage memory 113. The image signal is recorded on the memory card 110 by the card controller 109. The memory card 110 has a built-in flash memory (flash type EEPROM) and is detachably attached to the camera body.
A concave portion formed on the back surface of the memory card is provided with a contact for transmitting and receiving signals to and from the main body, while a rubber-like elastic connector is provided on the camera main body corresponding to the contact. By fixing the memory card 110 by crushing the rubber-like elastic connector, electrical connection and attachment to the camera body can be performed. However, the mounting mechanism of the memory card 110 is not limited to the above.

The main microcomputer 114 comprises the focus drive circuit 104, the aperture drive circuit 105, the pre-process circuit 106
And the operation of the signal processing circuit 108 and the like.
The sub-microcomputer 115 receives a detection result from a card detection sensor (not shown), and controls a power supply unit 116 for supplying power to each unit and a liquid crystal panel 117.

The captured image signal can be output as an NTSC video signal via a video amplifier 119. Further, an image signal can be transmitted to a personal computer or the like via an external serial port via a serial driver 118 controlled by the main microcomputer 114. The memory card 110 is inserted into a card slot of a personal computer by using a card adapter, so that the contents of the memory card 110 can be directly viewed on a personal computer or edited.

Here, the flash memory built in the memory card 110 has a mixture of a valid data area (latest data area) and an invalid data area (old data area) for a certain erasing unit (for example, erasing unit 1). When writing, only the data in the valid data area is written into the spare unit, and the spare unit is referred to as the erasing unit 1. On the other hand, all data in the original erasing unit is erased and used as a new spare unit. In this configuration, control for erasing the invalid data area and creating an empty area is performed. Hereinafter, the control for erasing invalid data and creating an empty area as described above is referred to as reclaim, and its execution timing will be described. I do.

In the time chart of FIG. 2 showing the first embodiment of the execution timing, a power switch is a power switch provided on a camera body operated by a photographer, and S1 and S2 are release switches. Indicates a half-pressed state and a fully-pressed state. Also, M-CP
The U task indicates the processing status of the main microcomputer 114. After the automatic exposure AE, the auto focus AF, and the auto white balance AWB are performed by turning on S1, the actual photographing is performed by turning on S2. Is performed (Expose), and the compression processing (Compe
After performing ssiond), recording of an image signal on the memory card (flash memory) 110 is performed.

In the first embodiment shown in FIG. 2, the reclaim is started when a memory card is inserted with the power switch turned on, and all invalid data (invalid sectors) in the flash memory are erased. It is configured to terminate the reclaim at the stage when it is performed. According to such a configuration, even when invalid data in the flash memory is increasing due to rewriting of recorded contents due to editing work on a personal computer, when inserting a memory card, in other words,
Before starting the photographing operation, all invalid data is collectively erased, so that a necessary and sufficient free area for recording a specified number of images can be secured. Therefore, it is possible to avoid the necessity of a reclaim at the stage of recording the image signal, and thus the continuous shooting is not hindered by the reclaim.

However, in the case of the first embodiment shown in the time chart of FIG. 2, if a memory card is mounted with the power switch turned off, the opportunity for memory erase control is lost. I will. Therefore, as in the second embodiment shown in the time chart of FIG. 3, even when the power switch is in the OFF state, a part related to the detection of the attachment of the memory card is set to the ON state, and the memory card is turned off when the power switch is in the OFF state. Even if is attached, the reclaim may be started by using such attachment as a trigger.

Here, the power supply of the main body may be turned on at the start of the reclaim, or the power supply may be turned off by itself if no image is taken within a predetermined time after the start. . When the reclaim is executed with the memory card being installed as a trigger, the reclaim is performed every time a predetermined delay time elapses from the detection of the installation in order to prevent the reclaim from being started before the memory card is completely installed. May be started.

Further, instead of a configuration in which the reclaim is performed with the insertion of the memory card as a trigger, the ON operation of the power switch (power switch) is triggered as in the third embodiment shown in the time chart of FIG. It may be configured such that a reclaim is executed every time the power switch is turned on. In the case shown in the time chart of FIG. 4, the reclaim starts when the power switch is turned on, and ends when all invalid data is erased. However, it is clear that the condition is that the memory card is loaded when the power switch is turned on.

Here, the configuration may be such that the mounting of the memory card is detected even in the OFF state of the power switch, and the reclaim is performed only at the first power-on after the mounting of the memory card. This is because if the memory card is once removed, invalid data may have increased more than usual due to rewriting by a personal computer, etc., and it may not be possible to record a predetermined image without reclaiming. This is because, when there is no such request, only invalid data expected to be generated by the normal photographing process and the request for reclaim is low.

Further, a configuration may be adopted in which the reclaim is started from the time when the power switch is turned off, and the power is self-cut off after the completion of the reclaim. In this case,
Although the reclaim will be made in a place that does not affect the shooting, it does not mean that the reclaim should be terminated before the shooting is performed, especially if a memory card with invalid data increased by processing with a personal computer is installed. In the case where photographing is started by the user, invalid data cannot be erased in advance. However, since the reclaim is performed when the power switch is turned off after the photographing is completed, if the memory card is not inserted / removed, the photographing is started with the invalid data deleted at the start of the next photographing. It is possible.

Incidentally, the reclamation when the power is turned on and the power is turned off
May be executed in combination with the reclamation at the time of power supply, or the reclaim at the first power-on after the memory card is mounted in the power-off state and the power-on.
It is also possible to adopt a configuration in which the memory card is combined with a reclaim at the time of mounting the memory card in the state. By the way, in the case of the embodiments shown in FIGS. 2 to 4, the reclaim is performed before the photographing operation is started, so that the reclaim is not actually performed when the photographing operation is started. However, if the amount of invalid data is large, it takes time to erase all invalid data, and the reclaim may not be completed before the photographer operates the release button.

In such a case, if photographing is not accepted because the camera is being reclaimed, it becomes necessary to wait until the end of the reclaim, so that a photographing opportunity is captured and the power switch is turned on or a memory card is inserted. However, there is a possibility that a photographing opportunity may be missed without taking a photograph. Therefore, as in the fourth embodiment shown in the time chart of FIG. 5, when the release button is pressed halfway down to S1 during the reclaim, the reclaim is interrupted at that point so that normal photographing processing can be performed, It is preferable that the reclaim is restarted after a series of photographing processes is completed after the recorded image is recorded on the memory card.

With such a configuration, it is possible to cause the photographer to prioritize the photographing intention even during the reclaim, and to prevent the photographing opportunity from being lost due to the reclaim while erasing invalid data. Can be avoided. In addition, since the reclaim is started before photographing, the reclaim can be sufficiently advanced before photographing, and the reclaim time after resuming can be shortened to sufficiently cope with continuous photographing.

In the example shown in FIG. 5, the reclaim started by triggering the mounting of the memory card in the power-on state is interrupted in synchronization with S1.
Similarly, in the configuration in which the memory card is mounted in the OFF state of the power switch shown in FIG. 4 or the reclaim is started with the ON operation of the power switch shown in FIG. It is good to interrupt.

In the time chart of FIG.
The configuration is such that the reclamation interrupted in step 1 is resumed after the image recording on the memory card is completed. However, as in the fifth embodiment shown in the time chart of FIG. Alternatively, a configuration may be adopted in which the reclaim is restarted when only the recording process on the flash memory remains, and the image is recorded on the memory card after the end of the reclaim.

With the configuration shown in FIG. 6, when an image signal is recorded in the flash memory, since the reclaim has been completed, the image signal can be reliably recorded in the flash memory. In the configuration shown in FIG. 6, if there is a sufficient free space for image recording when recording to the flash memory is attempted, the reclaim may be resumed after the recording is completed without resuming the reclaim. good.

Further, when S1 is pressed during the reclaim, the reclaim is not immediately interrupted irrespective of the size of the vacant area, but until the vacant area of the maximum image size is secured (set in advance). Until the empty area is reached), the reclaim may be continued prior to the image capturing, and the image capturing may be accepted when the empty area for the maximum image size is created. In particular, in the case shown in FIG. 5, since the reclaim is restarted after the recording is completed,
When recording is performed, if the number of empty sectors is insufficient, recording can not be performed, but if the minimum free area is secured before shooting and the shooting is accepted as described above, shooting can be performed. It is possible to reliably avoid a situation in which there is no free area for storing image signals.

In the case of FIG. 5 or FIG. 6, the rejection interrupted in S1 is continued until the recording of the image signal on the memory card is completed or the image signal processing such as the compression processing is completed. AE, A
The reclamation may be performed in small increments by using the idle time of the main microcomputer such as between F and AWB processes.

The time chart of FIG. 7 shows the sixth embodiment. At the stage when signal processing such as compression processing is completed, that is, immediately before recording, a reclaim operation is performed to secure an empty area for the maximum image size. Is performed at all times, an image signal is recorded in the flash memory when a free area corresponding to the maximum image size is created, and the invalid data remaining after the recording is completed is erased.

With this configuration, even when a memory card in which invalid data is greatly increased due to rewriting accompanying editing processing by a personal computer is installed, a free sector for the maximum image size is secured before recording. In addition, the photographed image can be reliably recorded, and the waiting time until the recording can be minimized. Further, if the configuration is such that the photographing process is prioritized for a reclaimed record resumed after recording is completed, the end of a series of photographing processes is only extended by the time to secure an empty sector for the maximum image size. Will be able to cope well. Furthermore, if there is sufficient time from the end of recording of the first photographing to the next photographing, all reclaims can be completed, so that photographing can be performed without reclaim processing from the next time. .

Here, it is also possible to adopt a configuration in which only the reclaim for the maximum image size immediately before recording to the memory card is performed at every photographing without resuming the reclaim after recording to the memory card is completed. According to such a configuration, even when there are many invalid data, by executing the reclaim only for the maximum image size for each photographing, it is possible to end all the reclaims necessary in a plurality of photographing processes.

Also, a configuration may be adopted in which invalid data is always deleted by a predetermined amount immediately after recording of an image signal on a memory card is completed, provided that a free area for the maximum image size is already secured. Further, when an image signal is deleted by a photographer in the camera,
Actually, the recording area of the erased image becomes an invalid data area, but when new data cannot be stored, instead of erasing the invalid data area, immediately when the erasure of the image signal is designated, It is preferable to erase the recording area of the erased image as an invalid data area.

According to such a configuration, the photographer recognizes that a new photographing has become possible by erasing a part of the recorded image and starts the photographing, but the reclaim is started to prevent the photographing. Can be avoided. Also, when invalid data increases due to processing by a personal computer or the like, the necessity of reclaim increases, so the total amount of invalid data is stored, and when a memory card is inserted,
Compare the amount of invalid data just before the stored memory card is removed with the amount of invalid data at the time of insertion.If the amount of invalid data is increasing, use the PC while the memory card is removed. It is presumed that the processing has been performed, and for example, while the reclaim triggered by the mounting operation is executed, if no increase in the invalid data amount is recognized, the reclaim is not performed. It is possible to execute the reclaim.

Further, the amount of invalid data is estimated, and when the total amount of invalid data exceeds a predetermined amount, a warning is displayed by indicating the fact on the liquid crystal panel, and there is a possibility that a reclaim will be started with photographing. You may be notified that there is something. According to such a configuration, even when the reclaim is performed when free space is insufficient when writing new data, the photographer can anticipate that the reclaim will be performed. Can be avoided. It is also possible to provide a button for instructing the execution of the reclaim, so that the photographer can execute the reclaim at an arbitrary timing based on the warning.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a hardware configuration of a still video camera according to an embodiment.

FIG. 2 is a time chart showing a first embodiment of erasing invalid data.

FIG. 3 is a time chart showing a second embodiment of erasing invalid data.

FIG. 4 is a time chart showing a third embodiment of erasing invalid data.

FIG. 5 is a time chart showing a fourth embodiment of erasing invalid data.

FIG. 6 is a time chart showing a fifth embodiment of erasing invalid data.

FIG. 7 is a time chart showing a sixth embodiment of erasing invalid data.

[Explanation of symbols]

 101 Focus lens 102 Aperture 103 CCD 104 Focus drive circuit 105 Aperture drive circuit 106 Pre-processing circuit 107 A / D converter 108 Signal processing circuit 109 Card controller 110 Memory card 111 Memory controller 114 Main microcomputer 115 Sub microcomputer

Continued on front page (72) Inventor Tomoe Nemoto 2970 Ishikawacho, Hachioji-shi, Tokyo Inside Konica Corporation

Claims (13)

[Claims] 1. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. A control for erasing only invalid data generated at the time of data rewriting stored in the flash memory and creating a free area when the memory card is inserted into a camera body. Digital still camera. 2. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. A digital still camera, characterized in that control for erasing only invalid data generated at the time of data rewriting and creating a free space stored in the flash memory is executed when a power switch of a camera body is operated. 3. A digital still camera in which a memory card having a built-in flash memory is detachably mounted on a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. Digitally controlling to erase only invalid data generated at the time of data rewriting and to create a free area stored in the flash memory immediately before recording an image signal in the flash memory. Still camera. 4. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. A digital still control unit for executing control immediately after recording of an image signal to the flash memory, to execute a control for erasing only invalid data generated at the time of data rewriting and creating a free area, stored in the flash memory. camera. 5. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. Executing a control for erasing invalid data generated at the time of data rewriting and creating a free area stored in the flash memory when an electric image signal recorded in the flash memory is erased. A digital still camera, characterized in that 6. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. A digital still camera, characterized in that control is performed to erase only invalid data generated at the time of data rewriting and to create a free area stored in the flash memory for a predetermined free area. 7. The digital still camera according to claim 6, wherein the preset empty area is a maximum image size. 8. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. A release operation is performed when a control for erasing only invalid data generated at the time of data rewriting stored in the flash memory and creating a free area is performed, and the flash memory at that time is operated. A digital still camera, characterized in that when the free space is equal to or larger than a predetermined free space, the control for creating the free space is interrupted, and the photographing process is preferentially executed. 9. The digital still camera according to claim 8, wherein the control for creating the interrupted empty area is restarted after the recording of the image signal in the flash memory is completed. 10. A method of resuming the control for creating an interrupted empty area before recording an image signal in the flash memory, and recording the image signal in the flash memory after the control for creating the empty area ends. 9. The digital still camera according to claim 8, wherein: 11. A digital still camera in which a memory card having a built-in flash memory is detachably attached to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. The control for erasing only invalid data generated at the time of data rewriting and creating an empty area, stored in the flash memory, is performed immediately before recording of an image signal in the flash memory by an amount corresponding to a preset empty area. A digital still camera for erasing invalid data remaining immediately after the end of recording the image signal in the flash memory. 12. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. The total amount of invalid data recorded in the flash memory and generated at the time of data rewriting is stored, and when the invalid data increases when a memory card is remounted, only the invalid data is erased to make room. A digital still camera characterized by executing control for creating an area. 13. A digital still camera in which a memory card having a built-in flash memory is detachably mounted to a camera body, and is configured to convert an optical image of a subject into an electric image signal and record the electric image signal in the flash memory. A digital still camera, wherein a warning is issued when the total amount of invalid data recorded at the time of data rewriting is greater than or equal to a predetermined amount recorded in the flash memory.