1. Field of the Invention
The present invention relates to an image capturing apparatus and a method of controlling thereof.
2. Description of the Related Art
Small-sized memory cards such as Compact Flash® cards or SD memory cards, whose storage media are semiconductor memories of a capacity in the range of several hundred bytes to several gigabytes, have conventionally been used in image input apparatuses, such as digital cameras, digital video cameras, and the like, as storage devices for image data.
Image data obtained through shooting is stored in such a memory card, the memory card being in a state in which it is inserted into a memory card slot provided in the body of the camera. However, the amount of image data that can be stored in a single memory card is limited, and increases in the amount of image data to be stored due to increases in the number of pixels used by image capturing devices have given rise to demand for higher-capacity storage media.
Meanwhile, HDDs (hard disk drives), whose storage media are magnetic disks, are being used as storage media with higher capacity and lower costs than semiconductor memories. Connecting this kind of HDD externally via USB or the like to a digital camera to use as the digital camera's storage medium, and utilizing the HDD in such a manner, has been proposed (see Japanese Patent Laid-Open No. 2001-238112).
FIG. 22 illustrates a configuration of such a conventional image input apparatus. An image input apparatus 10 includes a control unit 2, an image input and image processing unit 3, an optical member 4, a storage device 5, an operation unit 6, and a power control unit 7.
The power control unit 7 controls power within the image input apparatus 10, including the power of the storage device 5, in accordance with control signals from the control unit 2. The control unit 2 controls the power control unit 7 and the image processing unit 3 according to the status of the image input apparatus 10. The control unit 2 also communicates with the storage device 5 in order to acquire information for identifying the storage device 5.
The image processing unit 3 processes image information, the image information being inputted via the optical member 4 based on instructions to commence shooting operations accepted by the operation unit 6, generates image data, and sends the generated image data to the storage device 5. The image processing unit 3 may also include a display unit for displaying image data. This display unit may be configured of a liquid-crystal display, an organic EL display, or the like. The image processing unit 3 reads out image data from the storage device 5 based on instructions to commence image data play back operations accepted by the operation unit 6, and displays this image data on the display unit.
The storage device 5 internally stores the image data received from the image processing unit 3. The storage device 5 is realized by a semiconductor memory such as a Compact Flash® card or an SD memory card, which is inserted into a dedicated slot and integrated thereby with the image input apparatus 10.
The configuration of the power control unit 7 is illustrated in FIG. 23. The power control unit 1 includes a battery 30 and a DC-DC converter 11. The battery 30 is connected to the DC-DC converter 11. The DC-DC converter 11 performs voltage conversion on the power supplied by the battery 30 in accordance with a control signal 12 supplied by the control unit 2, and generates power 16 for the various constituent elements of the image input apparatus 10. Power 13 is also supplied by the DC-DC converter 11 to the storage device 5.
Next, a sequence through which the power control unit 7 of the image input apparatus 10 supplies power to the storage device 5 shall be described with reference to FIG. 24. In FIG. 24, 2401 represents operations performed with respect to the storage device 5. 2402 represents the waveform of the control signal 12, used for supplying power from the DC-DC converter 11 to the storage device 5. With regards to 2402, the LOW state represents a state in which the power supply from the DC-DC converter 11 is stopped, whereas the HIGH state represents a state in which power is being supplied from the DC-DC converter 11. 2403 represents the operational status of the storage device 5, which is supplied with power and operates in accordance with the control signal 12. Therefore, the operations of the storage device 5 are stopped when 2403 is in the LOW state pursuant to the control signal 12 being in the LOW state, whereas the storage device 5 is started up and is in an operational state when the control signal 12 is in the HIGH state. When the control signal 12 changes from the HIGH state to the LOW state, the operations of the storage device 5 are stopped in accordance therewith.
The horizontal axis in FIG. 24 expresses time. At time t11, a power button provided in the operation unit 6 is manipulated, thereby turning on the main power of the image input apparatus 10. Simultaneous to the main power being turned on, the control signal 12 enters the HIGH state; the power of the storage device 5 is turned on in accordance therewith, and the storage device 5 enters an operational state. Information of the storage device 5 is then acquired through information exchange carried out between the image processing unit 3 and the storage device 5, and furthermore, already-stored information is checked.
After this, at time t12, a shutter switch provided in the operation unit 6 is manipulated, and the image data generated in accordance with this operation is stored in the storage device 5. At time t13, a play back button provided in the operation unit 6 is manipulated, and the image data stored in the storage device 5 is read out in accordance with this operation.
Furthermore, at time t14, the power button is manipulated, cutting off the main power of the image input apparatus 10; accordingly, the control signal 12 enters the LOW state, in response to which the power to the storage device 5 is cut off, and the storage device 5 enters a state in which operations are stopped.
With this kind of method for supplying power to a storage device, the storage device is constantly in a state in which it is being supplied with power, even when not being accessed by the image processing unit; this leads to wasteful consumption of the power of the battery 30. If, under such conditions, the capacity of the storage device is increased in accordance with an increase in the size of images to be stored in the image input apparatus, the power is exhausted in order to keep the storage device in an operational state, giving rise to a problem in that shooting quickly becomes impossible. Furthermore, when using a device such as an HDD as the storage device which provides a large storage capacity at a low cost, amount of power consumed by the device is great, giving rise to another problem in that power cannot be supplied.
In the case where a mobile device such as a digital camera serves as a USB host machine, and a peripheral device such as an HDD is connected to the host machine, it is necessary to consider power management for the overall system, which is made up of both the mobile device and the peripheral device. For example, a power saving mode, which actively stops power from being supplied to the peripheral device and reduces power consumption thereby, is necessary.
Some USB-connected peripheral devices take several seconds or more to become operational after power is supplied thereto. In addition, with an HDD, it takes several seconds or more after the included magnetic disks begin spinning before actual reading/writing can take place.
Because of this, when using an HDD as a storage medium in a digital camera, it is impossible to avoid negatively influencing the storage timing, play back timing, and so on when shooting or when playing back image data. In mobile devices that demand quick responsiveness, such as digital cameras, the time required for the device to exit a power saving mode and become functional greatly affects the performance of the device.