Image pickup apparatus for producing a desired frame of image signals

An image pickup apparatus capable of outputting one of successive pictures that is picked up at a desired timing. When the operator of the apparatus selects a continuous shoot mode, sets a mode dial at a “Pre (prior)/Post (posterior)” position, and then presses a release button to a half-stroke position, the apparatus picks up a desired scene at preselected intervals. Up to nine latest frames of image data are written to a main memory while being sequentially updated. Subsequently, when the operator presses the release button to a full-stroke position, up to five additional latest frames of image data are written to the main memory. The image data stored in the main memory are read out and transformed to display data. The display data appear on an LCD (Liquid Crystal Display) panel in a multiframe format. When the operator, watching pictures appearing on the LCD panel, selects desired one of the pictures by operating preselected switches arranged on an operation panel, the image data representative of the above picture is recorded in an external memory removably mounted to the apparatus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup apparatus for picking up a scene with an image sensor and storing the resulting image signal. More particularly, the present invention relates to an image pickup apparatus capable of picking up a plurality of successive pictures in a continuous shoot mode.

2. Description of the Background Art

A digital still camera extensively used today uses a CCD (Charge Coupled Device) image sensor or similar solid-state image sensor in place of the traditional silver halide photosensitive type of film. This kind of camera is capable of storing image data output from the image sensor in a semiconductor memory or similar storage and reproducing it on a monitor in the form of a picture. This allows the operator of the camera, watching the monitor, to confirm the result of a shot immediately after the shot. However, it is not easy for the operator to determine a shutter chance while focusing the camera on a desired subject and selecting the range of a shot at the same time, and then pick up the scene at a desired timing. For example, the operator is apt to miss a shutter chance due to the delay of operator's decision or action or the delay of operation particular to the camera. This brings about a release time lag between the intended time for shooting and the time of the actual shot.

In light of the above, Japanese patent laid-open publication No. 205605/1997 discloses an image pickup system including an image pickup apparatus and a computer connected to each other. Image data generated by the image pickup apparatus earlier than the input of a shoot command by a period of time corresponding to the release time lag is input to the computer. The system measures a release time lag particular to the operator of the apparatus and includes a memory capable of storing image data to be picked up over the time lag. When the operator operates a shutter release button of the camera, image data representative of the oldest picture existing in an image buffer of the camera is displayed and written to an auxiliary memory.

The release time lag, however, depends on the person to operate the image pickup apparatus. The prior art system, therefore, must measure the time lag every time the person to operate the camera or the shooting conditions change. Moreover, even the picture taken with due consideration given to the release time lag is not always a picture picked up at a desired timing or shutter chance.

To allow the operator of a digital still camera to surely take a picture at a desired timing, the camera may be constructed to continuously pick up a desired scene while sequentially recording the resulting successive pictures in a memory in the same manner as a movie camera. However, simply picking up successive pictures and storing the whole data representative of the pictures not only wastes the limited capacity of the memory, but also increases processing loads. This makes it difficult to implement a digital camera capable of producing high-quality still pictures.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an image pickup apparatus capable of surely outputting a picture picked up at a desired timing.

An image pickup apparatus of the present invention includes an image sensor for picking up a scene in accordance with a control signal to thereby output an image signal representative of the scene, and a storage for storing a plurality of frames of image signals. A selecting device allows the operator of the apparatus to select desired one of the frames of image signals stored in the storage. Outputting circuitry reads the one frame of image signal selected by the operator out of the storage and outputs the one frame of image signal. A controller outputs the above control signal that causes the image sensor to pick up the scene at preselected intervals. The storage stores latest ones of frames of image signals picked up at the preselected intervals while sequentially updating them. The controller causes the storage to hold frames of image signals picked up during a period of time that is based on the operation of a release button. The selecting device allows the operator to select any one of the frames of image signals held in the storage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 2of the drawings, an image pickup apparatus embodying the present invention is shown and implemented as a digital camera by way of example. As shown, the digital camera, generally10, includes a CCD image sensor14to which an optical image representative of a scene to be picked up is incident via optics12. An image signal output from the image sensor14is processed and then written to an external memory16removably mounted to the camera10. An operation panel18includes a release button22(seeFIG. 1). When the operator of the camera10presses the release button22, a release switch, not shown, is operative in response to cause the camera10to pick up the scene and execute store processing in accordance with a mode selected by the operator on a single/continuous shoot mode dial, not shown, of the camera.

For example, assume that the operator selects a continuous shoot mode on the shoot mode dial and then sets a mode dial20(seeFIG. 1) assigned to the continuous shoot mode at its “Pre” position. Then, when the operator presses the release button22to its half-stroke position, the camera10sequentially stores a plurality of successive frames of image data in a main memory24while sequentially updating them. After the operator has pressed the release button22to its full-stroke position, the camera10allows the operator to designate desired one of the frames of image data stored in the main memory24and records the designated frame of image data in the external memory16.

When the operator sets the mode dial20at its “Pre/Post” position and then presses the release button22to the half-stroke position, the camera10executes the same procedure as when the operator sets the dial20at the “Pre” position. Subsequently, when the operator presses the release button22to the full-stroke position, the camera10further-picks up a preselected number of additional frames while storing the resulting image data in the main memory24. The camera10then allows the operator to select desired one of the frames of image data stored in the main memory24and records the designated frame in the removable memory16. Further, assume that the operator sets the mode dial20at its “Post” position. Then, the camera starts picking up a preselected number of successive frames when the operator presses the release button22to the full-stroke position, while storing the resulting image data in the main memory24. This also allows the operator to select desired one of the frames stored in the main memory24.

As stated above, in the continuous shoot mode, the camera10picks up a plurality of frames and stores them in the main memory24in a particular manner determined by the mode elected on the mode dial20and the half-stroke position of the release button22. At the same time, the camera10displays the successive frames or pictures picked up at consecutive times on an LCD (Liquid Crystal Display) panel or monitor26(seeFIG. 1) in a multiframe format. The operator, watching the LCD panel26, selects desired one of the frames on an “F (forward)” switch28, a “B (backward)” switch30, and an enter/store switch32. In response, the camera10writes image data representative of the frame selected by the operator in the external memory16.

Assume that the operator selects a single shoot mode on the previously mentioned single/continuous shoot mode dial. Then, the camera10picks up a single frame when the operator presses the release button22to the full-stroke position, and stores the resulting image data in the external memory16.

Referring again toFIG. 2, the optics12includes a lens system, an orifice diaphragm, and a mechanical shutter although not shown specifically. In response to drive signals fed from an optics driver34, the optics34adjusts the focal position of the lens and the opening of the orifice diaphragm and opens and closes the mechanical shutter. In the illustrative embodiment, the camera10controls a shutter speed, i.e., an exposure time at the time of a shot by controlling the mechanical shutter and an electronic shutter available with the CCD image sensor14.

The CCD image sensor, or bidimensional image sensor,14has photosensitive devices, not shown, arranged horizontally and vertically thereon. A color filter, not shown, is positioned in front of the photosensitive devices and made up of primary color filter segments R (red), G (green) and B (blue) corresponding one-to-one to the photosensitive devices. The photosensitive devices each generate a signal charge corresponding to a quantity of light incident thereto via the color filter. The signal charges are transferred from the photosensitive devices to vertical transfer paths and then to a single horizontal transfer path of the image sensor. As a result, R, G and B pixel signals are output from the image sensor14in accordance with the filter arrangement. A CCD driver36delivers a pixel clock, a transfer clock and other drive signals to the image sensor14in order to drive it under the control of a system controller38.

The output of the CCD image sensor14is connected to a CDS (Correlated Double Sampling) circuit40. The CDS circuit40is an analog preprocessing circuit for preamplifying the input pixel signals to a preselected level while canceling reset noise contained in the pixel signals. The preprocessed pixel signals are fed from the CDS circuit40to an ADC (Analog-to-Digital Converter)42. The ADC42converts the levels of the input pixel signals to R, G and B image data represented by ten or twelve bits and feeds the image data to a digital signal processing circuit44.

The digital signal processing circuit44executes gamma correction with the R, G and B image data in order to correct the tonality and levels thereof. In addition, the signal processor44adjusts the white balance of the image data. The processed image data are delivered from the signal processor44to a memory controller46. When R, G and B image data stored in the main memory24are to be transferred to the removable memory16or when they are to be fed to an NTSC (National Television System Committee) encoder48, the signal processor44transforms the R, G and B image data to Y (luminance) and C (chrominance) image data. The Y and C image data are input to the memory controller46.

Further, the digital signal processor44transforms the image data output from the ADC42or the main memory24to display data capable of being displayed on the LCD panel26and delivers them via the memory controller46and a bus50to an LCD driver56. The LCD driver56causes the LCD panel26to display a picture represented by the display data. Therefore, at the preparatory stage for a shot, the LCD panel26is capable of displaying pictures read out of the external memory16or moving pictures being picked up before the operation of the release button22, as needed. This allows the operator to manually adjust the angle of field, focus, brightness and so forth while watching the moving pictures. In this manner, in the illustrative embodiment, the LCD panel26plays the role of an electronic viewfinder for displaying a scene to be picked up beforehand in addition to the role of a display for displaying pictures read out of either one of the main memory24and external memory16.

Moreover, the digital signal processor44converts the image size of image data picked up to the display size of the LCD panel26. For example, assume that the operator selects the continuous shoot mode and continuously picks up a plurality of frames at preselected intervals of Δt. Then, the signal processor44arranges consecutive pictures represented by the resulting image data horizontally and vertically and generates data for causing the LCD panel26to display, e.g., nine pictures in a reduced scale. In the “Pre/Post” continuous shoot mode, the signal processor44processes successive frames of image data picked up and written to the main memory24at consecutive times t=−4 Δt, −3 Δt, . . . , 3 Δt, 4 Δt and causes the LCD panel26to display pictures represented by the processed image data in a multiframe format.FIG. 1shows a specific arrangement of pictures continuously picked up at the times t=−4 Δt through t=4 Δt and appearing on the LCD panel26.

In the “Pre” continuous shoot mode, the digital signal processor44processes consecutive frames of image data picked up at times t=−8 Δt, −7 Δt, . . . , −Δt, t=0 so as to generate data for displaying the above frames together in a reduced scale. Likewise, in the “Post” continuous shoot mode, the signal processor44processes consecutive frames of image data picked up at times t=0, −Δt, . . . , 7 Δt, 8 Δt so as to generate data for displaying such frames together in a reduced scale.

The system controller38delivers to the digital signal processor44a control signal for allowing the operator to select desired one of the pictures appearing on the LCD panel26. In response, the signal processor44changes the color and brightness of framework of the individual picture in order to distinguish pictures that can be selected from the other pictures.

Another function assigned to the digital signal processor44is calculating, based on the image data output from the ADC42, various estimated values for the adjustment of focus, brightness and other shooting conditions. Specifically, the signal processor44divides a frame into sixty-four blocks and calculates estimated values on the basis of block-by-block image data. For example, the signal processor44calculates the level of image data block by block by addition and then calculates the photometric value of the scene in accordance with the resulting sums and a photometry mode. The signal processor44sends the photometric value to the system controller38. The system controller38generates, based on the photometric data, control signals indicative of a lens opening and a shutter releasing period of time to be assigned to the optics12and delivers the control signals to the optics driver34. In addition, the system controller38feeds a control signal indicative of an electronic shutter speed to be assigned to the CCD image sensor14to the CCD driver36. In this sense, the system controller38has an automatic exposure adjusting function.

Still another function assigned to the digital signal processor44is shifting the focal position of the lens in order to separate the contrast components of the scene from the block-by-block image data, calculating estimated contrast values, and generating a control signal for locating the lens at a position where the estimated contrast value is greatest (automatic focusing function). In addition, when the system controller38specifies an AWB (Auto White Balance) mode, the signal processor44determines the condition of a light source included in the scene, i.e., color temperature and adjusts the color balance of the RGB signals in matching relation to the color temperature (AWB adjusting function).

The memory controller46interchanges image data with the signal processor44and controls the writing and reading of image data out of the main memory24(store control function). Further, the memory controller46controls data transfer between the various functional blocks connected to the bus50in response to control signals output from the system controller38. In the illustrative embodiment, the main memory24is capable of storing nine frames of image data picked up. The memory controller46feeds an address signal and a write control signal to the main memory24.

When the operator sets the mode dial20at the “Pre” position or the “Pre/Post” position, the memory controller46writes, in response to a control signal fed from the system controller38, nine consecutive frames of image data sequentially picked up at the intervals of Δt in the main memory24. When another frame of image data is input, the memory controller46deletes the oldest image data existing in the main memory24and writes the latest frame of image data in the resulting unoccupied area of the memory24. In this manner, the memory controller46cyclically writes the latest image data in the main memory24while deleting the oldest image data.

Assume that the operator selects the “Pre” position of the mode dial20and then presses the release button22to the full-stroke position. Then, the system controller38sends a control signal to the memory controller46for causing it to read nine latest frames of image data out of the main memory24and transferring them to the digital signal processor44. The signal processor44processes the nine frames of image data in the previously stated manner and delivers the processed image data to the bus50. On the other hand, assume that the operator selects the “Pre/Post” position of the mode dial20and then presses the release button22to the full-stroke position while the memory controller46is sequentially writing the latest image data in the main memory24. Then, the system controller38sends a control signal to the memory controller46for causing it to write a plurality of additional frames of image data less than nine frames in the main memory24while sequentially deleting the oldest image data existing in the memory24. For example, the memory controller46may write five frames of additional image data, including one frame of image data generated just after the release timing, in the main memory24.

Further, assume that the operator selects the “Post” position of the mode dial20and then presses the release button22to the full-stroke position. Then, the system controller46sends a control signal to the memory controller46for causing it to write in the main memory24nine consecutive frames of image data that are sequentially picked up at the intervals of Δt after the release timing.

The memory controller46reads the latest frames of image data stored in the main memory24in the above-described manner and delivers them to the digital signal processor44. The signal processor44processes the input image data for multiframe display and outputs the resulting display data to the bus50. When the operator selects the single shoot mode, as distinguished from the continuous shoot mode, the memory controller46writes a single frame of image data picked up at the full-stroke position of the release button22in the main memory24without regard to the position of the mode dial20.

A compression/expansion circuit52is connected to the bus50for coding the YC image data output from the digital signal processor44by compression. In the illustrative embodiment, for the compression/expansion circuit52, use is made of a JPEG (Joint Photographic Expert Group) system that divides YC data vertically and horizontally into 8 (horizontal)×8 (vertical) blocks, executes bidimensional orthogonal conversion and quantization with the blocks of YC data, and codes the quantized data by Huffman coding. The compression/expansion circuit52delivers the compressed image data to a memory I/F (interface)54on the bus50. The memory I/F54controls the writing and reading of image data out of the removable memory16by electrically matching the bus50and the memory16. For example, the memory I/F54includes a driver for driving the memory16. When the memory16is implemented by an EEPROM (Electrically-Erasable and Programmable Read Only Memory), a flash memory or similar semiconductor memory, the memory I/F54generates a write command and a read command for controlling the memory16.

More specifically, the external memory16is removably connected to the memory I/F54. The memory I/F54is a store control circuit for writing the compressed image data output from the compression/expansion circuit52in a preselected area of the memory16or reading the image data out of the memory16and transferring them to the compression/expansion circuit52. In the illustrative embodiment, the memory is implemented as a card-like support encapsulating an EEPROM, flash memory or similar semiconductor memory. Alternatively, use may be made of any other suitable type of data recording medium, e.g., a magneto-optical disk or similar rotary recording medium or an optical card. If the memory16has a capacity sufficiently greater than the amount of image data to be selected out of the main memory24, then the memory I/F54may receive non-compressed image data from the digital signal processor44or the main memory24and write them in the memory16.

The LCD driver56and NTSC encoder48are also connected to the bus50. The LCD driver56drives the LCD panel26and feeds the image data read out of the main memory24and processed by the digital signal processor44to the LCD panel26. As a result, the LCD panel26selectively displays still pictures or moving pictures in accordance with the input image data. As shown inFIG. 1, the LCD panel26of the illustrative embodiment is mounted on the back of the camera10in such a manner as to allow the operator to see the image of the scene mainly in the direction in which the operator is expected to look a scene through an optical viewfinder60. The LCD panel26includes an RGB color filter, a deflector plate and liquid crystal, which are interposed between a pair of transparent plates, and forms a visible image represented by the input image data. The LCD panel26may, of course, be replaced with an EL (Electro Luminescence) display panel, a PDP (Plasma Display Panel) or similar display device. If desired, the LCD driver56and other peripheral circuitry may be formed on the substrate of the LCD panel26.

The NTSC encoder48transforms the image data input on the bus50to an image signal capable of being input to a monitor, not shown, connectable to the camera10. In the illustrative embodiment, the NTSC encoder48transforms the RGB image data to an image signal having the NTSC format.

The system controller38controls the various sections of the camera10in response to the manual operation of the operation panel18and includes a CPU (Central Processing Unit), a ROM, a RAM (Random Access Memory), and peripheral circuitry. Particularly, when the operator selects the continuous shoot mode, the controller38executes pickup control and record control in accordance with the position of the mode dial20. Specifically, in the continuous shoot mode, the controller38determines the interval Δt between successive shots. For example, as shown inFIG. 3, the controller38determines an exposure value for a shot on the basis of the photometric value calculated by the digital signal processor44. The controller38then determines a shutter speed ST in accordance with the exposure value and an AE (Automatic Exposure) mode. Assume that the shutter speed ST is faster than or equal to 1/30 second, which is a period of time necessary for the transfer of one frame of pixel signals. Then, the controller38adds 1/30 second to an exposure time ST corresponding to the shutter speed ST and sets the resulting sum as the interval Δt. If the shutter speed ST is slower than 1/30 second, the controller38doubles the exposure time ST and sets the resulting product as the interval Δt. This product may be replaced with the sum of the exposure time ST and 1/30 second, if desired.

A timer58is connected to the system controller38. In response to a control signal fed from the system controller38, the timer58counts the interval Δt set by the controller38and generates a timing signal defining the interval Δt. The timer58feeds the timing signal to the system controller38as an interrupt signal every time the interval Δt expires. Every time the system controller38detects the interrupt signal within a preselected valid interrupt acceptance period, it accepts the interrupt and delivers control signals for a single shot to the optics driver34and CCD driver36.

The system controller38recognizes operation information detected by the operation panel18and executes control in accordance with the operation. As shown inFIG. 1, the operation panel18includes a power switch62, the release button22having the half-stroke position and full-stroke position, and the release switch. The release switch is implemented as two release switches S1and S2responsive to the half-stroke position and full-stroke position, respectively. The mode dial20is a switch capable of outputting information representative of any one of the “Pre”, “Pre/Post” and “Post” positions selected by the operator. When the “Pre/Post” position is selected, the system controller38may execute control such that five additional frames are picked up from the time t=0 just after the turn-on of the release switch S2and stored in the main memory24. Alternatively, two to eight additional frames may be picked up from the time just after the turn-on of the release switch S2at the intervals Δt for the purpose of varying the balance between the shots before the turn-on of the release switch S2and the shots after the same. Further, one frame or nine frames may be additionally picked up in order to execute the same operation as when the “Pre” position or the “Post” position is selected.

The “F” switch28, “B” switch30and enter/store switch32also arranged on the operation panel18are used to select desired one of the pictures stored in the main memory24and appearing on the LCD panel26. In response to signals output from the switches28, and32, the system controller38designates the desired picture picked up at the respective timing and causes it to be stored in the external memory16. When the desired picture is selected on the “F” switch28and “B” switch30, the frame of the picture has its attributes, including color and brightness, changed and is distinguished from the other pictures thereby. When the enter/store switch32is pressed, the desired picture is recorded in the memory16.

Further, the system controller38executes various adjustments for a shot, e.g., adjusts the focus and determines a lens opening and a shutter speed. The digital signal processor44calculates various estimated values for shot adjustment by using the image data output from the ADC42, as stated earlier. The system controller38controls the various sections of the camera10on the basis of the estimated values. Specifically, the controller38delivers to the optics driver34a control signal for controlling the focal position of the lens and a control signal for controlling the duration of opening of the mechanical shutter. Also, the controller38feeds an electronic shutter control signal to the CCD driver36for controlling the duration of charge storage in the CCD image sensor14. In addition, the controller38delivers a control signal for controlling the color balance of the image data to the digital signal processor44. The digital signal processor44adjusts the levels of the RGB image data in accordance with the color balance control signal, thereby adjusting white balance.

A specific operation of the camera10will be described with reference toFIGS. 4 through 9. As shown inFIG. 4, when a shoot mode is set via operator's mode setting operation, the system controller38determines whether or not the continuous shoot mode is selected (step400). If the answer of the step400is positive (Yes), the controller38executes a step402; if otherwise (No, step400), it executes a step403assigned to a single shoot mode. In the step402, the controller38identifies the position “Pre”, “Pre/Post” or “Post” of the mode dial20selected by the operator.

Subsequently, the controller38drives the optics12and CCD image sensor14via the optics driver34and CCD driver36, respectively, thereby starting image pickup for a monitoring purpose (step404). At this instant, the mechanical shutter is left open. The image sensor14continuously output pixel signals representative of the scene being picked up via the lens. The CDS circuit40and ADC42process the outputs of the image sensor14. The ADC42delivers the resulting image data to the digital signal processor44.

The digital signal processor44executes simple image processing for allowing moving pictures to be continuously displayed. The processed image data are input to the LCD driver56via the memory controller46and bus50. As a result, moving pictures representative of the scene being picked up appear on the LCD panel26as if the scene were seen through the optical viewfinder60, allowing the operator to confirm a desired subject. At the same time, the digital signal processor44and system controller38control the electronic shutter available with the image sensor14and set a lens opening on the basis of the image data, thereby adjusting brightness for the display of the moving picture. If desired, the focus of the lens may be automatically adjusted on the basis of the estimated values derived from the image data.

After the step404, the system controller38determines whether or not the release switch S1has been turned on, e.g., whether or not the release button22has been pressed to its half-stroke position (step406). If the answer of the step406is Yes, the controller38executes various kinds of adjustment for the pickup of a still picture that include automatic exposure adjustment, automatic focus adjustment and automatic white balance adjustment (step408). These adjustments are effected with higher accuracy than the adjustments assigned to the display of the moving pictures. When the switch S1once turned on is turned off before the release switch S2is turned on in a step414, which will be described later, the controller38repeats the steps404and406.

After the step408, the controller38determines an interval Δt between consecutive shots in accordance with a shutter speed or exposure time ST derived from a photometric value determined in the step408(step410). If the exposure time ST is longer than or equal to 1/30 second, the controller38adds 1/30 second to the shutter speed ST and uses the resulting sum as the interval Δt. Conversely, if the exposure time ST is shorter than 1/30 second, the controller38doubles the exposure time ST and uses the resulting product as the interval Δt. The controller38sets the interval Δt in the timer58and then starts the timer58(step412). The timer58generates a timing signal every time the interval Δt expires.

In a step414following the step412, the controller38executes processing based on the turn-on of the release switch S2and mode setting as well as processing for designating a desired picture and recording it. Specifically, as shown inFIG. 5, when the mode dial22is set at the “Pre” position, the controller38validates the acceptance of an interrupt due to the timing signal to be output from the timer58and accepts the interrupt when it occurs (step500). The controller38then executes interrupt processing a (step502).FIG. 6shows the interrupt processing a specifically. As shown, the controller38initializes a counter to “0” (step600) and then determines whether or not the acceptance of an interrupt is valid (step602). If the answer of the step602is Yes, the controller38determines whether or not the timing signal from the timer58has been detected as an interrupt signal (step604). Subsequently, the controller38starts pickup control (step606) and then increments the counter by 1 (one) (step608).

After the step608, the controller38determines whether or not the count of the counter has exceeded “9” (step610). If the answer of the step610is No, the controller38executes pickup control for causing the scene to be picked up and causing the resulting image data to be written to the main memory24(step612). If the answer of the step610is No, meaning that the count of the counter has not exceeded “9”, the controller38causes the oldest image data existing in the main memory24to be deleted (step614) and then executes the step612.

Subsequently, the controller38determines whether or not the release switch S2has been turned on (step616). If the answer of the step616is No, the operation returns to the step602. If the answer of the step616is Yes, the controller38ends the interrupt processing a and executes a step504shown inFIG. 5.

As stated above, in the interrupt processing a, nine latest frames of image data generated under the pickup control of the controller38are sequentially written to the main memory24while being sequentially deleted in the order in which they are written. As a result, the image data existing in the main memory24are cyclically updated. After the release switch S2has been turned on (Yes, step616), the controller38causes one additional frame to be picked up and causes the resulting image data to be written to the main memory24before executing the step504ofFIG. 5. Therefore, when the mode dial20is in the “Pre” position, one additional frame picked up just after the turn-on of the release switch S2is dealt with as a frame picked up at the time t=0.

In the step504following the interrupt processing a (step502), the controller38invalidates the acceptance of an interrupt (step504), ends the pickup control based on the timing signals, and ends the updating of the image data existing in the main memory24.

Subsequently, the controller38causes the nine frames of image data picked up at the times t=−8 Δt through t=0 to be sequentially read out of the main memory24(step506). The digital signal processor44transforms such image data to display data and delivers the display data to the LCD driver56on the bus50. The LCD driver56causes the LCD panel26to display the nine latest frames or pictures thereon in accordance with the above display data in a multiframe format.

After the step506, the controller38determines the statuses of the “F” switch28and “B” switch30operated by the operator to select desired one of the pictures appearing on the LCD panel26. The controller28then changes the color and brightness of the framework of the selected picture, showing the operator that the desired picture can be selected. When the operator, watching the LCD panel26, selects the desired picture on the enter/store switch32(Yes, step508), the controller38executes a step510. It is to be noted that the operator may select two or more of the pictures appearing on the LCD panel26by operating the switches28,30and32.

In the step510, the controller38causes the image data corresponding to the picture selected by the operator to be read out of the main memory24and input to the compression/expansion circuit52via the bus50. The compression/expansion circuit52codes the input image data by compression and delivers the coded image data to the memory I/F54. At this instant, the controller38feeds various control information relating to the coded image data, including the time of pickup, to the memory I/F54. The memory I/F54writes the image data and control information in the preselected area of the external memory16.

After the step510, the controller38executes a step416shown inFIG. 4for determining whether or not the operator has changed the operation mode or has turned off the power switch62(step416). If the answer of the step416is Yes, the controller38executes processing that matches with the operator's operation. If the answer of the step416is No, the controller38determines whether or not the operator has changed the position of the mode dial20(step418). If the answer of the step418is Yes, the controller38returns to the step402; if otherwise (No, step418) the controller38returns to the step404.

As stated above, when the mode dial20is located at the “Pre” position, nine latest frames of image data are written to the main memory24in response to the turn-on of the release switch S1. On the turn-on of the other release switch S2, one additional frame is picked up. As a result, image data including additional image data generated just after the turn-on of the release switch S2are stored in the main memory24. It follows that the image data picked up at a desired time can be selected and output.

When the mode dial20is located at the “Pre/Post” position, the system controller38executes, in the step414ofFIG. 4, a procedure different from the above-described procedure. This procedure differs from the previous procedure in that it picks up a plurality of additional frames, as distinguished from one additional frame, at consecutive times after the turn-on of the release switch S2. Specifically, as shown inFIG. 7, the controller38validates the acceptance of an interrupt (step700), as in the step500ofFIG. 5, and then executes the interrupt processing a in the manner shown inFIG. 6(step702). When the release switch S2is turned on, as determined in the step702, the controller38initializes the content of the register i to “0” (step704) and then executes interrupt processing b (step706).

As shown inFIG. 8, the interrupt processing b differs from the interrupt processing a,FIG. 6, in that the system controller38executes neither one of the steps600and step616. In steps800through812shown inFIG. 8, the controller38picks up frames at the intervals Δt and deletes the oldest frame existing in the main memory24so as to update one latest frame. On storing the image data in the step812, the controller38increments the content of the register by 1 (step708,FIG. 7) and then determines whether or not the content of the resister i is equal to “5” (step710). If the answer of the step710is No, the controller38repeatedly executes the steps706and708until the content of the register i reaches “5”. In this manner, during the interval between the turn-on of the release switch S1and the turn-on of the release switch S2, four consecutive frames of image data are sequentially written to the main memory24. Then, five consecutive frames of image data picked up after the turn-on of the release switch S2are sequentially written to the main memory24.

If the answer of the step710is Yes, meaning that the content of the register i has reached “5”, the controller38invalidates the acceptance of an interrupt and ends the pickup processing and the storage of the image data in the main memory24(step712). Subsequently, the controller38causes the image data picked up at the times t=−4 Δt through t=4 Δt to be read out of the main memory24and input to the digital signal processing circuit44. The digital signal processor44processes the input image data and delivers the processed image data to the LCD driver56. Consequently, the LCD panel26displays nine frames or pictures in total thereon in a multiframe format (step714).

Again, in a step716following the step714, the controller38determines the statuses of the “F” switch28and “B” switch30operated by the operator to select desired one of the pictures appearing on the LCD panel26. The controller28then varies the color and brightness of the framework of the desired picture, showing the operator that the desired picture can be selected. When the operator, watching the LCD panel26, selects the desired picture on the enter/store switch32(Yes, step716), the controller38causes image data of the picture selected to be read out of the main memory24, coded by compression, and then written to the removable memory16via the memory I/F54(step718).

After the step718, the controller38executes the step416shown inFIG. 4for determining whether or not the operator has changed the operation mode or has turned off the power switch62. If the answer of the step416is Yes, the controller38executes preselected processing that matches with the operator's operation. If the answer of the step416is No, the controller38determines whether or not the operator has changed the position of the mode dial20(step418). If the answer of the step418is Yes, the controller38returns to the step402; if otherwise (No, step418), the controller38returns to the step404.

As stated above, when the mode dial20is set at the “Pre/Post” position, nine latest frames of image data begin to be written to the main memory24when the release switch S1is turned on, while being sequentially updated. Subsequently, when the release switch S2is turned on, five additional frames of image data are picked up and written to the main memory24. As a result, nine frames of image data are stored in the main memory24in total. It follows that the image data picked up at a desired time can be selected and output.

When the mode dial20is set at the “Post” position, the system controller38executes, in the step414ofFIG. 4, a procedure shown inFIG. 9. As shown, the system controller38determines whether or not the release switch S2has been turned on (step900). If the answer of the step900is Yes, the controller38validates the acceptance of an interrupt (step902). The controller38then initializes the register i to “0” (step904). Thereafter, the controller38determines whether or not an interrupt has been detected (step906).

When an interrupt is detected (Yes, step906) the controller38executes pickup control and writes one frame of image data picked up in accordance with the timing signal in the main memory24(step908). The controller38then increments the register i by 1 (step910) and determines whether or not the content of the register i is equal to “9” (step912). If the answer of the step912is Yes, the controller38invalidates the acceptance of an interrupt (step914); if otherwise (No, step912), the controller38returns to the step906and waits for an interrupt.

The controller38therefore causes image data to be repeatedly picked up at the intervals Δt in accordance with the timing signals until the content of the register i reaches “9”. Consequently, nine consecutive frames of image data picked up at the times t=0 through t=8 Δt are stored in the main memory24. These frames or pictures are read out of the main memory24and displayed on the LCD panel26in a multiframe format (step916). The controller38then determines whether or not the operator has selected desired one of the nine pictures (step918). If the answer of the step918is Yes, the controller38records the picture selected in the external memory16(step920). The step920is followed by the step416shown inFIG. 4.

As stated above, when the mode dial20is set at the “Post” position, nine consecutive frames of image data are written to the main memory24in response to the turn-on of the release switch S2. This allows the operator to select any one of the image data picked up at a desired time.

In the illustrative embodiment, a plurality of frames of image data continuously picked up are sequentially written to the main memory24, so that the operator can select desired one of the frames stored in the memory24. A modification of the illustrative embodiment and the operation thereof will be described hereinafter. In the modification, the consecutive frames of image data picked up and then processed are sequentially recorded in the external memory16and then read out of the memory16to be displayed on the LCD panel26. This also allows the operator to select desired one of the frames appearing on the LCD panel26. In the modification, the frames stored in the memory16other than the frame selected are deleted.

Specifically, in the modification, the system controller38causes the compression/expansion circuit52to code the image data output from the digital signal processor44and feeds the coded image data to the memory I/F54. As a result, the consecutive frames of image data picked up at the intervals Δt are recorded in the removable memory16. To allow the operator to select a desired frame to be left undeleted in the memory16, the controller38feeds a control signal for reading all of the frames out of the memory16to the memory I/F54. The controller38then causes the compression/expansion52to decode the image data read out of the memory16via the memory I/F54by expansion. The decoded image data are written to the main memory24. Further, the controller38causes the digital signal processor44to convert the coded image data to display data and deliver the display data to the LCD driver56. Consequently, the consecutive frames are displayed on the LCD panel26in a multiframe format. When the operator manipulates the operation panel18in a preselected manner for selecting a desired frame to be left in the memory16, the controller38sends to the memory I/F54a control signal for deleting the frames stored in the memory16other than the desired frame.

FIG. 10shows the operation of the above-described modification more specifically on the assumption that the mode dial22is located at the “Pre/Post” position. As for the operation of the entire camera10, the operation shown inFIG. 10is identical with the operation described with reference toFIG. 4. As shown inFIG. 10, in the step414ofFIG. 4, the system controller38validates the acceptance of an interrupt due to the timing signal output from the timer58(step1000).

Subsequently, the controller38executes interrupt processing a (step1002).FIG. 11shows the interrupt processing a in detail. As shown, the controller38initializes the counter to “0” (step1100) and then determines whether or not the acceptance of an interrupt is valid (step1102). If the answer of the step1102is Yes, the controller38determines whether or not an interrupt derived from the timing signal has been detected (step1104). If the answer of the step1104is Yes, the controller38starts pickup control (step1106) and then increments the counter by 1 (step1108). Subsequently, the controller38determines whether or not the count of the counter has exceeded “9” (step1110).

If the answer of the step1110is No, the controller38writes image data generated by the pickup control in the memory16(step1112). If the answer of the step1110is Yes, controller causes the oldest one of the image data existing in the memory16to be deleted (step1114). The step1114is also followed by the step1112.

After the step1112, the controller38determines whether or not the release switch S2has been turned on (step1116). If the answer of the step1116is Yes, the controller38executes a step1004shown inFIG. 10; if otherwise (No, step1116), the controller38returns to the step1102,FIG. 11. In this manner, nine latest frames of image data generated by the pickup control are recorded in the memory16while the oldest image data with respect to the time of pickup is deleted. The image data stored in the memory16are therefore cyclically updated. After the release switch S2has been turned on (Yes, step1116) the controller38causes one additional frame to be picked up and written to the main memory24and then executes a step1004and consecutive steps shown inFIG. 10. Therefore, in the “Pre/Post” mode operation, one frame picked up just after the turn-on of the release switch S2is dealt with as a frame picked up at the time t=0.

After the interrupt processing a, the controller38initializes the register i to “0” (step1004) and then executes interrupt processing b (step1006).

FIG. 12shows the interrupt processing b specifically. As shown, the interrupt processing b is identical with the interrupt processing a ofFIG. 11except that it does not include the steps1100and1116. In a sequence of steps1200through1210, the system controller38executes pickup processing at the intervals Δt, deletes the oldest frame of image data stored in the removable memory16, and updates one latest frame of image data. After the image data have been fully written to the memory16(step1210), the controller38increments the content of the register by 1 (step1008,FIG. 10) and then determines whether or not the content of the register i is equal to “5” (step1010). If the answer of the step1010is No, the controller38repeats the steps1006through1010until the content of the register i reaches “5”. As a result, four consecutive frames picked up between the time when the release switch S1is turned on and the time when the release switch S2is turned on and five consecutive frames picked up after the turn-on of the switch S2are stored in the memory16.

If the answer of the step1010is Yes, the controller38invalidates the acceptance of an interrupt and thereby ends the pickup control and the storage of image data in the memory16(step1012). Subsequently, the controller38causes the nine frames of image data to be read out of the memory16and transferred to the main memory24. The nine frames of image data are delivered from the main memory24to the LCD driver56via the digital signal processor44. Consequently, the nine frames or pictures picked up at the times t=−4Δt through t=4Δt are displayed on the LCD panel26in a multiframe format (step1016).

When the operator, watching the LCD panel26, selects and enters desired one of the nine pictures (Yes, step1018), the controller38causes the pictures stored in the memory16other than the picture selected to be deleted (step1020). The controller38then determines whether or not the operator has selected another operation mode or has turned off the power switch62(step416,FIG. 4). If the answer of the step416is Yes, the controller38executes processing matching with the operator's operation. If the answer of the step416is No, the controller determines whether or not the operator has changed the position of the mode dial20(step418). The controller38returns to the step402if the answer of the step418is Yes or returns to the step404if otherwise.

As stated above, in the modification of the illustrative embodiment, a plurality of frames of image data sequentially picked up at consecutive times are recorded in the removable memory16. Subsequently, the frames stored in the memory16other than a desired frame are deleted, so that only the desired frame is left in the memory16. While the modification has concentrated on the “Pre/Post” position of the mode dial20, it is also practicable when the mode dial20is set at the “Pre” position or the “Post” position.

In the illustrative embodiment and its modification, the system controller38executes control on the basis of the status of the release switch S1responsive to the half-stroke position of the release button22. Alternatively, an arrangement may be made such that preparations for a shot performed by the operator are detected and interpreted as representing the turn-on of the release switch S1.

For example, as shown inFIGS. 1 and 2, a sensor64is mounted on the camera10at the left-hand side of the optical viewfinder60. When the operator positions the camera10in front of eye for looking in at the viewfinder60, the sensor64senses the operator's eye or skin adjoining the camera10. The sensor64is made up of an LED (Light Emitting Diode) or similar light emitting device66and a photo-sensitive device68. The light emitting device66emits, e.g., infrared rays intermittently while the photo-sensitive device68senses the infrared rays reflected by the operator and outputs a signal in accordance with the incident rays. The output signal of the sensor64is connected to the operation panel18. The operation panel18reports the output of the sensor60to the system controller38. In response, the system controller38interprets the sensor output as representing the turn-on of the release switch S1. This kind of function is desirable when, e.g., the operator turns off the LCD panel26for a power saving purpose and uses the optical viewfinder60.

Reference will be made toFIGS. 13 and 14for describing an alternative embodiment of the present invention. As shown, a digital camera, generally70, differs from the digital camera10in that it additionally has an automatic bracketing capability, i.e., picks up a scene while correcting the exposure value stepwise in the continuous shoot mode. In the figures, identical structural elements are designated by identical reference numerals, and a detailed description thereof will not be made in order to avoid redundancy.

As shown inFIG. 13, the camera70includes an automatic bracketing exposure (ABE hereinafter) dial72positioned on the operation panel18. The ABE dial72allows the operator, intending to use the automatic bracketing function, to set a desired step value. In the illustrative embodiment, the ABE dial72has a “0” position that cancels the automatic bracketing function, a “⅓” position that effects bracketing by a step of ⅓ EV, and a “⅔” position that effects bracketing by a step of ⅔ EV. A system controller74shown inFIG. 14has a pickup control function for executing automatic bracketing in addition to the various functions of the system controller38,FIG. 2. As for the automatic bracketing function, a ½ exposure step may be substituted for or combined with the ⅓ exposure step, if desired.

More specifically, assume that the operator selects the continuous shoot mode and sets the ABE dial72at the “⅓” or “⅔” position. Then, in response to the operation of the release button22, the system controller74corrects the exposure value by a step EV in the positive and negative directions during pickup control. The controller74causes a plurality of frames to be picked up in accordance with a desired continuous shoot mode. At this instant, the controller74controls the lens opening or the shutter speed ST in order to vary the exposure. Particularly, assume that the exposure time ST is increased due to the variation of the shutter speed, e.g., longer than 1/30 second as in the previous embodiment. Then, the controller74uses the double of the exposure time ST as the intervals Δt and so controls the optics driver34and CCD driver36as to pickup the scene at the intervals Δt. If the exposure time ST is equal to or shorter than 1/30 second, the controller74uses the sum of the exposure time ST and 1/30 second as the intervals Δt. The timer58feeds timing signals to the controller74at the intervals of Δt set by the controller74. On receiving the timing signal during valid interrupt acceptance period, the controller74accepts the timing signal and then executes pickup control while controlling the processing and transfer of the image data.

A specific operation of the camera70, particularly the system controller74, will be described with reference toFIGS. 15 through 17. The mode dial20is assumed to be set at the “Pre/Post” position by way of example. Basically, the system controller74also executes the main routine shown inFIG. 4.FIG. 15shows the step414of the main to be executed by the system controller74. As shown, the controller74validates an interrupt due to the timing signal output from the timer58(step1500).

Subsequently, the controller74executes interrupt processing a (step1502).FIG. 16shows the interrupt processing a specifically. As shown, the controller74initializes a counter to “0” (step1600) and then determines whether or not the acceptance of an interrupt is valid (step1602). If the answer of the step1602is Yes, the controller74determines whether or not the timing signal from the timer58has been detected as an interrupt signal (step1604). The controller74then starts pickup control (step1606) and then increments the counter by 1 (step1608).

After the step1608, the controller74determines whether or not the count of the counter has exceeded “81” (step1610). If the answer of the step1610is No, the controller74causes image data generated by the pickup control to be written to the main memory24(step1612). If the answer of the step1610is Yes, the controller74causes, among the image data stored in the main memory24, nine oldest image data to be deleted (step1614). The step1614is also followed by the step1612. In the step1612, the controller74sets −4 ΔEV in an exposure level register and thereby causes the exposure level ΔEV to be corrected by four steps in the negative direction from an adequate exposure value corresponding to photometric data.

Subsequently, the controller74causes the camera70to pick up the scene with the exposure level of −4 ΔEV and causes the resulting image data to be written to the main memory24(step1616). The controller74then adds ΔEV to the value set in the exposure level register (step1618) and determines whether or not the resulting sum is greater than +4 ΔEV (step1620). If the answer of the step1620is Yes, the controller74executes a step1622. If the answer of the step1620is No, the controller74returns to the step1616and repeats the pickup control and the storage of image data in accordance with the timing signals while maintaining the current exposure value.

In the step1622, the controller74determines whether or not the release switch S2has been turned on. If the answer of the step1622is Yes, the controller74executes a step1504shown inFIG. 15; if otherwise (No, step1622), the controller74returns to the step1602. In this manner, eighty-one latest frames of image data are sequentially written to the main memory24until the turn-on of the release switch S2has been detected. At the same time, the oldest image data existing in the main memory24are sequentially deleted, so that the image data in the main memory24are cyclically updated.

In the step1504following the interrupt processing a, the controller74initializes the content of the register i to “0”. The controller74then executes interrupt processing b (step1506). As shown inFIG. 17specifically, the interrupt processing b differs from the interrupt processing a ofFIG. 16in that it does not include the steps1600and1622. Steps1700through1716are executed to pick up the scene at the intervals t while sequentially deleting nine oldest frames stored in the main memory24. As a result, nine latest frames picked up with different exposure levels are updated.

When the content of the exposure level register exceeds 4 Δ EV (Yes, step1716), the controller74increments the content of the register i by 1 (step1508,FIG. 15) and determines whether or not the resulting content of the register i is equal to “5” (step1510). If the answer of the step1510is No, the controller74repeats the steps1506and1508until the content of the register i reaches “5”. Consequently, 4 (frames)×9 (steps) of frames, i.e., thirty-six frames in total picked up during the interval between the turn-on of the release switch S1and the turn-on of the release switch S2are sequentially written to the main memory24. Thereafter, 5 (frames)×9 (steps) of frames, i.e., forty-five frames in total picked up after the turn-on of the release switch S2are written to the main memory24. As a result, eighty-one consecutive frames of image data are stored in the main memory24.

When the content of the register i reaches “5” (Yes, step1510), the controller74invalidates the acceptance of an interrupt and ends the pickup processing and the storage of image data in the main memory24(step1512). Subsequently, the controller74causes the image data picked up at the times t=−4 Δt through t=4 Δt to be read out of the main memory24. At this instant, in the illustrative embodiment, the digital signal processor44transforms the image data picked up at the intervals Δt with the exposure value corresponding to the photometric value, i.e., without any correction (+/−0 EV) to display data. The display data are fed from the signal processor44to the LCD driver56. Consequently, the LCD panel26displays the four consecutive frames picked up before the turn-on of the release switch S2and the five consecutive frames picked up after the turn-on of the release switch S2, i.e., nine consecutive frames in total in a multiframe format (step1514).

The operator, watching the frames or pictures appearing on the LCD panel26, selects and enters desired one of the consecutive times t=−4 Δt through t=4 Δt (Yes, step1516). In response, the controller74causes the frames of image data picked up by automatic bracketing and relating to the time Δt selected by the operator to be read out of the main memory24.

When the above image data blanked at the exposure levels of −4 ΔEV through +4 ΔEV are read out of the main memory24, they are transformed to corresponding display data and then displayed on the LCD panel26in a multiframe format (step1518). The operator, watching the LCD panel26, selects desired one of the pictures, i.e., desired one of the various exposure levels (step1520). In response, the controller74causes the image data selected by the operator to be read out of the main memory24, coded by the compression/expansion circuit52, and then recorded in the removable memory16(step1522).

After the step1522, the controller74determines whether or not the operator has selected another operation mode or has turned off the power switch62(step416,FIG. 4). The controller74then executes the processing described previously with reference toFIG. 4.

As stated above, when the operator sets the mode dial22at the “Pre/Post” position and sets the ABE dial72at the “⅓” position or the “⅔” position, eighty-one latest frames of image data sequentially picked up with different exposure levels in response to the turn-on of the release switch S1are written to the main memory24while being sequentially updated. On the turn-on of the release switch S2, additional frames of image data are picked up. Consequently, thirty-six frames of image data generated before the turn-on of the release switch S2and forty-five frames of image data generated after the turn-on of the releases switch S2are stored in the main memory24. This allows the operator to select desired one of the eighty-one frames picked up at a particular time.

Again, the image data sequentially generated may be written to the external memory16, so that needless image data can be deleted. The illustrative embodiment is also practicable even when the mode dial20is set at the “Pre” position or the “Post” position.

Another alternative embodiment of the present invention will be described with reference toFIGS. 18 and 19. As shown inFIG. 19, a digital camera, generally80, includes a touch panel82in addition to the structural elements of the digital camera70described with reference toFIGS. 13 and 14. The touch panel82is a pointing device for inputting a bilevel picture. Specifically, the touch panel82is superposed on the LCD panel26and transparent for pictures appearing on the panel26. When the operator touches desired part of the touch panel82, the panel82sends coordinates data representative of the coordinates of the touched part to a system controller84. In the illustrative embodiment, the system controller84identifies a bilevel picture corresponding to the coordinates data and determines the degrees of correlation between the bilevel picture and the pictures picked up at the consecutive times. The system controller84then distinguishes the picture having a high degree of correlation with the bilevel picture from the other pictures by accentuating it. The system controller84has such a composition accentuating function in addition to the functions of the system controller74,FIG. 14.

More specifically, as shown inFIG. 20, a frame is divided into sixty-four blocks. The system controller84transforms the coordinates data input via the touch panel82to a bilevel picture corresponding to the sixty-four blocks and stores data representative of the bilevel picture. The controller84then compares, block by block, the bilevel picture and bilevel pictures derived from the image data stored in the main memory24to thereby calculate degrees of correlation therebetween. For example, assume that the operator designates an area2000indicated by hatching inFIG. 20on the touch panel82. Then, the controller84causes a bilevel picture corresponding to the designated area2000to be stored. When the subject comes into particular part of the picture corresponding to the area2000, the controller84detects a high degree of correlation. Assume that frames shown inFIG. 18appear on the LCD panel26in a multiframe format while the bottom left frame has a high degree of correlation with the area2000. Then, the controller84causes the digital signal processor44to accentuate the above particular frame, showing the operator that the accentuated frame corresponds to the bilevel picture designated on the touch panel82beforehand.

The controller84may cause the image data of the accentuated frame to be processed and automatically recorded in the removable memory16. Also, the image data input via the touch panel82may be written to the main memory24, external memory16or ROM, so that they can be read out at the time of calculation of the degrees of correlation.

Reference will be made toFIGS. 21 and 22for describing a specific operation of the digital camera80. Basically, the main routine described with reference toFIG. 4also applies to this embodiment. InFIG. 21showing the main routine, steps identical with the steps shown inFIG. 4are designated by identical reference numerals and will not be described specifically in order to avoid redundancy. As shown, the system controller84detects a bilevel picture as a composition factor based on the operation of the touch panel82and causes the resulting bilevel image data to be stored (step2100). After the step412, the controller84executes a step2102, which is shown inFIG. 22in detail. While the following description concentrates on the “Pre/Post” position of the mode dial20, the procedure of the illustrative embodiment also applies to the “Pre” and “Post” positions.

As shown inFIG. 22, the controller84validates the acceptance of an interrupt (step2200) and then executes interrupt processing a (step2202). The interrupt processing a may be identical with the processing described with reference toFIG. 6or11. Subsequently, the controller84initializes the content of the register i to “0” (step2204) and then executes interrupt processing b (step2206). The interrupt processing b may be identical with the processing described with reference toFIG. 8or12. The controller84then increments the content of the register i by 1 (step2208) and determines whether or not the content of the register i is equal to “5” (step2210). If the answer of the step2210is Yes, the controller84invalidates the acceptance of an interrupt (step2212); if otherwise (No, step2210) the controller84returns to the step2206.

After the step2212, the controller84causes nine frames of image data stored in the main memory24to be converted to corresponding bilevel pictures (step2214). Subsequently, the controller84compares the bilevel pictures and the bilevel picture input via the touch panel82block by block so as to calculate a degree of correlation with each of the pictures picked up at a particular time (step2216). The controller84, identified image data having the highest degree of correlation, causes display data representative of the nine frames of image data stored in the main memory24to be generated. As a result, nine frames or pictures appear on the LCD panel26in accordance with the display data (step2218). At the same time, the controller84accentuates the picture having the highest degree of correlation, showing the operator that the picture is closest to the bilevel picture input on the touch panel82. To accentuate the above frame, the controller84may cause the picture to blink or highlight the picture or may vary any attribute of the picture relating to display.

When the operator selects, e.g., the picture distinguished from the other pictures by accentuation (Yes, step2220), the controller84causes the image data representative of the picture selected to be read out of the main memory24, subjected to YC processing and compression, and then recorded in the memory16together with control information (step2222). In the step416,FIG. 21, following the step2222, the controller84ends the routine or executes processing matching with a new mode, as in the previous embodiments.

As stated above, the illustrative embodiment allows the operator to easily select one of a plurality of pictures having the highest degree of correlation with a bilevel picture that the operator has input beforehand. A picture picked up at the optical timing can therefore be easily selected and recorded. In addition, the operator can select a picture matching with the bilevel picture in accordance with the position of the subject or the composition. The image data of the picture selected may, of course, be automatically recorded in the removable memory16. Assume that the operator sets the ABE dial72at an other than the “0” position and uses automatic bracketing in combination with the continuous shoot mode. Then, the controller84may compare the bilevel picture input via the touch panel82and nine frames of image data picked up without exposure correction (+/−0 EV).

The illustrative embodiments shown and described each store, in the continuous shoot mode, a plurality of pictures picked up at preselected intervals in the main memory24. The operator can therefore select a picture picked up at a desired timing and cause it to be recorded in the external memory16. Alternatively, the consecutive pictures picked up may be written to the memory16and then deleted except for a desired picture.

Pictures picked up before and/or after the turn-on of the release switch S2are stored in accordance with the position of the mode dial20, so that the operator can select desired one of the pictures stored. Further, the automatic bracketing function allows the operator to select desired one of pictures subjected to bracketing, as distinguished from pictures subjected to simple automatic exposure. The image data representative of needless pictures may be deleted to prepare for the subsequent shots.

Leaving only the desired picture in the memory16is successful to save the capacity of the memory16. Also, a picture picked up at a desired timing with adequate brightness can be stored in the memory16. When a device for inputting a bilevel picture is available, it is possible to accentuate a picture having the highest degree of correlation with the bilevel picture in order to distinguish it from the other pictures. The operator can therefore easily select a picture corresponding in composition to the bilevel picture.

In summary, in accordance with the present invention, an image pickup apparatus includes storing means for storing, among consecutive frames picked up at preselected intervals, a preselected number of frames while sequentially updating them. The frames picked up before and/or after the turn-on of a release switch are written to the storing means in accordance with a mode selected by the operator. The operator can therefore select one of the frames picked up at a desired timing and stored in the storing means. For the same purpose, an external memory or similar removable recording medium may be so controlled as to delete the frames other the desired frame. By using automatic bracketing, it is possible to leave in the recording medium a frame picked up at an adequate timing with an adequate exposure level.

The entire disclosure of Japanese patent application No. 259867/1999 filed Sep. 14, 1999 including the specification, claims, accompanying drawings and abstract of the disclosure is incorporated herein by reference in its entirety.

While the present invention has been described with reference to the illustrative embodiments, it is not to be restricted by the embodiments. It is to be a appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.