JP2009188857A - Imaging apparatus, imaging method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of noise from an image signal to an analog signal independently of a reading pattern of the analog signal. <P>SOLUTION: A reading pattern of an analog signal read out from a CCD image sensor 14 when a high picture quality mode is set as a moving picture photographing mode is different from a reading pattern when a standard picture quality mode is set. In an electronic camera, an output pattern of an image signal is also changed in accordance with a different reading pattern of an analog signal, and only in a period that the reading of the analog signal is stopped, an image signal is outputted from a signal processing processor 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic camera, and more particularly to a technique for reducing noise included in an analog signal read from an image sensor.

  In the electronic camera, as shown in the block diagram of FIG. 9, analog signals (signal charges) are sequentially read out from the CCD, which is an image sensor, and converted into digital signals by AFE (analog front end). However, various digital processes are performed by the signal processor to generate an image signal. The generated image signal is sequentially output from a signal processor to a recording medium, and is recorded as image data.

  Here, in the process of recording the image signal, as shown in FIG. 8, a period in which the analog signal read from the CCD is read and a period in which the image signal is output from the signal processor are timed. When overlapping on the axis, noise generated from the image signal interferes with the analog signal, so that the image quality of the recorded image is deteriorated.

Therefore, there is a signal mixed system that stops the output of a digital clock signal when an analog signal rises and falls (for example, Patent Document 1). According to such a signal mixed system, it is said that the influence of digital noise on an analog signal can be reduced.
JP-A-9-135213

  Incidentally, recent digital cameras generally have a plurality of shooting modes. Therefore, the reading pattern of the analog signal read from the CCD differs depending on the shooting mode.

  For example, when shooting a moving image in the high image quality mode, the time for reading the analog signal is longer than the time for shooting the moving image in the standard image quality mode. This is because the number of recorded images has to be increased in order to improve the image quality of the moving image to be shot. To that end, the amount of data to be transferred must be increased by increasing the reading time of the analog signal read from the CCD. Because it must. Also, the frame rate is different between the high image quality mode and the standard image quality mode, and the time zone during which the analog signal is read may be different.

  Therefore, there is a demand to reduce the influence of noise when recording an image signal regardless of the reading pattern of the analog signal from the CCD. However, in the conventional signal mixed system, it is not assumed that the analog signal readout pattern is changed.

  An object of the present invention is to provide an imaging apparatus, an imaging method, and a program that can reduce the influence of noise from an image signal on an analog signal without being influenced by the readout pattern of the analog signal.

The invention described in claim 1
Setting means for arbitrarily setting the readout period of the analog signals sequentially output from the imaging unit;
First output control means for sequentially outputting analog signals from the imaging unit in a readout period set by the setting means;
An image signal generating means for converting the analog signal output by the first output control means into a digital signal, performing a predetermined process on the converted digital signal, and generating a digital image signal;
Second output control means for outputting the digital image signal generated by the image signal generation means in a blank period outside the predetermined readout period;
It is characterized by providing.
The invention according to claim 2
A shooting mode setting means for setting one shooting mode from a plurality of shooting modes;
The setting means sets the readout period according to the shooting mode set by the shooting mode setting means.
The invention according to claim 3
The imaging unit is in an exposure state during the blank period.
The invention according to claim 4
A setting step for arbitrarily setting a readout period of analog signals sequentially output from the imaging unit;
A first output control step for sequentially outputting analog signals from the imaging unit in the readout period set in the setting step;
The analog signal output in the first output control step is converted into a digital signal,
An image signal generation step for generating a digital image signal by performing predetermined processing on the converted digital signal;
A second output control step for outputting the digital image signal generated in the image signal generation step in a blank period outside the predetermined readout period;
It is characterized by including.
The invention according to claim 5
The computer of the imaging device,
Setting means for arbitrarily setting the readout period of the analog signals sequentially output from the imaging unit;
First output control means for sequentially outputting analog signals from the imaging unit in the readout period set by the setting means;
An image signal generating means for converting the analog signal output by the first output control means into a digital signal and performing a predetermined process on the converted digital signal to generate a digital image signal;
Second output control means for outputting the digital image signal generated by the image signal generating means in a blank period outside the predetermined readout period;
To function as.

  According to the present invention, the influence of noise from an image signal on an analog signal can be reduced regardless of the read pattern of the analog signal.

  FIG. 1 is a rear view of an electronic camera according to the present invention. On the back of the electronic camera, as shown in FIG. 1, a power button 1, a menu key 4 for displaying a menu screen, an execution key 5 for executing a selected content, selection of an item on the menu screen, A multi-function cross key 6 and an LCD monitor 10 for instructing frame advance and the like are provided.

  A mode dial 3 is provided on the upper surface of the camera. By rotating the mode dial 3, any one of a moving image shooting mode, a still image shooting mode, a playback mode, and the like can be set. A shutter button 2 is provided at the center of the mode dial 3. When pressed, the shutter button 2 outputs an operation signal instructing the start or end of shooting.

  FIG. 2 is a block diagram showing an internal configuration of the electronic camera shown in FIG. In FIG. 2, the subject image is formed on the light receiving surface of the CCD image sensor 14 via the photographing lens 12. The formed subject image is photoelectrically converted into a signal charge of an amount corresponding to the amount of incident light by each photodiode arranged on the light receiving surface and accumulated in each pixel of the CCD image sensor 14, so that the CCD image sensor 14 exposures are made.

  The accumulated signal charge is sequentially read out in units of one frame (image) as an analog signal (CCD output) corresponding to the signal charge based on the timing signal output (imaging clock) applied from the clock generation circuit 16. In order to read out an analog signal for one frame from the CCD image sensor 14, a reading period of a certain time is required.

  Each time an analog signal for one frame is read from the CCD image sensor 14, an A blank period occurs. The A blank period is a time during which reading of an analog signal from the CCD image sensor 14 is stopped. During the A blank period, the CCD image sensor 14 is in an exposure state.

  Analog signals sequentially read from the CCD image sensor 14 are added to the AFE 18. As shown in FIG. 3, the AFE 18 includes a CDS circuit 18A, an amplifier 18B, an A / D converter 18C, and the like. The CDS circuit 18A correlates an analog signal input based on a sampling pulse applied from the clock generation circuit 16. Double sampling processing. That is, the CDS circuit 18A extracts only the image signal component by performing the correlated double sampling on the analog signal input from the CCD image sensor 14 using the sampling pulses DS1 and DS2.

  The signal processed by the CDS circuit 18A is subjected to gain control by the amplifier 18B and then input to the A / D converter 18C. The A / D converter 18 </ b> C converts the input signal into a digital signal for each pixel of the CCD image sensor 14 based on the AD clock applied from the clock generation circuit 16.

  A digital signal that has been subjected to preprocessing such as analog processing and A / D conversion by the AFE 18 is taken into a line memory 201 in a signal processor 20 formed of a large scale integrated circuit (LSI). The captured digital signal is DMA transferred to the RAM 22. When the digital signal is transferred to the RAM 22, the digital signal is again taken into the line memory 201 from the AFE 18.

  The signal processor 20 performs overall control of each circuit based on inputs from the operation unit 24 including the shutter button 2, the mode dial 3, the execution key 5, the cross key 6 and the like shown in FIG. The signal processor 20 reads a necessary program from the ROM 26 in which a camera control program or the like is recorded, and executes various operations according to the program, thereby setting means, first output control means, and image signal generation means. , Function as second output control means, and shooting mode setting means.

  In addition, when the moving image shooting is performed in the moving image shooting mode, the signal processor 20 performs white on the digital signals for all the lines (entire screen) of the CCD image sensor 14 captured in the RAM 22 as described above. Various digital processing such as balance adjustment, gamma correction, YC processing, and compression processing are performed to generate an image signal compressed into a predetermined format.

  Thereafter, the generated image signal is sequentially output to the memory card 28 in units of one frame and recorded on the memory card 28. In order to record an image signal for one frame on the memory card 28, an output period of a certain time is required.

  Each time an image signal for one frame is recorded from the signal processor 20, a D blank period is generated. The D blank period is a period in which the output of the image signal from the signal processor is stopped. The image signal output operation from the signal processor 20 is executed in parallel with the analog signal read operation from the CCD image sensor 14.

  FIG. 5 is a flowchart for explaining the operation of the electronic camera according to the present invention. When the mode dial 3 is rotated to set the operation mode to the moving image shooting mode and the power button 1 is turned on, the signal processor 20 operates according to the program, thereby executing processing as shown in the flowchart of FIG. To do. That is, the signal processor 20 causes the LCD monitor 10 to display a through image based on image data for one frame (screen) captured from the CCD image sensor 14 and accumulated in the RAM 22 (step S1).

  When the user operates the execution key 5 in this state, a menu screen is displayed on the LCD monitor 10. Then, the display of the LCD monitor 10 is switched from the menu screen to the shooting mode setting screen by the user's operation (step S2). On the shooting mode setting screen, as shown in FIG. 4, selection items of “high image quality mode” and “standard image quality mode” are displayed. In the “high image quality mode”, the number of recording pixels of the image signal is larger than in the “standard image quality mode”, and a moving image with good image quality can be recorded.

  When a selection input is made for any of the items “high image quality mode” and “standard image quality mode” by the user's operation of the cross key 6 or the like on the shooting mode setting screen, the signal processor 20 performs shooting according to the selection input. A mode is set (step S3). The signal processor 20 controls the timing signal output operation and the image signal output operation by the clock generation circuit 15 in accordance with the set photographing mode.

  FIG. 6 is a timing diagram showing the signal waveform of the analog signal and the signal waveform of the image signal when “high image quality mode” is set as the moving image shooting mode. In the figure, the time axis is set to the right.

  When the “high image quality mode” is set as the moving image shooting mode, as shown in FIG. 6, the signal processor 20 has an analog signal reading period 100 for one frame of about 58 ms and an A blank period 101 of about 8 ms. The timing signal output operation by the clock generation circuit 15 is controlled so that the analog signals are sequentially read from the CCD image sensor 14 frame by frame (step S4). In the “high quality mode”, the frame rate is 15 fps, and the one frame period 102 is about 66 ms.

  Subsequent to step S4, the signal processor 20 is in a standby state to detect a shooting start instruction (step S5) unless the shutter button 2 is fully pressed (step S5; NO). When the shutter button 2 is fully pressed in this state, the signal processor 20 detects an operation signal instructing the start of shooting from the shutter button 2 (step S5; YES), and moving image shooting in the “high image quality mode” is performed. Done.

  That is, in the “high image quality mode”, the read analog signal is A / D converted into a digital signal and then taken into the RAM 22. The digital signal taken into the RAM 22 is subjected to various digital processes by the signal processor 20 to generate an image signal. Then, the signal processor 20 sequentially outputs the image signals one frame at a time so that the output period 104 of the image signal for one frame is about 4 ms and the D blank period 103 is about 62 ms, and records it on the memory card 28 ( Step S6). Note that the output of the image signal for the first frame (the first frame read after the start of reading of the analog signal) is started about 60 ms after the start of reading of the analog signal. The number of recorded pixels in the “high quality mode” is 1308 × 490 (the number of horizontal pixels × the number of vertical pixels).

  In this way, in the “high quality mode”, the image signal is output only during the time when the A blank period 101 occurs. Then, the analog signal readout period 100 and the image signal output period 104 do not overlap on the time axis, so that the influence of noise from the image signal on the analog signal can be reduced.

  FIG. 7 is a timing chart showing the signal waveform of the analog signal and the signal waveform of the image signal when the “standard image quality mode” is set as the moving image shooting mode. In the figure, the time axis is set to the right.

  When the “standard image quality mode” is set as the moving image shooting mode, as shown in FIG. 7, the signal processor 20 has an analog signal reading period 110 for one frame of about 29 ms and an A blank period 111 of about 4 ms. The timing signal output operation by the clock generation circuit 15 is controlled so that the analog signals are sequentially read from the CCD image sensor 14 frame by frame (step S7). In the “standard image quality mode”, the frame rate is 30 fps, and the one frame period 112 is about 33 ms.

  Subsequent to step S7, the signal processor 20 is in a standby state to detect a photographing start instruction (step S8) unless the shutter button 2 is fully pressed (step S8; NO). When the shutter button 2 is fully pressed in this state, the signal processor 20 detects an operation signal instructing the start of shooting from the shutter button 2 (step S8; YES), and moving image shooting in the “standard image quality mode” is performed. Done.

  That is, in the “standard image quality mode”, the read analog signal is A / D converted into a digital signal and then taken into the RAM 22. The digital signal taken into the RAM 22 is subjected to various digital processes by the signal processor 20 to generate an image signal. Then, the signal processor 20 sequentially outputs the image signal for each frame so that the image signal for one frame has an output period 114 of about 2 ms and a D blank period 113 of about 31 ms, and records it on the memory card 28 ( Step S9). Note that the output of the image signal for the first frame starts about 30 ms after the start of reading of the analog signal. Further, the number of recording pixels in the “high quality mode” is 1308 × 245 (the number of horizontal pixels × the number of vertical pixels).

  In this way, in the “standard image quality mode”, an image signal is output only at the time when the A blank period 111 occurs. Then, the analog signal readout period 110 and the image signal output period 114 do not overlap on the time axis, so that the influence of noise from the image signal on the analog signal can be reduced.

Subsequent to step S6 or step S9, unless the shutter button 2 is fully pressed again (step S11; NO), the signal processor 20 continues recording the image signal to the memory card 28, that is, the moving image recording (step S10). ). When the shutter button 2 is fully pressed during moving image recording, the signal processor 20 detects an operation signal instructing the end of shooting from the shutter button 2 (step S11; YES), and ends moving image recording. Thus, the operation according to the flowchart of FIG.

  As described above, the reading pattern of the analog signal read from the CCD image sensor 14 differs between when the “high image quality mode” is set as the moving image shooting mode and when the “standard image quality mode” is set. Therefore, in the electronic camera according to the present embodiment, the output pattern of the image signal is also changed in accordance with the different readout pattern of the analog signal, and the time when the readout of the analog signal is stopped (the time when the A blank period occurs) The image signal is output only to the. As a result, the analog signal readout period and the image signal output period do not overlap on the time axis regardless of the analog signal readout pattern, and the influence of noise from the image signal on the analog signal can be reduced. it can.

  The present invention is not limited to the electronic camera described in the above-described embodiment, and can be applied to a mobile phone having a photographing function, a PDA (personal digital assistant), and the like. The present invention is not limited to the above-described embodiment, and various design changes can be made without departing from the spirit of the present invention.

Rear view of electronic camera according to the present invention The block diagram which shows the internal structure of the electronic camera shown in FIG. Block diagram showing internal circuit of AFE Figure showing the shooting mode setting screen The flowchart which shows operation | movement of the electronic camera which concerns on this invention. Timing diagram showing signal waveform of analog signal and signal waveform of image signal in high image quality mode Timing diagram showing signal waveform of analog signal and signal waveform of image signal in standard image quality mode Timing chart showing signal waveform of analog signal and signal waveform of image signal in conventional electronic camera Block diagram showing the internal configuration of the electronic camera

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power button 2 Shutter button 3 Mode dial 4 Menu key 5 Execution key 6 Cross key 10 LCD monitor 12 Imaging lens 14 CCD image sensor 16 Clock generation circuit 18 AFE
20 signal processor 22 RAM
24 Operation unit 26 ROM
28 Memory card 100, 110 Analog signal readout period 101, 111 A Blank period 103, 113 D Blank period 104, 114 Image signal output period

Claims (5)

Setting means for arbitrarily setting the readout period of the analog signals sequentially output from the imaging unit;
First output control means for sequentially outputting analog signals from the imaging unit in a readout period set by the setting means;
An image signal generating means for converting the analog signal output by the first output control means into a digital signal, performing a predetermined process on the converted digital signal, and generating a digital image signal;
Second output control means for outputting the digital image signal generated by the image signal generation means in a blank period outside the predetermined readout period;
An imaging apparatus comprising: A shooting mode setting means for setting one shooting mode from a plurality of shooting modes;
The imaging apparatus according to claim 1, wherein the setting unit sets the readout period according to a shooting mode set by the shooting mode setting unit.   The imaging apparatus according to claim 1, wherein the imaging unit is in an exposure state during the blank period. A setting step for arbitrarily setting a readout period of analog signals sequentially output from the imaging unit;
A first output control step for sequentially outputting analog signals from the imaging unit in the readout period set in the setting step;
The analog signal output in the first output control step is converted into a digital signal,
An image signal generation step for generating a digital image signal by performing predetermined processing on the converted digital signal;
A second output control step for outputting the digital image signal generated in the image signal generation step in a blank period outside the predetermined readout period;
An imaging method comprising: The computer of the imaging device,
Setting means for arbitrarily setting the readout period of the analog signals sequentially output from the imaging unit;
First output control means for sequentially outputting analog signals from the imaging unit in the readout period set by the setting means;
An image signal generating means for converting the analog signal output by the first output control means into a digital signal and performing a predetermined process on the converted digital signal to generate a digital image signal;
Second output control means for outputting the digital image signal generated by the image signal generating means in a blank period outside the predetermined readout period;
Program to function as.

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