JP2006235719A - Imaging method and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem such that a bar-code recognition rate through a fixed focus lens is low because an object is small at a focal position and the object is out of focus in imaging in proximity thereto when imaging a small image such as a two-dimensional bar code in the use of the lens. <P>SOLUTION: When switching over to a bar-code imaging mode from a monitor mode of pixel-skipping reading, a scanning mode switching part 21 switches to an operation so as to reduce a scanning range of an imaging element 10 by a vertical scanning circuit 11 and a horizontal scanning circuit 12 and also reduce intervals of pixels to be read out than those in the monitor mode through a drive timing control part 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging method and an imaging apparatus using a solid-state imaging device, and more particularly to a technique for increasing the resolution of a captured image and speeding up reading from the imaging device.

  2. Description of the Related Art Conventionally, as a solid-state imaging device, a device including a MOS type imaging device (image sensor) including a plurality of pixels, a vertical scanning circuit, and a horizontal scanning circuit is known. Each pixel in the image sensor includes a photodiode that accumulates charges according to the amount of light received during the exposure period, and a charge accumulation unit that temporarily accumulates charges output from the photodiodes. Then, the charge accumulated in the photodiode is read out as a pixel signal. Each pixel is sequentially selected for each row by a read pulse and a reset pulse from the vertical scanning circuit, and pixel signals for one row are output for each column by a scanning pulse from the horizontal scanning circuit.

  In the image sensor, a reset pulse is applied only to the pixel cells in the selected row, and the potential of the charge accumulation unit in the selected row is set to a high potential, whereby the amplification transistor is turned on and a pixel signal is output. On the other hand, if the potential in the charge storage portion of the pixel cells in the non-selected row is kept low, the amplification transistor is turned off, so that the pixel signal in the non-selected row is not output. Specifically, the potential of the charge storage unit is set to the potential of the power supply voltage by the reset pulse, and the charge stored in the photodiode is read to the charge storage unit by the read pulse. A pixel signal corresponding to the read charge is amplified by the amplification transistor and output. Finally, the charge in the charge storage unit is cleared by the reset pulse. These operations are continuously performed on the pixels in each row.

  In each of the vertical scanning circuit and the horizontal scanning circuit, a pixel from which charges are read is selected using a shift register. Specifically, the drive timing control unit inputs a vertical scanning start pulse to a shift register serving as a vertical scanning circuit, selects a row while shifting it, and the above-described reset pulse and A lead pulse is being input. Further, a horizontal scanning start pulse is input to a shift register serving as a horizontal scanning circuit, and a column is selected while shifting this, and a scanning pulse is sent to the selected column.

  In this regard, according to the shift register according to the first prior art, it is possible to set the scan range of the image sensor by the preceding scan and scan an arbitrary range during the main scan. Specifically, a start pulse is input to the first stage of the shift register during the preceding scan, and when the start pulse is shifted to a desired position, information on each stage of the shift register is transferred to a separately provided memory. During the main scan, the information stored in the memory is returned to each stage of the shift register. Thereby, scanning can be started from a desired position. When scanning is stopped halfway, the stored information in the memory is cleared and the cleared information is transferred to each stage of the shift register (see Patent Document 1).

  In recent years, camera-equipped mobile phones equipped with small image sensors have been sold. In these mobile phone cameras, since it is necessary to focus at every distance, a fixed focus lens designed so that the focus can be adjusted from several tens of centimeters to infinity is often used. When performing normal shooting, a captured image is generally displayed on an LCD (Liquid Crystal Display) during monitoring before shooting a still image, and it is common to take a still image by determining the composition while viewing the image. In addition, all pixels are read in order to leave a high-quality image during still image shooting, but the output from the image sensor is thinned out in order to display an image on the LCD at a high frame rate during monitoring.

  Also, many recent mobile phones have a barcode recognition function. If a barcode containing URL (Uniform Resource Locator) and business card information is created in advance, the barcode can be read. It is possible to save time and effort when connecting to the Internet or exchanging addresses. In addition, input errors can be prevented. However, some cameras built in mobile phones still have poor resolution, so some effort is needed to recognize fine images such as barcodes.

According to the second prior art, when reading a barcode with a camera-equipped mobile phone, the setting is changed from that for normal photographing and optimized for barcode photographing. Specifically, the white balance and exposure are adjusted so that the contrast between light and dark in the code is emphasized, and the correction coefficient is adjusted so as to enhance the contour more (see Patent Document 2).
JP-A-6-350933 JP 2004-56696 A

  When shooting a small image such as a two-dimensional barcode using a fixed focus lens, the fixed focus lens is easy to focus on distant objects, and it is difficult to focus on nearby objects. May be out of focus when taken close to the subject. For this reason, the barcode recognition rate with a fixed focus lens is low, and a cellular phone with a camera having a barcode recognition function requires a macro lens and an AF (autofocus) function. However, due to cost, even a mobile phone that cannot be equipped with a macro lens or AF function needs to support a barcode recognition function.

  The present invention solves such a problem, and provides a driving method and an imaging apparatus for an image sensor at the time of barcode shooting that can be read at high resolution or can be read at high resolution and high speed. Objective.

  In order to solve the above problems, an imaging device of the present invention drives an imaging device (sensor) having a plurality of pixels arranged two-dimensionally and the image sensor to read out charges accumulated in the imaging device. A vertical scanning circuit and a horizontal scanning circuit. A monitor mode in which an imaging signal is formed at a first pixel interval, and an image recognition mode (for example, a bar code imaging mode) in which an imaging signal is formed at a second pixel interval that is narrower than the first pixel interval. Switching.

  For example, when the mode is switched to the barcode photographing mode, the sensor driving is switched so that the interval between pixels to be read is narrower than that in the monitor mode. In order to drive at a higher speed, when switching to the bar code shooting mode, the start pulse of vertical scanning or horizontal scanning is set so as to drive a range smaller than the entire pixel area, and the pixel read out from the monitor mode is set. Switch to sensor drive to narrow the interval.

  Further, when the mode is switched to the barcode photographing mode, it is difficult to keep the subject within the reading range because the angle of view is narrow. In order to solve this problem, a wide range is read immediately after switching to barcode shooting, and sensor driving is switched so that only a necessary range is read when a subject is detected.

  Further, in the sensor driving, the angle of view at the time of barcode shooting is narrowed, so that the influence of camera shake becomes large. In order to solve this problem, the movement of the subject is detected, and the reading position and the imaging range are changed according to the movement amount.

  According to the present invention, even with a fixed focus lens without an AF function or a macro lens, an imaging method with a high resolution or a high frame rate suitable for barcode photography can be performed by a start pulse without changing the structure of a sensor corresponding to an imaging device. And an imaging device is realizable.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration example of an imaging apparatus according to the present invention. The image pickup apparatus of FIG. 1 includes an image pickup element 10, a vertical scanning circuit 11, a horizontal scanning circuit 12, and a DSP (Digital Signal Processor) 20. The image sensor 10 is, for example, a MOS type image sensor, and has a pixel array of n rows and m columns (n and m are both even numbers of 2 or more). The vertical scanning circuit 11 and the horizontal scanning circuit 12 are circuits for driving the image sensor 10 so as to select pixels to be read from the image sensor 10, and each of the shift registers described as the first prior art is used. I have. That is, according to the vertical scanning circuit 11 and the horizontal scanning circuit 12 of FIG. 1, the scanning range of the image sensor 10 can be set by the preceding scanning, and an arbitrary range can be scanned during the main scanning.

  The DSP 20 includes a scanning mode switching unit 21, a drive timing control unit 22, a signal processing unit 23, an image output unit 24, a barcode detection unit 25, and a barcode recognition unit 26. When the scanning mode switching unit 21 receives the barcode imaging command, the scanning mode switching unit 21 switches the driving method of the image sensor 10 from the monitor mode to the barcode imaging mode. The drive timing control unit 22 is a circuit for controlling the operation of each of the vertical scanning circuit 11 and the horizontal scanning circuit 12, and vertically outputs the vertical scanning start pulse VSTP, the vertical scanning clock signal VCLK, and the vertical scanning range control signal VRNG. A horizontal scanning start pulse HSTP, a horizontal scanning clock signal HCLK, and a horizontal scanning range control signal HRNG are supplied to the scanning circuit 11 to the horizontal scanning circuit 12, respectively. Here, the vertical scanning range control signal VRNG and the horizontal scanning range control signal HRNG are signals for controlling the operation of the aforementioned memory for storing information of each stage of the shift register. The signal processing unit 23 receives the imaging signal PIX obtained from the imaging device 10 via the horizontal scanning circuit 12, and in addition to processing such as correlated double sampling, automatic gain adjustment, analog / digital conversion, white balance adjustment, contour Preprocessing such as enhancement is applied to the image signal PIX. The image output unit 24 controls digital image output to an LCD (not shown). The barcode detection unit 25 detects the position and size of the subject (barcode) from the signal imaged in the previous frame, and the direction and amount of movement of the subject from the signals imaged one frame before and two frames ago. It has a function to detect. The information thus obtained is sent to the scanning mode switching unit 21. The barcode recognition unit 26 performs a recognition process for the detected barcode.

  The scanning mode switching unit 21 can be realized by a microcode. The drive timing control unit 22 and the signal processing unit 23 may be outside the DSP 20.

  FIG. 2 shows an example in which the entire pixel area of the image sensor 10 is a pixel readout range. In this case, the scanning range of the vertical scanning circuit 11 is set to 1 to n, and the scanning range of the horizontal scanning circuit 12 is set to 1 to m. However, pixel decimation readout is executed in the monitor mode, and all pixel readout is executed in the barcode photographing mode.

  FIG. 3 is a timing diagram of the monitor mode corresponding to FIG. In the monitor mode, pixels to be read are thinned out in order to increase the frame rate. According to FIG. 3, as described below, pixels in the vertical direction are read out by thinning out one row at a time.

  First, in a row that is not thinned out, a row is selected while the vertical scanning start pulse VSTP supplied to the vertical scanning circuit 11 is shifted by the vertical scanning clock signal VCLK. Then, a horizontal scanning start pulse HSTP is supplied to the horizontal scanning circuit 12, and the horizontal scanning circuit 12 selects and selects pixels in the 1 to m columns in the horizontal direction while shifting the horizontal scanning start pulse HSTP by the horizontal scanning clock signal HCLK. Pixel readout is performed by sequentially outputting pixel signals of the pixels. One image signal PIX is composed of one pixel signal or a plurality of pixel signals read out. Here, the imaging signal PIX is a signal corresponding to one pixel when actually displayed on a display device. In actual readout of a MOS image sensor, a pixel signal is output by a combination of a plurality of pulses including a read pulse and a reset pulse. However, since it has already been described as the background art, description thereof is omitted here. On the other hand, since the horizontal scanning start pulse HSTP is not input to the thinned-out row, even if the row is selected by the vertical scanning circuit 11, the pixels in that row are not read out. By periodically repeating these two readout methods, high frame rate imaging can be realized.

  This will be described in more detail with reference to FIG. First, a vertical scanning start pulse (VSTP) 201 is supplied to a position corresponding to the first row of the image sensor 10 in the vertical scanning circuit 11. As a result, the first row of the image sensor 10 is selected. Further, a horizontal scanning start pulse (HSTP) 202 is supplied to the horizontal scanning circuit 12. As a result, pixels in 1 row and 1 column are selected and read out. Next, when the horizontal scanning clock signal HCLK is supplied to the horizontal scanning circuit 12, the horizontal scanning start pulse HSTP moves to the second column. As a result, pixels in 1 row and 2 columns are selected and read out. The above operation is repeated, and m horizontal scanning clock signals HCLK are input to the horizontal scanning circuit 12, whereby all pixels in the 1st to 1m columns in the first row are read out.

  Next, the vertical scanning clock signal (VCLK) 203 is supplied to the vertical scanning circuit 11, and the vertical scanning start pulse VSTP moves to the second row. As a result, the second line is selected. However, the horizontal scanning start pulse HSTP is not supplied. For this reason, no pixel is selected and readout is not performed.

  The drive timing control unit 22 divides a reference clock signal output from a clock generation circuit (not shown) to generate two types of a long clock signal and a short clock signal as the vertical scanning clock signal VCLK, and performs vertical scanning. This is supplied to the circuit 11. The reason why the vertical scanning clock signal (VCLK) 203 is a short clock signal is to read out the second row, so that the vertical scanning start pulse VSTP is quickly moved to the third row to increase the frame rate.

  Next, the vertical scanning clock signal (VCLK) 204 is supplied to the vertical scanning circuit 11, and the vertical scanning start pulse VSTP moves to the third row. As a result, the third line is selected. Further, a horizontal scanning start pulse (HSTP) 205 is supplied to the horizontal scanning circuit 12. As a result, pixels in 3 rows and 1 column are selected and read out. Thereafter, each time the horizontal scanning clock signal HCLK is supplied to the horizontal scanning circuit 12, the horizontal scanning start pulse HSTP moves, and the pixels in the first row to the 1st column are sequentially selected and read.

  By repeating the above, pixels in odd rows are read out, but pixels in even rows are not read out. When the reading of the pixels of one frame is completed, the vertical scanning start pulse VSTP is supplied again, and the reading of the pixels of the second frame is started.

  Note that the read-out line interval can be freely set according to the required frame rate. For example, when only one row is read out in three rows in order to further increase the frame rate, the horizontal scanning start pulse HSTP is supplied once every time the vertical scanning clock signal VCLK is supplied to the vertical scanning circuit 11 three times. do it. Another driving method may be used when reading by thinning. Further, pixel thinning may be performed in the horizontal direction.

  FIG. 4 is a timing chart of the barcode photographing mode corresponding to FIG. Initially, the imaging apparatus of FIG. 1 is in the monitor mode. In the monitor mode, the above-described pixel thinning readout is performed in order to monitor a moving image. Here, when the barcode photographing mode is switched by a user operation or the like, the scanning mode switching unit 21 switches the driving method of the image sensor 10 from pixel thinning readout to all pixel readout.

  When the barcode mode is switched by the scanning mode switching unit 21, first, the scanning range of the vertical scanning circuit 11 and the horizontal scanning circuit 12 is determined. In other words, it is determined from which row to start reading and from which row to finish reading, and from which column to start reading and from which column to finish reading. In the example of FIG. 4, the vertical scanning circuit 11 is set to scan in the range of 1 to n, and the horizontal scanning circuit 12 is set to scan in the range of 1 to m. That is, the entire range is scanned. The relationship between the vertical scanning circuit 11 and the horizontal scanning circuit 12 is that when the shift register of the horizontal scanning circuit 12 is shifted m times, the shift register of the vertical scanning circuit 11 is shifted once.

  Since the vertical scanning circuit 11 is set to be reset when scanning is performed from 1 to n and the horizontal scanning circuit 12 is scanned from 1 to m, when the pixel reading of the scanning range is completed in each shift register, the next frame is set. Move on to reading. The detailed flow will be described below.

  (1) The scanning mode switching unit 21 performs a switching process for changing the sensor drive. Specifically, a drive switching signal for switching the reading method is supplied to the drive timing control unit 22.

  (2) The scanning range of the vertical scanning circuit 11 is set to 1 to n, and the scanning range of the horizontal scanning circuit 12 is set to 1 to m.

  (3) The vertical scanning start pulse VSTP is input to the first stage of the vertical scanning circuit 11, and the horizontal scanning start pulse HSTP is input to the first stage of the horizontal scanning circuit 12. While the first row is selected by the vertical scanning circuit 11, the horizontal scanning clock signal HCLK is sequentially supplied to the horizontal scanning circuit 12, whereby pixels in the 1 to m columns are sequentially selected, and reading is performed from each pixel. . When pixel reading of the mth column is completed, the horizontal scanning start pulse HSTP in the horizontal scanning circuit 12 is reset.

  (4) The vertical scanning clock signal VCLK is supplied to the vertical scanning circuit 11 to select the second row, and the horizontal scanning start pulse HSTP is input to the first stage of the horizontal scanning circuit 12. Then, the horizontal scanning clock signal HCLK is sequentially supplied to the horizontal scanning circuit 12, whereby pixels in the 1st to 1m columns from the second row are sequentially selected, and signals are read from the respective pixels.

  By repeating the above processing up to the nth row without performing row thinning, all n × m pixels can be read out. The read n × m pixel signals are input to the subsequent image processing as n × m image signals PIX.

  As described above, in the image pickup apparatus of FIG. 1, the frame rate is increased by performing pixel thinning in the monitor mode, while the resolution is increased by reading all pixels during bar code shooting, and there is no fixed AF function or macro lens. Even with a focus lens, the barcode recognition rate can be improved.

  Although the barcode recognition rate increases by performing all-pixel reading, barcode recognition is difficult if the area occupied by the barcode in the imaging region is too small. For this reason, it is better to display a guide indicating in which area the user should copy the barcode on the monitor using OSD (On Screen Display).

  Now, since the sensor drive in FIG. 4 captures an image even in a portion unnecessary for barcode recognition, the frame rate in the barcode photographing mode becomes slow. Therefore, a method for improving the barcode recognition rate without reducing the frame rate will be described.

  FIG. 5 shows an example in which the pixel readout range in the barcode shooting mode of the imaging apparatus of FIG. 1 is limited from the j-th row to the k-th row. That is, the scanning range is j to k for the vertical scanning circuit 11, and the pixel reading range is narrowed. However, the pixel readout range may be narrowed also in the horizontal direction.

  FIG. 6 is a timing diagram corresponding to the pixel readout range of FIG. When the barcode mode is switched by the scanning mode switching unit 21, first, the scanning range of the vertical scanning circuit 11 and the horizontal scanning circuit 12 is determined. In the example of FIG. 6, the vertical scanning circuit 11 is set to scan the range of j to k, and the horizontal scanning circuit 12 is set to scan the range of 1 to m.

  Since the vertical scanning circuit 11 is set to be reset when the horizontal scanning circuit 12 is scanned up to k and the horizontal scanning circuit 12 is scanned up to m, when the vertical scanning circuit 11 is scanned from j to k, the next frame is read out. It is necessary to generate the vertical scanning start pulse VSTP. When the horizontal scanning circuit 12 is scanned from 1 to m, it is necessary to generate a horizontal scanning start pulse HSTP for reading the next row. The detailed flow will be described below.

  (1) The scanning mode switching unit 21 performs a switching process for changing the sensor drive. Specifically, a drive switching signal for switching the reading method is supplied to the drive timing control unit 22.

  (2) The scanning range of the vertical scanning circuit 11 is set to j to k, and the scanning range of the horizontal scanning circuit 12 is set to 1 to m.

  (3) The vertical scanning start pulse VSTP is input to the j-th stage of the vertical scanning circuit 11, and the horizontal scanning start pulse HSTP is input to the first stage of the horizontal scanning circuit 12. While the j-th row is selected by the vertical scanning circuit 11, the horizontal scanning clock signal HCLK is sequentially supplied to the horizontal scanning circuit 12, whereby pixels in 1 to m columns are sequentially selected, and reading is performed from each pixel. . When pixel reading of the mth column is completed, the horizontal scanning start pulse HSTP in the horizontal scanning circuit 12 is reset.

  (4) The vertical scanning clock signal VCLK is supplied to the vertical scanning circuit 11 to select the (j + 1) th row, and the horizontal scanning start pulse HSTP is input to the first stage of the horizontal scanning circuit 12. Then, by sequentially supplying the horizontal scanning clock signal HCLK to the horizontal scanning circuit 12, pixels of 1 to m columns from the (j + 1) th row are sequentially selected, and signals are read from the respective pixels.

  By repeating the above processing up to the k-th row without performing line thinning, all (k−j + 1) × m pixels can be read out. The read out (k−j + 1) × m pixel signals are input to subsequent image processing as (k−j + 1) × m imaging signals PIX. When the reading of the k-th row is completed, the vertical scanning start pulse VSTP is input again to the vertical scanning circuit 11, whereby the reading of the next frame is started.

  As described above, according to the sensor driving of FIG. 6, it is possible to increase the resolution and improve the barcode recognition rate by performing all pixel readout in a necessary area at the time of barcode shooting compared to the monitor mode. Become. Furthermore, since the number of pixels to be read out is not so large even in the barcode shooting mode, barcode recognition can be performed quickly and the frame rate can be improved. In particular, in the case of a fixed focus lens that does not have a macro lens, the area that actually includes the barcode is reduced, and the number of pixels to be read is also reduced. In addition, even if the barcode imaging area is not displayed on the OSD, it is only necessary to copy the barcode as large as possible in the read area, so that the user can easily perform the barcode recognition operation.

  Next, a method for automatically determining the pixel readout range in the barcode photographing mode based on information from the barcode detection unit 25 will be described.

  FIGS. 7A and 7B show an operation of changing the pixel readout range based on information on the position and size of the subject (barcode) in order to improve user operability. Immediately after switching to barcode shooting, as shown in FIG. 7A, the sensor is switched to drive so as to read out all n × m pixels. The scanning range of the vertical scanning circuit 11 is set to 1 to n and the scanning range of the horizontal scanning circuit 12 is set to 1 to m by the preceding scanning. The barcode is detected by the barcode detection unit 25 from the image taken at this time. When a bar code is detected, as shown in FIG. 7B, the driving is switched to read out only the range near the bar code. Specifically, the pixel readout range is determined from the detected barcode position and size. When the reading range is determined to be 1 to j, the scanning range of the vertical scanning circuit 11 is set to 1 to j, and the scanning range of the horizontal scanning circuit 12 is set to 1 to m. As a result, only the necessary range is automatically read out from a wide imaging range, so that the photographer does not have to keep the barcode in a narrow angle of view.

  FIGS. 8A and 8B show an operation of changing the pixel readout range based on information on the moving direction and moving amount of the subject (barcode) in order to eliminate, for example, the influence of camera shake. . According to FIG. 8A, by setting the scanning range of the vertical scanning circuit 11 to i to j, the barcode as the subject is within the pixel readout range. However, when camera shake occurs, the subject does not fit in the pixel readout range as indicated by a thick broken line in FIG. 8B with the scanning range of the vertical scanning circuit 11 set to i to j. Therefore, the barcode detection unit 25 recognizes an image that becomes a mark such as a cut-out symbol from images of two consecutive frames, and detects the movement direction and the movement amount. When the movement is detected in this way, the scanning mode switching unit 21 and the drive timing control unit 22 set the reading start position in the vertical direction of the next frame to k = (j + movement amount) and the reading end position to l = (k +). Read width). Here, if the movement direction detected by the barcode detection unit 25 is the minus direction and the movement amount is x, the input position of the vertical scanning start pulse VSTP is changed to (i + x), the movement direction is the plus direction, and the movement amount. If x is x, the vertical scan start pulse VSTP input position is changed to (i-x).

  As described above, according to the sensor driving described in FIGS. 8A and 8B, the movement amount is detected from the previous frame, and the movement of the subject is followed by changing the reading start position. Can do. Further, since the movement amount detection is performed by MPEG compression coding or the like in the conventional imaging apparatus, if the motion vector in MPEG is used, the increase in circuit scale is small. Any number of previous frames may be used as a frame for detecting the motion of the subject. For example, the movement may be detected in three consecutive frames, and the reading start position may be changed from the next frame. When the movement of the subject is not detected, the scanning mode switching unit 21 may maintain the sensor driving in the previous frame without performing the sensor driving switching process. Further, when the reading range is narrowed also in the horizontal direction, motion detection may be performed both in the horizontal direction and in the vertical and horizontal directions.

  The above-described embodiment is merely an example, and the present invention is not limited to this, and various modifications can be made. A modification will be described below.

  In the above-described embodiment, all the pixels are read out in the barcode imaging mode, but it is not always necessary to read out all the pixels. The characteristic configuration of the present invention is to increase the number of imaging signals PIX in the same area in the barcode imaging mode compared to the monitor mode, in other words, to narrow the interval of the readout imaging signals PIX. In the best mode, all the pixels are read out to minimize the interval between the imaging signals PIX.

  Image processing mode adjusted for barcode shooting is prepared, and exposure, gradation characteristics, white balance, etc. are adjusted to emphasize the contrast of the code, and the edge enhancement correction coefficient is changed to enhance the outline. You may do it. Further, by further zooming, the area occupied by the barcode may be widened to increase the recognition rate.

  In the above embodiment, the vertical scanning circuit 11 and the horizontal scanning circuit 12 use shift registers that can input start pulses at arbitrary positions. However, a shift register capable of inputting pulses only in the normal first row or first column may be used. For example, the vertical scanning start pulse VSTP is skipped without inputting the horizontal scanning start pulse HSTP until the required area is reached, and all the horizontal scanning start pulses HSTP are input within the necessary area. If the horizontal scanning start pulse HSTP is not input again after the pixel readout is completed, all the pixels are read out in a necessary area.

  Further, the object of the present invention is effective not only for barcodes but also for text (for example, URLs) and for shooting an arbitrary range with high resolution during normal shooting.

  The present invention enables bar code photography with a high recognition rate even when it is difficult to mount a macro lens in terms of cost and mounting area, and is particularly effective in a mobile phone with a camera. However, the recognition rate can be further increased by using the macro lens and the AF function at the same time.

  In the above-described embodiment, an example in which pixel decimation readout is performed in the monitor mode and all pixel readout is performed in the barcode photographing mode has been described. In pixel mixed readout, signals from a plurality of pixels are mixed to form one image signal PIX. Even in the pixel mixture readout, all pixels may be read out. However, the difference from the all pixel readout is that one imaging signal PIX is composed of pixel signals from one pixel or pixel signals from a plurality of pixels. Whether one imaging signal PIX is configured or not. That is, in the monitor mode, all pixels are read out, and one image pickup signal PIX is constituted by pixel signals from a plurality of pixels (pixel mixture reading mode). In the bar code shooting mode, all pixels are read out and read from one pixel. A form in which one image pickup signal PIX is configured with pixel signals is conceivable. It is not always necessary to read out all the pixels in the pixel mixture reading, and the pixel signals read out while performing pixel thinning may be mixed to form one imaging signal PIX.

  The imaging method and the imaging apparatus according to the present invention are effective for an information terminal such as a mobile phone with a barcode recognition function and a text reader function. It is also effective when shooting an image that you want to retain at high resolution.

It is a block diagram which shows the structural example of the imaging device which concerns on this invention. It is a conceptual diagram which shows an example of the pixel read-out range in the imaging device of FIG. FIG. 3 is a timing diagram of a monitor mode corresponding to the pixel readout range in FIG. 2. FIG. 3 is a timing diagram of a barcode shooting mode corresponding to the pixel readout range of FIG. 2. FIG. 2 is a conceptual diagram illustrating an example of a pixel readout range in a barcode shooting mode of the imaging apparatus of FIG. FIG. 6 is a timing diagram corresponding to the pixel readout range of FIG. 5. FIG. 2 is a conceptual diagram illustrating an operation of changing a pixel readout range based on information on the position and size of a barcode that is a subject in the imaging apparatus of FIG. 1. FIG. 2 is a conceptual diagram illustrating an operation of changing a pixel readout range based on information on a moving direction and a moving amount of a barcode that is a subject in the imaging apparatus of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image pick-up element 11 Vertical scanning circuit 12 Horizontal scanning circuit 20 DSP
21 Scanning mode switching unit 22 Drive timing control unit 23 Signal processing unit 24 Image output unit 25 Barcode detection unit 26 Barcode recognition unit HCLK Horizontal scanning clock signal HRNG Horizontal scanning range control signal HSTP Horizontal scanning start pulse PIX Imaging signal VCLK Vertical scanning Clock signal VRNG Vertical scanning range control signal VSTP Vertical scanning start pulse

Claims (17)

An imaging method for imaging using an imaging element having a plurality of pixels arranged two-dimensionally,
Performing imaging in a monitor mode in which imaging signals are formed at first pixel intervals;
Switching the mode from the monitor mode to an image recognition mode in which an imaging signal is formed at a second pixel interval;
Recognizing a target image while performing imaging in the image recognition mode,
The imaging method, wherein the second pixel interval is narrower than the first pixel interval. The imaging method according to claim 1,
In the horizontal direction of the image sensor, the first pixel interval and the second pixel interval are equal, and in the vertical direction of the image sensor, the second pixel interval is greater than the first pixel interval. An imaging method characterized by being narrow. The imaging method according to claim 1,
The imaging method, wherein the second pixel interval is narrower than the first pixel interval in both the vertical direction and the horizontal direction of the imaging element. The imaging method according to claim 1,
The imaging method according to claim 1, wherein the image recognition mode is a barcode photographing mode for photographing a barcode and performing a recognition process. The imaging method according to claim 1,
An imaging method, wherein an area of the imaging element in which the imaging signal is formed is smaller in the image recognition mode than in the monitor mode. The imaging method according to claim 5, wherein
The area of the image sensor in which the image signal is formed is equal in the monitor mode and the image recognition mode in the horizontal direction of the image sensor, and in the image recognition mode in the vertical direction of the image sensor. An imaging method characterized by being narrower than the mode. The imaging method according to claim 5, wherein
In the image recognition mode, pixel signals are read from all the pixels in the area of the imaging element where the imaging signals are formed, and one imaging signal is configured by pixel signals read from one pixel. A characteristic imaging method. The imaging method according to claim 5, wherein
In the monitor mode, an imaging signal is formed by pixel thinning readout in which pixels constituting a predetermined row of the imaging device are thinned and pixel signals are read out. The imaging method according to claim 5, wherein
In the monitor mode, an image pickup signal is formed by mixing pixel signals that are read from each of a plurality of pixels of the image pickup device to form a single image pickup signal, thereby forming an image pickup signal. The imaging method according to claim 5, wherein
Detecting the position of the target image from within the entire pixel region of the image sensor;
An imaging method comprising: determining a region of the imaging element in which the imaging signal is formed according to the detected position of the target image. The imaging method according to claim 5, wherein
Detecting the movement of the subject from the imaging signal using a plurality of frames that are continuous in time series; and
And a step of moving a region of the image sensor in which the imaging signal is formed in accordance with the detected movement of the subject. The imaging method according to claim 11.
The step of detecting the motion of the subject is a step of detecting a motion vector in MPEG compression coding. The imaging method according to claim 1,
An imaging method, wherein at least one of contour enhancement, gradation characteristics, contrast, brightness, white balance, exposure, and UV gain is changed between the monitor mode and the image recognition mode. An image sensor having a plurality of pixels arranged two-dimensionally;
A vertical scanning circuit and a horizontal scanning circuit for driving the image sensor to read out electric charges accumulated in the image sensor;
A switching unit for switching between a monitor mode in which an imaging signal is formed at a first pixel interval and an image recognition mode in which an imaging signal is formed at a second pixel interval;
Recognizing means for performing recognition processing of a target image captured in the image recognition mode,
The imaging device, wherein the second pixel interval is narrower than the first pixel interval. The imaging device according to claim 14.
A control means for controlling the operation of each of the vertical scanning circuit and the horizontal scanning circuit;
The image pickup apparatus according to claim 1, wherein the control unit performs control so that an area of the image pickup element where the image pickup signal is formed is smaller in the image recognition mode than in the monitor mode. The imaging device according to claim 15, wherein
Means for detecting the position of the target image from within the entire pixel region of the image sensor;
An image pickup apparatus, wherein an area of the image pickup element in which the image pickup signal is formed is determined according to the detected position of the target image. The imaging device according to claim 15, wherein
Means for detecting movement of the subject from the imaging signal using a plurality of frames that are continuous in time series,
An image pickup apparatus that moves in the region of the image pickup device where the image pickup signal is formed in accordance with the detected movement of the subject.

Images