JP2008301095A - Imaging device and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily change over a plurality of photographing modes having different dynamic ranges. <P>SOLUTION: An imaging device has a switch 21 changing over a first mode sensing an image in a first dynamic range and a second mode sensing the image in a second dynamic range narrower than the first dynamic range. A compression ratio to be applied in response to the mode selected by the switch 21 is changed, and processing for covering all the dynamic ranges in an image signal within a specified output dynamic range is conducted using the applied compression ratio. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an imaging method suitable for application to a video camera used for broadcasting or movie shooting, for example.

  2. Description of the Related Art Conventionally, moving image capturing devices such as video cameras have been developed and designed mainly for use in broadcasting. However, in recent years, it has become possible to shoot high-resolution images even with video cameras, such as HD (High Definition) shooting, and video cameras are also being used for movie shooting.

  In movie shooting, a technique is used to create images by post-processing after shooting, not at the time of shooting. In post-processing after shooting, the gradation to be expressed more carefully is selected from the shot images. Processing is performed. The choice of gradation is left to the producer's intention, and the image signal to be imaged contains a lot of information on not only low brightness areas but also high brightness areas. Is desirable. That is, in an imaging apparatus used for movie shooting, how much dynamic range can be taken is regarded as important.

  The dynamic range in the video camera is indicated by a ratio between the minimum luminance and the maximum luminance that can identify the gradation. In other words, the dynamic range is a numerical value indicating how much light intensity is output as a video signal without saturation in the video camera.

Patent Document 1 discloses a video camera device that can optimize a dynamic range.
JP-A-11-146230

  By the way, in a video camera used for broadcasting, the S / N ratio tends to be more important than the wide dynamic range. This is because, when shooting a broadcast program, it is important to obtain a video with less noise because a method of creating an image on the spot while shooting is used. Therefore, the conventional video camera designed and developed mainly for use in broadcasting has a rich mechanism and user interface (hereinafter referred to as UI) capable of creating an image with an emphasis on S / N. There were many cases.

  Even in such a video camera designed and developed mainly for use in broadcasting, it is possible to change the setting to a wide dynamic range by adjusting the sensitivity setting and gain setting. However, since it is necessary to adjust sensitivity, gain, and the like while considering what the final dynamic range is, there is a problem that setting takes time.

  The present invention has been made in view of such a point, and an object thereof is to easily switch between a plurality of shooting modes having different dynamic ranges.

  The present invention includes a switch for switching between a first mode in which imaging is performed in the first dynamic range and a second mode in which imaging is performed in a second dynamic range that is narrower than the first dynamic range. Then, the compression rate to be applied is changed according to the mode selected by the switch, and the processing to fit all the dynamic ranges in the image signal within the predetermined output dynamic range is performed using the applied compression rate. did.

  With such a configuration, the image signal is compressed with a different compression ratio according to the dynamic range in the mode selected by switching the switch, and is output within a predetermined output dynamic range. It becomes like this.

  According to the present invention, it is possible to easily switch between two shooting modes having different dynamic ranges by switching the switch.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating an internal configuration example of an imaging apparatus 100 configured as a video camera. This imaging apparatus is configured to be switchable between two modes, a normal mode that can express a dynamic range up to 600% and an extended mode that can express a dynamic range up to 800%. .

  The imaging apparatus 100 photoelectrically converts the lens 1, a diaphragm 2 that adjusts the amount of light passing through the lens 1, a diaphragm driving unit 3 that drives the diaphragm 2, and subject light incident through the lens 1, and outputs an electric signal. The image sensor 4 that outputs as The imaging element 4 is configured by an element such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), for example.

  In addition, the imaging apparatus 100 includes a signal processing unit 10 that performs signal processing on an electrical signal output from the imaging element 4, an image processing unit 20 that performs image processing on an output signal from the signal processing unit 10, and imaging. A timing generator 14 that controls the operation timing of the element 4, the signal processing unit 10, and the image processing unit 20, an operation unit 30 that is configured by buttons and switches, and that generates and outputs an operation signal according to the operation content by the user; Consists of an external storage medium I / F unit 31 that controls input / output of data to / from an external storage medium such as a semiconductor memory, and an LCD (Liquid Crystal Display), etc., for mode switching of images and dynamic ranges corresponding to video signals A display unit 32 that displays a menu screen of the image sensor, and a control unit 33 that includes a CPU (Central Processing Unit) and the like and controls each unit of the imaging apparatus 100. That.

  The signal processing unit 10 amplifies a correlated double sampling (CDS) 11 that removes reset noise included in the electrical signal output from the image sensor 4 and a signal output from the CDS 11 to a certain level. AGC (Automatic Gain Control) 12 that adjusts to the size of the AGC, and an A / D converter 13 that converts an analog signal output from the AGC 12 into a digital signal. In this example, it is assumed that the A / D converter has a resolution of 14 bits.

  The image processing unit 20 switches the dynamic range mode based on the operation signal input from the operation unit 30, and the output signal from the A / D conversion unit 14 according to the mode selected by the switch 21. A dynamic range selection unit 22 that performs bit assignment (gradation assignment) processing of a dynamic range and resolution with respect to the image, and a white balance by performing gain adjustment processing individually for each of the RGB pixels in the output signal from the dynamic range selection unit 22 The white balance adjustment unit 23 that corrects the image and the particularly high-luminance portion of the output signal from the white balance adjustment unit 23 are compressed at a predetermined compression rate according to the dynamic range mode, and are determined by the video signal output standard A non-linear processing unit 24 for adjusting the output signal level within the range, and a non-linear processing unit 2 The output signal from the encoder 25 is converted into a signal of a predetermined format such as the NTSC (National Television Standards Committee) system or the PAL (Phase Alternating Line) system, and the digital signal output from the encoder 25 is converted into an analog signal. And a D / A conversion unit 26 for outputting. In the nonlinear processing unit 24, for example, knee correction and γ correction are performed. Details of the dynamic range selection unit 22 will be described later.

  In the imaging apparatus 100 configured as described above, subject light incident on the imaging device 4 via the lens 1 and the diaphragm 2 is photoelectrically converted by the imaging device 4 and output to the signal processing unit 10 as an electrical signal. The electrical signal input to the signal processing unit 10 is removed from the reset noise by the CDS 11, the gain is controlled by the AGC 12, and converted into a digital signal by the A / D conversion unit 13. The signal digitized by the A / D conversion unit 13 is output to the dynamic range selection unit 22 of the image processing unit 20. The dynamic range selection unit 22 performs bit assignment processing on the input signal in accordance with the mode selected by the switch 21 and performs bit assignment conversion processing in accordance with the selected mode.

  The output signal from the dynamic range selection unit 22 is adjusted in white balance by the white balance adjustment unit 23 and then output to the non-linear processing unit 24. The non-linear processing unit 24 outputs the dynamic range selected by the switch 21. Compression is performed at a compression rate corresponding to the mode. The signal compressed to a prescribed output signal level by the non-linear processing unit 24 is converted into a signal of a predetermined format by the encoding unit 25 and converted to an analog signal by the D / A conversion unit 26. The image signal analogized by the D / A conversion unit 26 is displayed on the display unit 32 as an image. On the other hand, the image signal processed by the nonlinear processing unit 24 and encoded by an encoding unit (not shown) is recorded in a semiconductor memory or the like via the external storage medium I / F unit 31.

  Next, a processing example in the dynamic range selection unit 22 will be described with reference to FIGS. FIG. 2 shows an example of a menu screen for allowing the user to select a dynamic range mode. FIG. 3 is a flowchart showing an example of processing in the dynamic range selection unit 22. First, a configuration example of a menu screen for switching the dynamic range mode will be described with reference to FIG.

  As described above, the imaging apparatus 100 of the present example has two modes: a normal mode (second mode) in which the dynamic range is set to 600%, and an extended mode (first mode) in which the dynamic range is set to 800%. It has a mode. Switching between the two modes can be performed by the user selecting an item on the menu screen displayed on the display unit 32. When the user wants to switch the dynamic range mode, first, a menu screen activation button or switch (not shown) is operated to display the menu screen as shown in FIG. Let In the menu screen MN1 shown in FIG. 2A, items “DYNAMIC RANGE” are displayed together with items such as “KNEEE”, “DETAIL”, and “SKIN DETAIL”. It is shown that any item can be selected.

  When “DYNAMIC RANGE” is selected on the menu screen MN1 shown in FIG. 2A based on an operation input from the user, the menu screen transitions to that shown in FIG. FIG. 2B shows two types of “DYNAMIC RANGE”, “NORMAL” and “EXTEND”, and these items are also displayed when the user operates the cursor CS1 in the vertical direction. , Is to be selected. The imaging apparatus 100 has a configuration in which the connection destination of the internal switch 21 (see FIG. 1) is changed depending on whether “NORMAL” is selected or “EXTEND” is selected. Thereby, even in the imaging apparatus 100, it is possible to determine which mode of “NORMAL” or “EXTEND” is selected by the operation of the switch 21.

  In this example, the configuration in which the selection of the dynamic range mode can be performed on the menu screen is taken as an example. However, according to the switching operation of a button or a switch provided on the housing of the imaging apparatus 100, two modes can be selected. You may apply to the structure from which a mode switches. The dynamic range mode is not limited to two types, and may be three types, four types, or the like. The value of the allocated dynamic range mode is not limited to the above-described value, and other values such as 400% may be used.

  Next, a processing example in the dynamic range selection unit 22 will be described with reference to the flowchart of FIG. The dynamic range selection unit 22 first determines whether or not the mode selected by the switch 21 is the extended mode (step S1). When the mode selected by the switch 21 is the extended mode, a process of assigning a predetermined bit in the resolution direction to the black level (0%) of the digital signal input from the A / D converter 13 is performed. (Step S2) A process of assigning a value of about 1/8 of the maximum level of the dynamic range to 100% (white peak level) is performed (Step S3). In this example, it is assumed that the numerical value assigned as the black level in step S2 is 512, and the numerical value assigned to 100% in step S3 is 2264.

  If it is determined in step S1 that the selected mode is not the extended mode, the normal mode is selected, and in step S4, a predetermined bit in the resolution direction of the input signal is assigned to the black level. Is performed (step S4), and a process of assigning a value of 1/6 of the maximum level of the dynamic range to 100% is performed (step S5). In step S4, 682 is assigned as the black level, and in step S5, 3018 is assigned as 100%.

  Then, a bit assignment conversion process is performed (step S6). The bit assignment conversion process means that 0%, 100%, and full range values assigned in steps S4 and S5 are multiplied by 600/800 = 0.75, and the obtained values are 0%, 100%. %, Full range value processing. 0% is 682 * 0.75 = 512, 100% is 3018 * 0.75 = 2264, and the full range is 16383 * 0.75 = 1288. That is, by performing this processing, the number of gradations assigned between 0% and 100% is the same in the extended mode and the normal mode.

  In FIG. 4, the dynamic range selection unit 22 assigns the black level and white peak level bits to the 14-bit signal as a result of the processing of step S3 or step S5 of FIG. Is shown. FIG. 4A shows an example when the extended mode is selected, and FIG. 4B shows an example when the normal mode is selected. 4 (a) and 4 (b), the maximum level value is 16383, but it is shown as a ratio between the maximum level value based on the black level and the value of 100% based on the black level. The maximum level of dynamic range is different between the two. In the example shown in FIG. 4A, maximum level = (maximum value−black level value) / (value assigned to 100% −black level value) * 100 = (16383-512) / (2264-512) In the example shown in FIG. 7B, (16383-682) / (3018-682) = 672%. That is, in the example of the extended mode shown in FIG. 4A, the gradation assigned from the black level (0%) to the white peak level (100%) is 2264-512 = 1752 gradations. In the example of the normal mode shown in FIG. 4B, 3018−682 = 2336 gradations are provided.

  In this state, by performing the bit assignment conversion process in step S6 of the flowchart shown in FIG. 3, the values of 0% and 100% in the normal mode become the same values as those in the extended mode. This state is shown in FIG. 6A shows the dynamic range in the extended mode, and FIG. 6B shows the dynamic range in the normal mode. In both FIG. 6A and FIG. 6B, the value assigned to 0% is 512, and the value assigned to 100% is 2264. Therefore, in any mode, the number of gradations assigned between 0% and 100% is 1752 gradations.

  Thus, the bit assignment process corresponding to the mode selected by the switch 21 is performed on the digital signal input to the dynamic range selection unit 22, and when the selected mode is the normal mode, By converting the bit assignment to the bits assigned in the extended mode, a dynamic range corresponding to the mode is assigned. In the extended mode, an image signal having a wide dynamic range can be obtained although the S / N is not so good. In the normal mode, an image signal having a good S / N is obtained although the dynamic range is not so wide. You will be able to get

  Next, a processing example in the non-linear processing unit 24 will be described with reference to the flowchart of FIG. 7 and the input / output characteristic diagram of FIG. The non-linear processing unit 24 performs processing for compressing the image signal at different compression rates in accordance with the mode selected by the switch 21 and adjusting the output signal level according to the output signal standard in the transmission path.

  In FIG. 7, it is first determined whether or not the value of the input dynamic range is less than 70% (step S11). If it is less than 70%, a common table is used regardless of which mode is selected by the switch 21. Is used to output a linear value with respect to the input value (step S12). This process is repeated as long as the value of the input dynamic range does not exceed 70%.

  If it is determined in step S11 that the input dynamic range is 70% or more, it is next determined whether or not the mode selected by the switch 21 is the extended mode (step S13). When the extended mode is selected, the first compression rate is applied (step S14), and when the normal mode is selected, the second compression rate is applied (step S15). The first compression ratio is a compression ratio for keeping a range of, for example, 70% to 905% of the input range within a range of 70% to 109% of the output range, and the second compression ratio is This is a compression ratio for keeping the range from 70% to 672% of the input range within the range from 70% to 109% of the output range.

  FIG. 8 is a characteristic diagram of the input / output dynamic range in the nonlinear processing unit 24. Note that the value of the input dynamic range here is a value in the output signal from the dynamic range selection unit 22, and is actually 672% instead of 600% and 905% instead of 800%. In FIG. 8, for simplicity of explanation, the value of the input dynamic range is the same as the dynamic range in each of the normal mode and the extended mode.

  In FIG. 8, the slope SL1 (curve) that outputs a value proportional to the input value is applied while the input dynamic range is up to 70%, and when the input range exceeds 70%, the slope SL2 having a different slope or It is shown that slope SL3 is applied. The slope SL2 is applied when the extended mode is selected, and by applying this slope, the range from 70% to 800% (905%) of the input range becomes 70% of the output range. To 109%. The slope SL3 is applied when the extended mode is selected, and by applying this slope, the range from 70% to 600% (672%) of the input range becomes 70% of the output range. To 109%.

  As described above, the non-linear processing unit 24 outputs information in a dark part of 0% to 70% of the input range without being compressed, regardless of whether the normal mode or the extended mode is selected. Information on bright areas of% or more is output with the compression ratio changed according to the mode selected by the switch 21. Another feature is that the full value of the input dynamic range falls within the output dynamic range without being clipped. The numerical value of 70%, which is a branch point for changing the compression rate, is given as an example, and other numerical values may be applied. However, it is preferable not to use a very large numerical value so that the full dynamic range can be accommodated within the transmission path.

  As described above, since the dynamic range can be changed through the user interface of the normal mode and the extended mode, for example, when it is desired to perform shooting with an emphasis on S / N in broadcasting applications, etc. Therefore, it is possible to easily use a wide dynamic range for shooting.

  In addition, in a conventional imaging apparatus, a high-intensity signal that has been clipped in the process of adjusting to an output level that meets the transmission path standard is not clipped in this example, and is kept within the range of the transmission system or recording system. It is done. For this reason, even when the gradation to be expressed is selected in the post-processing stage after shooting, particularly in movie shooting applications, the signal of the clipped area in the conventional imaging device can also be used. Become.

  In addition, regardless of whether the normal mode or the extended mode is selected, information in a dark area from 0% to 70% is output without being compressed, so that it can be used for either broadcasting or movie shooting. In this case, it is possible to make full use of information on dark areas that are important for image creation.

  In the embodiment described so far, the dynamic range allocation is adjusted by the dynamic selection unit 22 in accordance with the mode selected by the switch 21, and the nonlinear processing unit is adjusted by the mode selected by the switch 21. Although the configuration in which the compression rate at 24 is changed is taken as an example, it may be applied to a configuration in which the nonlinear processing unit 24 adjusts the compression rate including the slope of the slope according to the mode selected by the switch 21. .

  An example of the internal configuration of the imaging apparatus 100 ′ in this case is shown in FIG. In FIG. 9, parts having the same configuration as in FIG. In the imaging apparatus 100 ′ shown in FIG. 9, there is no block corresponding to the dynamic range selection unit 22 in FIG. 1, and the dynamic range adjustment unit 24 ′, which is a dynamic range adjustment unit, adjusts the dynamic range and outputs in accordance with the standard. The level compression process is performed.

  FIG. 10 shows the input / output characteristics of the nonlinear processing unit 24 ′. FIG. 10 shows that slopes having different inclination angles are applied when the normal mode is selected and when the extended mode is selected. When the normal mode is selected, a linear value is output with respect to the input value in the input dynamic range from 0% to 70%, and the input value in the range from 70% to 600% of the input range. Is applied to the slope S4 in a range from 70% to 109% of the output range. When extended mode is selected, 800% of the input dynamic range falls within 109% of the output dynamic range, so the slope of the slope is tight in the input dynamic range from 0% to 70%, and the subsequent input dynamic range. For the range, a slope S5 with a slanted slope is applied. That is, in the nonlinear processing unit 24 ′, adjustment including the slope inclination angle is performed according to the mode selected by the switch 21. Even with such a configuration, it is possible to realize a dynamic range according to the mode selected by the switch 21, and only the information in the bright area is compressed without compressing the information in the dark area. It is also possible to realize the processing.

  8 and 10, the slope indicating the input / output characteristics is shown as a straight line, but the compression rate may be applied so that a curve having a predetermined angle is drawn. For example, knee processing that combines slopes having a plurality of inclinations, gamma correction processing, or the like may be applied, or a log curve may be applied.

  In the above-described embodiment, in the configuration in which the dynamic range switching is performed using the two blocks of the dynamic range selection unit 22 and the nonlinear processing unit 24, the output of the switch 21 is input to the two blocks. Although an example in which the configuration is configured is given, the configuration may be applied to a configuration in which the dynamic range selection unit 22 and the nonlinear processing unit 24 are linked. That is, the output of the switch 21 may be performed only to the dynamic range selection unit 22, and the non-linear processing unit 24 may be configured to adjust the compression rate according to the output value from the dynamic range selection unit 22.

  Further, in the above-described embodiment, in the bit assignment conversion process in the dynamic range selection unit 22, the value of the normal mode with a narrower dynamic range to be allocated is converted on the basis of the extended mode capable of obtaining a wide dynamic range. As an example, the bit assignment in the extended mode may be converted based on the value of the normal mode.

  Moreover, although the example applied to the imaging device 100 including the display unit 32 has been described in the above-described embodiment, the present invention may be applied to an imaging device including only a video output terminal.

1 is a block diagram illustrating an example of an internal configuration of an imaging apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the example of a display of the dynamic range selection menu by one embodiment of this invention. It is a flowchart which shows the process example of the dynamic range selection part by one embodiment of this invention. It is explanatory drawing which shows the example of a bit assignment process by one embodiment of this invention. It is explanatory drawing which shows the example of a bit assignment conversion process by one embodiment of this invention. It is explanatory drawing which shows the example of the dynamic range after the bit assignment conversion by one embodiment of this invention. It is a flowchart which shows the process example of the nonlinear processing part by one embodiment of this invention. It is a characteristic view which shows the characteristic of the input-output signal in the nonlinear processing part by one embodiment of this invention. It is a block diagram which shows the internal structural example of the imaging device by other embodiment of this invention. It is a characteristic view which shows the characteristic of the input-output signal in the nonlinear processing part by other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lens, 2 ... Aperture, 3 ... Aperture drive part, 4 ... Image sensor, 10 ... Signal processing part, 11 ... CDS, 12 ... AGC, 13 ... A / D conversion part, 14 ... Timing generator, 20 ... Image processing Unit, 21 ... switch, 22 ... dynamic range selection unit, 23 ... white balance adjustment unit, 24 ... non-linear processing unit, 25 ... encoding unit, 26 ... D / A conversion unit, 30 ... operation unit, 31 ... external storage medium I / F section, 32 ... display section, 33 ... control section

Claims (8)

An imaging unit that photoelectrically converts subject light to generate an image signal;
A switch for switching between a first mode for imaging in a first dynamic range and a second mode for imaging in a second dynamic range narrower than the first dynamic range;
A dynamic ratio that changes a compression ratio to be applied in accordance with a mode selected by the switch, and that performs processing for keeping all the dynamic ranges in the image signal within a predetermined output dynamic range using the applied compression ratio. An imaging apparatus comprising: a range adjustment unit. The imaging device according to claim 1,
The imaging apparatus according to claim 1, wherein the dynamic range adjustment unit does not compress a signal from 0% to a predetermined level in a dynamic range in an image signal output from the imaging unit. The imaging device according to claim 1,
The dynamic range adjustment unit is configured with reference to a predetermined level at which the output gradation does not change between when the first mode is selected and when the second mode is selected by the switch. An imaging apparatus comprising: a dynamic range selection unit that defines a dynamic range by a ratio with respect to a reference and performs a ratio conversion process of a gradation to be assigned to a signal level of the image signal. The imaging device according to claim 3.
When the second mode is selected by the switch, the dynamic range selection unit determines a gradation assigned to the signal level of the image signal with respect to the first dynamic range of the second dynamic range. An image pickup apparatus that performs a process of converting to a gradation obtained by integrating with a ratio. The imaging device according to claim 3.
The non-linear processing unit is a case where any mode is selected by the switch for a signal from 0% to a predetermined level in the dynamic range in the image signal output from the dynamic range selection unit. An image pickup apparatus that outputs without compression even if it exists. The imaging device according to claim 5.
The non-linear processing unit, with respect to a signal of the predetermined level or higher, has different compression ratios when the first mode is selected by the switch and when the second mode is selected. An imaging device characterized in that is applied. The imaging device according to claim 3.
The non-linear processing unit changes a compression rate for compressing the image signal in accordance with an output value from the dynamic range selection unit. A procedure for photoelectrically converting subject light to generate an image signal;
A procedure for switching between a first mode for imaging in a first dynamic range and a second mode for imaging in a second dynamic range narrower than the first dynamic range;
Changing the compression ratio to be applied in accordance with the switched mode, and using the applied compression ratio, the entire dynamic range of the image signal within a predetermined output dynamic range. An imaging method characterized by.

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