JP2006333177A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an imaging apparatus using a linear log sensor capable of obtaining an image with a photographer's intention included by preventing a high luminance part of an object from being uselessly compressed while reproducing the object with large luminance width. <P>SOLUTION: The imaging apparatus is provided with a point of inflection control means for controlling to change a point of inflection to be a boundary between a linear conversion region and a logarithmic conversion region and a luminance detecting means for detecting luminance values of a plurality of positions of a field on the basis of an output of an imaging element, wherein the point of inflection control means controls to change the point of inflection so as to saturate a prescribed luminance value when positions that exceed the prescribed luminance value among the luminance values of the plurality of positions of the field obtained by the luminance detecting means exceed a prescribed number. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus having an image pickup device capable of outputting an electric signal linearly converted with respect to an incident light amount and an electric signal converted logarithmically with respect to the incident light amount.

  2. Description of the Related Art Conventionally, an imaging device that photoelectrically converts subject light is used in an imaging device such as a digital camera, an in-vehicle camera, or a camera module built in a portable terminal. As this imaging device, there is a solid-state imaging device such as a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor. Further, these image pickup devices generally output an electrical signal that is linearly converted with respect to the amount of incident light.

  The imaging device that outputs the linearly converted electric signal has a drawback that the dynamic range that can be reproduced is narrow because the output is proportional to the amount of generated photocharge.

On the other hand, an image sensor (linear log sensor) capable of outputting an electrical signal linearly converted with respect to the amount of incident light and an electric signal converted logarithmically with respect to the amount of incident light has been proposed as a solution to this drawback. (For example, refer to Patent Document 1 and Patent Document 2).
JP 2002-223392A JP 2004-088312 A

  The above linear log sensor has a much wider dynamic range than conventional image sensors that only convert linearly, and prevents overexposure in high-luminance areas, especially when reproducing subjects with a wide luminance range. Can and is very useful.

  However, simply widening the dynamic range with a wide luminance range as the log area will compress the high-intensity part even in scenes that the photographer wants to intentionally blow out, such as sparkling due to reflection of sunlight on the sea surface. May be reproduced and the image may be contrary to the photographer's intention.

  In other words, setting an appropriate inflection point based on the subject condition and the photographer's intention can provide an imaging apparatus that more effectively uses the advantages of the linear log sensor.

  In view of the above problems, the present invention enables reproduction of a subject with a wide luminance width, prevents unnecessary compression of the high-luminance portion of the subject, and obtains an image incorporating the photographer's intention. An object of the present invention is to obtain an imaging apparatus using a linear log sensor.

  The above problem can be solved by the following configuration.

  1) An image sensor having a plurality of pixels capable of outputting an electric signal linearly converted with respect to the amount of incident light and an electric signal logarithmically converted with respect to the amount of incident light; An imaging optical system that makes light incident; an inflection point control unit that controls and controls an inflection point that is a boundary between a linear transformation region and a logarithmic transformation region in an electrical signal output from the imaging device; and Brightness detecting means for detecting brightness values at a plurality of positions in the scene based on the output, and a predetermined brightness among the brightness values at the plurality of positions in the scene obtained by the brightness detecting means. The inflection point control means changes and controls the inflection point so that the position exceeding the predetermined luminance value is saturated when the position exceeding the value exceeds a predetermined number.

  2) When detecting the luminance values at a plurality of positions in the object scene by the luminance detecting means, the inflection point control means changes and controls the inflection points so that at least the predetermined luminance value or less is not saturated. Imaging device.

  3) The imaging device according to 1) or 2), wherein the predetermined luminance value can be changed.

  4) When detecting the luminance values at a plurality of positions in the object scene by the luminance detecting means, the inflection point control means changes and controls the inflection points so that all areas become logarithmic transformation areas. Imaging device.

  According to the first aspect of the invention, it is possible to reproduce an object with a wide luminance width, and to prevent the high-luminance portion of the object from being unnecessarily compressed, and to obtain an image incorporating the photographer's intention. It is possible to obtain an imaging device using a linear log sensor.

  According to the above invention 2), an imaging device that can detect the luminance values at a plurality of positions in the object field by one sampling, can shorten the time for preparation for photographing, and does not miss a photo opportunity. can do.

  According to the third aspect of the invention, an imaging apparatus capable of obtaining an image in which the high-luminance portion is overexposed according to the photographer's intention can be obtained.

  According to the invention 4), it is possible to detect luminance values at a plurality of positions in the object field by one sampling, to shorten the time for preparation for photographing, and to obtain an imaging device that does not miss a photo opportunity. be able to.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.

  FIG. 1 is an external perspective view of an imaging apparatus 1 according to the present embodiment. The image pickup apparatus 1 shown in FIG. 1 is a digital camera. FIG. 1A shows the front side of the camera, and FIG. 1B shows the back side of the camera.

  As shown in FIG. 2A, a lens unit 3 that collects image light of a subject at a predetermined focal point is disposed in the vicinity of the center of the front surface of a housing 2 included in the imaging apparatus 1. The shaft is provided so as to be orthogonal to the front surface of the housing 2. An imaging element (not shown) that photoelectrically converts the reflected light of the subject incident through the lens unit 3 into an electric signal is provided inside the housing 2 and behind the lens unit 3.

  In addition, a flash light emitting unit 5 that irradiates light as auxiliary light at the time of photographing is provided in the vicinity of the front upper end portion of the housing 2. The flash light emitting unit 5 of the present embodiment is configured by an electric flash built in the imaging apparatus 1, but may be configured by an external flash or a high-intensity LED. A light control sensor 6 is provided near the upper portion of the lens unit 3 on the front surface of the housing 2 to receive the reflected light from the subject of the light emitted from the flash light emitting unit 5. Reference numeral 14a denotes an entrance window on the objective side of the optical viewfinder.

  A release switch 16 for performing shutter release is provided on the upper surface. The release switch 16 can be operated in a “half-pressed state” in which it is pressed halfway and in a “fully pressed state” in which it is further pressed. On the side surface, a USB terminal 18 for connecting a USB cable for connecting the imaging device 1 to a personal computer or the like is provided.

  Furthermore, a circuit board including circuits such as a system control unit and a signal processing unit (not shown) is provided inside the housing 2 included in the imaging apparatus 1.

  Further, as shown in FIG. 2B, an image display monitor 11 is provided on the back surface of the housing 2. The monitor 11 includes an LCD (Liquid Crystal Display), an organic EL display, and the like, and can display a subject preview screen and a captured image.

  A zoom button W12 (Wide: wide angle) and a zoom button T13 (Telephoto: telephoto) for adjusting the zoom are provided in the vicinity of the upper rear portion of the imaging apparatus 1. In addition, an optical viewfinder eyepiece 14b for confirming a subject from the back side of the housing 2 is disposed above the position where the lens unit 3 is provided on the back side of the imaging device 1. .

  Further, on the rear surface of the image pickup apparatus 1, a selection cross key 15a including a cursor displayed on the screen of the monitor 11, a window, or a cross key for changing a designated range of the window is provided. . Next to the selection cross key 15a, a confirmation key 15b for confirming the contents designated by the cursor or window is provided.

  In addition, a recording unit such as a battery and a memory card (not shown) is loaded in the housing 2.

  Although described with a compact camera type digital camera, the imaging device of the present invention includes a single-lens reflex digital camera, a mobile phone with a camera, an electronic device having a photographing function such as an in-vehicle camera, a mobile phone, A camera unit incorporated in an electronic device such as an in-vehicle camera is also included.

  FIG. 2 is a block diagram illustrating a functional configuration of the imaging apparatus 1 according to the present embodiment.

  As described above, the imaging apparatus 1 includes the system control unit 7 on the circuit board inside the housing 2. The system control unit 7 includes a CPU (Central Processing Unit), a RAM (Random Access Memory) composed of rewritable semiconductor elements, and a ROM (Read Only Memory) composed of a nonvolatile semiconductor memory.

  Further, each component of the imaging device 1 is connected to the system control unit 7, and the system control unit 7 develops a processing program recorded in the ROM on the RAM and executes the processing program by the CPU. These components are driven and controlled.

  As shown in the figure, the system control unit 7 includes a lens unit 3, an aperture control unit 19, an image sensor 4, a signal processing unit 8, a timing generation unit 20, a recording unit 10, a flash light emitting unit 5, and a light control sensor 6. The monitor 11, the operation unit 21, and the inflection point changing unit 22 are connected.

  The lens unit 3 includes a plurality of lenses that form a subject light image on the imaging surface of the image sensor 4 and a diaphragm unit that adjusts the amount of light collected by the lenses.

  The diaphragm control unit 19 drives and controls the diaphragm unit that adjusts the amount of light collected by the lens in the lens unit 3. That is, the aperture controller 19 closes the aperture that is opened during the imaging operation of the image sensor 4 based on the control value input from the system controller 7 after a predetermined exposure time has passed, In some cases, the amount of incident light is controlled by blocking the incident light on the image sensor 4.

  The image sensor 4 captures the incident light of each color component of R, G, and B, which is a subject light image, by photoelectrically converting it into an electrical signal.

  FIG. 3 is a block diagram illustrating a configuration of the image sensor according to the present embodiment.

As shown in the figure, the image pickup device 4 has a plurality of pixels G _{11 to} G _mn (where n and m are integers of 1 or more) arranged in a matrix (matrix arrangement).

Each of the pixels G _{11 to} G _mn photoelectrically converts incident light and outputs an electrical signal. These pixels G _{11 to} G _mn can switch the conversion operation of the electric signal according to the amount of incident light. More specifically, the pixel G _{11 to} G _mn perform a logarithmic conversion and a linear conversion operation for linearly converting incident light into an electric signal. The logarithmic conversion operation is switched. In the present embodiment, linear conversion or logarithmic conversion of incident light into an electric signal means conversion into an electric signal that linearly changes the time integral value of the light amount, or electric conversion that changes logarithmically. Logarithmic conversion to a signal.

A filter (not shown) of any one of red (Red), green (Green), and blue (Blue) is disposed on the lens unit 3 side of each of the pixels G _{11 to} G _mn . The pixels G _{11 to} G _mn have power supply lines 23, signal application lines L _{A1 to} L _An , L _{B1 to} L _Bn , L _{C1 to} L _Cn , and signal readout lines L _{D1 to} L N as shown in FIG. _Dm is connected. Note that lines such as a clock line and a bias supply line are also connected to the pixels G _{11 to} G _mn , but these are not shown in the figure.

The signal application lines L _{A1 to} L _An , L _{B1 to} L _Bn , and L _{C1 to} L _Cn give signals φ _v , φ _VD and φ _VPS to the pixels G _{11 to} G _mn (see FIGS. 4 and 5). It has become. A vertical scanning circuit 24 is connected to these signal application lines L _{A1 to} L _An , L _{B1 to} L _Bn , and L _{C1 to} L _Cn . The vertical scanning circuit 24 applies signals to the signal application lines L _{A1 to} L _An , L _{B1 to} L _Bn , and L _{C1 to} L _Cn based on signals from the timing generator 20 (see FIG. 2). The signal application lines L _{A1 to} L _An , L _{B1 to} L _Bn , and L _{C1 to} L _Cn to which signals are applied are sequentially switched in the X direction.

The electric signals generated by the pixels G _{11 to} G _mn are derived from the signal readout lines L _{D1 to} L _Dm . Constant current sources D _{1 to} D _m and selection circuits S _{1 to} S _m are connected to these signal read lines L _{D1 to} L _Dm . Further, a DC voltage V _PS is applied to one end (lower end portion in the figure) of the constant current sources D _{1 to} D _m .

The selection circuits S _{1 to} S _m sample-hold the noise signals given from the pixels G _{11 to} G _mn through the signal readout lines L _{D1 to} L _Dm and the electrical signals at the time of imaging. A horizontal scanning circuit 25 and a correction circuit 26 are connected to these selection circuits S _{1 to} S _m . The horizontal scanning circuit 25 sequentially switches selection circuits S _{1 to} S _m that sample and hold an electric signal and transmit the electric signal to the correction circuit 26 in the Y direction. The correction circuit 26 removes the noise signal from the electric signal based on the noise signal transmitted from the selection circuits S _{1 to} S _m and the electric signal at the time of imaging.

As the selection circuits S _{1 to} S _m and the correction circuit 26, those disclosed in Japanese Patent Laid-Open No. 2001-223948 can be used. In the present embodiment, it is assumed that only one correction circuit 26 is provided for the entire selection circuits S _{1 to} S _m , but the correction circuit 26 is provided for each of the selection circuits S _{1 to} S _m. It is good also as providing one by one. Next, the pixels G _{11 to} G _{mn included} in the image sensor 4 will be described.

  FIG. 4 is a circuit diagram illustrating a configuration of a pixel included in the image sensor according to the present embodiment.

As shown in the figure, each of the pixels G _{11 to} G _mn includes a photodiode P, transistors T _{1 to} T _6, and a capacitor C. The transistors T _{1 to} T ₆ are P-channel MOS transistors.

The light passing through the lens unit 3 hits the photodiode P. A DC voltage V _PD is applied to the cathode P _{k of the} photodiode P, and the drain T _1D of the transistor T ₁ is connected to the anode P _A.

The signal φ _S is inputted to the gate T _1G of the transistor T ₁ , and the gate T _2G and the drain T _2D of the transistor T ₂ are connected to the source T _1S .

A signal application line L _C (corresponding to L _{C1 to} L _Cn in FIG. 3) is connected to the source T _2S of the transistor T ₂ , and the signal φ _VPS is input from the signal application line L _C. ing. Here, the signal φ _VPS is a voltage signal, and more specifically, a voltage value VL for operating the transistor T ₂ in the subthreshold region when the incident light amount exceeds the predetermined incident light amount th, and the transistor T ₂ are The voltage value VH to be in a conductive state is taken.

Also, gate T _3G of the transistor T ₃ is connected to a source T _1S of the transistor T _1. A DC voltage V _PD is applied to the drain T _3D of the transistor T ₃ . Further, the source T _3S of the transistor T ₃ has one end of a capacitor C, a drain T _5D of the transistor T _5, and the gate T _4G of the transistor T ₄ is connected.

A signal application line L _B (corresponding to L _{B1 to} L _Bn in FIG. 3) is connected to the other end of the capacitor C, and a signal φ _VD is given from this signal application line L _B. Here, the signal φ _VD is a ternary voltage signal. More specifically, the voltage value Vh when the capacitor C is integrated, the voltage value Vm at the time of reading out the photoelectrically converted electric signal, and the noise signal reading out. It takes three values with the hourly voltage value Vl.

A DC voltage V _RG is input to the source T _5S of the transistor T ₅ , and a signal φ _RS is input to the gate T _5G . The DC voltage V _PD is applied to the drain T _4D of the transistor T _{4 in} the same manner as the drain T _3D of the transistor T ₃ , and the drain T _6D of the transistor T ₆ is connected to the source T _4S. ing.

A signal readout line L _D (corresponding to L _{D1 to} L _Dm in FIG. 3) is connected to the source T _6S of the transistor T ₆ , and a signal application line L _A (L in FIG. 3) is connected to the gate T _6G . _A signal φ _V is input from _{A1 to} L _An ).

By adopting such a circuit configuration, each of the pixels G _{11 to} G _mn performs the following reset operation.

  FIG. 5 is a diagram illustrating a timing chart of the operation of the pixels provided in the image sensor according to the present embodiment.

As shown in the figure, the vertical scanning circuit 24 performs a reset operation of the pixels G _{11 to} G _mn . Specifically, from the state where the signal φ _S is Low, the signal φ _V is Hi, the signal φ _VPS is VL, the signal φ _RS is Hi, and the signal φ _VD is Vh, the vertical scanning circuit 24 generates the pulse signal φ and _V, after outputted an electric signal by applying a pulse signal phi _VD of the voltage value Vm in the pixel G ₁₁ ~G _mn to the signal reading line L _D, to the transistors T ₁ and OFF signals phi _S as Hi It has become.

Next, the vertical scanning circuit 24 to the signal phi _VPS and VH, the gate T _2G and drain T _2D of the transistor T _2, and quickly recombine negative charges accumulated in the gate T _3G of the transistor T ₃ It is supposed to let you. Further, the vertical scanning circuit 24 sets the signal φ _RS to Low and turns on the transistor T ₅ to initialize the voltage at the connection node between the capacitor C and the gate T _4G of the transistor T ₄ .

Next, the vertical scanning circuit 24 sets the signal φ _VPS to VL to return the potential state of the transistor T _{2 to} the original state, and then sets the signal φ _RS to Hi and turns off the transistor T ₅ . Next, the capacitor C performs an integration operation. As a result, the voltage at the connection node between the capacitor C and the gate T _4G of the transistor T ₄ becomes in accordance with the reset gate voltage of the transistor T ₂ .

Next, the vertical scanning circuit 24 is turned ON transistor T ₆ by giving a pulse signal phi _V to the gate T _6G of the transistor T _6, is a pulse signal phi _VD voltage value Vl to be applied to the capacitor C ing. At this time, since the transistor T ₄ operates as MOS transistor of a source follower type, the noise signals on the signal reading line L _D appears as a voltage signal.

The vertical scanning circuit 24 applies the pulse signal φ _RS to the gate T _5G of the transistor T ₅ to reset the voltage at the connection node between the capacitor C and the gate T _4G of the transistor T ₄ , and then sets the signal φ _S to Low. It is adapted to the transistor T ₁ and oN. As a result, the reset operation is completed, and the pixels G _{11 to} G _mn are ready for imaging.

Each of the pixels G _{11 to} G _mn performs the following imaging operation.

When light charges corresponding to the amount of incident light from the photodiode P flows into the transistor T _2, photocharge is adapted to be accumulated in the gate T _2G of the transistor T _2.

Here, when the luminance of the subject is low and the amount of light incident on the photodiode P is smaller than the predetermined amount of incident light th, the transistor T ₂ is in the cut-off state, so that it is accumulated in the gate T _2G of the transistor T ₂ . A voltage corresponding to the amount of photocharge appears at the gate _T2G . Therefore, a voltage obtained by linearly converting incident light appears at the gate T _3G of the transistor T ₃ .

On the other hand, the luminance of the subject is high and the amount of incident light with respect to the photodiode P is larger than the predetermined amount of incident light th, the transistor T ₂ is adapted to perform the operation in the sub-threshold region. Therefore, a voltage obtained by logarithmically converting incident light with a natural logarithm appears at the gate T _3G of the transistor T ₃ .

In the present embodiment, the predetermined value is the same among the pixels G _{11 to} G _mn .

When the voltage on the gate T _3G of the transistor T ₃ appears, the current flowing from the capacitor C to the drain T _3D of the transistor T ₃ in accordance with the amount of voltage is adapted to be amplified. Therefore, a voltage obtained by linear conversion or logarithmic conversion of incident light from the photodiode P appears at the gate T _4G of the transistor T ₄ .

Next, the vertical scanning circuit 24 _sets the voltage value of the signal φ _VD to Vm and sets the signal φ _V to Low. As a result, a source current corresponding to the gate voltage of the transistor T ₄ flows to the signal read line L _D via the transistor T ₆ . At this time, since the transistor T ₄ operates as MOS transistor of a source follower type, the signal reading line L _D so that the electrical signal at the time of imaging appears as a voltage signal. Here, since the signal value of the electric signal output through the transistors T ₄ and T ₆ is a value proportional to the gate voltage of the transistor T ₄ , the signal value is linearly converted or logarithmized from the incident light of the photodiode P. It becomes the converted value.

The vertical scanning circuit 24 _sets the voltage value of the signal φ _VD to Vh and sets the signal φ _V to Hi, thereby completing the imaging operation.

When operating as described above, the potential value between the gate and the source of the transistor T ₂ increases as the voltage value VL of the signal φ _VPS during imaging decreases and the difference from the voltage value VH of the signal φ _VPS during reset increases. difference therebetween increases, the proportion of subject brightness that transistor T ₂ is operated in a cut-off state is increased. Therefore, as shown in FIG. 6 below, the lower the voltage value VL, the larger the ratio of subject luminance to be linearly converted. As described above, the output signal of the image sensor 4 according to the present embodiment has a linear region and a logarithmic region that change continuously according to the amount of incident light.

  Therefore, for example, when the subject luminance range is narrow, the voltage value VL is lowered to widen the luminance range for linear conversion, and when the subject luminance range is wide, the voltage value VL is increased to perform logarithmic conversion. By widening, the photoelectric conversion characteristics suitable for the characteristics of the subject can be obtained. It should be noted that when the voltage value VL is minimized, it is possible to always perform linear conversion, and when the voltage value VH is maximized, it is possible to always perform logarithmic conversion.

The dynamic range can be switched by switching the voltage value VL of the signal φ _VPS given to the pixels G _{11 to} G _mn of the image sensor 4 operating in this way. That is, the system control unit 2 can change the inflection point at which the linear conversion operation of the pixels G _{11 to} G _mn is switched to the logarithmic conversion operation by switching the voltage value VL of the signal φ _VPS. ing.

FIG. 6 is a graph showing an output with respect to the exposure amount to the image sensor according to the present embodiment. As shown in the figure, the system control unit 2 can change the voltage value VL so that the inflection point at which the linear conversion operation of the pixels G _{11 to} G _mn is switched to the logarithmic conversion operation can be changed. It has become.

  Note that the image pickup device 4 according to the present embodiment may be any device that automatically switches between linear conversion operation and logarithmic conversion operation in each pixel, and is an image pickup device 4 including pixels having a configuration different from that shown in FIG. Also good.

In the present embodiment, the linear conversion operation and the logarithmic conversion operation are switched by changing the voltage value VL of the signal φ _VPS at the time of imaging. However, the voltage value VH of the signal φ _VPS at the time of reset is changed. Thus, the inflection point between the linear conversion operation and the logarithmic conversion operation may be changed. Further, the inflection point between the linear conversion operation and the logarithmic conversion operation may be changed by changing the reset time.

  In addition, although the image pickup device 4 of the present embodiment is provided with an RGB filter in each pixel, it may be provided with other color filters such as cyan, magenta, and yellow.

  Returning to FIG. 2, the signal processing unit 8 includes an amplifier 27, an A / D converter 28, a black reference correction unit 29, an AE evaluation value calculation unit 30, a WB processing unit 31, a color interpolation unit 32, a color correction unit 33, and tone conversion. Part 34 and a color space conversion part 35.

  Among these, the amplifier 27 amplifies the electrical signal output from the image sensor 4 to a predetermined specified level to compensate for a lack of level in the captured image. The A / D converter 28 (ADC) converts the electrical signal amplified by the amplifier 27 from an analog signal to a digital signal.

  The black reference correction unit 29 corrects the black level that is the lowest luminance value to the reference value. That is, since the black level varies depending on the dynamic range of the image sensor 4, the black reference correction is performed by subtracting the signal level that becomes the black level from the signal level of each RGB signal output from the A / D converter 28. It has come to be.

  The AE evaluation value calculation unit 30 has two functions for AE (automatic exposure) from the electric signal after black reference correction. A function of calculating the average value of the luminance representing the luminance range of the subject by confirming the luminance value of the electrical signal composed of each RGB primary color component, and outputting it to the system control unit 7 as the AE evaluation value for setting the incident light amount A luminance detection unit that calculates luminance values at a plurality of positions determined in advance in the entire subject image (referred to as a scene) obtained by the imaging device 4, and a scene obtained by the luminance detection unit A counting unit that counts the number of positions that exceed a predetermined luminance value among the luminance values of the plurality of positions, and a comparison unit that determines whether or not the count value exceeds the predetermined value. If it exceeds, the system control unit 7 has a function of outputting that the predetermined value is exceeded.

  The system control unit 7 changes the inflection according to whether or not the number of positions exceeding a predetermined luminance value out of the luminance values at a plurality of positions in the scene obtained by the luminance detection unit exceeds the predetermined value. The point changing unit 22 is controlled.

  The WB processing unit 31 adjusts the level ratio (R / G, B / G) of each of the R, G, and B color components of the captured image by calculating a correction coefficient from the electric signal after the black reference correction, thereby generating a white color. Is displayed correctly. The color interpolation unit 32 can obtain R, G, and B color component values for each pixel when the signals obtained at the pixels of the image sensor 4 are only one or two of the primary colors. Color interpolation processing for interpolating missing color components for each pixel is performed. The color correction unit 33 corrects the color component value for each pixel of the image data input from the color interpolation unit 32, and generates an image in which the hue of each pixel is emphasized. In order to reproduce the image faithfully, the gradation conversion unit 34 sets the response characteristic of the image gradation to the image pickup apparatus 1 in order to realize the ideal gradation reproduction characteristic with gamma being 1 from the input of the image to the final output. A gamma correction process is performed to correct the curve according to the gamma value.

  The color space conversion unit 35 converts the color space from RGB to YUV. YUV is a management method for expressing a color with two chromaticities: a luminance (Y) signal, a blue color difference (U, Cb), and a red color difference (V, Cr), and converting the color space to YUV. This facilitates data compression of only the color difference signal.

  The timing generation unit 20 controls the photographing operation (charge accumulation based on exposure, reading of accumulated charge, etc.) by the image sensor 4. That is, a predetermined timing pulse (a pixel driving signal, a horizontal synchronizing signal, a vertical synchronizing signal, a horizontal scanning circuit driving signal, a vertical scanning circuit driving signal, etc.) is generated on the basis of a photographing control signal from the system control unit 7 and an image pickup device. 4 is output. The timing generation unit 20 also generates an A / D conversion clock used in the A / D converter 28.

  The recording unit 10 is a recording memory composed of a semiconductor memory or the like, and has an image data recording area for recording image data input from the signal processing unit 8. The recording unit 10 may be a built-in memory such as a flash memory, a removable memory card, or a magnetic recording medium such as a hard disk.

  The flash light emitting unit 5 emits light at a predetermined light emission timing under the control of the system control unit 7 when the brightness of the surrounding environment detected at the time of photographing the subject is insufficient. The light control sensor 6 receives the reflected light of the flash light reflected from the subject side in order to control the light emission amount, and outputs the light reception result to the system control unit 7.

The monitor 11 functions as a display unit, displays a preview image of a subject, displays a photographed image that has been subjected to image processing by the signal processing unit 8 based on control of the system control unit 7, and allows the user to A text screen such as a menu screen for selecting a function is displayed. That is, the monitor 11 displays a shooting mode selection screen for selecting a still image shooting mode or a moving image shooting mode, a strobe mode selection screen for selecting any one of an auto mode, an off mode, and an on mode. .
The operation unit 21 includes a zoom button W12, a zoom button T13, a selection cross key 15a, a release switch 16, a power switch 17, and the like. When the user operates the operation unit 21, the function of each button or switch is configured. Is transmitted to the system control unit 7, and each component of the imaging apparatus 1 is driven and controlled in accordance with the instruction signal.

  Of these, the selection cross key 15a functions to move a cursor or window on the screen of the monitor 11 when the cross key is pressed, and also functions to confirm the selection contents by the cursor or window when the enter key 15b is pressed. Yes. That is, by pressing the cross key of the selection cross key 15a, the cursor displayed on the monitor 11 is moved to open the shooting mode selection screen from the menu screen, and the desired shooting mode is displayed on the shooting mode selection screen. When the cursor is moved to the button and the enter key 15b is pressed, the shooting mode can be determined.

  The zoom button W12 has a function of adjusting the zoom when pressed to make the subject appear small, and the zoom button T13 has a function of adjusting the zoom when pressed to make the subject appear larger.

  The release switch 16 starts a shooting preparation operation by half-pressing (hereinafter referred to as ON of the switch S1) in the still image shooting mode, and the image sensor 4 is pressed fully (hereinafter referred to as ON of the switch S1). A series of photographing operations is performed such that exposure is performed, electric signals obtained by the exposure are subjected to predetermined signal processing and recorded in the recording unit 10. When the power switch 17 is pressed, the imaging device 1 is turned on and off in order.

  The above is the outline of the imaging device 4 according to the present embodiment and the imaging device 1 including the imaging device 4. Below, operation | movement of the imaging device 1 is demonstrated.

  The imaging device 1 has a still image shooting mode, a moving image shooting mode, a playback mode, a setup mode, and the like. However, the present invention relates to a still image or moving image shooting mode. The shooting mode will be described as an example in detail.

  Furthermore, the present invention intentionally controls the inflection point control means by means of the inflection point control means when the position exceeding a predetermined luminance value exceeds a predetermined number among the luminance values at a plurality of positions in the scene. Shooting exposure is performed so that a subject with a luminance value exceeding the value reaches a saturation level, and in this embodiment, such a shooting mode is referred to as a whiteout shooting mode.

  FIG. 7 is a flowchart showing a schematic operation in the still image shooting mode. FIG. 8 is a flowchart showing a schematic operation when the overexposure shooting mode in the still image shooting mode is selected. In the following, description will be given according to the flow shown in FIGS.

  In the flowchart of FIG. 7, when the still image shooting mode is entered, driving of the image pickup unit such as an image pickup device, an amplifier, an A / D converter, etc. is started (step S150), and live view display is performed on a monitor which is an image display unit ( Step S151).

  Here, it is determined whether the main switch is ON (step S152). When the main switch is turned off (step S152; No), the live view display is stopped (step S180), the driving of the imaging unit is stopped (step S185), and the process is terminated.

  If the main switch is ON (step S152; Yes), it is determined again whether the still image shooting mode is set (step S153). When the mode is switched to a mode other than the still image shooting mode (step S153; No), the mode is switched to another switched mode (step S170).

  If it is the still image shooting mode (step S153; Yes), it is next determined whether or not the whiteout shooting mode is set in advance (step S154).

  For example, as described with reference to FIGS. 1 and 2, the setting of the overshooting shooting mode is performed by opening a shooting mode selection screen from the menu screen on the monitor 11, and further selecting the cross key 15a for selection on the shooting mode selection screen. By pressing the cross key, the cursor is moved to the overexposure shooting mode displayed on the monitor 11 and when the enter key 15b is pressed down, the overexposure shooting mode is set.

  If the overexposure shooting mode is set in advance (step S154; Yes), the operation shifts to the overexposure shooting mode (step S200). An outline of the operation in the overexposure shooting mode will be described first.

  FIG. 8 is a flowchart showing a schematic operation in the overexposure shooting mode in the still image shooting mode.

  In the flowchart of FIG. 8, when the whiteout shooting mode is entered, it is first determined whether or not the switch S1 is turned on (step S201).

  If the switch S1 is not turned on (step S201; No), the process returns to step S152 shown in FIG. That is, until the switch S1 is turned on, the live view display is performed and the main switch, the mode selection, or the switch S1 is waited to be operated.

  When the switch S1 is turned on (step S201; Yes), for example, an inflection point is set so that the image sensor output is logarithmically converted for all luminances with a predetermined exposure time and aperture value (step S202). . This is performed by the system control unit 7 controlling the inflection point changing unit 22 (see FIG. 2).

  Next, the image of the scene is captured as image data in the logarithmic transformation region (step S203). Next, luminance values at a plurality of predetermined positions are obtained by calculation from the obtained image data of the object scene (step S204).

This can be determined, for example, as follows. For example, when the image data is an image having a resolution of 1600 pixels × 1200 pixels, the obtained image data of the object scene is divided into 30000 blocks of 200 in the long side direction and 150 in the short side direction, and 8 pixels in each block The average value AveR of 16 pixels of R (red), the average value AveG of 32 pixels of G (green), and the average value AveB of 16 pixels of B (blue) are calculated from 64 pixels of 8 pixels, and logarithmic conversion After converting the data into linear conversion data, assuming that the luminance is Y, and K1, K2, and K3 are weighting coefficients,
Y = AveR × K1 + AveG × K2 + AveB × K3
Is required. Similarly, the luminance Y is obtained for each block obtained by dividing the object scene.

  Next, among the obtained blocks, that is, the luminance Y at each position of the object scene, the number of positions exceeding a predetermined luminance value is counted (step S205). In this example, the predetermined luminance value is a high luminance value such as the sparkle of sunlight reflected by a coastal wave. For example, EV 15 or the like is used in terms of ISO sensitivity 100.

  Further, it is determined whether or not there are a predetermined number or more of positions that exceed a predetermined luminance value that is a count value (step S206). When the number of positions exceeding the predetermined luminance value does not exceed the predetermined number (step S206; No), the process proceeds to step S156 shown in FIG.

  Note that the predetermined number is a number set in advance as a value necessary for identifying the subject in which the whiteout is surely generated with respect to the variation unique to the sensor. For example, in the case of the above-mentioned image having a resolution of 1600 pixels × 1200 pixels, a value of about 25 is used. In the case of an image having a resolution of 2272 × 1704 pixels, a value of about 50 is desirable. However, the value is not limited to this, and is appropriately set according to specifications.

  When the number of positions exceeding the predetermined luminance value is greater than or equal to the predetermined number (step S206; Yes), focusing is performed as an AF operation, and the aperture value and shutter speed are determined to be predetermined. The inflection point is changed and controlled so that the luminance is equal to or higher than the saturation level (step S207).

Next, it is determined again whether the switch S1 is turned on (step S208). If the switch S1 is not turned on, that is, turned off (step S208; No), the process returns to step S152 shown in FIG.
When the switch S1 is turned on (step S208; Yes), it waits for the switch S2 to be turned on (step S209). If the switch S2 is not turned on (step S209; No), the process returns to step S208.

  When the switch S2 is turned on (step S209; Yes), the shooting operation is executed under the shooting conditions determined in step S207 (step S210), and the process proceeds to step S161 shown in FIG. Record image data.

  By having such a whiteout shooting mode, for example, the reflection of sunlight due to the wavefront on the coast can be overexposed, and the high brightness part of the subject is compressed unnecessary according to the photographer's intention to draw Therefore, it is possible to obtain an imaging apparatus capable of obtaining an image incorporating the photographer's intention.

  Returning to step S154 in FIG. 7, when the overexposure shooting mode is not set (step S154; No), the process proceeds to step S155, and it is determined whether the switch S1 is turned on (step S155). If the switch S1 is not turned on (step S155; No), the process returns to step S152.

  When the switch S1 is turned on (step S155; Yes), an AF operation and an AE preparation operation (step S156) are performed. Here, the AE preparation operation refers to, for example, changing and controlling the inflection point so that the entire luminance of the object scene can be reproduced, and determining the aperture value and the shutter speed that is the exposure time.

  Thereafter, it is confirmed again whether the switch S1 is turned on (step S157). If the switch S1 is not turned on (step S157; No), the process returns to step S152. When the switch S1 is turned on (step S157; Yes), it waits for the switch S2 to be turned on (step S158). If the switch S2 is not turned on (step S158; No), the process returns to step S157.

  When the switch S2 is turned on (step S158; Yes), it is confirmed whether flash photography is performed (step S159). This is determined at the time of the AE preparation operation in step S156, and this is confirmed. If it is not flash photography (step S159; No), a photographing operation using stationary light is executed (step S160), the photographed image data is recorded on the memory card (step S161), and the photographed image is stored in the image display unit. After the time after view display (step S162), the display returns to the live view display in step S151.

  On the other hand, in the case of flash photography (step S159; Yes), flash photography is performed (step S175), and the process proceeds to step S161.

  The above is the outline of the operation of the imaging apparatus according to the present embodiment.

  FIG. 9 is a diagram showing an outline of the control of the inflection point in the whiteout shooting mode.

  FIG. 4A shows a case where the number of positions exceeding a predetermined luminance value exceeds a predetermined number and the luminance width of the difference between the predetermined luminance and the minimum luminance is narrow. That is, when the luminance width is narrow, the logarithmic conversion area is not used, and as shown in the figure, the luminance exceeding the predetermined luminance value becomes a saturation level, and the luminance portion lower than the predetermined luminance value is expressed as a linear conversion area. The exposure is performed as follows.

  FIG. 4B shows a case where the number of positions exceeding a predetermined luminance value exceeds a predetermined number, and the luminance width of the difference between the predetermined luminance and the minimum luminance slightly exceeds the width of the linear conversion area. In this case, the luminance exceeding the predetermined luminance value becomes a saturation level, and the inflection point is set so that the luminance part lower than the predetermined luminance value is located in the linear transformation region where the minimum luminance of the object scene can be reproduced. As shown in the drawing, exposure is performed so that a predetermined luminance is equal to or lower than a predetermined luminance and the vicinity of the predetermined luminance is a logarithmic conversion region, and the low luminance portion is a linear conversion region.

  FIG. 3C shows a case where the number of positions exceeding a predetermined luminance value exceeds a predetermined number and the luminance width of the difference between the predetermined luminance and the minimum luminance is much larger. In this case, the luminance exceeding the predetermined luminance value becomes a saturation level, and the luminance portion lower than the predetermined luminance value is located in the linear conversion region where the minimum luminance of the object field can be reproduced, and the predetermined luminance. Exposure is performed by controlling the inflection point so that all of the luminance widths below the value are included in the linear or logarithmic transformation region.

  As described above, in addition to the mode in which the inflection point is changed and controlled so that all the brightness of the entire scene can be reproduced, a predetermined brightness value among the brightness values at a plurality of positions in the scene When the number of positions exceeding the predetermined number exceeds a predetermined number, for example, reflection by the wave front of sunlight can be blown out by providing a mode for changing and controlling the inflection point so that the predetermined luminance value is saturated. Thus, it is possible to obtain an imaging device using a linear log sensor that can also obtain an image incorporating the photographer's intention corresponding to the subject.

  In the above-described embodiment, the luminance value to be saturated is converted into ISO sensitivity 100, for example, and described in EV15. However, the photographer may input it from the menu screen according to the intention and change it. In this case, it is preferable that the brightness value to be saturated is set at the same time when setting the whiteout shooting mode.

  In the above flow, the inflection point is set so that the output of the image sensor becomes a logarithmic conversion region for all luminances. However, a predetermined exposure time and an aperture value are used to determine a predetermined inflection point. The inflection point is changed and controlled so that the luminance value is in the logarithmic transformation region, or the predetermined luminance value or more is saturated and the linear transformation region is below the predetermined luminance value. The inflection point may be controlled.

  In addition, the still image shooting mode has been described as an example, but it goes without saying that the still image shooting mode can also be applied to the moving image shooting mode.

It is an external appearance perspective view of the imaging device concerning this embodiment. It is a block diagram which shows the functional structure of the imaging device which concerns on this Embodiment. It is a block diagram which shows the structure of the image pick-up element which concerns on this Embodiment. It is a circuit diagram which shows the structure of the pixel with which the image pick-up element which concerns on this Embodiment is provided. It is a figure which shows the timing chart of operation | movement of the pixel with which the image pick-up element which concerns on this Embodiment is provided. It is a graph which shows the output with respect to the incident light quantity of the image pick-up element which concerns on this Embodiment. It is a flowchart which shows the outline operation | movement at the time of still image shooting mode. It is a flowchart which shows the general | schematic operation | movement at the time of the overexposure photography mode in still image photography mode. It is a figure which shows the outline of control of the inflection point at the time of a whiteout photography mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Case 3 Lens unit 4 Image pick-up element 5 Flash light emission part 6 Light control sensor 7 System control part 8 Signal processing part 11 Monitor 12 Zoom button W
13 Zoom button T
DESCRIPTION OF SYMBOLS 14 Optical finder 15 Selection cross key 16 Release switch 17 Power switch 18 USB terminal 22 Inflection point change part 27 Amplifier 28 A / D converter 29 Black reference correction part 30 AE evaluation value calculation part 31 WB process part 32 Color interpolation part 33 Color correction unit 34 Gradation conversion unit 35 Color space conversion unit

Claims (4)

An image sensor having a plurality of pixels capable of outputting an electric signal linearly converted with respect to the amount of incident light and an electric signal converted logarithmically with respect to the amount of incident light; An imaging optical system to be incident, an inflection point control means for changing and controlling an inflection point that is a boundary between a linear transformation region and a logarithmic transformation region in an electric signal output from the imaging device, and an output of the imaging device Luminance detecting means for detecting luminance values at a plurality of positions in the scene based on
In the case where the position exceeding a predetermined luminance value exceeds a predetermined number among the luminance values at a plurality of positions of the object scene obtained by the luminance detecting means,
The inflection point control means changes and controls an inflection point so that a position exceeding the predetermined luminance value is saturated. The inflection point control means changes and controls the inflection point so that at least the predetermined luminance value or less is not saturated when the luminance value is detected by the luminance detection means at a plurality of positions in the scene. The imaging device according to claim 1. The imaging apparatus according to claim 1, wherein the predetermined luminance value is changeable. The inflection point control means changes and controls the inflection points so that all areas become logarithmic transformation areas when the luminance values are detected by the luminance detection means at a plurality of positions in the object scene. The imaging device according to claim 1.

Images