JP2007028167A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus using an imaging device having a plurality of different photoelectric conversion characteristics and allowing a user to perform image pickup to which user's intention is reflected while imaging the finishing of the image by allowing the user to specify which characteristic out of the different photoelectric conversion characteristics is used for photographing an area selected by the user out of a photographed picture. <P>SOLUTION: The imaging apparatus capable of photographing the area selected by the user in the photographed image by the photoelectric conversion characteristic specified by the user by setting the connection points of a plurality of different photoelectric conversion characteristics in accordance with user's selection can be provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and in particular, by using a plurality of imaging elements having different photoelectric conversion characteristics, the user specifies which characteristic of the different photoelectric conversion characteristics is to be used to capture an area specified by the user in the imaging screen. The present invention relates to an image pickup apparatus that can select.

  Conventionally, in an imaging apparatus such as a digital camera, many methods have been proposed for reproducing a main subject, which is a main target of imaging, on a captured image with exposure and gradation characteristics intended by the user.

  For example, according to Patent Document 1, an effective photometry frame is set in a screen and its size is variable, so that the user can specify the range of the effective photometry frame, and photometry outside the effective photometry frame There has been proposed a method for performing good automatic exposure control corresponding to the size of the subject by weighting the output and then adding it to the photometric output within the effective photometric frame.

According to Patent Document 2, imaging is performed using a solid-state imaging device having pixels having two photoelectric conversion units of different sizes, and the obtained high-sensitivity image data and low-sensitivity image data are weighted. There has been proposed a method of obtaining a wide dynamic range composite image by performing addition and suppression processing.
JP-A-10-276360 Japanese Patent Application Laid-Open No. 2004-221928

  However, in the method of Patent Document 1, since the entire area selected by the user operates so as to be properly exposed, the exposure is appropriate for the average luminance of the entire selected area. However, in practice, there are many cases in which the main subject and the non-existing part are mixed in the selected area. For example, when the user selects an area with a luminance higher than that of the main subject and the main subject, the method of Patent Document 1 Since the image is captured so that the exposure is appropriate for the average luminance, there is a problem that the main subject is underexposed as a result.

  In the method of Patent Document 2, the obtained high-sensitivity image data and low-sensitivity image data are weighted, added, and subjected to suppression processing to synthesize an image. It is not possible to grasp whether it is a characteristic, and it is necessary to confirm whether the desired gradation characteristic is secured in the completed image, and the user performs post-processing on the obtained high-sensitivity image data and low-sensitivity image data There is annoyance. In addition, the imaging apparatus needs to have a large capacity memory necessary for image composition, which leads to an increase in the cost of the apparatus.

  The present invention has been made in view of the above circumstances, and in an imaging apparatus using an imaging device having a plurality of different photoelectric conversion characteristics, an area selected by a user in an imaging screen is selected from which of the different photoelectric conversion characteristics. It is an object of the present invention to provide an imaging apparatus that allows the user to specify whether or not to take an image, and to allow the user to take an image reflecting the intention of the user by reflecting the image finish.

  The object of the present invention can be achieved by the following constitution.

(Claim 1)
An image sensor having a plurality of different photoelectric conversion characteristics;
In an imaging apparatus comprising a photometric means for measuring the inside of an imaging screen of the imaging element and outputting a photometric signal,
An area selection unit that is used by a user to select a desired area in the imaging screen and outputs an area selection signal when the selection is made;
Used by the user to specify which characteristic of the plurality of different photoelectric conversion characteristics is used for the area selected by the area selecting means, and outputs a designation signal when the designation is performed. Photoelectric conversion characteristic designation means;
Control parameter calculation means for calculating a control parameter of the image sensor based on the photometric signal, the area selection signal, and the designation signal;
An image pickup apparatus comprising: an image pickup control unit that controls the image pickup element based on the control parameter.

(Claim 2)
Exposure calculation means for calculating a shutter speed and an aperture value based on the photometric signal;
Exposure control means for controlling exposure based on the shutter speed and the aperture value;
Without changing the shutter speed and the aperture value calculated by the exposure calculation means, the area selected using the area selection means is selected from the plurality of different photoelectric conversion characteristics using the photoelectric conversion characteristic designating means. The imaging apparatus according to claim 1, wherein the desired characteristic can be designated.

(Claim 3)
The imaging apparatus according to claim 1, wherein the imaging element can arbitrarily set connection points of the plurality of different photoelectric conversion characteristics.

(Claim 4)
4. The photoelectric conversion characteristic of a low luminance part among the plurality of different photoelectric conversion characteristics has higher gradation than the photoelectric conversion characteristic of a high luminance part. The imaging device described.

(Claim 5)
5. The photoelectric conversion characteristic of the low luminance part is a linear characteristic among the plurality of different photoelectric conversion characteristics, and the photoelectric conversion characteristic of the high luminance part is a logarithmic characteristic. The imaging device described in 1.

(Claim 6)
The image sensor has pixels arranged two-dimensionally on a matrix, and the pixels include a photoelectric conversion unit, a reset transistor, an amplifier transistor, and a selection transistor, and the potential of the gate of the reset transistor is controlled by controlling the potential of the gate 6. The imaging apparatus according to claim 5, wherein a connection point between the linear characteristic and the logarithmic characteristic can be arbitrarily set.

(Claim 7)
The image sensor has pixels arranged two-dimensionally on a matrix, and the pixel has a photoelectric conversion unit, a transfer gate, a reset transistor, an amplifier transistor, and a selection transistor, and controls the potential of the transfer gate. 6. The imaging apparatus according to claim 5, wherein a connection point between the linear characteristic and logarithmic characteristic can be arbitrarily set.

(Claim 8)
The image sensor has pixels arranged two-dimensionally on a matrix, and the pixel has a photoelectric conversion unit, a transfer gate, a reset transistor, an amplifier transistor, and a selection transistor, and controls the gate potential of the reset transistor. The imaging apparatus according to claim 5, wherein a connection point between the linear characteristic and logarithmic characteristic can be arbitrarily set.

  According to the first aspect of the present invention, the user selects a desired area in the imaging screen and designates the photoelectric conversion characteristics of the area, so that the user captures an image with the image finish level. It is possible to provide an imaging device capable of performing the above.

  According to the second aspect of the invention, the photoelectric conversion characteristics of the area in the screen can be designated as desired characteristics without changing the shutter speed and the aperture value calculated from the normal exposure calculation. It is possible to provide an imaging apparatus that can capture an image of the degree of finish of an image based on the experience of the above.

  According to the third aspect of the present invention, the use of an image sensor that can arbitrarily set connection points having different photoelectric conversion characteristics allows the photoelectric conversion characteristics of the area in the screen to be designated as desired characteristics. It is possible to provide an imaging apparatus that can obtain an image that matches the intention.

  According to the fourth aspect of the present invention, the photoelectric conversion characteristic of the area in the screen is set to the desired characteristic by using the imaging device in which the photoelectric conversion characteristic on the low luminance side has a higher gradation than the photoelectric conversion characteristic on the high luminance side. By specifying, it is possible to provide an imaging apparatus that can increase the gradation on the low luminance side, widen the dynamic range, and obtain an image suitable for the user's intention.

  According to the fifth aspect of the present invention, by specifying the photoelectric conversion characteristic of a desired area in the screen using an image sensor having a linear characteristic on the low luminance side and a logarithmic characteristic on the high luminance side, the gradation on the low luminance side is specified. Therefore, it is possible to provide an imaging apparatus capable of obtaining a high-performance and wide dynamic range and obtaining an image suitable for the user's intention.

  According to the invention described in any one of claims 6 to 8, by using the image pickup device that can arbitrarily set the connection point between the linear characteristic and the logarithmic characteristic by controlling the potential of the reset transistor or the transfer gate of the pixel, By specifying the photoelectric conversion characteristics of a desired area in the image pickup device, the gradation property on the low luminance side can be increased, the dynamic range can be widened, and an image suitable for the user's intention can be obtained. Can be provided.

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

  1A and 1B are schematic external views of a digital camera 1 that is an example of an imaging apparatus according to the present invention. FIG. 1A is a front view and FIG. 1B is a rear view.

  In FIG. 1A, an interchangeable lens 20 is attached to the front surface of the body 10. A release button 101, which is an operation member for imaging, is installed on the upper surface of the body 10, and an AF that operates in the first stage of pressing the release button 101 inside the body 10 is below the release button 101. A switch 101a and a two-stage switch constituting the release switch 101b that operates in the second stage of pressing the release button are arranged. A flash 102 is built in the upper part of the body 10 and a mode setting dial 112 for setting the operation mode of the digital camera 1 is arranged.

  In FIG. 1B, on the back of the body 10, a power switch 111 for turning on / off the power of the digital camera 1, a change dial 113 for changing various setting conditions of the digital camera 1, up, down, left, right, and center The jog dial 115 for performing various settings in each operation mode of the digital camera 1, the finder eyepiece 121a, and the image display means 131 for displaying recorded images and various information are arranged. ing.

  FIG. 2 is a block diagram showing an example of a circuit of the digital camera 1 shown in FIG. In the figure, the same parts as those in FIG.

  The camera control means 150 for controlling the digital camera 1 is composed of a CPU (Central Processing Unit) 151, a work memory 152, a storage means 153, etc., and reads a program stored in the storage means 153 to the work memory 152, Each part of the digital camera 1 is centrally controlled according to the program.

  The camera control means 150 receives inputs from the power switch 111, the mode setting dial 112, the change dial 113, the jog dial 115, the AF switch 101a, the release switch 101b, etc., and communicates with the photometry module 122 on the optical viewfinder 121. Thus, the photometry operation is controlled, the AF operation is controlled by communicating with the AF module 144, the reflex mirror 141 and the sub mirror 142 are driven via the mirror drive means 143, and the mechanical shutter 145 is provided via the shutter drive means 146. And the flash 102 is controlled. That is, the camera control unit 150 functions as an exposure calculation unit, an exposure control unit, and a control parameter calculation unit in the present invention. The photometry module 122 and the camera control means 150 function as photometry means in the present invention.

  Further, the camera control means 150 functions as a communication means between the body 10 and the interchangeable lens 20, and a BL communication means (body side) 172 provided on the mount (body side) 171 and a mount (lens side) 271. Through the BL communication means (lens side) 272 provided above, the lens control means 241 for controlling the focus and zoom of the lens 211 and the diaphragm control means for controlling the diaphragm 221 via the lens interface 251 of the interchangeable lens 20. 222, the entire interchangeable lens 20 is controlled by communicating with the lens information storage unit 231 storing the unique information of the interchangeable lens 20.

  An image formed by the lens 211 of the interchangeable lens 20 is photoelectrically converted by the image sensor 162, amplified by the amplifier 163, converted into digital data by the analog / digital (A / D) converter 164, and image processing is performed. The data is converted into digital image data subjected to predetermined image processing by means 165, temporarily recorded in the image memory 181, and finally recorded on the memory card 182. These operations are controlled by the imaging control unit 161 under the control of the camera control unit 150. The imaging control unit 161, the amplifier 163, the A / D conversion unit 164, and the image processing unit 165 constitute an imaging circuit 160.

  The camera control unit 150 displays captured image data and various information on the image display unit 131 and displays various information on the infinder display unit 132. In other words, the camera control unit 150, the image display unit 131, the finder display unit 132, and the jog dial 115 function as an area selection unit and a photoelectric conversion characteristic designation unit in the present invention.

  Next, an example of the image sensor 162 according to the present invention will be described with reference to FIGS.

  FIG. 3 is a schematic diagram illustrating an example of an arrangement of each constituent element included in the image sensor 162.

  The image sensor 162 includes a plurality of pixels 162b arranged in the horizontal and vertical directions on the imaging surface 162a, a vertical scanning circuit 162c, a sample hold circuit 162d, an output circuit 162e, an output amplifier 162g, a horizontal scanning circuit 162f, a timing generator ( TG) 162h and the like, and each horizontal row of the pixels 162b and the vertical scanning circuit 162c are connected to each other by a row selection line 162i, and each vertical column of the pixels 162b and the sample and hold circuit 162d are They are connected by a vertical signal line 162j.

  The imaging operation of the imaging element 162 is controlled by the timing generator 162 h according to the control from the imaging control unit 161, and the image data 162 k that is the output of the imaging element 162 is input to the amplifier 163.

  FIG. 4 is a circuit diagram illustrating a first example of a circuit of the pixel 162b configuring the imaging element 162.

  The pixel 162b includes an embedded photodiode PD (hereinafter referred to as a PD section) and N-channel MOSFETs (metal oxide semiconductor field effect transistors: hereinafter referred to as transistors) Q1 to Q4. The connection portion between the drain of the transistor Q1 and the source of Q2 is formed of a floating diffusion FD (hereinafter referred to as FD portion). φRSB, φRST, φTX, and φV indicate signals (potentials) for the respective transistors, VDD indicates a power supply, and GND indicates ground.

  The PD unit is a photoelectric conversion unit, and generates a photocurrent IPD corresponding to the amount of incident light from the subject. Since the PD unit cannot directly extract the photoelectrically converted photocurrent IPD, the photocurrent IPD is accumulated as a charge QPD in the parasitic capacitance CPD of the PD unit, and the accumulated signal charge QPD is a transistor Q1 (hereinafter referred to as a transfer gate). It is output by being completely transferred to the FD section by the transfer gate Q1). The transferred signal charge QPD is accumulated in the parasitic capacitance CFD of the FD portion.

  The transistor Q2 is called a reset transistor (hereinafter referred to as a reset transistor Q2), and resets the FD portion to a predetermined potential (φRSB) when turned on. During this reset operation, there is a case where noise called reset noise occurs that causes the potential of the FD portion to vary with respect to φRSB each time the reset operation is performed.

  The transistor Q3 constitutes a source follower amplifier circuit, and functions to lower the output impedance by performing current amplification with respect to the potential VFD of the FD section.

  The transistor Q4 is a signal readout transistor, and has a gate connected to the above-described row selection line 162i, and operates as a switch that is turned on / off according to the signal φV applied by the vertical scanning circuit 162c. The source of the transistor Q4 is connected to the vertical signal line 162j. When the transistor Q4 is turned on, the potential VFD of the FD portion is reduced in impedance by the transistor Q3 and is derived as the pixel output VOUT to the vertical signal line 162j. Is done.

  FIG. 5 is a diagram showing a driving method and characteristics of the pixel 162b shown in FIG. 4. FIG. 5A is a timing chart showing a driving method of a type for controlling the potential of the transfer gate Q1, and FIG. FIG. 5B is a schematic diagram showing photoelectric conversion characteristics when driven by the driving method shown in FIG. 5A, and FIG. 5C is a timing chart showing a driving method for controlling the potential of the reset transistor Q2. is there.

  FIG. 5A shows a drive system called a so-called global shutter system, in which the mechanical shutter 145 is opened during the imaging operation. At timing T11, the gate potential φRST and drain potential φRSB of the reset transistor Q2 and the gate potential φTX of the transfer gate Q1 are set to a high potential (H), so that the charge QPD remaining in the parasitic capacitance CPD of the PD portion is FD. The FD portion is also reset to the potential of φRSB.

  By setting φTX to a medium potential (M) at timing T12 (imaging timing), light from the subject is photoelectrically converted by the PD unit to become a photocurrent IPD, and when the photocurrent IPD is small, the linear characteristic is large. In this case, it is converted into logarithmic characteristics (hereinafter referred to as linear / logarithmic characteristics) and stored in the parasitic capacitance CPD of the PD section. The connection point between the linear characteristic and the logarithmic characteristic can be arbitrarily changed by setting the level of the medium potential (M) of φTX. Further, during the timing T12, φRST and φRSB are always at a high potential (the reset transistor Q2 is always on), and a current flowing through the transfer gate Q1 is supplied during logarithmic characteristics.

  At the beginning of timing T13, φRST is set to a low potential and φTX is set to a high potential (H), whereby the charge accumulated in the parasitic capacitance CPD of the PD portion is completely transferred to the FD portion (VFD), and the timing T14 Initially, the mechanical shutter 145 is closed and φV is set to a high potential, so that the potential VFD of the FD portion is reduced in impedance by the transistor Q3 and is used as a pixel output VOUT (in this case, the imaging signal SIGNAL) as a vertical signal line. It is derived to 162j and held in the sample hold circuit 162d.

  At timing T15, φRST and φRSB are set to a high potential, and the FD portion is reset to the potential of φRSB. In this example, φTX is also set to a high potential at this time, and the PD unit is also reset at the same time, but this is not essential. By making φV high at timing T16, the potential VFD of the FD portion is reduced in impedance by the transistor Q3, and is led to the vertical signal line 162j as the pixel output VOUT (in this case, the noise signal NOISE). It is held in the sample hold circuit 162d.

  In the sample hold circuit 162d, for example, noise can be removed by taking the difference between the held imaging signal SIGNAL and the noise signal NOISE in an analog manner (so-called CDS method: correlated double sampling method). Of course, the noise removal may be performed by digitally taking the difference between the imaging signal SIGNAL converted into digital data by the A / D conversion means in the subsequent stage and the noise signal NOISE.

  FIG. 5B shows photoelectric conversion characteristics when driven by the driving method shown in FIG. 5A. The horizontal axis represents the luminance B of the subject, and the vertical axis represents the pixel output VOUT along the linear axis. .

  As described above, when the gate potential φTX of the transfer gate Q1 is controlled to the medium potential (M), the pixel output shows the linear characteristic 501 when the subject brightness B is low, and the medium potential M when the subject brightness B is high. Depending on the setting, logarithmic characteristics are shown. For example, in the case where the potential M of φTX is M = M3, the connection point 513 between the linear characteristic 501 and the logarithmic characteristic 523 is a point of pixel output VOUT = Vth3. Similarly, when M = M2, the connection point 512 is VOUT = Vth2. In the example shown in FIG. 5B, when M = M1, the connection point 511 is VOUT = Vth1 = Vmax (pixel output level). Maximum value = saturation value).

  Therefore, when M = M1, the linear characteristic 501 is shown up to the subject brightness B1, and when the subject brightness exceeds B1, a saturation signal 524 of the pixel output VOUT = Vmax is shown. That is, the dynamic range in this case is D1 from darkness to subject brightness B1. Similarly, when M = M2, the subject luminance B21 shows a linear characteristic 501, the subject luminance B21 to B2 shows a logarithmic characteristic 522, and the subject luminance B2 or higher shows a saturation signal 524, which is dynamic. The range is D2 up to subject brightness B2. When M = M3, the linear characteristic 501 is shown up to the subject brightness B31, and the logarithmic characteristic 522 is shown above the subject brightness B31, and the dynamic range has no upper limit in the range shown in FIG. 5B. D3.

  In this way, by controlling the intermediate potential (M) of the gate potential φTX of the transfer gate Q1, it is possible to freely set a connection point between a linear characteristic with rich gradation and a logarithmic characteristic with a wide dynamic range. It is possible to freely reflect the situation of the subject and the intention of drawing, and it is also possible to make any part of the image blown out by using the saturation value Vmax of the pixel output VOUT.

  Similarly to FIG. 5A, FIG. 5C is a driving system called a so-called global shutter system, and the mechanical shutter 145 is opened during the imaging operation. The difference from FIG. 5A is that the connection point of the photoelectric conversion characteristics is set not by controlling the gate potential φTX of the transfer gate Q1, but by controlling the gate potential φRST of the reset transistor Q2.

  At timing T21, the gate potential φRST and drain potential φRSB of the reset transistor Q2 and the gate potential φTX of the transfer gate Q1 are set to a high potential (H), so that the charge QPD remaining in the parasitic capacitance CPD of the PD portion is FD. The FD portion is also reset to the potential of φRSB.

  By setting φTX to a high potential at the beginning of timing T22 (imaging timing), the charge due to the photocurrent IPD of the PD portion is completely transferred to the FD portion, and at the same time φRST is set to the middle potential (M). Thus, when the photocurrent IPD is small, it is converted into a linear characteristic, and when it is large, it is converted into a logarithmic characteristic and stored in the FD section. The connection point between the linear characteristic and the logarithmic characteristic can be arbitrarily changed by setting the level of the medium potential (M) of φRST. At the end of the timing T22, φTX and φRST are set to a low potential (L), and the imaging is finished, and the mechanical shutter 145 is closed.

  At the last time point of timing T22, charges due to imaging are accumulated in the FD portion, so that φV is set to a high potential at timing T23, so that the potential VFD of the FD portion is lowered in impedance by the transistor Q3. The pixel output VOUT (in this case, the imaging signal SIGNAL) is derived to the vertical signal line 162j and held in the sample and hold circuit 162d.

  The timing after timing T24 is the same as that shown in FIG. The photoelectric conversion characteristics when driven by the driving method shown in FIG. 5C are the same as those in FIG.

  As described above, by controlling the gate potential φTX of the transfer gate Q1 or the gate potential φRST of the reset transistor Q2, the connection point between the linear characteristic with rich gradation and the logarithmic characteristic with a wide dynamic range can be freely set. can do.

  Next, an example of the area selection method in the present invention will be described with reference to FIGS.

  FIG. 6 is a schematic diagram illustrating an example of a subject and a selection area. FIG. 6A shows an example of a subject. A person 602 as a main subject is on the right of the screen 601, a house 603 is on the left, and a cloud 604 is on the upper left. FIG. 6B is a schematic diagram showing an example of the area. In this example, the photometric area of the photometric element 122a of the photometric module 122 that functions as the photometric means is shown as it is. The photometry area is composed of 14 photometry areas including hexagonal partial photometry areas A1 to A13 and the entire photometry area A0 excluding the partial photometry area. In this example, this is the selection area for designating the photoelectric conversion characteristics as it is. Of course, the selection area for designating the photoelectric conversion characteristics is not limited to the photometric area of the photometric element 122a, and may be a combination of a plurality of photometric areas. When the image sensor 162 is used as the photometric means, In an extreme case, each pixel may be used as a selection area, or may be arbitrarily set by the user.

  FIG. 6C shows the screen of FIG. 6A overlaid on FIG. 6B. Areas A4, A8, A9, and A13 overlap with the person 602, and areas A1, A2, A5, A6, A7, A10, and A11 overlap with the house 603. The cloud 604 overlaps part of the area A0. As will be described later, when the photoelectric conversion characteristic of the selected area is designated, the selected area is displayed on the finder 122 or the image display means 131 as shown in FIG.

  FIG. 7 is a schematic diagram showing a method for designating photoelectric conversion characteristics of each selected area. FIG. 7A is a diagram when the photoelectric conversion characteristics of each area are designated, and FIG. 7B is a luminance distribution at that time. FIG.

  In FIG. 7A, areas A4, A8, A9, and A13 that overlap the person 602 that is the main subject are designated as the linear characteristic area 701, and A1 that overlaps the wall in the area that overlaps the house 603. , A2, A5, and A7 are designated in the logarithmic characteristic area 702. At this time, in FIG. 7B, by setting M = M2 in FIG. 5B, if the connection point between the linear characteristic 501 and the logarithmic characteristic 522 is set to the point of Vth2 of the pixel output VOUT, linearity is obtained. The luminances of the area 701 specified by the characteristic and the area 702 specified by the logarithmic characteristic are distributed in the respective ranges of 701a and 702a in FIG. 7B. In addition, the brightness of the cloud 604 is 703a in FIG. 7B, and it can be seen that the cloudy whiteout occurs because it exceeds the saturation value Vmax of the pixel output VOUT.

  In this way, by selecting an area in the imaging screen and designating its photoelectric conversion characteristics, the user can image the finish of the image and take an image reflecting the intention.

  Here, an example in which an image sensor having a linear characteristic on the low luminance side and a logarithmic characteristic on the high luminance side has been described. However, the present invention is not limited to this, and a plurality of different photoelectric conversion characteristics, for example, FIG. FIG. 7 is a schematic diagram showing an image sensor in which the low luminance side has a linear characteristic 711 with a large pixel output inclination with respect to the subject luminance, and the high luminance side has a linear characteristic 712 with a small pixel output inclination with respect to the subject luminance. This is also true for an image pickup device or the like whose schematic diagram is shown in (d), where the low luminance side has a linear characteristic 721 and the high luminance side has a known nonlinear characteristic 722.

  Next, an example of the operation flow of the area selection method according to the present invention will be described with reference to FIGS. FIGS. 8 to 14 are flowcharts showing an example of the flow of area selection operation. FIG. 8 is a main routine, FIGS. 9 to 14 are subroutines, and FIG. 15 is a schematic diagram for explaining the connection point calculation in FIG. FIG.

  In FIG. 8, first, the operation mode of the digital camera 1 is confirmed in step S101. Here, for example, assuming that the camera mode is set using the mode setting dial 112 (step S101; YES), the camera mode is started. When the operation mode other than the camera mode (for example, the playback mode) is set (step S101; NO), the control proceeds to each mode. Description is omitted.

  In step S111, it is confirmed whether or not the “photoelectric conversion characteristic designation mode” for designating the photoelectric conversion characteristic of each area is set. Here, for example, assuming that the photoelectric conversion characteristic designation mode is set using the jog dial 115 (step S111; YES), the process proceeds to step S121. When the photoelectric conversion characteristic designation mode is not set, that is, when the normal imaging mode is set, the process proceeds to normal imaging control. Description is omitted.

  In step S121, it is confirmed whether or not the photoelectric conversion characteristics of each area are designated by looking through the finder 121. When specifying in the finder 121 (step S121; YES), in step S131, for example, the infinder display means 132 made of color liquid crystal is used on the focusing screen 121c in the finder, for example, as shown in FIG. As shown, the selection areas A0 to A13 are displayed, and in step S132, AF and photometry are started using the AF module and photometry module.

  Next, the process proceeds to the “photoelectric conversion characteristic designation subroutine” in step S140, and the photoelectric conversion characteristic is designated. When the specification of the photoelectric conversion characteristics of each selected area is completed, one frame is imaged in the “single frame imaging subroutine” in step S150, and specified in step S140 in the “connection point (Vth) calculation subroutine” in step S160. A connection point satisfying the photoelectric conversion characteristics is calculated. If the calculation has been completed, imaging is performed in the “imaging A subroutine” in step S170, and a series of operations is completed. If the calculation could not be performed in step 160, a warning “cannot be specified” is displayed in the finder 121, and the process returns to step 140 to re-specify the photoelectric conversion characteristics.

  When the photoelectric conversion characteristics of each area are not designated by looking through the finder 121 in step S121, that is, when designated using the image display means 131 (step S121; NO), the “image display means in area display subroutine” of step S180 is entered. Then, the live view image and the selection area are displayed on the image display means 131, and the process proceeds to the “photoelectric conversion characteristic specifying subroutine” in step 140 to specify the photoelectric conversion characteristic.

  When the specification of the photoelectric conversion characteristics of each selected area is completed, a connection point that satisfies the photoelectric conversion characteristics specified in step S140 is calculated in the “connection point (Vth) calculation subroutine” in step S160. If the calculation is completed, imaging is performed in the “imaging B subroutine” in step S190, and a series of operations is completed. If the calculation cannot be performed in step 160, a warning “not specified” is displayed on the image display means 131, and the process returns to step 140 to re-specify the photoelectric conversion characteristics.

  FIG. 9 is a flowchart of the “photoelectric conversion characteristic designation subroutine” in step 140. In step S401, an area to be designated as a linear characteristic in the selected area is designated by a method such as selecting an area using the up / down / left / right keys of the jog dial and determining using the center key. In step S402, the linear characteristic area designated in step S401 is displayed on the finder display means 132, for example, in blue.

  In step S403, the area desired to be specified in the logarithmic characteristic is selected and specified in the same manner as in step S401. In step S404, the area is displayed on the finder display unit 132 in red, for example. Further, in step S405, an area to be designated as a whiteout area is selected and designated, and in step S406, for example, white is displayed on the finder display means 132, and the process returns to the main routine.

  FIG. 10 is a flowchart of the “single frame imaging subroutine” in step S150. In step S501, the photoelectric conversion characteristic (M potential of φTX) of the image sensor 162 is set to a predetermined standard characteristic. In step S502, the interchangeable lens 20 is obtained from the photometric result in step S132 in FIG. 8 or step S805 in FIG. The aperture value of the aperture 221 is set, the reflex mirror 141 and the sub mirror 142 are mirrored up in step S503, the mechanical shutter 145 is opened in step S504, and an image is captured using the electronic shutter function of the image sensor 162 in step S505. In step S506, imaging is completed using the electronic shutter function of the image sensor 162. In step S507, the mechanical shutter 145 is closed. In step S508, the reflex mirror 141 and the sub-mirror 142 are mirrored. In step S509, the image sensor. 1 2 transfers image data to the subsequent imaging circuit 150 from returning to the main routine. The operation from step S504 to S507 is the same as the timing T11 to T13 in FIG.

  FIG. 11 is a flowchart of the “connection point (Vth) calculation subroutine” in step S160. In step S601, based on the luminance of each selected area calculated from the photometric result of step S132 of FIG. 8 or step S805 of FIG. 13 described later, logarithmic characteristics are designated by the “photoelectric conversion characteristic designation subroutine” of step S140. It is determined whether or not the brightness of the area specified in (1) is higher than the brightness of the area specified in the linear characteristic. If all are high luminance, that is, if there is no reversal of luminance between the linear characteristic and the logarithmic characteristic (step S601; YES), the process proceeds to step S611.

  If there is a luminance reversal between the linear characteristic and the logarithmic characteristic (step S601; NO), the designated content of the reversed area is changed from the logarithmic characteristic to the linear characteristic in step S602, and in step S603, the finder display unit In the area displayed by color-coding 132 or the image display means 131, the red display (indicating logarithmic characteristics) of the area whose designated content has been changed is changed to blue display (indicating linear characteristics) to the user. The change of the designated content is notified, and the process proceeds to step S611. If necessary, the area where the designated content has been changed may be flashed for a certain period of time for further emphasis and notification.

  Here, in order to obtain an image with as high a gradation as possible, the area specified in the logarithmic characteristic of the reverse portion has been described as being changed to the linear characteristic, but of course, the area specified in the logarithmic characteristic. The area designated as the linear characteristic having higher luminance may be changed to the logarithmic characteristic, or the reverse part may be displayed on the finder display unit 132 or the image display means 131 and designated again by the user. It may be received.

  In step S611, Vth of the connection point between the linear characteristic and the logarithmic characteristic satisfying the designated content is calculated from the designated content and the photometric result of each selected area. In step S611, an exposure control value (aperture value of the aperture 221) determined from an Ev (Exposure value) value calculated by a normal exposure calculation (referred to as an APEX (Additive system of Photographic Exposure) operation) based on the photometric result. The pixel output Vth at the connection point satisfying the photoelectric conversion characteristics of each designated area is calculated without changing the electronic shutter time of the image sensor 162.

  This is a calculation aimed at making the main subject an appropriate exposure in the normal exposure calculation. Therefore, the exposure of the main subject (usually specified in a linear characteristic region with high gradation) is set to an appropriate exposure. This means that the photoelectric conversion characteristic is manipulated while keeping it, and the Vth of the connection point between the linear characteristic and the logarithmic characteristic satisfying the user-specified contents is calculated.

  FIG. 15A illustrates this relationship. Specifying the linear characteristic and logarithmic characteristic by changing the position of the connection point 613 between the linear characteristic 501 and the logarithmic characteristic 612 while maintaining the exposure of the main subject at an appropriate exposure, that is, keeping the slope of the linear characteristic 501 constant. Vth of the connection point satisfying the above is calculated. Similarly to FIG. 7B, the pixel output of the connection point 512 that satisfies the luminance distribution 701 of the area specified by the linear characteristic including the main subject and the luminance distribution 702 of the area specified by the logarithmic characteristic is Vth2. .

  Next, in step S621, it is confirmed whether or not the calculation in step S611 was possible. If it can be calculated (step S621; YES), the process proceeds to step S641, and the slope of the linear characteristic (that is, the aperture value of the aperture 221 and the electronic shutter time of the image sensor 162) and the Vth of the connection point are determined and the main routine is executed. Return.

  If the calculation in step S611 is impossible in step S621 (step S621; NO), the slope of the linear characteristic (that is, the aperture value of the aperture 221 and the electronic shutter time of the image sensor 162) is also changed in step S622. The degree of freedom of setting is further increased, and the Vth of the connection point between the linear characteristic and the logarithmic characteristic satisfying the specified content is calculated.

  FIG. 15B illustrates this relationship. Similarly to FIG. 15A, considering the luminance distribution 711 of the area specified as the linear characteristic including the main subject and the luminance distribution 712 of the area specified as the logarithmic characteristic, the same linear characteristic 501 as in FIG. 15A. In the combination of the logarithmic characteristic 522, the high luminance side of the area 711 designated as the linear characteristic becomes the logarithmic characteristic. However, in the combination of the linear characteristic 501 and the logarithmic characteristic 521 that satisfy all of the linear characteristic area 711, the logarithmic characteristic area 712 exceeds the maximum value Vmax of the pixel output, resulting in whiteout.

  Therefore, the linear characteristic is changed from 501 to 601 (specifically, the diaphragm 221 is slightly narrowed or the electronic shutter time of the image sensor 162 is slightly shortened), and the combination with the logarithmic characteristic 623 is used. Both area 711 and logarithmic characteristic area 712 can be satisfied. As a result, the exposure of the main subject becomes Vth 623 which is slightly under the appropriate exposure, but there is an advantage that the photoelectric conversion characteristics with a higher degree of freedom can be specified.

  In step S631, it is confirmed whether or not the calculation in step S622 was possible. If it is possible (step S631; YES), the process proceeds to step S641, and the slope of the changed linear characteristic (that is, the aperture value of the aperture 221 and the electronic shutter time of the image sensor 162) and the Vth of the connection point are determined. Return to the routine.

  If the calculation is impossible in step S631 (step S631; NO), in step S651, a warning indicating “not specified” is displayed on the finder display unit 132 or the image display means 131, and the main routine is displayed. Returning to step 140, the photoelectric conversion characteristics are designated again.

  FIG. 12 is a flowchart of the “imaging A subroutine” in step S170. In steps S701 and S702, the inclination of the linear characteristic determined in step S641 in FIG. 11, that is, the aperture value of the aperture 221 and the electronic shutter time of the image sensor 162 are set. In step S703, also determined in step S641 in FIG. A medium potential M of φTX corresponding to Vth of the connected node is set.

  Waiting for the release switch 101b to be turned on in step S704 and turning it on (step S704; YES), the aperture 221 is controlled to the aperture value set in step S701 in step S711, and the reflex mirror 141 in step S712. In step S713, the mechanical shutter 145 is opened. In step S714, imaging is started using the electronic shutter function of the imaging element 162. In step S715, imaging is performed using the electronic shutter function of the imaging element 162. In step S716, the mechanical shutter 145 is closed, and in step S721, the reflex mirror 141 and the sub-mirror 142 are mirrored down.

  In step S722, image data is transferred from the image sensor 162 to the subsequent imaging circuit 150. In step S723, the image processing unit 165 performs necessary image processing and JPEG compression, and in step S724, the JPEG compressed image processed in step S723. Is once recorded in the image memory 181, the JPEG compressed image recorded in the image memory 181 is recorded in the memory card 182 in step S 725, and the process returns to the main routine.

  FIG. 13 is a flowchart of “area display subroutine for image display means” in step S180. In step S801, the photoelectric conversion characteristic of the image sensor 162 (M potential of φTX) is set to a predetermined standard characteristic. In step S802, the reflex mirror 141 and the sub mirror 142 are mirrored. In step S803, the mechanical shutter 145 is opened. In step S804, the imaging device 162 and the imaging circuit 160 are driven to start live view imaging (the number of readout pixels may be reduced or the frame rate may be reduced), and in step S805, the image output of the live view image is used. In step S811, the display of the live view image is started on the image display unit 131. In step S812, the display of the selected area is started by being superimposed on the live view image.

  In step S813, in order to confirm which characteristic the photoelectric conversion characteristic of each selected area is based on the standard photoelectric conversion characteristic (M potential of φTX) of the image sensor 162 set in step S801, the number of read pixels At least one frame of normal imaging without thinning out or reducing the frame rate is performed, the photoelectric conversion characteristics of each selected area are calculated using the image output normally captured at step S813 at step S814, and the calculation at step S814 is performed at step S815 The photoelectric conversion characteristics of each selected area are displayed in the same manner as in FIG. 9, with the linear characteristics displayed in blue, the logarithmic characteristics displayed in red, and the whiteout areas displayed in white, and the process returns to the main routine.

  During normal imaging in step S813, it is desirable that the live view image should not be interrupted by, for example, displaying the live view image immediately before that on the image display unit 131 again.

  FIG. 14 is a flowchart of the “imaging B subroutine” in step S190. The same step numbers are assigned to the same parts as in FIG. The “imaging B subroutine” of FIG. 14 differs from the “imaging A subroutine” of FIG. 12 in step S912 after the mechanical shutter 145 that has been left open for live view display is once closed, and then the step. The point is to open again for imaging in S713. Further, when the mechanical shutter 145 is closed in step S912, the live view display is ended.

  As described above, by using multiple image sensors that have different photoelectric conversion characteristics, select an area in the image capture screen and specify the photoelectric conversion characteristics to achieve both low-brightness gradation and dynamic range. Thus, an image suitable for the user's intention can be obtained.

  Next, a second example of the pixel 162b constituting the image sensor 162 will be described with reference to FIGS.

  FIG. 16 is a circuit diagram illustrating a second example of the circuit of the pixel 162b configuring the image sensor 162. The same parts as those in FIG. The pixel circuit of FIG. 16 differs from the pixel circuit of FIG. 4 in that the transfer gate Q1 is eliminated. By reducing the number of transistors constituting the pixel 162b, the pixel 162b can be miniaturized and the aperture ratio of the PD portion can be increased. In this example, since there is no transfer gate Q1, the PD unit is directly connected to the FD unit, and the charge due to the photocurrent IPD photoelectrically converted by the PD unit is accumulated in the capacitor CFD of the FD unit. Others are the same as in the example of FIG.

  FIG. 17 is a timing chart showing a driving method of the second example of the pixel 162b shown in FIG. In this example, since there is no transfer gate Q1, an electronic shutter cannot be realized using the transfer gate as shown in FIGS. 5 (a) and 5 (c). Therefore, the global shutter method cannot be used, and the global reset method for performing imaging using the mechanical shutter 145 shown in FIG. 17A or the rolling shutter method shown in FIG. 17B is used. In many cases, the global reset method is mainly used for capturing a still image, and the rolling shutter method is mainly used for capturing a moving image.

  In FIG. 17A, first, with the mechanical shutter 145 closed, the reset transistor Q2 is turned on by setting φRST and φRSB to a high potential at timing T31, and the FD portion (= PD portion) is set to φRSB. By resetting to high potential and setting φRST to medium potential (M) at the end of timing T31, a state where imaging with linear / logarithmic characteristics is possible is set.

  Next, at timing T32, the mechanical shutter 145 is opened and closed, and exposure to the image sensor 162, that is, imaging is performed. After the mechanical shutter 145 is closed, φRST is set to a low potential, and the reset transistor Q2 is turned off. An imaging signal is stored in the FD unit. Subsequently, φV is set to a high potential at timing T33, so that the potential VFD of the FD portion is reduced in impedance by the transistor Q3 and is derived to the vertical signal line 162j as the pixel output VOUT (in this case, the imaging signal SIGNAL). And held in the sample hold circuit 162d.

  At timing T34, φRST and φRSB are set to a high potential, and the FD portion (= PD portion) is reset to a high potential of φRSB. By making φV high at timing T35, the potential VFD of the FD portion is reduced in impedance by the transistor Q3, and is led to the vertical signal line 162j as the pixel output VOUT (in this case, the noise signal NOISE). It is held in the sample hold circuit 162d. The subsequent steps are the same as those in FIG.

  In FIG. 17B, the mechanical shutter 145 is always opened during moving image capturing. By resetting φRST and φRSB to high potential at timing T41, the reset transistor Q2 is turned on, and the FD portion (= PD portion) is reset to high potential of φRSB. At timing T42 in parallel with timing T41, the potential VFD of the FD portion is lowered by the transistor Q3 at timing T42, and the vertical signal is output as the pixel output VOUT (in this case, the noise signal NOISE). Derived to the line 162j and held in the sample and hold circuit 162d. At the end of timing T41, φRST is set to a medium potential (M), whereby imaging with linear / logarithmic characteristics is started, and imaging is performed at timing T43.

  By making φV high at timing T44, the potential VFD of the FD portion is reduced in impedance by the transistor Q3, and is led to the vertical signal line 162j as the pixel output VOUT (in this case, the imaging signal SIGNAL). It is held in the sample hold circuit 162d. This is repeated for moving image capturing. Although the timing T43 (imaging) time appears to be short in the figure, the timings T41, T44 and the like actually operate at a very high speed, so that T43 can be made long.

  As described above, even with a pixel circuit that does not have the transfer gate Q1, imaging with the global reset method combined with the mechanical shutter or the rolling shutter method enables linear characteristics with rich gradation and logarithmic characteristics with a wide dynamic range. Since the connection point can be freely set, it is possible to freely reflect the state of the subject and the intention of drawing.

  As described above, according to the present invention, in an imaging apparatus using an imaging device having a plurality of different photoelectric conversion characteristics, the area selected by the user in the imaging screen can be determined by any of the different photoelectric conversion characteristics. By specifying whether to capture images, the user can image the finish of the image and reflect his intention, and achieve both low-brightness gradation and dynamic range. It is possible to provide an imaging apparatus capable of performing the imaging.

  The detailed configuration and detailed operation of each component constituting the imaging apparatus according to the present invention can be changed as appropriate without departing from the spirit of the present invention.

1 is a schematic external view of a digital camera that is an example of an imaging apparatus according to the present invention. It is a block diagram which shows an example of the circuit of the digital camera shown in FIG. It is a mimetic diagram showing an example of arrangement of each component which constitutes an image sensor. It is a circuit diagram showing the 1st example of the circuit of the pixel which constitutes an image sensor. FIG. 5 is a diagram illustrating a driving method and characteristics of the pixel illustrated in FIG. 4. It is a schematic diagram which shows an example of a to-be-photographed object and a selection area. It is a schematic diagram which shows the designation | designated method of the photoelectric conversion characteristic of each selection area. It is the main routine of the flowchart which shows an example of the flow of operation | movement of area selection. 9 is a flowchart of a “photoelectric conversion characteristic designation subroutine” in FIG. 8. 9 is a flowchart of a “single frame imaging subroutine” in FIG. 8. 9 is a flowchart of a “connection point (Vth) calculation subroutine” in FIG. 8. FIG. 9 is a flowchart of an “imaging A subroutine” in FIG. 8. FIG. 9 is a flowchart of “area display subroutine in image display means” in FIG. 8. FIG. FIG. 9 is a flowchart of “imaging B subroutine” in FIG. 8. FIG. It is a schematic diagram which shows the calculation method of FIG. It is a circuit diagram which shows the 2nd example of the circuit of the pixel which comprises an image sensor. FIG. 17 is a timing chart showing a driving method of the second example of the pixel shown in FIG. 16.

Explanation of symbols

1 Digital Camera 10 Body 101 Release Button 101a AF Switch 101b Release Switch 111 Power Switch 112 Mode Setting Dial 113 Change Dial 115 Jog Dial 115
121 finder 122 photometric module 131 image display means 132 infinder display means 144 AF module 145 mechanical shutter 150 camera control means 151 CPU (central processing unit)
160 Image pickup circuit 161 Image pickup control means 162 Image pickup element 162b Pixel 163 Amplifier 164 Analog / digital (A / D) conversion means 165 Image processing means 181 Image memory 182 Memory card 20 Interchangeable lens 211 Lens 221 Aperture 222 Aperture control means 701 Linear characteristic area 702 Logarithmic characteristics area

Claims (8)

An image sensor having a plurality of different photoelectric conversion characteristics;
In an imaging apparatus comprising a photometric means for measuring the inside of an imaging screen of the imaging element and outputting a photometric signal,
An area selection unit that is used by a user to select a desired area in the imaging screen and outputs an area selection signal when the selection is made;
Used by the user to specify which characteristic of the plurality of different photoelectric conversion characteristics is used for the area selected by the area selection unit, and outputs a designation signal when the designation is performed. Photoelectric conversion characteristic designation means;
Control parameter calculation means for calculating a control parameter of the image sensor based on the photometric signal, the area selection signal, and the designation signal;
An image pickup apparatus comprising: an image pickup control unit that controls the image pickup element based on the control parameter. Exposure calculation means for calculating a shutter speed and an aperture value based on the photometric signal;
Exposure control means for controlling exposure based on the shutter speed and the aperture value;
Without changing the shutter speed and aperture value calculated by the exposure calculation means, the area selected using the area selection means is selected from the plurality of different photoelectric conversion characteristics using the photoelectric conversion characteristic designating means. The imaging apparatus according to claim 1, wherein the desired characteristic can be designated. The imaging apparatus according to claim 1, wherein the imaging element can arbitrarily set connection points of the plurality of different photoelectric conversion characteristics. 4. The photoelectric conversion characteristic of a low luminance part among the plurality of different photoelectric conversion characteristics has higher gradation than the photoelectric conversion characteristic of a high luminance part. The imaging device described. 5. The photoelectric conversion characteristic of the low luminance part is a linear characteristic among the plurality of different photoelectric conversion characteristics, and the photoelectric conversion characteristic of the high luminance part is a logarithmic characteristic. The imaging device described in 1. The image sensor has pixels arranged two-dimensionally on a matrix, and the pixels include a photoelectric conversion unit, a reset transistor, an amplifier transistor, and a selection transistor, and the potential of the gate of the reset transistor is controlled by controlling the potential of the gate 6. The imaging apparatus according to claim 5, wherein a connection point between the linear characteristic and the logarithmic characteristic can be arbitrarily set. The image sensor has pixels arranged two-dimensionally on a matrix, and the pixel has a photoelectric conversion unit, a transfer gate, a reset transistor, an amplifier transistor, and a selection transistor, and controls the potential of the transfer gate. 6. The imaging apparatus according to claim 5, wherein a connection point between the linear characteristic and logarithmic characteristic can be arbitrarily set. The image sensor has pixels arranged two-dimensionally on a matrix, and the pixel has a photoelectric conversion unit, a transfer gate, a reset transistor, an amplifier transistor, and a selection transistor, and controls the gate potential of the reset transistor. The imaging apparatus according to claim 5, wherein a connection point between the linear characteristic and logarithmic characteristic can be arbitrarily set.

Images