JP2007306064A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of executing exposure control in a photographable way without causing deterioration in image quality depending on the lightness of an object. <P>SOLUTION: The imaging apparatus including an imaging element provided with light receiving elements with high sensitivity and light receiving elements with low sensitivity applies photometry to the lightness of the object (100), applies exposure control on the basis of a photometry value and the sensitivity of the light receiving elements with the high sensitivity when the photometry value is less than a prescribed value A (108, 110), applies exposure control on the basis of a photometry value and the sensitivity of the light receiving elements with the low sensitivity when the photometry value is the prescribed value A or over (104, 106), and executes photographing and recording by using a signal outputted from the light receiving elements used for the exposure control in a state subjected to the exposure control as above (112). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus having an image pickup element including light receiving elements having a plurality of different sensitivities.

  Digital cameras equipped with an image sensor (CCD) are widely used, but in recent years, CCDs have become larger and finer in order to increase resolution. Therefore, the pixel pitch of the CCD is becoming very small.

  On the other hand, the aperture value (F value) is adjusted in exposure control at the time of shooting, but it is known that when the F value is increased, the image quality (resolution) deteriorates due to a diffraction phenomenon. Further, as the pixel pitch of the CCD becomes smaller, the deterioration occurs with a smaller F value.

In view of this, a camera has been proposed in which the aperture value at the minimum aperture is limited to a predetermined value or less, and an ND filter is provided to limit the amount of light (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-8803

  However, since the aperture value is limited in the technique described in Patent Document 1, exposure control is difficult when the subject is bright. In addition, providing an ND filter increases the cost.

  The present invention has been made to solve the above problem, and an object of the present invention is to provide an imaging apparatus capable of performing exposure control so as to be capable of photographing without deterioration of image quality in accordance with the brightness of a subject.

  In order to achieve the above object, an imaging apparatus of the present invention receives light from a subject, receives a plurality of first light receiving elements having a predetermined sensitivity for outputting a signal corresponding to the received light amount, and receives light from the subject. And an image sensor including a plurality of second light receiving elements having a sensitivity lower than the predetermined sensitivity for outputting a signal corresponding to the received light amount, a photometric means for measuring the brightness of the subject, and a photometric measurement of the photometric means When the value is less than the predetermined value, exposure control is performed based on the photometric value and the sensitivity of the first light receiving element. When the photometric value of the photometric means is greater than or equal to the predetermined value, the photometric value and the second light receiving element An image forming unit that forms an image of the subject using an exposure control unit that performs exposure control based on sensitivity, and a signal output from a light receiving element that is used for the exposure control in a state in which the exposure control unit performs exposure control. Means comprising That.

  As described above, in an imaging apparatus including an imaging device including a first light receiving element having a predetermined sensitivity and a second light receiving element having a sensitivity lower than the predetermined sensitivity, the photometric value of the photometric means is less than the predetermined value, that is, the subject is dark. Performs exposure control based on the photometric value and the sensitivity of the first light receiving element, and when the photometric value of the photometric means is a predetermined value or more, that is, when the subject is bright, the exposure is based on the photometric value and the sensitivity of the second light receiving element. Since the control is performed, in any case, the exposure amount determined by the photometric value and the sensitivity is appropriately adjusted, and the exposure can be controlled so that the image can be taken without deterioration of the image quality. Further, since the image of the subject is formed using the signal output from the light receiving element used for the exposure control in the exposure controlled state, the image can be taken without deterioration in image quality. In other words, according to the present invention, exposure control can be performed so as to enable photographing without deterioration of image quality according to the brightness of the subject, and the subject can be photographed with high image quality.

  In the formation of the subject image, the image may be formed only with the signal output from the light receiving element used for exposure control, but the signal output from the light receiving element used for exposure control is a main signal, The signal output from the other light receiving element may be used as a sub-signal, the main signal may be used as a main image to form an image, and if necessary, the sub-signal may be combined with the main signal to form an image of the subject. .

  The imaging apparatus further includes a correction unit that corrects a signal output from a light receiving element used when forming an image of the subject with a correction coefficient determined according to a photometric result of the photometric unit, and the exposure control The means performs exposure control based on the photometric value and the correction sensitivity obtained by correcting the sensitivity of the first light receiving element with the correction coefficient when the photometric value of the photometric means is less than a predetermined value, and the photometric value of the photometric means Is equal to or greater than a predetermined value, exposure control can be performed based on the photometric value and the correction sensitivity obtained by correcting the sensitivity of the second light receiving element with the correction coefficient.

  As described above, according to the present invention, there is an effect that exposure control can be performed in accordance with the brightness of a subject so that photographing can be performed without deterioration in image quality.

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

  FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 10 according to the present embodiment.

  The photographing optical system 12 of the image pickup apparatus 10 includes a photographing lens 14 and a diaphragm 16. The photographic lens 14 is composed of one or a plurality of lenses, and may be a single focal length (fixed focal length) lens or a variable focal length such as a zoom lens or a telephoto / wide-angle bifocal switching lens. Good.

  The subject image formed on the light receiving surface of the CCD 18 via the photographing optical system 12 is converted into a signal charge having an amount corresponding to the amount of incident light. The signal charge accumulated in this way is read out by a CCD drive pulse applied from the CCD drive circuit 20, and is sequentially output from the CCD 18 as a voltage signal (analog image signal) corresponding to the signal charge. The detailed configuration of the CCD 18 will be described later.

  The signal read from the CCD 18 is subjected to correlated double sampling (CDS) processing in the CDS circuit 22 and color separation processing into R, G, B color signals to adjust the signal level of each color signal (pre-white balance). Process).

  The image signal that has undergone the predetermined analog signal processing is applied to the A / D converter 24, converted into R, G, B digital signals by the A / D converter 24, and then stored in the memory 26. .

  A timing signal generation circuit (TG) 28 provides appropriate timing signals to the CCD drive circuit 20, the CDS circuit 22 and the A / D converter 24 in response to a command from the CPU 30, and each circuit generates a timing signal. It is driven in synchronism with a timing signal applied from the circuit 28.

  The CPU 30 is a control unit that performs overall control of each circuit of the imaging apparatus 10 by executing a program stored in a ROM (not shown), and a gain adjustment circuit 34, a gamma correction circuit 36, and luminance / color differences via a bus 32. A signal processing circuit (referred to as a YC processing circuit) 38, a compression / decompression circuit 40, a card interface 44 of the memory card 42, a display driver 48 for driving the display unit 46, and the like are connected.

  The CPU 30 controls the corresponding circuit block based on the input signal from the operation unit 50, and controls the zooming operation, the automatic focus adjustment (AF) operation of the photographing lens 14, the automatic exposure adjustment (AE), and the like. .

  The operation unit 50 includes a release button that gives an instruction to start image recording, a mode selection unit of the imaging apparatus, a zoom operation unit, and other various input units. These input means have various forms such as switch buttons, dials, and slide-type knobs. There is also an aspect in which a setting menu or a selection item is displayed on the screen of the touch panel or the liquid crystal monitor display unit, and a desired item is selected with a cursor. . The operation unit 50 may be disposed in the imaging apparatus main body, or may be configured to be separated from the imaging apparatus 10 main body as a remote control transmitter.

  The CPU 30 performs various calculations such as a focus evaluation calculation and an AE calculation based on the image signal output from the CCD 18, and based on these calculations, driving means (for example, an AF motor or an iris motor) for the photographing lens 14 and the diaphragm 16. Etc.) 52 is controlled to move the focus lens to the in-focus position, and the aperture 16 is set to an appropriate aperture value.

  For example, a contrast AF method in which the focus lens is moved so that the high frequency component of the G signal is maximized is employed for the AF control. In the AE control, EV (Exposure Value, also referred to as “exposure value” in the present embodiment) is obtained based on an integrated value obtained by integrating the R, G, and B signals of one frame, and based on the exposure value EV. The aperture value and shutter speed are determined, the aperture 16 is driven via the driving means 52, and the charge accumulation time of the CCD 18 is controlled by the electronic shutter so that the determined shutter speed is obtained. Therefore, only by directing the photographing lens 14 of the imaging apparatus 10 toward the subject, the optimum exposure adjustment is performed and the focusing is automatically performed.

  At the time of shooting and recording, when the release button is “half-pressed”, the above-mentioned photometric operation is repeated a plurality of times to obtain an accurate exposure value EV, and finally the aperture value and shutter speed at the time of shooting are determined based on this exposure value EV. decide. Then, when the release button is “fully pressed”, the aperture 16 is driven so that the final determined aperture value is obtained, and the charge accumulation time is controlled by the electronic shutter so that the determined shutter speed is obtained. In addition to the method of measuring and controlling AE and AF based on the image signal acquired from the CCD 18, the AE and AF are measured using a well-known photometric sensor or using a distance measuring sensor composed of an AF light projecting / receiving sensor. It may be controlled by measuring the distance.

  In addition, the imaging device 10 includes a strobe light emitting device 54 and a light receiving element 56 for dimming, and automatically controls the strobe light emitting device 54 at low brightness in response to an operation of a strobe mode setting button included in the operation unit 50. Are set to “low-brightness automatic light-emission mode” for causing the flash to emit light, “forced light-emission mode” for causing the strobe light-emitting device 54 to emit light regardless of subject brightness, “light-emission prohibiting mode” for prohibiting light emission of the strobe light-emitting device 54,

  The CPU 30 controls charging of the main capacitor of the strobe light emitting device 54 and discharge (light emission) timing to the light emitting tube (for example, a xenon tube) according to the strobe mode selected by the user, and performs measurement from the light receiving element 56. Based on the result, the emission stop is controlled. The light receiving element 56 receives the reflected light from the subject illuminated by the light emission of the strobe and converts it into an electrical signal corresponding to the amount of light received. The signal of the light receiving element 56 is integrated by an integration circuit (not shown), and the strobe light emission is stopped when the integrated light receiving amount reaches a predetermined appropriate light receiving amount.

  Data output from the A / D converter 24 is stored in the memory 26 and added to the integrating circuit 60. The integration circuit 60 divides the photographing screen into a plurality of blocks (for example, 64 blocks of 8 × 8), and performs integration calculation of the received G signal for each block. Note that the luminance signal (Y signal) may be generated from the R, G, and B data, and the luminance signal may be integrated. Further, the integrating circuit 60 can also be used as an AE arithmetic circuit. Information on the integrated value (calculation result) obtained by the integrating circuit 60 is input to the CPU 30.

  The CPU 30 determines a gain value (amplification factor) in the gain adjustment circuit 34 in accordance with a predetermined algorithm based on information from the integration circuit 60. The CPU 30 controls the gain amount in the gain adjustment circuit 34 according to the determined gain value.

  The R, G, B image data stored in the memory 26 is sent to the gain adjustment circuit 34, where it is amplified. The amplified image data is subjected to a gamma correction process in a gamma correction circuit 36 and then sent to a YC processing circuit 38. The RGB data is converted into a luminance signal (Y signal) and a color difference signal (Cr, Cb signal). Converted.

  The luminance / color difference signal (abbreviated as YC signal) generated in the YC processing circuit 38 is written back to the memory 26. The YC signal stored in the memory 26 is supplied to the display driver 48, converted into a predetermined signal (for example, an NTSC color composite video signal), and output to the display unit 46. As the display unit 46, a liquid crystal display or other display device capable of color display is used. The display unit 46 may be a YC signal input type or an RGB signal input type, and a driver corresponding to the display device is applied.

  Image data (YC signal) is periodically rewritten by the image signal output from the CCD 18, and a video signal generated from the image data is supplied to the display unit 46, so that an image captured by the CCD 18 is a moving image in real time. It is displayed on the display unit 46 as a (live image) or as a substantially continuous image although not in real time.

  The display unit 46 can be used as an electronic viewfinder, and the photographer can check the shooting angle of view by using a display image on the display unit 46 or an optical viewfinder (not shown). In response to a predetermined recording instruction (shooting start instruction) operation such as a release button pressing operation, capturing of image data for recording is started.

  When the photographer inputs a shooting / recording instruction from the operation unit 50, the CPU 30 sends a command to the compression / expansion circuit 40 as necessary, whereby the compression / expansion circuit 40 converts the YC signal on the memory 26 into JPEG or another predetermined format. Compress according to The compressed image data is recorded on the memory card 42 via the card interface 44.

  When the mode for recording non-compressed image data (non-compression mode) is selected, the image data is recorded on the memory card 42 without being compressed without performing the compression processing by the compression / decompression circuit 40. The

  In the imaging apparatus 10 of the present embodiment, a memory card 42 is used as means for storing image data. Specifically, a recording medium such as smart media is applied. The form of the recording medium is not limited to the above, and various forms such as a PC card, a micro drive, a multimedia card (MMC), a magnetic disk, an optical disk, a magneto-optical disk, and a memory stick are possible. Corresponding signal processing means and interfaces are applied.

  In the reproduction mode, the image data read from the memory card 42 is decompressed by the compression / expansion circuit 40 and output to the display unit 46 via the display driver 48.

  Here, the structure of the CCD 18 according to the present embodiment will be described in detail. As the CCD 18, a honeycomb CCD as shown in FIG.

  As shown in FIG. 2, the image pickup unit of the CCD 18 is assigned one by one for one color of one pixel and has a predetermined arrangement pitch (horizontal arrangement pitch = Ph (μm), vertical arrangement pitch = Pv (μm)). And adjacent light receiving elements PD1 are arranged so as to bypass a plurality of light receiving elements PD1 that are two-dimensionally shifted in the vertical direction and the horizontal direction, and an opening AP formed in the front surface of the light receiving element PD1. In addition, a vertical transfer electrode VEL that takes out a signal (charge) from the light receiving element PD1 and transfers it in the vertical direction and a vertical transfer electrode VEL that is positioned at the lowest in the vertical direction are arranged on the lower side in the vertical direction, and from the vertical transfer electrode VEL A horizontal transfer electrode HEL for transferring the transferred signal to the outside. In the example shown in the figure, the opening AP is formed in an octagonal honeycomb shape.

  Here, each of the vertical transfer electrode groups constituted by a plurality of vertical transfer electrodes VEL arranged in a straight line in the horizontal direction has one of the vertical transfer drive signals V1, V2,. Can be applied simultaneously. In the example shown in the figure, the vertical transfer drive signal V3 is applied to the first-stage vertical transfer electrode group, and the vertical transfer drive signal V4 is applied to the second-stage vertical transfer electrode group. A vertical transfer drive signal V5 for the transfer electrode group, a vertical transfer drive signal V6 for the fourth vertical transfer electrode group, a vertical transfer drive signal V7 for the fifth vertical transfer electrode group, 6 The vertical transfer drive signal V8 for the vertical transfer electrode group at the stage, the vertical transfer drive signal V1 for the vertical transfer electrode group at the seventh stage, and the vertical transfer drive signal for the vertical transfer electrode group at the eighth stage. V2 can be applied to each.

  On the other hand, each light receiving element PD1 is configured to be electrically connected to one adjacent vertical transfer electrode VEL via a transfer gate TG. In the example shown in the figure, each light receiving element PD1 is configured to be connected to a vertical transfer electrode VEL adjacent to the lower right via a transfer gate TG.

  In the figure, the opening AP formed on the front surface of the light receiving element PD1 in which “R” is entered is covered with a color separation filter (color filter) that transmits red light, and “G” is entered. The opening AP formed on the front surface of the light receiving element PD1 is covered with a color separation filter that transmits green light, and the opening AP formed on the front surface of the light receiving element PD1 on which “B” is written is blue. It is covered with a color separation filter that transmits light. That is, the light receiving element PD1 in which “R” is written receives red light, the light receiving element PD1 in which “G” is written receives green light, and the light receiving element PD1 in which “B” is written receives blue light. Each analog signal corresponding to the amount of received light is output.

  The CCD 18 further includes a light receiving element PD2 that is less sensitive than the light receiving element PD1 described above. As shown in FIG. 2, the light receiving element PD2 is provided between the plurality of light receiving elements PD1. Similarly to the light receiving element PD1, the light receiving element PD2 is formed with an opening AP having a smaller area than the opening of the light receiving element PD1, and is electrically connected to one adjacent vertical transfer electrode VEL by the transfer gate TG. It is connected. Further, in the light receiving element PD2, any one of RGB color filters is mounted in the opening AP formed on the front surface thereof, similarly to the light receiving element PD1. Thus, since the light receiving area of the light receiving element PD2 is smaller than the light receiving area of the light receiving element PD1, an RGB signal having a lower sensitivity than the light receiving element PD1 can be obtained. FIG. 3 shows an example of the relationship between the exposure amount and the signal output in the light receiving elements PD1 and PD2. As can be seen from the figure, the signal output of the highly sensitive light receiving element PD1 is saturated at a lower exposure level compared to the signal output of the low sensitive light receiving element PD2.

  The electrode to which the transfer gate TG of the light receiving element PD2 is connected is provided different from the electrode to which the transfer gate TG of the adjacent light receiving element PD1 is connected.

  The subject image formed on the light receiving surface of the CCD 18 via the photographing optical system 12 is converted into signal charges of an amount corresponding to the amount of incident light by each of the light receiving elements PD1 and PD2. Each of the high-sensitivity or low-sensitivity signal charges accumulated in this way is read to the shift register by the read gate pulse applied from the CCD drive circuit 20, and sequentially as a voltage signal corresponding to the signal charge by the register transfer pulse. Read out. The CCD 18 has a so-called electronic shutter function that can sweep out the accumulated signal charge by a shutter gate pulse, thereby controlling the charge accumulation time (shutter speed).

  The signal output from the CCD 18 is input to the CDS circuit 22. The subsequent signal flow is as described above.

  In the present embodiment, the light receiving element used for photographing is switched according to the brightness of the subject. For example, when the subject is dark, an image of the subject is formed and recorded (photographs the subject) using a signal read from the high sensitivity light receiving element PD1, and when the subject is bright, the image is read from the low sensitivity light receiving element PD2. The subject is photographed using the output signal. The exposure control is performed according to the sensitivity of the light receiving element used at the time of photographing.

  Hereinafter, the processing at the time of shooting by the imaging apparatus 10 will be described in detail. FIG. 4 is a flowchart showing a flow of processing at the time of photographing.

  In step 100, subject photometry is performed. Specifically, as described above, when the release button is half-pressed, RGB image signals output from the CCD 18 are integrated to obtain a photometric value BV (Brightness Value) indicating the brightness of the subject.

  In step 102, it is determined whether or not the photometric value BV is equal to or greater than a predetermined value A. If it is determined that the photometric value BV is equal to or greater than the predetermined value A, the process proceeds to step 104, where the light receiving element used for photographing is set to the low sensitivity light receiving element PD2. The predetermined value A used for determining the brightness of the subject and setting the light receiving element is obtained by setting a suitable value in advance through experiments or the like.

  In step 106, the exposure value EV is obtained by the following equation (1) using the sensitivity SV (Speed Value, here a value indicating ISO sensitivity) and the photometric value BV of the low-sensitivity light receiving element PD2.

                        EV = SV + BV (1).

  Further, an aperture value AV (Aperture Value) and a shutter speed TV (Time Value) are set based on the obtained exposure value EV. The relationship between the exposure value EV, the aperture value AV, and the shutter speed TV is shown in the following formula (2).

                        EV = AV + TV (2).

  There are various control methods for exposure control. For example, in the case of program control, an appropriate aperture value AV and shutter speed TV are determined according to the value of the exposure value EV (or obtained by a predetermined arithmetic expression). ) This controls the exposure. For example, in the case of shutter speed priority control, the aperture value AV is obtained according to the exposure value EV and the shutter speed TV.

  Regardless of the control method, when the subject is bright, the low-sensitivity light receiving element PD2 is used for exposure control and subject image formation, so that the exposure value EV is higher than when the high-sensitivity light receiving element PD1 is used. Can be reduced. Therefore, the aperture value AV set in the exposure control is not so large.

  In step 112, when the release button is fully pressed, the diaphragm 16 is driven so as to achieve the set aperture value AV, and the charge accumulation time is controlled by the electronic shutter so as to achieve the set shutter speed. To do. Then, a subject image is formed and recorded using the image signal output from the low sensitivity light receiving element PD2. That is, from the image signal output from the low-sensitivity light receiving element PD2, as described above, gain correction, gamma correction processing, and YC conversion processing are performed, and the YC signal stored in the memory 26 is read from the memory 26 and compressed and expanded. The data is compressed by the circuit 40 and recorded on the memory card 42. Here, the signal output from the highly sensitive light receiving element PD1 is not used for photographing.

  In this way, when the subject is bright, the exposure is controlled using the sensitivity SV and the photometric value BV of the low-sensitivity light receiving element PD1, so that the high-quality subject image is generated without causing a small aperture blur. Can be taken.

  On the other hand, if it is determined in step 102 that the photometric value BV is less than the predetermined value A, the process proceeds to step 108, and the light receiving element used for photographing is set to the highly sensitive light receiving element PD1.

  In step 110, the exposure value EV is obtained by the above formula (1) using the sensitivity SV and the photometric value BV of the highly sensitive light receiving element PD1. Further, the aperture value AV and the shutter speed TV are set from the relationship represented by the above equation (2).

  Here, the high-sensitivity light receiving element PD1 is used for exposure control and subject image formation. However, since the subject is relatively dark and the photometric value BV is small, the value of the exposure value EV is not so large. Accordingly, the aperture value AV set in the exposure control is not so large.

  In step 112, when the release button is fully pressed, the diaphragm 16 is driven so as to achieve the set aperture value AV, and the charge accumulation time is controlled by the electronic shutter so as to achieve the set shutter speed. To do. Then, a subject image is formed and recorded using the image signal output from the highly sensitive light receiving element PD1. Here, the signal output from the low-sensitivity light receiving element PD2 is not used for photographing. Thus, even when the subject is dark, appropriate exposure control can be performed accordingly, and a high-quality subject image can be taken.

  The signal output from the light receiving element is amplified by the gain adjustment circuit 34 as described above and used for image formation of the subject. However, the correction sensitivity obtained by correcting the sensitivity of the light receiving element with the gain value of the gain adjustment circuit 34 is used. It may be used to perform exposure control.

  FIG. 5 is a flowchart showing processing at the time of shooting when exposure control is performed using the correction sensitivity.

  In step 200, photometry is performed in the same manner as described above to obtain a photometric value BV.

  In step 202, it is determined whether or not the photometric value BV is equal to or greater than a predetermined value A. If it is determined that the photometric value BV is equal to or greater than the predetermined value A, the process proceeds to step 204, where the light receiving element used for photographing is set to the low sensitivity light receiving element PD2.

  In step 206, first, the sensitivity at the time of photographing is determined according to a predetermined algorithm based on the photometric value BV obtained based on the information from the integrating circuit 60. At this time, if the imaging apparatus 10 has a restriction on sensitivity, it follows that. Since the determined sensitivity is the sensitivity when the signal output from the light receiving element is corrected (amplified) with the gain value in the gain adjustment circuit 34, it is hereinafter referred to as correction sensitivity SVa. The gain value in the gain adjustment circuit 34 is obtained and set from the sensitivity SV of the light receiving element PD2 set as the light receiving element used when photographing and the determined correction sensitivity SVa. For example, when the sensitivity of the low-sensitivity light receiving element PD2 is ISO50 and the correction sensitivity SVa is ISO100, the gain value is 2.

  In step 208, the exposure value EV is obtained by the following equation (3) based on the correction sensitivity SVa and the photometric value BV.

                        EV = SVa + BV (3).

  Further, an aperture value AV and a shutter speed TV are set based on the obtained exposure value EV. The relationship between the exposure value EV, the aperture value AV, and the shutter speed TV is expressed by the above equation (2).

  Here, since the exposure is set using the correction sensitivity SVa corrected with the gain value, the exposure can be corrected with higher accuracy, and the correction sensitivity SVa can be corrected as compared with the case where the high-sensitivity light receiving element PD1 is used even when the gain value is corrected. The exposure value EV can be reduced. Therefore, the aperture value AV set in the exposure control is not so large.

  In step 216, when the release button is fully pressed, the diaphragm 16 is driven so as to achieve the set aperture value AV, and the charge accumulation time is controlled by the electronic shutter so as to achieve the set shutter speed. To do. Then, a subject image is formed and recorded using the image signal output from the low sensitivity light receiving element PD2. The gain value calculated above is used as the gain value for amplifying the image signal by the gain adjustment circuit 34. Here, the signal output from the highly sensitive light receiving element PD1 is not used for photographing. As described above, when the subject is bright, the sensitivity at the time of shooting can be suppressed and shooting can be performed with a reduced aperture value, so that a high-quality subject image can be shot without causing a small aperture blur.

  On the other hand, if it is determined in step 202 that the photometric value BV is less than the predetermined value A, the process proceeds to step 210, and the light receiving element used for photographing is set to the highly sensitive light receiving element PD1.

  In step 212, the sensitivity (correction sensitivity SVa) at the time of photographing is determined according to a predetermined algorithm based on the photometric value BV obtained based on the information from the integrating circuit 60. Further, the gain value in the gain adjustment circuit 34 is obtained and set from the sensitivity SV and the correction sensitivity SVa of the light receiving element PD1 set as the light receiving element used when photographing.

  In step 214, the exposure value EV is obtained using the above equation (3) based on the correction sensitivity SVa and the photometric value BV. Further, the aperture value AV and the shutter speed TV are set from the relationship represented by the above equation (2).

  Here, the exposure control is performed using the correction sensitivity SVa obtained by correcting the sensitivity of the high sensitivity light receiving element PD1 with the gain value. However, since the photometric value BV is small, the exposure value EV is not so large. Accordingly, the aperture value AV set in the exposure control is not so large.

  In step 216, when the release button is fully pressed, the diaphragm 16 is driven so as to achieve the set aperture value AV, and the charge accumulation time is controlled by the electronic shutter so as to achieve the set shutter speed. To do. Then, a subject image is formed and recorded using the image signal output from the highly sensitive light receiving element PD1. The gain value calculated above is used as the gain value for amplifying the image signal by the gain adjustment circuit 34. Here, the signal output from the low-sensitivity light receiving element PD2 is not used for photographing. Thus, even when the subject is dark, appropriate exposure control can be performed accordingly, and the subject can be photographed with high image quality.

  In this way, by performing exposure control with the correction sensitivity corrected with the gain value, it is possible to perform exposure control so that the range of brightness of a photographic subject can be expanded and small aperture blur does not occur. .

  In the above embodiment, a light receiving element used for photographing is set according to the brightness of the subject, and the photometric value BV and the sensitivity SV of the set light receiving element or the corrected sensitivity SVa obtained by correcting the sensitivity are used. Although an example in which exposure adjustment is performed and a subject image is formed (photographed) using only the signal output from the set light receiving element has been described, the present invention is not limited to this. That is, at the time of photographing, the subject image may be formed using not only the signal output from the set light receiving element but also the signal output from the other light receiving element.

  Specifically, for example, when the signal output from the set light receiving element is the main signal and the signal output from the other light receiving element is the sub signal, the subject image is only used in the predetermined gradation range using only the main signal. The subject image can be formed using a synthesized signal obtained by synthesizing the sub signal with the main signal outside the predetermined gradation range. However, in the exposure control, similarly to the above, the aperture value AV and the shutter speed are obtained using the sensitivity SV of the light receiving element set according to the brightness of the subject or the corrected sensitivity SVa obtained by correcting the sensitivity, and the photometric value BV. Set up the TV.

  As described above, even when an image is formed using both the signals output from the high-sensitivity light-receiving element PD1 and the low-sensitivity light-receiving element PD2 at the time of shooting, the one set according to the brightness of the subject is selected. Since exposure control is performed using the sensitivity SV of the light receiving element or the corrected sensitivity SVa obtained by correcting the sensitivity, it is always possible to perform appropriate exposure without degrading the image quality regardless of whether the subject is bright or dark. You can shoot in the state.

  In the above embodiment, the CCD 18 provided with each of the high-sensitivity light receiving element PD1 and the low-sensitivity light receiving element PD2 has been described as an example. However, as shown in FIG. The light receiving area is divided into a high sensitive light receiving area 92 having a large light receiving area for receiving light with high sensitivity by a channel stopper 94 and a low sensitive light receiving area 90 having a small light receiving area for receiving light with low sensitivity. It is good also as a structure from which a signal and a low sensitivity signal are obtained. Since the light receiving element PD is provided with the channel stopper 94, the signal received with high sensitivity and the signal received with low sensitivity are not mixed, and both signals can be received separately. .

  In this case, the first light receiving element of the present invention corresponds to the high sensitivity light receiving region 92, and the second light receiving element of the present invention corresponds to the low sensitivity light receiving region 90.

It is a block diagram which shows the structure of the imaging device which concerns on embodiment. It is the figure which showed the structure of CCD mounted in the imaging device. It is an example of the relationship between exposure amount and signal output in a high sensitivity light receiving element and a low sensitivity light receiving element. It is the flowchart which showed the flow of the process at the time of imaging | photography. It is the flowchart which showed the flow of the process at the time of imaging | photography when exposure control is carried out using a correction sensitivity. It is a modification of CCD.

Explanation of symbols

10 Imaging device 12 Imaging optical system 18 CCD
30 CPU
34 Gain adjustment circuit 60 Integration circuit PD1 High sensitivity light receiving element PD2 Low sensitivity light receiving element

Claims (2)

A plurality of first light receiving elements having a predetermined sensitivity for receiving light from the subject and outputting a signal corresponding to the received light amount, and the predetermined sensitivity for receiving light from the subject and outputting a signal corresponding to the received light amount An imaging device comprising a plurality of second light receiving elements having lower sensitivity;
Metering means for metering the brightness of the subject;
When the photometric value of the photometric means is less than a predetermined value, exposure control is performed based on the photometric value and the sensitivity of the first light receiving element, and when the photometric value of the photometric means is greater than or equal to the predetermined value, Exposure control means for performing exposure control based on the sensitivity of the second light receiving element;
Image forming means for forming an image of the subject using a signal output from a light receiving element used for exposure control in a state in which exposure control is performed by the exposure control means;
An imaging apparatus including: A correction unit that corrects a signal output from a light receiving element used when forming an image of the subject with a correction coefficient determined according to a photometric result of the photometric unit;
The exposure control means performs exposure control based on a correction sensitivity obtained by correcting the photometry value and the sensitivity of the first light receiving element with the correction coefficient when the photometry value of the photometry means is less than a predetermined value, and the photometry means The imaging apparatus according to claim 1, wherein exposure control is performed on the basis of a correction sensitivity obtained by correcting the photometry value and the sensitivity of the second light receiving element with the correction coefficient when the photometric value is greater than or equal to a predetermined value.

Images