JP4282262B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus particularly suitable for a digital camera having a solid-state imaging device.
[0002]
[Prior art]
Conventionally, in the case of an imaging apparatus such as a digital still camera or a digital video camera using a general imaging device such as a CCD (Charge Coupled Device), the photoelectric conversion characteristics of the imaging device are schematically shown in FIG. It was as shown in
[0003]
In the figure, the horizontal axis indicates the amount of incident light, and the vertical axis indicates the output signal level logarithmically. In the figure, UL indicates the high luminance side limit level, and LL indicates the low luminance side limit level.
[0004]
The high luminance side limit level UL is a level that substantially corresponds to the saturation level of the image sensor, while the low luminance side limit level LL is not the lowest noise level NL itself, but can be enjoyed even when coexisting with noise. It is set as a signal level having a predetermined limit S / N ratio.
[0005]
The effective luminance region is between the high luminance side limit level UL and the low luminance side limit level LL. The difference DR = UL−LL (on the logarithmic axis) is the imaging range (= dynamic range). It becomes. The dynamic range DR varies depending on the design and manufacture of the imaging device, but in many cases is about 5 to 6 EV (30 to 36 dB).
[0006]
On the other hand, a silver salt camera using a silver salt film that is already widely used has a difference between a color negative film, a monochrome film, and a color reversal film, but a color negative film that is more commonly used is about 10 EV. Dynamic range (= latitude).
[0007]
Therefore, when shooting with a digital camera with the expectation of a dynamic range comparable to that of a silver halide camera, the part of the resulting image that reaches the upper and lower limit levels of brightness is `` whiteout '' or `` blackout '' It is often disappointing as a result of lowering the overall image quality.
[0008]
However, many attempts have been made to expand the dynamic range with a digital camera using an image sensor. For example, a multi-plate image sensor that shoots images in different exposure states by branching the imaging optical path. A single-chip image sensor that has been subjected to dot-sequential coding of the density filter (that is, configured so that the sensitivity is different for each pixel), a field-sequential method using a moving image output in the field accumulation mode, and all-pixel readout ( And a special field sequential method using a sequential scanning image sensor.
[0009]
Here, a simple description will be given of a device using an all-pixel readout (sequential scanning) imaging device and a field sequential method using a moving image output in a field accumulation mode.
[0010]
FIG. 6 shows the drive timing of the image sensor using an image sensor for reading all pixels (sequential scanning). Prior to exposure, in the state where the mechanical shutter is open as shown in FIG. 6 (1), the horizontal / vertical is driven by the clocks φH and V for driving the horizontal / vertical transfer path of the image pickup device shown in FIG. 6 (4). The transfer path is driven to discharge at high speed, and unnecessary charges are wiped out.
[0011]
Thereafter, the transfer of the clocks φH and V is stopped, and at the same time, the exposure is started by outputting the final pulse of the charge discharge pulse VSUB shown in FIG. When the time T1 has elapsed, the exposure of the first frame is terminated by the charge transfer pulse TG (referred to as “1stTG” in the figure) of the first frame.
[0012]
Then, when the time T2 further elapses, the mechanical shutter is closed as shown in FIG. Thereafter, after the charge amount corresponding to all the pixels in the first frame is read out, a charge transfer pulse TG (referred to as “2ndTG” in the figure) in the second frame is output. Read the corresponding charge amount.
[0013]
Since the image of the first frame and the image of the second frame obtained in this way have different shooting ranges due to the difference between the exposure times T1 and T2, an image having a larger dynamic range based on these two image signals is obtained. I want to get it.
[0014]
FIG. 7 shows the drive timing of the image sensor in the field sequential method using the moving image output in the field accumulation mode that can be employed in a digital video (movie) camera.
[0015]
This figure shows an example in which charges are accumulated for each field by an interlaced image sensor. In the first field, exposure is started after the charge discharge pulse VSUB shown in FIG. When a charge transfer pulse TG (referred to as “1stTG” in the figure) of the first field shown in FIG. 7A is output when T1 has elapsed, the charge stored in each pixel is transferred to a light-shielded transfer path. Transport.
[0016]
On the other hand, in the second field, exposure is started after the charge discharge pulse VSUB shown in FIG. 7 (3) is output, and when the time T2 has elapsed, the charge transfer in the second field shown in FIG. 7 (2). When a pulse TG (referred to as “2ndTG” in the figure) is output, the charge stored in each pixel is transferred to a light-shielded transfer path.
[0017]
While performing exposure in the second field, the charge amount of each pixel transferred to the transfer path in the preceding first field is positioned directly below the pixel (A) on the odd-numbered line. Reading is performed by adding (A + B) the respective charge amounts of the pixels (B) of the even-numbered lines, and when the exposure in the first field is started again, the previous second field is in the meantime. Then, the charge amount of each pixel transferred to the transfer path is added (B + A) to the charge amount of the pixel (B) of the even-numbered line and the pixel (A) of the odd-numbered line located immediately below it. Read out by using interlaced driving in a so-called field accumulation mode in which the addition target is shifted by one pixel for each odd / even field. Depending on the image signal It is intended to obtain a image enlarged more dynamic range based on the two image signals.
[0018]
[Problems to be solved by the invention]
However, in the case of a multi-plate type imaging device that divides a photographing optical path into a plurality of images and shoots in different exposure states, the configuration of the apparatus becomes large and complicated, and the cost becomes high. Absent.
[0019]
In addition, in the case of using the all-pixel readout (sequential scanning) imaging device described in FIG. 6 above, since the first exposure and the second exposure are not performed at the same time but are performed with a time difference, they are strictly the same. In principle, it is impossible to obtain two optical images with different exposure conditions for a subject image, and it is not possible to deal with a subject image that moves particularly rapidly.
[0020]
Similarly, the field sequential method using the moving image output in the field accumulation mode described with reference to FIG. 7 does not perform two exposures at the same time, but causes a time difference. I can not cope.
[0021]
In addition, in the field sequential method using the moving image output in the field accumulation mode, since the components of two adjacent pixels are added and read out, the original number of pixels of the image sensor cannot be utilized. A decrease in vertical resolution is inevitable.
[0022]
Further, a single-plate image pickup device that has been subjected to dot-sequential coding of density filters has problems such as not only a decrease in versatility but also a decrease in resolution and generation of moire.
[0023]
As described above, many attempts have been made to expand the dynamic range with a digital camera. However, there has not yet been a practical method with a simple device configuration.
[0024]
The present invention has been made in view of the above circumstances, and its purpose is to capture a plurality of images with different exposure conditions at the same time without complicating the apparatus configuration and reducing the resolution. An object of the present invention is to provide an imaging apparatus capable of obtaining an image with a larger dynamic range.
[0025]
[Means for Solving the Problems]
  According to the first aspect of the present invention, the image pickup device, the driving unit capable of individually reading out the electric charge of each pixel of the image pickup device by interlace driving, and effective exposure for the image pickup device are started simultaneously for all the pixels, Exposure control means for giving an effective exposure time different from that of the other fields by performing effective exposure termination different from that of the other fields in at least one of the plurality of fields constituting one frame by the interlace driving; Regarding the pixel information of the subject luminance range where the effective imaging ranges of the plurality of fields generated by the different effective exposure times overlap each other, all the pixel information is used as pixel information about the pixel, and the subject luminance is For pixel information of fields that deviate from the effective imaging range, etc. ; And a pixel signal correction means for outputting what subject luminance is interpolated by the pixel information of the fields not deviate from the effective imaging range as the pixel information on the pixelsThe pixel signal correcting unit further relates to pixel information of a field in which subject luminance deviates from the effective imaging range, and pixel information in the vicinity of another field to be used for interpolation also deviates from the effective imaging range. In this case, the interpolation is prohibited and the original pixel information is output as pixel information related to the pixel.It is characterized by that.
[0026]
  With such a configuration, a plurality of fields constituting one frame are not completely identical in timing, but since one is included in the other, the exposure portion on the short time side is simultaneous, so there is no time difference, In addition, it is possible to take an image with an expanded dynamic range without reducing the resolution.In addition, it is possible to select and process only pixel portions that can be expanded in the dynamic range in the image, and it is possible to reliably prevent the image quality from being deteriorated due to excessive interpolation processing.
[0027]
According to a second aspect of the present invention, in the first aspect of the present invention, the pixel signal correcting means compensates for a signal level difference with respect to the same luminance subject that the pixel signals of the fields having different effective exposure times have each other. It has the means.
[0028]
With this configuration, in addition to the operation of the first aspect of the present invention, the subject image portion photographed within the common dynamic range of a plurality of fields is completely different from that captured by a conventionally known imaging device. Imaging signals having the same resolution can be obtained.
[0031]
  Claim 3The invention described is the above claim 1.Or 2In the described invention, it has an optical shutter means for blocking the input of the subject image to the imaging surface of the image sensor, and the exposure control means ends the effective exposure for at least one field among the plurality of fields. Controlling by transfer from the pixel portion, which is a photoelectric conversion storage portion of the image sensor, to a light-shielded transfer path, and controlling the end of effective exposure for at least one other field by opening and closing the optical shutter means. Features.
[0032]
  With such a configuration, the above-mentioned claim 1.Or 2In addition to the operation of the described invention, the exposure control means can be realized more easily by using a general optical shutter means.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a digital still camera will be described with reference to the drawings. For ease of explanation, it is assumed here that a monochrome image is taken.
[0034]
FIG. 1 shows a circuit configuration of a digital camera 10 according to the embodiment. In the figure, a lens optical system 12 and a diaphragm 13 are provided in a lens barrel 11 of the digital camera 10.
[0035]
The optical image obtained through the lens barrel 11 is formed on the imaging surface of the CCD 15 which is an imaging element after passing through the mechanical shutter 14.
[0036]
The CCD 15 accumulates and outputs charges for each pixel during the exposure time, and the output is input to the preprocess circuit 16.
[0037]
The preprocess circuit 16 adjusts the gain according to the sensitivity appropriately set by the amplifier for each primary color component of RGB in the state of the analog value signal, and then performs A / D conversion to obtain a digital value image signal. 17 output.
[0038]
The digital process circuit 17 temporarily stores and holds the digital image signal in the buffer memory 18, reads the image signal stored and held in the buffer memory 18, and then performs various signal processing including pixel interpolation processing.
[0039]
The digital process circuit 18 finally performs gamma processing on the standard transmission signal for the image signal subjected to various signal processing in this way, and then sends it to the D / A converter 19 where it is converted into an analog value and then backed up. A monitor display is performed on the TFT-LCD panel 20 having a light.
[0040]
The image signal subjected to the gamma processing is also read out to the compression / decompression circuit 21 and used as a recording medium of the digital camera 10 after the data amount is appropriately compressed by a designated compression method such as JPEG. The data is recorded and stored in a removable memory card 22 composed of a flash memory.
[0041]
When the image signal stored in the memory card 22 is read out in the reproduction mode, it is decompressed by the compression / decompression circuit 21 by a method opposite to that used for recording and restored to a bitmap image signal. The obtained image signal is stored in the buffer memory 18 by the digital process circuit 17, and is displayed and output on the TFT-LCD panel 20 via the D / A converter 19.
[0042]
The system controller 23 controls the digital camera 10 as a whole. The AE processing circuit 24 performs an AE (automatic exposure) calculation at the time of shooting, and the AF at the time of shooting. An AF processing circuit 25 for performing (automatic focusing) calculation, a timing generator (TG) 26, and a synchronization signal generator (SG) 27 are connected.
[0043]
The synchronization signal generator 27 oscillates a vertical synchronization signal as a reference for driving the CCD 15 under the control of the system controller 23 and sends it to the timing generator 26.
[0044]
The timing generator 26 oscillates various timing signals based on the vertical synchronization signal and sends them to the CCD driver 28 that drives the preprocess circuit 16 and the CCD 15.
[0045]
The system controller 23 is also connected to first to third motor drivers 29 to 31 and a strobe controller 32.
The first motor driver 29 drives a first motor (M) 33 that opens and closes the mechanical shutter 14.
The second motor driver 30 drives a second motor 34 that rotates the diaphragm 13.
The third motor driver 31 drives a third motor 35 that moves the lens optical system 12.
The strobe control unit 32 performs switching control of charging and light emission in the strobe light emitting unit 36 in accordance with instructions from the system controller 23.
[0046]
The system controller 23 is directly input with operation signals from an operation switch (SW) unit 37 including a power switch, a release switch, a zoom switch, a strobe switch, a cursor switch, a menu switch and the like (not shown). The accompanying operation state, the storage state in the memory card 22 and the like are displayed and output by a liquid crystal display unit 38 constituted by a monochrome type liquid crystal display panel provided with a backlight. Are connected to an EEPROM 39 which stores a control program for performing the overall operation of all the circuits.
[0047]
Next, the operation of the above embodiment will be described.
[0048]
Incidentally, the CCD 15 is a general one similar to that used in the description of the above prior art, and the charge of each pixel is obtained by performing interlaced driving of the CCD driver 28 in a so-called frame accumulation mode. It is assumed that the pixel information of the frame can be read individually as two fields (without adding pixel charges).
[0049]
First, FIG. 2 shows the drive timing of the CCD 15, which is an image sensor. In the figure, first, prior to exposure, the clocks φH, V for driving the horizontal / vertical transfer paths of the CCD 15 shown in FIG. 2 (5) with the mechanical shutter 14 open as shown in FIG. 2 (1). As a result, the horizontal / vertical transfer path is driven to be discharged at high speed, and unnecessary charges are wiped out.
[0050]
Thereafter, the transfer of the clocks φH and V is stopped, and at the same time, the final pulse of the charge discharge pulse VSUB shown in FIG.
[0051]
When the time T1 elapses, the first field charge transfer pulse TG (referred to as “1stTG” in the figure) is output to end the exposure of the CCD 15 in the first field (odd field).
[0052]
This 1stTG is different from that of the conventional example (FIG. 7) in that only the charges stored in the pixels of the odd-numbered line (A) are transferred to the light-shielded transfer path. At this time, since the charge stored in the pixels of the even-numbered line (B) is not read out, this means that charge accumulation (exposure) continues, and at the start of exposure, charge is discharged as described above. One of the features of the present invention is that the time when the last pulse of the pulse VSUB is output is common to A (first field) and B (second field).
[0053]
Then, when the time T1 × 3 has elapsed and the time T2 (= T1 × 4) has elapsed for the second field, the mechanical shutter 14 is closed as shown in FIG. This completes the exposure.
[0054]
Thereafter, as shown in FIG. 2 (5), after the charge amount corresponding to the pixel in the first field is read out, the charge transfer pulse TG in the second field (even field) shown in FIG. In this case, the amount of charge corresponding to the pixel in the second field is read out.
[0055]
Unlike the conventional example (FIG. 7), the 2ndTG transfers only the charges stored in the pixels of the even-numbered lines (B) to the light-shielded transfer path. During this period, the pixels on the odd-numbered line (A) are exposed to charges after 1stTG, and thus charges are generated. However, these charges are not used but are discharged as unnecessary charges thereafter.
[0056]
The image signals for two images with different exposure times read out in two fields in this way are processed after the digital process circuit 17 once holds them in the buffer memory 18 under the control of the system controller 23.
[0057]
FIG. 3 shows the photoelectric conversion characteristics corresponding to these two image signals. The signal level obtained by the amount corresponding to the difference in exposure time is parallel to the left and right along the horizontal axis representing the luminance of the subject. It has been moved.
[0058]
For the two image signals obtained in this way, the digital process circuit 17 performs a pixel signal generation process for the values of individual pixel signals constituting the image signal as follows.
[0059]
(First field pixel):
(Condition 1) When the own pixel signal has a value larger than the low luminance side limit level LL, a value twice as large as the value of the own pixel signal is set as the pixel signal value.
(Condition 2) When the own pixel signal is lower than or equal to the low luminance side limit level LL → The result of determining the pixel signal values of two second field pixels adjacent above and below the self,
(Condition 2-a) When it is larger than the low-luminance side limit level LL and smaller than the high-luminance side limit level UL → the value of ½ of the value of the second field pixel (the average value if both are satisfied) Is a pixel signal value.
(Condition 2-b) When it is lower than the low luminance side limit level LL or higher than the high luminance side limit level UL → The pixel signal value is set to twice its own pixel signal value.
[0060]
(Second field pixel):
(Condition 1) When the own pixel signal has a value smaller than the high luminance side limit level UL → 1/2 of the own pixel information value is set as the pixel signal value.
(Condition 2) When the own pixel signal is equal to or higher than the high-luminance-side limit level UL → The result of determining the pixel signal values of two first field pixels adjacent above and below the self
(Condition 2-a) When it is larger than the low luminance side limit level LL and smaller than the high luminance side limit level UL, the pixel is set to a value twice the value of the first field pixel (the average value when both the upper and lower sides are satisfied) The signal value.
(Condition 2-b) When it is below the low luminance side limit level LL or above the high luminance side limit level UL → 1/2 of its own pixel signal value is set as the pixel signal value.
[0061]
In the pixel signal generation process as described above, the condition 1 basically means that if each pixel in the first and second fields is “within a predetermined imaging range (effective luminance range), information on the pixel is used as it is. In this case, each pixel is multiplied by a predetermined coefficient (that is, a digital value corresponding to the reference exposure amount (corresponding to the intermediate auxiliary line AS in FIG. 3) (ie, digital). Compensate by adjusting gain).
[0062]
Therefore, with respect to the subject image within the common shooting range of both the first and second fields, the individual subject information (pixel information) received by each pixel is generated as it is independently (apart from sensitivity compensation). Since it is used as information, the resolution does not decrease, and the resolution inherent in the imaging device (D range expansion imaging is not adopted, for example, the same as that captured by a general imaging device that performs progressive (non-interlaced) scanning, for example) Resolution) image signal.
[0063]
On the other hand, the condition 2-a is “if the pixel signal value of the self deviates from the shooting range, and if the pixel signals of other fields adjacent to the upper and lower sides do not deviate from the shooting range, the interpolation is performed by that”. It means that. That is, with respect to “a high-luminance or low-luminance subject portion that is covered only in the shooting range of one of the fields”, a signal in which the pixel density (vertical resolution) is halved is obtained.
[0064]
In this case, when the exposure amount indicated by the auxiliary line AS in FIG. 3 is used as a reference, the second field has twice the exposure amount and the first field has a half exposure amount. That is, the imaging range is shifted by 1 EV (6 dB) at a time, and the 2 EV (12 dB) imaging range is expanded.
[0065]
If the dynamic range DR = 6EV (36 dB) obtained when a general progressive scan CCD is used is the limit, an imaging device with a wide dynamic range of 8 EV (48 dB) can be obtained according to this embodiment. it can.
[0066]
In this case, the common range of the first and second fields, that is, the range in which high resolution can be obtained is 4 EV. Therefore, there is no decrease in resolution in normal shooting, and the resolution is reduced only in the highlight portion and the shadow portion. Just do it.
[0067]
Such overall characteristics are shown in FIG. In the figure, the two characteristics are vertically translated along the signal level on the vertical axis by the above-described digital gain adjustment, and are superimposed on the auxiliary line AS. EUL, ELL, etc. in the figure are the enlarged high and low luminance limit levels, respectively.
[0068]
As described above, since the dynamic range of the image signal obtained by the imaging is expanded, the reproduction range in the high luminance portion is expanded, and the S / N ratio in the low luminance portion is improved to reduce noise. .
[0069]
On the other hand, the condition 2-b is that “when both the imaging ranges of the first and second fields deviate from each other, the original pixel information is used as it is (after gain adjustment is performed)”. I mean.
[0070]
Therefore, the original high resolution can be obtained again for a subject that deviates from the expanded total range. This is to prevent a problem that the resolution of the obtained image signal is lowered when photographing a complete monochrome pattern, for example, a special pattern such as a resolution chart.
[0071]
In this way, an image signal having a greatly expanded dynamic range can be generated from the image signals for the first and second fields constituting one frame, and the digital process circuit 17 is controlled by the system controller 23. Based on the image signal generated in this way, the data is displayed on the TFT-LCD panel 20 via the D / A converter 19 or the data amount is compressed by the compression / expansion circuit 21 and then recorded and stored in the memory card 22.
[0072]
In this way, the first and second shooting fields constituting one frame are not completely identical in timing, but one (first field) is included in the other (second field), so the short time side. Since the exposed portion (T1) is simultaneously, it is possible to take an image with no time difference and with an expanded dynamic range without reducing the resolution.
[0073]
Further, the correction process for each pixel signal value executed by the digital process circuit 17 on the image signals having different exposure times obtained in the two fields is performed on the subject image having the same luminance included in each pixel signal value. This is realized by compensating the signal level difference.
[0074]
In this way, the subject image portion photographed within the dynamic range common to the two fields has the same resolution as that captured by a general non-interlaced all-pixel readout imaging device. Imaging signals can be obtained.
[0075]
In addition, in the pixel signal value correction processing, regarding the pixel signal value of the portion where the luminance of the subject image deviates from the common dynamic range between both fields, the neighboring pixel information of the other field to be used for interpolation is also obtained. Further, when the effective imaging range is deviated, the interpolation is prohibited and the original pixel information is output as pixel information related to the pixel.
[0076]
This makes it possible to select and process only pixel portions that can be expanded in the dynamic range in the image, and reliably avoid the unnecessary deterioration of the image quality of other portions due to excessive interpolation processing. Can do.
[0077]
The exposure in the second field is optically terminated by blocking the photographing optical path by the mechanical shutter 14, and the incident of the photographing light to the CCD 15 is optically blocked by the mechanical shutter 14. In this state, each pixel signal value in the first field is read out, and thereafter each pixel signal value in the second field is read out.
[0078]
Therefore, by using the mechanical shutter 14 that is also used in general silver halide cameras, exposure control can be realized more easily, and the readout timing of the image signal in each field should be relatively high. Can do.
[0079]
In the above-described embodiment, the second field exposure time T2 is 4 × T1 with respect to the first field exposure time T1, but the present invention is not limited to this, and a plurality of field times are used. It is assumed that the amount of exposure time shift can be set arbitrarily.
[0080]
In the above embodiment, the timing at which the exposure of the second field is completed is controlled by the timing at which the mechanical shutter 14 is closed. However, as compared with the error in the electronic shutter time accompanying the drive of the CCD 15. The time error included in the opening / closing operation of the mechanical shutter 14 is very large.
[0081]
Therefore, as one means for compensating for the error of the pixel signal value based on the operation error of the mechanical shutter 14, uniform light from the diffusion plate is applied to a part of the CCD, for example, a peripheral part adjacent to the OB (optical dark part) of the horizontal line An incident region may be provided, and the content of gain adjustment performed for each pixel signal of the analog value in the subsequent preprocess circuit 16 may be appropriately increased or decreased based on luminance information obtained in this region.
[0082]
In this embodiment, the CCD 15 is assumed to be a monochrome type that does not have a color filter and the monochrome image data of only the luminance signal is handled for the sake of easy explanation. Needless to say, the present invention can also be applied to an imaging apparatus that handles the above.
[0083]
Further, although it has been described that one frame has two fields according to a television system such as NTSC, which is general for interlace driving, the present invention is not limited to this, and any interlace in which one frame has three fields or four fields or more is possible. It can also be applied to driving, and by setting the exposure time of each field differently, it has a very wide dynamic range and has a high resolution with respect to an image of a luminance part that falls within a predetermined shooting range. Thus, it is possible to obtain a processed image signal.
[0084]
In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.
[0085]
Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, at least one of the problems described in the column of the problem to be solved by the invention can be solved, and described in the column of the effect of the invention. In a case where at least one of the obtained effects can be obtained, a configuration in which this configuration requirement is deleted can be extracted as an invention.
[0086]
【The invention's effect】
  According to the first aspect of the present invention, although a plurality of fields constituting one frame are not completely identical in timing, since one is included in the other, the exposure portion on the short time side is simultaneous, so that the time difference is And can capture images with an expanded dynamic range without reducing resolutionIn addition, it is possible to select and process only pixel portions that can be expanded in the dynamic range in the image, and it is possible to reliably prevent the image quality from being deteriorated due to excessive interpolation processing.
[0087]
According to the second aspect of the present invention, in addition to the effect of the first aspect, the subject image portion photographed within a common dynamic range of a plurality of fields is captured by a conventionally known imaging device. It is possible to obtain an imaging signal with exactly the same resolution.
[0089]
  Claim 3According to the described invention, the above-mentioned claim 1Or 2In addition to the effects of the described invention, the exposure control means can be more easily realized by using a general optical shutter means.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a circuit configuration of a digital camera according to an embodiment of the present invention.
FIG. 2 is a diagram showing drive timing of a CCD that is an image sensor according to the embodiment;
FIG. 3 is a view showing photoelectric conversion characteristics corresponding to image signals for two fields according to the embodiment;
FIG. 4 is a view showing overall characteristics of pixel signals obtained by pixel signal generation processing according to the embodiment;
FIG. 5 is a diagram showing photoelectric conversion characteristics of a general image sensor.
FIG. 6 is a diagram showing drive timing of an image sensor for all-pixel reading (sequential scanning), which is one method for expanding a conventional dynamic range.
FIG. 7 is a diagram showing drive timing of an image sensor in a field sequential method using a moving image output in a field accumulation mode, which is one method for expanding a conventional dynamic range.
[Explanation of symbols]
10. Digital camera
11 ... Lens barrel
12 ... Lens optical system
13 ... Aperture
14 ... Mechanical shutter
15 ... CCD
16: Preprocess circuit
17 ... Digital process circuit
18 ... Buffer memory
19 ... D / A converter
20 ... TFT-LCD panel
21 ... Compression / decompression circuit
22 ... Memory card
23 ... System controller
24 ... AE processing circuit
25. AF processing circuit
26 ... Timing generator (TG)
27. Synchronization signal generator (SG)
28 ... CCD driver
29 ... 1st motor driver
30 ... Second motor driver
31 ... Third motor driver
32 ... Strobe control unit
33 ... first motor
34 ... Second motor
35 ... Third motor
36 ... Strobe light emitting part
37. Operation switch part
38 ... Liquid crystal display
39… EEPROM

Claims (3)

An image sensor;
Driving means capable of individually reading out the charge of each pixel of the imaging element by interlace driving;
The effective exposure of the image sensor is started at the same time for all pixels, and at least one of a plurality of fields constituting one frame by the interlace driving is performed by ending effective exposure different from other fields. Exposure control means for providing an effective exposure time different from the field of
Regarding the pixel information of the subject luminance range where the effective imaging ranges of the plurality of fields generated by the different effective exposure times overlap each other, all the pixel information is used as pixel information about the pixel, and the subject luminance is As for pixel information of a field that deviates from the effective imaging range, pixel signal correction means for outputting, as pixel information relating to the pixel, interpolated by pixel information of a field in which other subject luminance does not deviate from the effective imaging range; equipped with,
The pixel signal correcting means further relates to pixel information of a field in which subject luminance deviates from the effective imaging range, and pixel information in the vicinity of other fields to be used for interpolation also deviates from the effective imaging range. An image pickup apparatus that prohibits the interpolation and outputs original pixel information as pixel information related to the pixel .   2. The image pickup apparatus according to claim 1, wherein the pixel signal correcting means includes level compensating means for compensating for a signal level difference with respect to the same luminance subject which the pixel signals of the fields having different effective exposure times have. It has an optical shutter means for blocking the input of the object image on the imaging surface of the upper Symbol image pickup device,
The exposure control means controls the end of effective exposure for at least one of the plurality of fields by transfer from a pixel portion which is a photoelectric conversion accumulation portion of the imaging element to a light-shielded transfer path, and at least the other field 3. The image pickup apparatus according to claim 1, wherein the effective exposure end for one field is controlled by opening and closing the optical shutter means.

Images