JP3824349B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus using a solid-state imaging device and having a wide dynamic range.
[0002]
[Prior art]
Conventionally, it has been desired to expand the dynamic range of a solid-state imaging device, and various techniques have been proposed.
For example, in Japanese Patent Application Laid-Open No. 5-308573 by the present applicant, two screens having different exposure amounts are read out by controlling an integration time using a solid-state image pickup device (CMD; Charge Modulation Device) of an XY address method, A technique related to an imaging apparatus that attempts to expand a dynamic range by a correction unit that corrects an image is disclosed.
[0003]
Further, Japanese Patent Laid-Open No. 7-38815 by the present applicant relates to a CMD that independently obtains two types of pixel signals having different exposure times within one frame period by performing two different readout operations within a horizontal period. Technology is disclosed.
[0004]
Here, FIG. 11 is a conceptual diagram of CMD.
In the figure, 101 is a vertical scanning circuit, 102 is a horizontal scanning circuit, and 103 is a light receiving section in which photoelectric conversion elements are arranged in two dimensions as pixels.
[0005]
Hereinafter, the operation of the vertical scanning circuit 101 will be described with reference to the timing chart of FIG. Within the vertical effective period of the image, the read voltage VRD is sequentially applied from the first line to the nth line in the vertical scanning circuit 101. Next, a selection pulse is sequentially output in the horizontal scanning circuit 102, and signals are sequentially read from the pixels of the line to which this voltage is applied. The reset voltage VRS is applied to the line from which one line of signal has been read. The accumulated charges are reset in the pixels on the line to which the reset voltage is applied, and are exposed until the next readout period. This operation is repeated from the first line to the nth line, and a signal of one screen is read out. VOF is an overflow voltage, and unnecessary holes are swept out as a signal by applying this VOF during the horizontal blanking period.
[0006]
In the solid-state image pickup device of the XY address method, since the signal is read as described above, the exposure timing is a vertical focal plane method shifted for each line as shown in FIG.
[0007]
[Problems to be solved by the invention]
However, the image pickup apparatus disclosed by the above-mentioned Japanese Patent Application Laid-Open No. 5-308573 does not describe the operation when a light source such as a strobe is used.
As shown in FIG. 14, the light emission characteristic of the strobe light emitting tube 20 is a characteristic that immediately after light emission, it rises immediately and becomes a maximum light quantity at the beginning of light emission, and then attenuates. Compared with a period in which an image formed on the surface is scanned and one screen is output as a video signal, the time is short. For this reason, when a light emitting means that emits light for a short time, such as a strobe, is used, it is unclear which area is exposed and only a part of one screen is exposed.
[0008]
Furthermore, in the imaging apparatus described in the above-mentioned Japanese Patent Application Laid-Open No. 5-308573, an image with a dynamic range is synthesized from two screens having different exposure amounts by the image correction means, and two screens having different exposure amounts are combined. The integration time is controlled as a method to obtain. Therefore, there is no problem when the exposure amount is proportional to the integration time. However, when a light emitting device that emits light for a short time, such as a strobe, is used, the exposure amount and the exposure time are not proportional. There was a fault that it was not.
[0009]
On the other hand, in the image sensor described in JP-A-7-38815, the exposure period is controlled as a method for obtaining screens with different exposure amounts. In this case as well, there is no problem when the exposure amount is proportional to the integration time, but when a light emitting means such as a strobe is used, the exposure amount and the exposure time are not proportional. There was a shortcoming that could not be obtained.
[0010]
Furthermore, the means for synthesizing an image with an expanded dynamic range from two screens with different exposure amounts performs composition using the exposure amount ratio of the two screens, so that the exposure amount ratio is a predetermined value set in advance. In this case, image synthesis is performed correctly (a specific synthesis method is described in detail in the above prior art). In normal operation, images with different exposure amounts are obtained by controlling the exposure period, so the exposure amount ratio is kept constant, but the light emission means such as strobes vary in the light emission amount due to variations in charging voltage, etc. Produce. For this reason, there has been a drawback that an error occurs in the image composition by the image composition means and the image quality deteriorates.
[0011]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus capable of obtaining an appropriate image even when an XY address type solid-state imaging device and a light emitting means are used. is there.
[0012]
[Means for Solving the Problems]
  In order to achieve the above object, an imaging apparatus according to a first aspect of the present invention includes a solid-state imaging device that photoelectrically converts incident light from an object and outputs it as an electrical signal, and a strobe that irradiates the subject with strobe light. Arc tube and the solid-state image sensorTo obtain images with different exposures in different fieldsDifferent field periodsGapEachDepending on the amount of emitted light andControl means for causing the strobe arc tube to emit light within a vertical blanking period;Depending on the different light emissionObtained by exposure based on light emission of multiple strobe arc tubesDifferent exposureAnd a combining means for combining a plurality of images.
[0015]
  That is, in the imaging apparatus according to the first aspect of the present invention, light from the subject incident on the solid-state imaging device is photoelectrically converted and output as an electrical signal, and the subject is irradiated with strobe light from the strobe arc tube. Of the solid-state imaging deviceTo obtain images with different exposures in different fieldsDifferent field periodsGapEachDepending on the amount of emitted light andThe strobe arc tube emits light within the vertical blanking period, and the combining meansDepending on the different light emissionObtained by exposure based on light emission of multiple strobe arc tubesDifferent exposureMultiple images are combined.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an imaging apparatus according to the first embodiment of the present invention.
As shown in the figure, a lens 1 is disposed to form an image of subject light on the surface of the image sensor 3, and an optical filter 2 is disposed on the optical path between the lens 1 and the image sensor 3. It is installed. The optical filter 2 includes an optical LPF (Low Pass Filter) that removes unnecessary high-frequency components from subject light and an IR cut filter that removes unnecessary infrared components. The image sensor 3 photoelectrically converts light incident through the lens 1 and the optical filter 2 and outputs the result as an electrical signal. In the present embodiment, an on-chip color filter is provided on the surface of the image sensor 3.
[0019]
The output of the image sensor 3 is connected to a fixed pattern noise (FPN) canceller 7 via a preamplifier 4 and an A / D converter 5. The preamplifier 4 amplifies the signal from the image sensor 3, performs optical black (OB) clamp processing, and matches the input level of the A / D converter 5 in the subsequent stage. The A / D converter 5 converts an input analog signal from the imaging process into a digital signal. The FPN canceller 7 removes the FPN that the image sensor 3 has.
[0020]
The output of the FPN canceller 7 is connected to the memory 22 for storing image data for one screen and the input of the color processing circuit 9, and the output of the color processing circuit 9 is supplied to the white balance circuits 10r, 10g, 10b. Via the monitor I / F 12. The color processing circuit 9 performs processing according to the arrangement of color filters formed on the surface of the image sensor 3 and separates and outputs the signals to R, G, and B signals. The white balance circuits 10r, 10g, and 10b are for balancing colors by multiplying each R, G, and B signal output from the color processing circuit 9 by a predetermined coefficient. The monitor I / F 12 is for converting and outputting signals from the white balance circuits 10r, 10g, and 10b so as to conform to a display system (monitor) standard (not shown). In the present embodiment, a general method is adopted in which an input digital signal is converted into an analog signal by a D / A converter and a synchronization signal is added.
[0021]
On the other hand, a sensor driving circuit 17 is connected to the image pickup device 3, and an output of the sensor driving circuit 17 is connected to a strobe light emitting tube 20 via a light emission control circuit 18 and a light emission driving circuit 19. The sensor drive circuit 17 controls the operation of the image sensor 3. The light emission control circuit 18 receives a light emission permission signal (S_-EN) based on the light emission signal (S_-PULSE) is output to control the light emission timing and light emission amount of the strobe arc tube 20.
[0022]
The amount of strobe light emitted is controlled by controlling the time from the start of light emission to the end of light emission of the strobe arc tube. That is, when the time is short, the light emission amount is small, and when the time is long, the light emission amount is large. Here, the light emission time for obtaining a desired light emission amount is generated by the light emission drive circuit 19, but it may be a pulse having a time width to obtain this light emission time. It may be a pulse having a corresponding peak value. Of course, in the latter case, it is necessary to provide a decoder for converting the value of the pulse voltage into a pulse interval.
[0023]
The light emission drive circuit 19 has the S_-This is a drive circuit for causing the strobe arc tube to emit light based on PULSE. The strobe arc tube 20 irradiates the subject with light. In the following description, the configuration including the light emission control circuit 18, the light emission drive circuit 19, and the strobe light emitting tube 20 is simply referred to as “strobe”. The operation of each part is controlled by the system controller 16.
[0024]
Next, the operation of the imaging apparatus according to the first embodiment having the above-described configuration will be described.
First, the operation during normal shooting will be described. In the above configuration, the subject light is incident through the lens 1, and after unnecessary high frequency components and infrared components are removed by the optical filter 2, an image is formed on the surface of the image sensor 3. The imaging device 3 receives the incident optical image, converts it into an electrical signal, and outputs it to the preamplifier 4 at the subsequent stage. At this time, the sensor drive circuit 17 outputs various pulses for driving the horizontal scanning circuit and the vertical scanning circuit of the image sensor 3 to the image sensor 3, scans the pixels of the image sensor 3, and outputs the video signal to the preamplifier 4. To read.
[0025]
The signal input to the preamplifier 4 is subjected to amplification OB clamp processing and then converted to a digital signal by the A / D converter 5. The digital signal thus converted is input to the color processing circuit 9 after the noise of the fixed pattern of the image sensor 3 is removed by the FPN canceller 7. In this color processing circuit 9, color processing is performed according to the arrangement of on-chip color filters formed on the element surface of the image sensor 3, converted into R, G, and B signal forms and output. There are various color processing methods for each type and arrangement of color filters, but the processing content is not a part related to the present invention, and is not limited here.
[0026]
The signal output from the color processing circuit 9 is output to the monitor I / F 12 by the white balance circuit 10 by multiplying each of the R, G, and B signals by a predetermined gain to balance the colors. The monitor I / F 12 converts the input digital signal to an analog signal with a D / A converter in order to output it in a form that conforms to a display system (monitor) standard (not shown), and then adds a synchronization signal. Output. The system controller 16 includes an operation unit as a user interface, a CPU that manages the operation mode of the apparatus according to the settings of the operation unit, and the subject image is normally displayed on the monitor according to the above operation.
[0027]
Next, the operation during the strobe operation will be described. In general, when the subject image is dark, appropriate exposure cannot be obtained, and illumination light from a light source is required. Therefore, strobe light emission is necessary. For example, a xenon strobe arc tube is used as the strobe arc tube 20 as a light source and is driven by a light emission drive circuit 19. The light emission drive circuit 19 is connected to a light emission control circuit 18 that controls the light emission and stop of the strobe light emitting tube 20 and the light emission time. The light emission control circuit 18 receives the reference signal from the sensor drive circuit 17 and the light emission permission signal (S_-EN), the light emission signal (S_-PULSE) is generated and supplied to the light emission drive circuit 19, and the light emission timing and light emission amount of the strobe circuit 20 are controlled by the light emission control circuit 18.
[0028]
Next, the operation of the light emission control circuit 18 will be described in detail with reference to FIG.
FIG. 2 (a) shows a signal V serving as a field reference._-BLANK is shown, and FIG. 2B shows a signal H serving as a reference of the line_-BLANK is shown, and FIG. 2C shows the reading and exposure timing of the first to nth lines. As described above, the exposure timing of the XY address type solid-state imaging device 3 is a vertical focal plane method that is shifted for each line. When the user instructs strobe shooting by operating an operation unit (not shown), the system controller 16 allows the light emission control circuit 18 to emit light as shown in FIG. 2D within the vertical blanking period in which all pixels can be exposed. Signal S_-Output EN.
[0029]
The light emission control circuit 18 receives the light emission permission signal S._-When EN is received, the reference signal V from the sensor drive circuit 17 is received._-BLANK, H_-Based on BLANK, the light emission signal S shown in FIG._-PULSE is output to the light emission drive circuit 19. The light emission drive circuit 19 generates a light emission signal S._-Since the strobe light-emitting tube 20 is driven by PULSE, the strobe light-emitting tube 20 generates a light emission signal S._-Light is emitted at the timing of PULSE.
[0030]
In addition, the image from which the strobe light-emitting tube 20 emits light and obtains proper exposure is only the pixel that is exposed when the strobe light-emitting tube 20 emits light, and when the reset voltage VRS is applied next, the strobe light emission does not occur. In the subsequent normal exposure, proper exposure cannot be obtained. For this reason, as shown in FIG. 2 (f), image signals obtained with proper exposure are sequentially stored in the memory 22. When the signal of one screen is stored, the signal stored in the memory 22 is output from the next timing. As a result, an image obtained by appropriate exposure is displayed as a still image.
[0031]
According to the first embodiment described above, there is an effect that an appropriate image can be obtained even when an XY address type solid-state imaging device such as CMD and a short-time-emitting light emitting unit such as a strobe are used. .
[0032]
Next, FIG. 3 shows a configuration of an imaging apparatus according to the second embodiment.
Note that the description of the same configuration and operation as in the first embodiment is omitted.
As shown in the figure, in this embodiment, the output of the FPN canceller 7 is connected to the concentration connection circuit 8 via the synchronization memory 21 or directly, and the output of the concentration connection circuit 8 is It is connected to the monitor I / F 12 via the color processing circuit 9, the white balance circuits 10r, 10g, and 10b and the compression circuits 11r, 11g, and 11b. Further, the outputs of the white balance circuits 10r, 10g, and 10b are connected to the compression circuits 11r, 11g, and 11b via the luminance generation circuit 13 and the compression rate generation circuit 14, respectively. The output of the luminance generation circuit 13 is also connected to the system controller 16 via the frame memory 15. Other configurations are the same as those of the first embodiment described above.
[0033]
The density connection circuit 8 synthesizes image data of two screens having different exposure amounts, and creates image data in which the dynamic range of one screen is expanded. The compression circuits 11r, 11g, and 11b compress the image data whose dynamic range is expanded to the dynamic range of a display system (monitor) (not shown). The luminance generation circuit 13 creates a luminance signal from each color signal (RGB) with an extended dynamic range. The compression rate generation circuit 14 generates a compression rate from the compression coefficient from the system controller 16 and the luminance signal. The frame memory 15 stores a luminance signal for one screen and outputs it to the system controller. The synchronization memory 21 stores image data for one field. In this embodiment, the means for synthesizing the two screens includes the density connection circuit 8, the compression circuit 11, the luminance generation circuit 13, and the compression rate generation circuit 14. However, the present invention is not limited to this. For example, it can of course be constituted by a density connection circuit 8 and a lookup table.
[0034]
Hereinafter, the operation of the light emission control circuit 18 in the second embodiment will be described in detail with reference to FIG. FIG. 4A shows a signal V serving as a field reference._-BLANK is shown, and FIG._-BLANK is shown, and FIG. 4C shows the reading and exposure timing of the first to nth lines. When the user operates an operation unit (not shown) to instruct strobe shooting, the system controller 16 sends a light emission permission signal S to the light emission control circuit 18._-EN is output (see FIG. 4D).
[0035]
The light emission control circuit 18 receives the light emission permission signal S._-When EN is received, the reference signal V from the sensor drive circuit 17 is received._-BLANK, H_-Based on VLANK, a light emission signal S for causing light emission with a small light emission amount during a period in which all pixels are exposed in an odd field._-A light emission signal S that outputs PULSE and emits a large amount of light during the period in which all pixels are exposed in the even field._-PULSE is output (see FIG. 4E).
[0036]
The light emission drive circuit 19 is connected to the light emission signal S._-Since the strobe arc tube 20 is driven by PULSE, the strobe arc tube 20 emits light with a small amount of light in an odd field and emits light with a large amount of light in an even field. Thereby, two screens having different exposure amounts in the odd field and the even field can be obtained.
[0037]
The signal from which the fixed pattern noise of the image sensor 3 is removed by the FPN canceller 7 is stored in the synchronization memory 21 in the odd field. In the even field, the signal from the FPN canceller 7 is output to the density connection circuit 8, and the image data of the odd field is read from the synchronization memory 21 in synchronization with the timing of the sensor driving circuit 17 and is sent to the density connection circuit 8. Is output (see FIG. 4F).
[0038]
An odd field signal and an even field signal with different exposure amounts are input to the density connection circuit 8, and an image with an expanded dynamic range is synthesized from the two signals and output to the color processing circuit 9. The operation for synthesizing an image with an expanded dynamic range from two image signals having different accumulation times of the image sensor 3 is described in detail in Japanese Patent Application Laid-Open No. 5-308573 by the present applicant. Detailed description is omitted here.
[0039]
The output from the white balance circuit 10 is input to the compression circuit 11 and to the luminance generation circuit 13. The luminance generation circuit 13 generates a luminance signal from the R, G, and B signals, and is input to the compression rate generation circuit 14 and the frame memory 15, and the frame memory 15 stores image data for one screen. Is done.
[0040]
Thereafter, the stored image data is output in accordance with reading from the system controller 16. The system controller 16 obtains an appropriate compression coefficient from the luminance signal of the captured image and outputs it to the compression rate generation circuit 14.
[0041]
The compression rate generation circuit 14 outputs the compression rate to the compression circuit 11 that has generated the compression rate based on the luminance signal from the luminance generation circuit 13 and the compression coefficient from the system controller 16. The compression circuit 11 multiplies the signal from the white balance 10 by the compression rate from the compression rate generation circuit 14 and outputs the result to the monitor I / F. As a result, an image with an expanded dynamic range is displayed on the monitor.
[0042]
According to the second embodiment described above, an image with a small exposure amount can be obtained in an odd field even when a solid-state imaging device of an XY address system and a light emitting unit such as a strobe are used. In the even field, an image with a large exposure amount can be obtained, and two screens with different exposure amounts can be obtained by matching the timing in the synchronization memory, so that an image with an expanded dynamic range can be obtained by the image composition unit.
[0043]
It is obvious that the same effect can be obtained even if the relationship between the odd field and the light emission amount in the second embodiment is reversed. In the second embodiment, the composition by the image by the two exposures has been described, but it goes without saying that the image may be composed by performing the exposure more times.
[0044]
This embodiment is applied when the natural light is negligible compared to the strobe light. When natural light is bright, even if the ratio of the strobe light brightness in the odd field and the even field is a predetermined value, the ratio of the accumulated charges does not become the predetermined value. This is the case according to the third embodiment described below. Solved.
[0045]
Next, FIG. 5 shows and describes the configuration of an imaging apparatus according to the third embodiment.
Note that description of the same configuration and operation as those of the second embodiment is omitted.
As shown in the figure, in the third embodiment, the output of the A / D converter 5 is connected to the input of the synchronization circuit 6, and the output of the synchronization circuit 6 is fed to the FPN cancellers 7a and 7b. This is different from the second embodiment in that it is connected to the input of the concentration connection circuit 8 via
[0046]
The synchronization circuit 6 synchronizes the timings of two screens that are read out with time axis compression within a horizontal period. The sensor driving circuit 17 drives the image sensor 3 so that two screens with different exposure amounts are obtained independently within one field period. Details of the principle are described in detail in Japanese Patent Application Laid-Open No. 7-38815, and thus detailed description thereof is omitted here.
[0047]
The operation of the light emission control circuit 18 in the third embodiment will be described below with reference to FIGS. 6 (a) to 6 (c).
In the line to which the reset voltage VRS is applied, the accumulated charge is reset and exposure is started. Thereafter, a read voltage VRD is applied after a certain period (4H), and a signal is read out. As a result, a signal having an exposure period of 4H is read out. Since this reading is performed non-destructively, exposure is continued without applying a reset voltage.
[0048]
After that, after one field period, the read voltage VRD is applied again to read out the signal. As a result, a signal having an exposure period of one field is read out. After this reading, a reset voltage VRD is applied to reset the accumulated charge.
[0049]
As is clear from FIG. 6, it is necessary to simultaneously read out the short-term exposure performed non-destructively and the long-term exposure after four lines. Thus, within one horizontal period, the short exposure period is read at double speed in the first half period, and the long exposure read operation is performed at double speed in the second half period. Thereby, signals of two screens having different exposure amounts are read out in a time division manner within one horizontal period. The image data converted into a digital signal by the A / D converter 5 is converted by the synchronization circuit 6 so that the timings of the short exposure period signal and the long exposure period signal are the same.
[0050]
The actual operation returns the horizontal time axis that is time-axis compressed using the line memory. Further, the vertical time axis shift is adjusted using a field memory. Thereafter, each signal is input to the individual FPN canceller 7, and the fixed pattern noise of the image sensor 3 is removed and input to the density connection circuit 8. As a result, a signal having an expanded dynamic range at a normal moving image rate can be obtained.
[0051]
Next, with reference to FIGS. 7A to 7E, an operation when the strobe arc tube 20 is used in the imaging apparatus will be described. Here, the case of the short exposure period 4H will be described as an example. The light emission control circuit 18 receives a light emission permission signal S from the system controller 16._-When EN is received, based on the reference signal from the sensor drive circuit 17, the light emission signal S is 4H after the start of the field._-PULSE is output. Thereafter, light emission signals are output at intervals of 4H over approximately two field periods.
[0052]
First, signal readout in a short exposure period will be described. Since the first light emission is within the short exposure period of the pixels from the first line to the fourth line, the first line to the fourth line are exposed by the first light emission. Next, the fifth to eighth lines are exposed by the second light emission. The same operation is repeated to expose the (n-3) th line to the nth line by n / 4 (n is the total number of lines) light emission. By this operation, readout signals for short-time exposure performed in a non-destructive manner for each line are exposed by one light emission.
[0053]
Next, signal readout in the long exposure period will be described. From the first line to the fourth line, the exposure is sequentially repeated by the light emission from the first light emission to the readout 2, that is, the first to (n / 4) +1 light emission. Next, from the fifth line to the eighth line, the exposure is sequentially repeated from the second light emission to the (n / 4) + 2nd light emission. Since the same operation is performed for each line, exposure of all the lines is performed by (n / 4) +1 times of the same number of light emission.
[0054]
In this way, the light exposure circuit of the strobe arc tube 20 in each exposure period differs at a constant ratio between the signal of the short exposure period that is nondestructive and the signal of the long exposure period of normal reading. As a result, two screens having different exposure amounts are obtained, and the exposure amount ratio is the ratio between the short exposure period and the long exposure period, and this ratio is a target value that is less affected by the brightness of natural light. In the above description, the light emission interval is set to the short exposure period. However, light may be emitted at a shorter interval, or the light emission interval may be further shortened to provide substantially continuous light emission.
[0055]
According to the third embodiment described above, an XY address type solid-state imaging device, a nondestructive readout unit that reads a signal nondestructively and obtains a signal with a short signal accumulation time, and a relatively long signal Even in the case of using a light emitting means that emits light for a short time, such as a strobe, a readout unit that obtains an accumulation time signal can obtain two screens with different exposure amounts. can get. Also, an image can be obtained at a normal moving image rate. Further, since the ratio of the amount of light by the strobe and the ratio of the exposure period are the same, the light from the strobe arc tube 20 reaches (the exposure amount depends on the light emission amount) and the light amount of the subject and the light emitting means does not reach (the exposure amount depends on the exposure period). In the background, since the exposure amount ratios are equal to each other, an image in which an appropriate dynamic range is expanded in both the subject and the background can be obtained by the image composition means.
[0056]
Next, FIG. 8 shows an image pickup apparatus according to a fourth embodiment.
The description of the same configuration and operation as those in the first to third embodiments is omitted.
As shown in the figure, in the fourth embodiment, the output of the A / D converter 5 is connected to the inputs of the FPN cancellers 7a and 7b via the synchronization circuit 6, and the FPN canceller 7a The output is directly connected to the density connection circuit 8, and the output of the FPN canceller 7 b is connected to the density connection circuit 8 via the correction circuit 24.
[0057]
Further, the outputs of the FPN cancelers 7 a and 7 b are also connected to a detection circuit 23, and the output of the detection circuit 23 is connected to a correction circuit 24. Other configurations are the same as those of the third embodiment described above. The detection circuit 23 detects a variation in light emission amount from image data of two screens having different exposure amounts. The correction circuit 24 corrects the image data based on the signal obtained by the detection circuit 23.
[0058]
In such a configuration, the signal from the FPN canceller 7 is taken into the detection circuit 23. The detection circuit 23 calculates an average value (for example, 1H period) of the image data of the short exposure period signal and the long exposure period signal. The ratio between the ratio of the two average values and the ratio of the exposure time is output to the correction circuit 24 as a correction coefficient. The correction circuit 24 multiplies the image data by the correction coefficient and outputs it to the density connection circuit 8. Thus, the ratio of the short exposure period signal to the long exposure period signal becomes the same as the exposure time ratio, and the variation in the light emission amount is corrected.
[0059]
As described above, according to the fourth embodiment, two screens with different desired exposure amounts can be obtained even when an X-Y address type solid-state imaging device and a light emitting means such as a strobe are used. Therefore, the image composition unit can increase the dynamic range and obtain an image. Further, since the detection circuit 23 for detecting the variation in the light emission amount of the light emitting unit and the correction circuit 24 for correcting the image data are provided, the image synthesis by the synthesis unit is appropriately performed, so that deterioration of the image quality can be prevented. In addition, the detection circuit 23 performs calculation using the image data that is actually used for the synthesis to detect the light emission unevenness, so that the detection accuracy is high and accurate correction can be performed.
[0060]
Next, FIG. 9 shows an image pickup apparatus according to a fifth embodiment of the present invention.
The same configuration and operation as those in the first to fourth embodiments are omitted.
As shown in the figure, this embodiment has a light receiving element 25 that receives light from a subject, converts it into an electrical signal, and outputs it to a detection circuit 23. The outputs of the FPN cancelers 7a and 7b are not connected to the detection circuit 23. Other configurations are the same as those of the fourth embodiment.
[0061]
In such a configuration, the light receiving element 25 integrates the exposure amount of each exposure period in synchronization with the drive timing of the image sensor 3 and converts it into an electrical signal proportional to the exposure amount, and outputs it to the detection circuit 23. . The detection circuit 23 outputs the ratio between the input electric signal and the reference value to the correction circuit 24 as a correction coefficient. The correction circuit 24 multiplies the image data by the correction coefficient and outputs it to the density connection circuit 8.
[0062]
In the fifth embodiment described above, the detection circuit 23 detects uneven light emission using a signal from the light receiving element 25, and therefore calculates the average value described in the fourth embodiment. Therefore, it is possible to perform correction with a simple configuration without requiring a means for the purpose, and it is possible to prevent deterioration in image quality due to image composition by the composition unit.
[0063]
Next, FIG. 10 shows an image pickup apparatus according to a sixth embodiment of the present invention.
The same configuration and operation as those in the first to fourth embodiments are omitted.
As shown in the figure, this embodiment is different from the fifth embodiment in that the detection circuit 23 and the correction circuit 24 are eliminated and the output of the light receiving element 25 is connected to the light emission control circuit 18. To do. Other configurations are the same.
[0064]
In such a configuration, the light receiving element 25 integrates and converts the exposure amount in each exposure period into an electric signal in synchronization with the drive timing of the imaging element, and outputs it to the light emission control circuit 18. Based on a signal from the light receiving element 25, the light emission control circuit 18 continues to emit light when the planned light quantity does not reach due to uneven light emission, and emits light by well-known direct photometry that stops the light emission when the planned light quantity is reached. The light emission drive circuit 19 is controlled so that the amount becomes constant.
[0065]
In the sixth embodiment described above, the light emission control circuit 18 controls the light emission drive circuit 19 so that there is no variation in the amount of light emitted by a signal from the light receiving element 25 that receives light from the subject and converts it into an electrical signal. Since the control is performed, an appropriate composite image can be obtained with a simple configuration as compared with the case of correcting the image data.
[0066]
The embodiment of the present invention has been described above, but the present invention is not limited to this, and it is needless to say that various improvements and modifications can be made without departing from the spirit of the present invention. For example, an example in which CMD is used as an XY address type solid-state imaging device has been described, but the present invention is not limited to this.
[0067]
In addition, the following invention is contained in the said embodiment of this invention.
(1) a solid-state imaging device that photoelectrically converts incident light from an object and outputs the result as an electrical signal;
A strobe arc tube for illuminating the subject,
Control means for causing the strobe arc tube to emit light within a vertical blanking period of the solid-state imaging device;
An imaging apparatus comprising:
[0068]
  The present invention corresponds to the first and second embodiments.
  With the configuration as described above, there is an effect that an appropriate image can be obtained even when an XY address type solid-state imaging device such as CMD and a short-time light emitting unit such as a strobe are used.
  (2) a solid-state image pickup device that photoelectrically converts light from an incident subject and outputs it as an electrical signal;
  A strobe tube that emits strobe light on the subject;
  Of the solid-state image sensorTo obtain images with different exposures in different fieldsDifferent field periodsGapEachDepending on the amount of emitted light andControl means for causing the strobe arc tube to emit light within a vertical blanking period;
  Depending on the different light emissionObtained by exposure based on light emission of multiple strobe arc tubesDifferent exposureA combining means for combining a plurality of images;
An imaging apparatus comprising:
[0069]
  The present invention corresponds to the second embodiment.
  With the configuration as described above, even when a light emitting means such as a strobe is used, the dynamic range is expanded by obtaining two images with different exposure amounts in the odd field and the even field and combining the images with different exposure amounts. Since an image can be obtained, an image with an expanded dynamic range can be obtained with an appropriate exposure amount.
  (3)A solid-state imaging device capable of reading image signals non-destructively,
  A strobe arc tube that illuminates the subject,
  First solid-state image pickup device for accumulating signals in a first accumulation time, then reading nondestructively, and obtaining a first signal;
  Second control means for obtaining a second image signal that is read out after storing a signal for a second storage time longer than the first storage time;
  An interval equal to the first accumulation time or an interval shorter than the first accumulation time from when the signal is accumulated at the first accumulation time to when the signal is accumulated at the second accumulation time. A third control means for causing the strobe arc tube to emit light,
An imaging apparatus comprising:
[0070]
The present invention corresponds to the third embodiment.
With the above configuration, an image with an appropriately expanded dynamic range can be obtained at a moving image rate even when both light (natural light, fluorescent light, etc.) other than strobe light and strobe light are required. (In the structure of claim 2, since one screen is composed of two fields, the video rate is reduced to half.)
(4) The synthesis means includes
Detecting means for detecting the light emission amount of the light emitting means;
The imaging apparatus according to any one of the above items (2) and (3), further comprising a correction unit that corrects a video signal obtained from the solid-state imaging unit based on a signal detected by the detection unit. .
[0071]
The detecting means includes
4. The imaging apparatus according to any one of the items (2) and (3), wherein a variation in light emission amount is detected based on a signal from the imaging means.
[0072]
The detecting means includes
The imaging apparatus according to any one of the above items (2) and (3), comprising a light emitting element that receives light from a subject and converts the light into an electrical signal.
[0073]
The present invention corresponds to the fourth and fifth embodiments.
With the above configuration, the exposure amount error caused by the variation in the light emission amount of the two images is detected, and the video signal obtained from the solid-state imaging unit is corrected based on the detected result before the two images are combined. Therefore, it is possible to prevent the deterioration of the image due to the variation in the light emission amount.
(5) The light emission control means includes:
The imaging apparatus according to any one of items (2) and (3), wherein the imaging apparatus is controlled based on an output from a light receiving element that receives light from a subject and converts the light into an electrical signal.
[0074]
The present invention corresponds to the sixth embodiment.
With the above configuration, the light emitting unit is controlled so as to eliminate the variation in the amount of light emission based on the output from the light receiving element that receives the light from the subject and converts it into an electrical signal. Images can be combined.
[0075]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide an imaging apparatus capable of obtaining an appropriate image even when an XY address type solid-state imaging device and light emitting means are used.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an imaging apparatus according to a first embodiment.
FIG. 2 is a timing chart showing the operation of the light emission control circuit according to the first embodiment.
FIG. 3 is a diagram illustrating a configuration of an imaging apparatus according to a second embodiment.
FIG. 4 is a timing chart showing the operation of the light emission control circuit of the second embodiment.
FIG. 5 is a diagram illustrating a configuration of an imaging apparatus according to a third embodiment.
FIG. 6 is a timing chart showing the operation of the light emission control circuit of the third embodiment.
FIG. 7 is a timing chart for explaining an operation when a strobe arc tube is used in the imaging apparatus according to the third embodiment.
FIG. 8 is a diagram illustrating a configuration of an imaging apparatus according to a fourth embodiment.
FIG. 9 is a diagram illustrating a configuration of an imaging apparatus according to a fifth embodiment.
FIG. 10 is a diagram illustrating a configuration of an imaging apparatus according to a sixth embodiment.
FIG. 11 is a conceptual diagram of CMD.
FIG. 12 is a timing chart for explaining the operation of the CMD vertical scanning circuit;
FIG. 13 is a diagram for explaining a focal plane method related to exposure timing of an XY address method solid-state imaging device;
FIG. 14 is a diagram showing the light emission characteristics of a strobe arc tube.
[Explanation of symbols]
1 Lens system
2 Optical filter
3 Image sensor
4 Preamplifier
5 A / D converter
6 Synchronization circuit
7 FPN canceller
8 Concentration connection circuit
9 color processing circuit
10 White balance circuit
11 Compression circuit
12 Monitor I / F
13 Luminance generation circuit
14 Compression rate generation circuit
15 frame memory
16 System controller
17 Sensor drive circuit
18 Light emission control circuit
19 Light emission drive circuit
20 Strobe arc tube

Claims (1)

A solid-state imaging device that photoelectrically converts light from an incident subject and outputs it as an electrical signal;
A strobe tube that emits strobe light on the subject;
In different emission amount corresponding to between their respective different fields period for obtaining images of different exposure amounts in different fields each of the solid-state imaging device, and the strobe light emission tube in the vertical blanking period of the each field period Control means for emitting light,
A synthesizing means for synthesizing a plurality of images having different exposure amounts obtained by exposure based on light emission of the plurality of strobe arc tubes with different light emission amounts ;
An imaging apparatus comprising:

Images