JP3131435B2 - Electronic camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic camera capable of effectively capturing and inputting an object having a wide dynamic range and displaying the image on an image monitor.

[Related Art] In recent years, various solid-state imaging devices such as a CCD image sensor and a MOS image sensor have been developed, and an electronic camera that electronically images a subject using these solid-state imaging devices is, for example, a video camera or a video camera. Various electronic still cameras have been developed. This type of electronic camera is an image signal (video signal) of a subject image electronically captured and input by a solid-state imaging device.
Is recorded on a magnetic recording medium such as a so-called video tape or floppy disk, an IC memory card, or the like, and is used for image display on an image monitor such as a TV receiver.

By the way, the dynamic range of a video signal that can be displayed by an image monitor such as the TV receiver is at most about 40 dB. For this reason, in general, the imaging capability (dynamic range) of the solid-state imaging device is often set to about 50 dB.

On the other hand, the dynamic range of a subject to be imaged by the solid-state imaging device (electronic camera) often reaches about 80 dB. That is, the dynamic range (signal level width) of the subject often exceeds the dynamic range that can be displayed on the image monitor and that can be input by the solid-state imaging device.

If such a subject having a wide dynamic range is electronically imaged and input by the solid-state imaging device as it is, saturation of the solid-state imaging device occurs at a high signal level portion (high luminance portion), and a so-called overexposure state occurs. appear. Conversely, if this saturation is to be suppressed, a portion where the signal level is low (a low luminance portion) will be underexposed, and it is unavoidable that a so-called blackout condition will occur. In other words, there is a problem that a signal component that does not fall within the dynamic range of the solid-state imaging device or the image monitor cannot be imaged and input and cannot be displayed.

[Problems to be Solved by the Invention] In the related art, there are many subjects having a dynamic range wider than the dynamic range of the solid-state imaging device. In such a case, there is a problem that subject information in a high-level portion or a low-level portion is damaged. In other words, despite the fact that the subject has a wide dynamic range, when this is electronically imaged and input by the solid-state image sensor,
The dynamic range of a subject is limited by the dynamic range of a solid-state image sensor or an image monitor, and eventually an image signal (video signal) having a limited dynamic range
There was a problem that it could only be obtained.

The present invention has been made in view of such circumstances,
The purpose is to effectively capture and input a subject having a dynamic range exceeding the dynamic range of the solid-state imaging device, and to provide an image display on an image monitor without causing problems such as so-called overexposure and crushed black. It is an object of the present invention to provide a highly practical electronic camera that can perform the functions.

[Means for Solving the Problems] According to a first aspect of the present invention, in an electronic camera that electronically captures an object using a solid-state imaging device and provides the image display on an image monitor, A solid-state imaging device capable of reading out of the device at a higher speed than the image display period; and capturing an image of a subject by the solid-state imaging device and reading out the image signal a plurality of times within the image display period. Means for repeatedly performing at a high speed, means for logarithmically converting the image signal each time an image signal is repeatedly read from the solid-state imaging device, means for A / D converting the logarithmically converted image signal, Means for sequentially accumulating the A / D-converted image signals a plurality of times within the image display cycle.

According to the second aspect of the present invention, in an electronic camera that electronically captures an object using a solid-state imaging device and provides the image display on an image monitor, the image signal input and captured is higher than the period of the image display. A solid-state imaging device that can be read out of the device at a high speed, and means for repeatedly performing imaging of a subject by the solid-state imaging device and reading of an image signal at a high speed a plurality of times within the image display cycle, Means for performing A / D conversion on the image signal by predictive coding every time an image signal is repeatedly read from the solid-state imaging device; anda plurality of A / D-converted image signals in a cycle of the image display. Means for sequentially accumulating data over the electronic camera.

According to a third aspect of the present invention, the apparatus further comprises means for adjusting a dynamic range of the accumulated and added image signal and outputting the adjusted image signal to the image monitor.
Alternatively, an electronic camera according to a second aspect is provided.

That is, the exposure time of the subject by the solid-state imaging device is reduced by repeatedly performing the imaging of the subject by the solid-state imaging device and the reading of the image signal at a high speed,
This prevents saturation of the high-level signal in the solid-state imaging device. Then, the image signal obtained by the short-time exposure is repeatedly read at a high speed and cumulatively added to obtain an image signal having an expanded dynamic range, thereby obtaining a dynamic signal that does not substantially impair the dynamic range of the subject. It is characterized in that an image signal with a wide range is obtained.

[Operation] First, according to the first aspect of the present invention, an image signal input by imaging is read out of the solid-state imaging device at a higher speed than the period of image display, and a subject by the solid-state imaging device is read out. Imaging and reading of the image signal are repeatedly performed at a high speed a plurality of times within the period of the image display, and each time an image signal repeatedly read from the solid-state imaging device is read, logarithmic conversion is performed. After A / D conversion of the converted image signal, by successively accumulating a plurality of times within the period of the image display, an inexpensive general-purpose A / D converter provides high-precision A / D conversion. While the conversion becomes possible, the dynamic range of the accumulated image signal can be expanded by the number of times of accumulation while suppressing the dynamic range of each image signal itself to be narrow. It is possible to obtain an image signal having an improved S / N by the addition.

Further, according to the second aspect of the present invention, the image signal input and captured is read out of the element at a higher speed than the period of the image display, and the imaging of the subject by the solid-state image sensor and the reading of the image signal are performed. Is repeatedly performed at a high speed a plurality of times within the period of the image display, and each time an image signal is repeatedly read from the solid-state imaging device, the image signal is A / D-converted by predictive coding. By sequentially accumulating the A / D-converted image signals a plurality of times within the image display cycle, the same operation and effect as in the first aspect are obtained, and the S / N is improved in real time. High-quality image display can be performed.

According to the third aspect of the present invention, in the electronic camera according to the first or second aspect, it is possible to adjust the dynamic range of the accumulated and added image signal and output the adjusted image signal to an image monitor.

As a result, even for a subject having a wider dynamic range than the solid-state imaging device, an image signal with a wide dynamic range is obtained by effectively imaging and inputting the subject without being restricted by the dynamics of the solid-state imaging device. It becomes possible.

Then, the image signal of this wide dynamic range is compressed in accordance with the dynamic range of the image monitor, and the resulting image signal is used for image display. It is possible to display an image that does not exist.

Hereinafter, an electronic camera according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a main part of an electronic camera according to an embodiment, and 1 is a solid-state imaging device that electronically captures an image of a subject. The solid-state imaging device 1 basically includes a plurality of photoelectric conversion units arranged in a matrix. The solid-state imaging device 1 is driven by an imaging control unit (not shown) to supply a signal charge corresponding to a light amount of a subject to each of the photoelectric conversion units. The exposure is performed by the occurrence. By sequentially reading out pixel signals corresponding to the signal charges generated in these photoelectric conversion units, an image signal electronically captured by the solid-state imaging device 1 is obtained.

Here, an AMI (amplification type MOS imager) having a function capable of reading out an image signal of a subject electronically captured and input at a high speed is used as the solid-state imaging device 1. The imaging of the subject by the solid-state imaging device 1 and the reading of the image signal are repeatedly performed at a high speed a plurality of times within the image display cycle. The image signal read out from the solid-state imaging device 1 at a high speed in this manner is amplified to a predetermined signal level via the preamplifier 2, and then subjected to clipping processing and the like via the signal processing circuit 3, and thereafter, In the A / D converter 4, for example, a 12-bit signal is sequentially digitally encoded.

That is, conventionally, in general, when the solid-state imaging device 1 captures an image of a subject, the imaging and the reading of the image signal are performed, for example, every one field cycle (17 mSec) corresponding to the image display cycle on the image monitor. Here, however, the solid-state imaging device 1 is driven at a high speed, and the imaging and the reading of the image signal are repeated at a high speed, for example, ten times within the one-field period.

As described above, the image signals repeatedly read out from the solid-state imaging device 1 at high speed are sequentially digitally encoded as described above.

The digitally encoded image signal is added to the adder 5.
Are sequentially stored in the frame memory 6 for each frame. The adder 5 adds the image signal stored and stored in the frame memory 6 and the image signal of the next one frame which is sequentially and repeatedly read from the solid-state imaging device 1, and rewrites the image signal in the frame memory 6. By doing so, the image signals repeatedly read out on the frame memory 6 are cumulatively added as described above. The cumulative addition of such image signals is performed over the above-described image display cycle,
For example, the dynamic range of the image signal is expanded by repeating the process over one field cycle.

That is, in this electronic camera, the electronic imaging input of the subject by the solid-state imaging device 1 is repeatedly performed a plurality of times (for example, 10 times) within the image display cycle (one field) as described above. Is set sufficiently short. However, the amount of signal charge generated in the solid-state imaging device 1 in accordance with the amount of light of the subject increases in proportion to the exposure time, and when the exposure time is set short as described above, the dynamic range of the subject is reduced. It is possible to perform exposure without causing saturation of the solid-state imaging device 1 even when the dynamic range is sufficiently wider than the dynamic range of the solid-state imaging device. That is, the exposure is performed in a state where the high luminance portion of the subject is not saturated. However, the exposure amount for the low-luminance portion of the subject is insufficient for the short exposure time.

Then, such an image signal is transmitted at the image display period (1).
By repeatedly accumulating the image signal a plurality of times within the field, the level of the image signal is increased by the number of repetitions, and the dynamic range is substantially expanded. For example, an image signal is repeatedly read out n times within one field period of image display, and the cumulative addition is performed, whereby the dynamic range of the cumulatively added image signal is increased by n times compared with the dynamic range of each image signal. It has been expanded to.

Incidentally, a random noise component such as a dark current mixed into an image signal at the time of subject exposure by the solid-state imaging device 1 increases in a square root function with respect to the length of the exposure time. ), The noise level becomes as shown in FIG. To be reduced.

Specifically, when the exposure time is set to (1/10), the noise level is Thus, a dynamic range improvement effect of 10 dB can be expected. In addition, such an increase in the noise component due to the above-described cumulative addition of the image signal is caused by the cumulative addition of n times because the noise component itself has randomness. It just becomes. As a result, the dynamic range of the image signal cumulatively added n times is That is, it is improved by n times.

In this way, the solid-state imaging is performed by repeatedly reading out the image signal from the solid-state imaging device 1 for electronically capturing and inputting the subject, and by accumulating the image signal using the frame memory 6 and the adder 5. The level of the image signal captured within the dynamic range of the element 1 is increased, and the dynamic range is expanded.

In other words, the dynamic range of the solid-state imaging device 1 is expanded n times by accumulatively adding the image signals imaged and input n times within the dynamic range of the solid-state imaging device 1. This is because the dynamic range of a subject having a wide luminance level width compared to the dynamic range of the solid-state imaging device 1 can be reduced by the above-described short-time exposure compression of the dynamic range and the dynamic range expansion by the cumulative addition by the high-speed reading. This means that imaging input is performed effectively. As a result, for example, by effectively using the solid-state imaging device 1 having a dynamic range of 50 dB,
Image input of a subject with a dynamic range of 80 dB,
The dynamic range of the image signal can be set to 80 dB.

In addition, for imaging input of a subject having such a wide dynamic range, it is only necessary to change the driving conditions of the solid-state imaging device 1 as described above and provide a means for cumulatively adding image signals that are repeatedly read at high speed. It is very simple in hardware. Therefore, the dynamic range of an image signal to be imaged and input can be expanded very simply and effectively.

By the way, the video processor 7 which inputs the image signal of which the dynamic range is cumulatively added as described above and whose dynamic range is expanded, separates and extracts the luminance signal component Y from the image signal, and converts the image signal into RGB signals. Separate into primary color components. The dynamic range control circuit 8 that inputs the luminance signal component Y converts the dynamic range of the image signal (80 dB in the above-described example) into the dynamic range (eg, 40 dB) of the image monitor (eg, TV receiver).
The compression coefficient for performing the compression conversion is calculated.

That is, when an image monitor having a dynamic range of only 40 dB is used to display an image signal having a wide dynamic range as described above, if the offset is set to [0], as shown in FIG. Only the image can be displayed, and the high-luminance portion is in a whiteout state due to saturation. Conversely, if the offset is set to a negative value and the high-brightness portion is adjusted to the maximum display level of the image monitor, only the high-range 40 dB of the image signal can be displayed as shown in FIG. 3B. In this case, the low-luminance level portion of the image signal is in a blackened state.

Therefore, as shown in FIG. 3C, the dynamic range control circuit 8 compresses the dynamic range of the image signal and solves the above-mentioned problem and displays the entire dynamic range of the image signal on the image monitor. , A compression coefficient corresponding to the dynamic range of the image signal is obtained.

In this embodiment, in order to easily and effectively compress the dynamic range of the image signal (the separated three primary color components R, G, B), the image signal is separated into the three primary color components R, G, B. The image signal and the luminance signal component Y are each logarithmically converted, and then the signal subjected to dynamic range control is subjected to antilogarithmic conversion to restore the original signal form.

As a method of controlling the dynamic range, for example, the method proposed in Japanese Patent Application Laid-Open No. 63-232591 can be used as it is. Therefore, here, the control of the dynamic range will be briefly described.

That is, the dynamic range control circuit 8 logarithmically converts the luminance signal component Y into logY via a log amplifier 8a and takes it in. Then, for example, through a two-dimensional filter 8b configured as shown in FIG. Remove components. This 2
The dimensional filter 8b corrects the luminance signal obtained through the two-dimensional LPE according to, for example, the error between the average level of the luminance signal obtained by the average value circuit (AVE) and the reference level as shown in FIG. After clipping the luminance signal component, the luminance signal component is subtracted from the luminance signal component to remove the illuminance unevenness component.

The signal from which the illuminance non-uniformity component has been removed via the two-dimensional filter 8b is converted to a dynamic range / gain controller (DGC) 8 configured as shown in FIG. 5, for example.
c, and output log in which the dynamic range of the luminance signal component Y is adjusted to the dynamic range of the image monitor.
.alpha.Y ^beta (where, alpha is a gain adjustment factor, beta is a dynamic adjustment factor) seeking. In FIG. 5, a D / A converter is provided at the input and an A / D converter is provided at the output. However, the same processing may be performed by a digital circuit system, and the D / A and A / D converters may be omitted.

A similar output can be obtained even if the circuit portion surrounded by the dotted line in FIG. 5 is simplified as shown in FIG. 6, for example. Such LogarufaY ^beta and the ratio log of the luminance signal component logY the (αY ^{β /} Y) by calculating by the subtractor 8e, and a compression factor that indicates whether to this degree of dynamic range compression.

That is, the DGC 8c performs feedback control so that the standard deviation value of one screen (or a part thereof) of the luminance signal is constant. That is, by feeding back the error amplification value between the average value of the luminance signal and the gain reference voltage to the adder, the gain is adjusted so that the average value of the luminance signal becomes equal to the gain reference voltage, and the dynamic It is configured to adjust the range. Thus by obtaining a ratio log (αY ^{β /} Y) between the way the output LogarufaY ^beta of DGC8e the dynamic range is kept constant by the luminance signal component logy, the image signal value is captured entered as described above The compression coefficient indicates how much compression the dynamic range can be adjusted to the dynamic range of the image monitor.

The three primary color components R, G, and B of the image signal converted and output by the video processor 7 are log amplifiers 9r and 9 respectively.
The logarithm is converted as logR, logG, logB via g, 9b. Each of these signals logR, logG, logB is a delay circuit 10
r, 10 g, via 10b adder 11r, 11g, respectively given in 11b, the dynamic range compression factor log obtained in DGC8c (αY β ^/ Y) is added, respectively. As a result,
The adder 11r, 11g, each output of 11b ^{is, logR + log (αY β /} Y) = logR (αY β / Y) logG + log (αY β / Y) = logG (αY β / Y) logB + log (αY β / Y) = logB (αY β ^/ Y) becomes, which inverse logarithmic amplifier 12r, 12 g, 12b and inverse logarithmic transformation through, D / a converters 13r, 13 g, signals output via 13b is (.alpha.Y ^beta / Y) R, the ^{(αY β / Y) G (} αY β / Y) signal component dynamic range compression respectively as B.

Thus, if the dynamic range for the output image signal is adjusted using such a dynamic range adjusting means, the image signal having a wide dynamic range required as described above can be effectively adapted to the dynamic range of the image monitor. Becomes As a result, as shown in FIG. 3, the image signal can be displayed effectively without causing overexposure and underexposure.

In the above-described embodiment, the illuminance unevenness is removed by the two-dimensional filtering process in the dynamic range control circuit 8, and then the luminance signal adjusted in the dynamic range by the DGC 8c is obtained. From this, the compression coefficient for the dynamic range control is obtained. However, the dynamic range of the luminance signal can be suppressed to a certain range only by removing the illuminance unevenness by the two-dimensional filtering process.

Therefore, in such a case, for example, 2 shown in FIG.
The output of the clipping circuit for adjusting the luminance signal level in the dimensional filter 8b is directly used as the adders 11r, 11g,
Instead of 11b, it may be applied to subtractors 31r, 31g, 31b as shown in FIG. In other words, if the illuminance unevenness of the subject is removed, the dynamic range of the image signal can be generally suppressed to 40 to 50 dB. Therefore, even if the compression coefficient obtained from the two-dimensional filter 8b is used as it is, the dynamic range can be adjusted to a certain extent. It can be performed. Further, with this configuration, the configuration can be simplified as much as the above-mentioned DGC 8c and the like become unnecessary.

The above-described embodiment is an example of a video movie camera in which a subject is continuously imaged and input for each image display period and is used for image display. Recently, however, a still image is imaged and input using the solid-state image sensor 1. Various electronic still cameras have also been developed. For example, while monitoring an image continuously captured and input by a solid-state imaging device incorporated in an endoscope, a certain screen is captured as a still image, and this is stored in a mass storage such as a digital VTR or digital video file. An accumulation is performed.

When the present invention is applied to such a system, the system may be configured as shown in FIG. 8, for example. In FIG. 8, the same parts as those in FIG. 1 are denoted by the same reference numerals.

That is, in the case of this embodiment, the color difference signals (RY) and (BY) are also obtained by the processor 7 at the same time. Then, the color difference signals (RY) and (BY) and the luminance signal Y are loaded into the memories 21a, 21b and 21c over one field in accordance with the release timing. Then, the respective signal components taken into these memories 21a, 21b, 21c are converted into parallel / serial converters 22.
Via the data compression unit 23 and the recording modulation unit 24.
Are subjected to data compression processing and recording modulation processing in series, and are recorded in the mass storage unit 25.

The image signal read and reproduced from the mass storage unit 25 is decoded and reproduced from the demodulation unit 26 via the data decoding unit 27, and the serial / parallel conversion unit 28 performs the above-described color difference signals (RY), (B -Y) and a luminance signal Y. Then, the matrix circuit 29 calculates three primary color components from the color difference signals (RY) and (BY) and the luminance signal Y.
R, G, and B are determined respectively.

The image signal required from the solid-state imaging device 1 is processed or the mass storage unit is provided to the above-described dynamic range adjustment unit of the embodiment including the image signal recording / reproducing unit. What is necessary is just to incorporate a switch circuit 30 for switching whether to process the image signal read from 25.

According to such an embodiment, a wide dynamic range image signal captured and input as described above is masked with good quality in the form of its luminance signal Y and color difference signals (RY) and (BY). The data can be stored in the storage unit 25.
Then, it becomes possible to effectively adjust the dynamic range of the recorded and saved image signal of a wide dynamic range, and to provide the image signal on an image monitor.

Further, in each of the above-described embodiments, it is necessary to quantize the noise component of the image signal in order to secure the dynamic range of the image signal, and about 12 bits are required as the quantization bit number. However, a 12-bit high-speed operation type A / D converter that can be operated at a television signal rate, which is currently in practical use, is very expensive. Moreover, as the resolution of an image increases and its frequency band becomes wider, an A / D converter having a quantization accuracy of about 12 bits may not be able to cope with the above-described image processing.

On the other hand, conventional digital image processing is often performed in units of 8 bits. Therefore, in the present invention, it is practically preferable to apply an image signal in 8 bits.

Therefore, as shown in FIG. 9, an image signal repeatedly read out from the solid-state
At this time, the signal is converted into a luminance signal Y and three primary color components R, G, B, and these signals are logarithmically converted. Then, each of the logarithmically converted signal components is digitally coded into 8 bits, and then these signal components are respectively written into the frame memories 6a, 6b, 6g, 6r and cumulatively added. The dynamic range of each signal component is expanded by the cumulative addition. Each signal component whose dynamic range has been expanded becomes, for example, a 12-bit digital signal, and is thus converted into bit shifters 14a, 14b,
The data is compressed to 8 bits via 14g and 14r, and then subjected to the dynamic range compression processing described above.

By configuring such a signal processing circuit, it is possible to handle an 8-bit signal in most of the signal system,
It is possible to construct an electronic camera using existing general-purpose image processing circuit components (such as semiconductor ICs) as they are. A /
The noise component is greatly amplified by the log amplifier provided in the preceding stage of the D converter.However, as described above, the effect of improving the S / N by cumulative addition works, and the bit signal of the cumulatively added image signal is shifted. Therefore, the noise component can be kept very small. As a result, it is possible to display an image with good S / N.

Next, another embodiment for reducing the number of quantization bits of the A / D converter will be described below. In this embodiment, for example, pre-value prediction coding is adopted, and a desired digital conversion for an image signal is performed using an A / D converter having a smaller number of quantization bits than a required number of quantization bits.

FIG. 11 is a schematic configuration diagram of a digital conversion circuit that employs pre-value prediction encoding, which realizes 12-bit digital encoding using an 8-bit A / D converter. This digital conversion circuit uses an analog subtractor 40 to find the difference between the current input analog signal and the signal one data before generated by the decoding circuit 32, and uses this as a prediction signal. This prediction signal is nonlinearly converted by a nonlinear conversion unit 33, and the output is digitally converted to a high speed using an 8-bit high-speed operation type A / D converter. The non-linear converter 33 includes the analog subtractor 40
Since the predicted signal obtained in is concentrated near zero,
For example, a non-linear conversion characteristic as shown in FIG. 12 is set so as to finely sample the predicted signal value near zero.

By performing such non-linear conversion, the analog input signal (predicted signal) is converted into an 8-bit digital signal whose quantization precision is fine near zero and whose quantization precision becomes coarser as the value increases.

Thus, the decoding circuit 32 linearly converts the 8-bit digital signal using a linear conversion unit 35 having input / output characteristics opposite to those of the nonlinear conversion unit 33. By this linear conversion, the quantization accuracy of the 8-bit digital signal is made uniform. The digital adder 36 that inputs the linearized digitized prediction signal is sequentially added to the value (previous value) output one data before and output as 12-bit data.

The previous value is obtained by delaying the output of the digital adder 36 by one data interval via the delay circuit 37, and multiplying the output value by a predetermined coefficient γ in the coefficient unit 38. The coefficient γ is often given as a value close to [1]. When [γ = 1], the coefficient unit 38 is unnecessary.

The previous value (the output value one data before) output from the coefficient unit 38 is fed back to the digital adder 36, so that the predicted value at the current data timing is added and generated to the output value one data before. Output. At the same time,
The previous value output from 38 (the output value one data before) is D / A
The signal is converted into an analog signal via the converter 39 and is supplied to the analog subtractor 40.

As described above, the digital conversion circuit shown in FIG. 11 obtains, as a prediction signal, a difference between a signal obtained by converting the digital conversion result one data sample before from analog and an analog input signal at the current data timing, and this prediction signal is obtained. After the nonlinear conversion, the digital conversion is performed at a high speed using an 8-bit A / D converter 34. Then, by adding the digitally converted predicted value to the digital conversion result one data sample before, a digital signal having a desired quantization bit number (12 bits) is obtained.

As a result, an inexpensive 8-bit general-purpose
A digital conversion result in the number of quantization bits can be obtained by effectively using the A / D converter 34, and the image processing in each of the above-described embodiments can be easily realized.

Here, the predictive coding is referred to as the previous value prediction in the frame. However, even if various inter-frame predictive coding, three-dimensional predictive coding, and various plane predictive coding other than the preceding value predictive are appropriately adopted, As described above, using the inexpensive high-speed 8-bit A / D converter 34, a digital conversion process of a desired quantization bit number, such as obtaining a 12-bit digital signal, can be realized.

Note that the present invention is not limited to the above embodiments. For example, in each embodiment, the image signal is converted into three primary color components R, G, B
To adjust the dynamic range, the dynamic range may be adjusted by decomposing the image into three complementary colors (yellow, magenta, and cyan).
Further, the dynamic range may be adjusted for the color difference signals (RY) and (BY). However, in this case, since the color difference signals (RY) and (BY) have positive and negative polarities, a log amplifier that performs logarithmic conversion of them has, for example, the characteristics shown in FIG. Need to be kept. In addition, the number of repetitive readings of image signals from the solid-state imaging device 1, the adjustment means of the dynamic range, and the like can be variously modified in accordance with the specifications. In short, the present invention can be variously modified without departing from the gist thereof. Can be implemented.

[Effects of the Invention] As described above, according to the present invention, the dynamic range of an image signal captured and input by a solid-state imaging device can be very simply and effectively increased, and a subject having a wide dynamic range can be obtained. Can be effectively imaged and input. In addition, a great effect in practical use can be obtained, such as an effect of improving the S / N.

[Brief description of the drawings]

FIG. 1 shows an electronic camera according to the present invention.
FIG. 2 is a schematic configuration diagram showing a first embodiment, FIG. 2 is a diagram for explaining an S / N improvement effect by cumulative addition of image signals, and FIG.
The figure shows the relationship between the dynamic range of the image signal and the dynamic range of the image monitor. FIG. 4 shows an example of the configuration of a two-dimensional filter used in the embodiment. FIG. 5 shows the dynamic range used in the embodiment. FIG. 6 shows a configuration example of a gain controller. FIG. 6 shows a dynamic range.
FIG. 7 is a diagram illustrating a modification of the gain controller, illustrating a main part thereof, and FIG. 7 is a diagram illustrating a modification for adjusting a dynamic range. FIG. 8 is a schematic configuration diagram showing a second embodiment of the present invention,
FIG. 9 is a schematic structural view showing a third embodiment of the present invention, and FIG.
FIG. 11 is a diagram showing characteristics of a log amplifier used in the fourth embodiment. FIG. 11 is a diagram showing a configuration example of a digital conversion circuit.
FIG. 12 is a diagram showing characteristics of nonlinear conversion in the digital conversion circuit shown in FIG. 1 ... solid state imaging device (AMI), 2 ... preamplifier, 3 ...
... Signal processing circuit, 4 ... A / D converter, 5 ... Adder, 6
…… Frame memory, 7 …… Video processor, 8 ……
Dynamic range control circuit, 9b, 9g, 9r ... log amplifier, 11b, 11g, 11r ... adder, 12b, 12g, 12r ... inverse log amplifier, 13b, 13g, 13r ... D / A converter, 14 , 14b, 14g, 14r ……
Bit shifters, 21a, 21b, 21c ... memory, 25 ... mass storage unit, 29 ... matrix circuit, 31 ... analog subtractor, 33 ... decoding circuit, 33 ... nonlinear conversion unit, 34 ...
A / D converter, 35: linear converter, 36: digital adder, 37: delay circuit, 38: coefficient unit, 39: D / A converter.

Claims (3)

(57) [Claims] An electronic camera for electronically imaging a subject using a solid-state imaging device and displaying the image on an image monitor. A readable solid-state imaging device, a unit that repeatedly performs imaging of a subject by the solid-state imaging device and reading of an image signal at a high speed a plurality of times within a period of the image display, and Means for performing logarithmic conversion of the image signal each time the image signal is repeatedly read; means for A / D converting the logarithmically converted image signal; and a period of the image display of the A / D converted image signal. Means for sequentially accumulating a plurality of times within the electronic camera. 2. An electronic camera for electronically imaging a subject using a solid-state imaging device and displaying the image on an image monitor. A readable solid-state imaging device, a unit that repeatedly performs imaging of a subject by the solid-state imaging device and reading of an image signal at a high speed a plurality of times within a period of the image display, and Means for performing A / D conversion on the image signal by predictive coding every time the image signal is repeatedly read out; and sequentially accumulating and adding the A / D converted image signal a plurality of times within the image display cycle. An electronic camera, comprising: 3. The electronic camera according to claim 1, further comprising means for adjusting a dynamic range of the accumulated and added image signal and outputting the adjusted image signal to the image monitor.