JPH03224368A - Electronic camera - Google Patents

Abstract

PURPOSE:To effectively input an object of a high dynamic range by image pickup by repeating pickup of an object and readout of a picture signal by a solid-state image pickup element over plural number of times at a high speed within a period of picture display, accumulating and outputting the picture signals read repetitively from the solid-state image pickup element over the period of picture display. CONSTITUTION:A picture signal read out at a high speed from a solid-state image pickup element 1 is amplified to a prescribed signal level via a preamplifier 2 and subject to clipping processing via a signal processing circuit 3 and digitized sequentially into, e.g. a 12-bit signal at an A/D converter 4. Then the picture signal digitized is stored sequentially in a frame memory 6 for each frame via an adder 5. The adder 5 adds a picture signal stored in the frame memory 6 and a picture signal of a succeeding frame read out sequentially repetitively form the solid-state image pickup element 1 and writes the result again in the frame memory 6 to add and accumulate the picture signal read out repetitively in the frame memory 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic camera that can effectively image and input a subject with a wide dynamic range and display the image on an image monitor.

[Prior Art] Recently, various solid-state image sensors such as CCD image sensors and MO3O3 time sensors have been developed, and electronic cameras that use these solid-state image sensors to electronically image a subject are, for example, video cameras and electronic still cameras. A variety of methods have been developed. This type of electronic camera records an image signal (video signal) of a subject image electronically captured and input using a solid-state image sensor on a so-called magnetic recording medium such as a videotape or floppy disk, or an IC memory card. This 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 on an image monitor such as a TV receiver is at most 4.0.
It is about dB. For this reason, the imaging capability (dynamic range) of solid-state imaging devices for boat fishing is often set at about 50 dB.

In comparison, the dynamic range of a subject to be imaged by the solid-state image sensor (electronic camera) often reaches about 80 dB. That is, compared to the dynamic range that can be displayed by an image monitor and manually captured by a solid-state imaging device, the dynamic range (signal level width) of the subject often greatly exceeds this.

If a subject with such a wide dynamic range is to be imaged and input electronically using the above-mentioned solid-state image sensor,
Saturation of the solid-state image sensor occurs in areas where the signal level is high (high brightness areas), resulting in a so-called overexposure condition. On the other hand, if an attempt is made to suppress this saturation, the portions with low signal levels (low brightness portions) will be underexposed, resulting in a so-called blackout condition. In other words, there is a problem in that signal components that do not fall within the dynamic range of the solid-state image sensor or image monitor cannot be imaged and input, nor can they be displayed.

[Problems to be Solved by the Invention] As described above, in the past, there were many subjects that had a dynamic range wider than the dynamic range of the solid-state image sensor, and it was possible to electronically capture and input the images directly using the solid-state image sensor. In some cases, there is a problem in that object information in high-level or low-level areas is lost. In other words, even though the subject has a wide dynamic range,
When this is electronically captured and input using a solid-state image sensor, the dynamic range of the subject is limited by the dynamic range of the solid-state image sensor and the image monitor, and in the end, only image signals (video signals) with a limited dynamic range are obtained. There was a problem that I couldn't do it.

The present invention was made in consideration of these circumstances, and its purpose is to effectively capture and input a subject having a dynamic range that exceeds the dynamic range of a solid-state image sensor, and to eliminate so-called blown-out highlights and blown-out shadows. It is an object of the present invention to provide a highly practical electronic camera that can be used for image display on an image monitor without causing such problems.

[Means for Solving the Problems] The present invention relates to an electronic camera that electronically captures and inputs images of a subject using a solid-state image sensor and displays the image on an image monitor, and includes the following: A solid-state image sensor that can be read out at a comparatively high speed is used, and imaging of a subject by the solid-state image sensor and readout of the image signal are repeatedly performed at high speed multiple times within the image display cycle. The present invention is characterized in that the image signals repeatedly read out from the solid-state image sensing device in this manner are cumulatively added over the period of image display and output.

Further, the present invention is characterized in that the dynamic range of the cumulatively added image signal is compressed and then output to an image monitor.

In other words, by repeatedly capturing an image of an object using a solid-state image sensor and reading out its image signal at high speed, the exposure time of the object using the solid-state image sensor can be shortened, thereby reducing the saturation of the solid-state image sensor for high-level signals. prevent from happening. The image signals obtained from this short exposure are repeatedly read out at high speed and cumulatively added to obtain an image signal with an expanded dynamic range. It is characterized in that an image signal with a wide range is obtained.

[Function] According to the present invention, the exposure of the object by the solid-state image sensor and the readout of its image signals are repeatedly performed at high speed within the image display period, and the results are cumulatively added. While keeping the range narrow, it is possible to expand the dynamic range of cumulatively added image signals by the number of cumulative additions.

As a result, even for subjects with a wider dynamic range than those of solid-state image sensors, an image signal with a wide dynamic range can be obtained by effectively capturing and inputting the subject without being subject to the dynamic limitations of the solid-state image sensor. becomes possible.

On top of that, this wide dynamic range image signal is
Since the dynamic range is compressed in accordance with the dynamic range of the image monitor and used for image display, it is possible to display images without causing problems such as so-called blown-out highlights and blown-out shadows.

[Embodiment] 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 diagram of the main parts of an electronic camera according to an embodiment.
(2) is a solid-state image sensor that electronically captures and inputs an image of a subject. This solid-state image sensor 1 basically includes a plurality of photoelectric conversion sections arranged in a matrix, and is driven by an image pickup control section (not shown) to send signal charges to each of the photoelectric conversion sections according to the amount of light of the subject. The exposure is done by the occurrence.

By sequentially reading out pixel signals corresponding to signal charges generated in each of these photoelectric conversion sections, an image signal electronically captured by the solid-state image sensor 1 is obtained.

Here, however, as the solid-state imaging device 1, an AMI (amplification type MOS imager) is used which has a function of being able to read out at high speed an image signal of a subject that has been imaged electronically. The imaging of the object by the solid-state imaging device 1 and the reading of the image signal thereof are repeated at high speed multiple times within the image display period. The image signal read out at high speed from the solid-state image sensor 1 in this way is amplified to a predetermined signal level via the preamplifier 2, and then subjected to clipping processing etc. via the signal processing circuit 3. The A/D converter 4 sequentially digitally encodes, for example, a 12-bit signal.

That is, in conventional boat fishing, the image input of the object by the solid-state image sensor l is performed by capturing the image and reading out the image signal every one field period (17 m5ec), for example, corresponding to the cycle of image display on the image monitor. Here, the solid-state image sensor 1 is driven at high speed, and the imaging and image signal reading are repeated at high speed, for example, 10 times within the one field period.

In this way, the image signals repeatedly read out from the solid-state image sensor 1 at high speed are sequentially digitally encoded as described above.

The digitally encoded image signal is then sequentially stored in a frame memory 6 frame by frame via an adder 5. The adder 5 adds the image signal stored in the frame memory 6 and the image signal of the next frame which is sequentially and repeatedly read out from the solid-state image sensor 1, and rewrites the result in the frame memory 6. By doing so, the image signals that are repeatedly read out as described above are cumulatively added to the frame memory 6. By repeating such cumulative addition of image signals over the above-mentioned image display period, for example over one field period, the dynamic range of the image signal can be expanded.
Furthermore, it is possible to improve the S/N ratio of the image signal.

That is, in this electronic camera, the electronic image capture input of the subject by the solid-state image sensor 1 is repeatedly performed multiple times (for example, 10 times) within the image display period (one field), as described above. The subject exposure time is set to be short enough. Therefore, the amount of signal charges generated in the solid-state image sensor 1 according to the amount of light from the object increases in proportion to the exposure time, and when the exposure time is set short as described above, the dynamic range of the object increases Even if the dynamic range is sufficiently wider than the dynamic range of the solid-state image sensor l, it is possible to perform exposure without causing saturation of the solid-state image sensor l. In other words, exposure is performed without saturating high-brightness areas of the subject. However, since the exposure time is short, the amount of exposure for low-luminance portions of the subject is insufficient.

By repeatedly and cumulatively adding such image signals over a plurality of times within the image display period (one field), the level of the image signal is increased by the number of repetitions, and the dynamic range is substantially increased. Expansion is planned. For example, by repeatedly reading image signals n times within one field period of image display and performing cumulative addition, the dynamic range of the cumulatively added image signal can be compared with the dynamic range of each individual image signal. The image is enlarged by n times.

Note that random noise components such as dark current mixed into the image signal when the solid-state image sensor 1 exposes the object increase exponentially with the length of the exposure time. For example, when the exposure time (
When the noise level is reduced to (1/n), the noise level is reduced to (1/fW) as illustrated in FIG.

Specifically, when the exposure time is set to (1/10), the noise level becomes (1/ff1), and an S/N improvement effect of 10 dB can be expected. Further, the increase in noise components due to the above-mentioned cumulative addition of image signals is only increased by f times by n times of cumulative addition, since the noise components themselves have randomness. As a result, the S/N of the image signal cumulatively added over n times is improved to Cl/J (lower)X(1/f1), that is, (1/n).

In this way, solid-state imaging is achieved by the above-mentioned high-speed repeated readout of image signals from the solid-state imaging device 1 that electronically captures and inputs images of the subject, and by the cumulative addition of the image signals 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, the dynamic range is expanded, and the S/N ratio is improved.

In other words, by cumulatively adding image signals inputted within the dynamic range of the solid-state image sensor l over n times, the dynamic range is expanded n times, and the S/N is (1 /n) times. This means that when photographing a high dynamic range subject with a wide brightness level range compared to the dynamic range of the solid-state image sensor 1, the dynamic range can be compressed by short-time exposure as described above, and expanded by cumulative addition through high-speed readout. This means more effective image input. As a result, for example, by effectively using the solid-state image sensor 1 having a dynamic range of 50 dB,
It becomes possible to input an image of a subject having a dynamic range of 80 dB and set the dynamic range of the image signal to 80 dB.

Moreover, in order to take an image of such a high dynamic range object, it is sufficient to simply change the driving conditions of the solid-state image sensor 1 as described above and provide a means for accumulatively adding image signals that are repeatedly read out at high speed. In terms of hardware, it is very simple. Therefore, make it very simple,
It becomes possible to effectively expand the dynamic range of the image signal to be imaged and input.

By the way, as mentioned above, the video processor 7 inputs the image signal whose dynamic range has been expanded by cumulative addition.
separates and extracts the luminance signal component Y from the image signal, and also decomposes the image signal into three primary color components of R, G, and B, respectively. The dynamic range control circuit 8 inputting this luminance signal component Y controls the dynamic range of the image signal (80 dB in the above example) on the image monitor (
For example, a compression coefficient for compression conversion to a dynamic range (for example, 40 dB) possessed by a TV receiver) is determined.

In other words, when displaying an image signal with a wide dynamic range as described above using an image monitor with a dynamic range of less than 40 dBL, if the offset is set to [0], the low frequency range of the image signal is 40 dBL or less, as shown in A in Figure 3. The image cannot be displayed, and the high-brightness portion becomes blown out due to saturation.

On the other hand, 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, it becomes impossible to display an image at a high range of 40 dBL of the image signal, as shown in FIG. 3B. In this case, the low luminance level portion of the image signal becomes a black-out state.

Therefore, the dynamic range control circuit 8 compresses the dynamic range of the image signal as shown in C in FIG. The compression coefficient is determined according to the dynamic range of the image signal.

However, in this embodiment, the dynamic range of the image signal (separated three primary color components R, G, B) can be easily compressed.
In order to do this effectively, the image signal separated into the three primary color components R, G, and B and the luminance signal component Y are each subjected to logarithmic transformation, and then the dynamic range controlled signal is subjected to antilogarithmic transformation. and is configured to restore the original signal form.

Regarding the method of controlling this dynamic range,
For example, the method proposed in Japanese Patent Application Laid-Open No. 63-232591 can be used as is. Therefore, here:
This dynamic range control will be briefly explained.

That is, the dynamic range control circuit 8 takes in the luminance signal component Y by logarithmically converting it into log Y via the log amplifier 8a, and converts the luminance signal component Y into log Y via the two-dimensional filter 8b configured as shown in FIG. Remove ingredients. This two-dimensional filter 8b is a two-dimensional LPF according to 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. 4, for example.
By correcting the brightness signal obtained through the above, clipping it, and subtracting it from the brightness signal component, the uneven illuminance component is removed.

Then, the signal from which the uneven illuminance component has been removed is passed through the two-dimensional filter 8b to a dynamic range gain controller (DGC) configured as shown in FIG.
) 8c, and an output logaY'' (where α is a gain adjustment coefficient and β is a dynamic adjustment coefficient) is obtained by matching the dynamic range of the luminance signal component Y to the dynamic range of the image monitor.

Note that the same output can be obtained even if the circuit portion shown surrounded by the dotted line in FIG. 5 is simplified and configured as shown in FIG. 6, for example. The ratio log (αY'/Y) between such log αYj and the luminance signal component 10gY is obtained by the adder 8e, and this is used as a compression coefficient indicating the degree of dynamic range compression to be performed.

That is, this DGC8c performs feedback control so that the standard deviation value of one screen (or one part thereof) of the luminance signal is constant. In other words, by feeding back the amplified error value between the average value of the luminance signal and its gain reference voltage to the adder,
The gain is adjusted so that the average value of the luminance signal is equal to the gain reference voltage, thereby making the dynamic range constant. Therefore, D G C8c with a constant dynamic range in this way
If we calculate the ratio og (αYβ/Y) between the output logαYβ and the luminance signal component IogY, we can calculate the value as described above. This is a compression coefficient that indicates whether or not it can be adjusted to the range.

The three primary color components R, G, and B of the image signal converted and outputted by the video processor 7 are each converted to a log amplifier 9.
logR, IogG via r, 9g, 9b
.

It is logarithmically transformed as IogB. Each of these signals 1ogR, IogG, logB is sent to the delay circuit 1.
0r.

Adders 11r, 11g, ll via 10g, 10b
The dynamic range compression coefficient log (αY' /Y
) are added respectively. As a result, the adder 11r
, l1g, and llb are each output as follows: 1ogR+log(αYβ/Y) −logR(αYβ/Y)
β/Y)ogG+log(αY'/Y) = lo
gG (αYB/Y)IogB+log(αY'/Y
) = logB ((2Yβ/Y), which is then subjected to antilogarithmic transformation via inverse log amplifiers 12r, 12g, and 12b, and the signals output via D/A converters 13r, 13g, and I3b are (αYβ /Y) R, (αYβ/Y) G(αYβ/Y)
B is a signal component whose dynamic range has been compressed.

Thus, by adjusting the dynamic range of the output image signal using such a dynamic range adjusting means, it is possible to effectively match the required high dynamic range image signal to the dynamic range of the image monitor as described above. It becomes possible. As a result, as shown in FIG. 3, it becomes possible to effectively display the image signal without causing blown-out highlights or blown-out shadows.

In addition, in the embodiment described above, the dynamic range control circuit 8
, illuminance unevenness was removed using two-dimensional filtering processing, and then a luminance signal with dynamic range adjustment was obtained using D G C8c, and from this, a compression coefficient for dynamic range control was obtained. It is possible to suppress the dynamic range of the luminance signal within a certain range simply by removing illuminance unevenness through filtering processing.

Therefore, in such a case, for example, in the two-dimensional filter 8c shown in FIG. 4, the output of the clipping circuit for adjusting the luminance signal level is directly converted into the three primary color components 1ogR and logB which are logarithmically converted.

It is also possible to obtain the compression coefficient for 10gG and apply it to subtracters 31r, 31g, and 31b, respectively, as shown in FIG. 7, for example, instead of the adders fir, l1g, and llb. In other words, if uneven illumination of the subject is removed, the dynamic range of the image signal can be suppressed to 40 to 50 dB, so even if the compression coefficient obtained from the two-dimensional filter 8c is used as is, it will be effective to some extent. Dynamic range adjustment can be performed. Also, if you do this, the above-mentioned D G
Since the C8c and the like are not required, the configuration can be simplified.

By the way, the above-mentioned embodiment is an example of a video movie camera that continuously captures and inputs an image of a subject at each image display cycle and displays the image, but recently, still images are captured and input using a solid-state image sensor. Various electronic still cameras have also been developed. For example, while monitoring images that are continuously captured manually using a solid-state image sensor built into an endoscope, the resulting screen is captured as a still image and stored in mass storage such as a digital VTR or digital video file. will be held.

When the present invention is applied to such a system, it may be configured as shown in FIG. 8, for example.

In FIG. 8, the same parts as in FIG. 1 described above are designated by the same reference numerals.

That is, in this embodiment, the processor 7 also obtains the color difference signals (RY) and (B-Y) at the same time. Then, the color difference signals (RY), (B-Y) and the luminance signal Y are respectively taken into the memories 21a, 21b, and 21c over one field according to the release timing.

Then, each signal component taken into these memories 21a, 21b, and 21c is sequentially read out via the parallel/serial converter 22, and the data compression section 23. Recording modulation section 24
The data is serially subjected to data compression processing and recording modulation processing, and then recorded in the mass storage unit 25.

The image signal to be read and reproduced from the mass storage section 25 is decoded and reproduced from the demodulation section 2B via the data decoding section 27, and the above-mentioned color difference signal (R-Y), (B -Y) and a luminance signal Y. Thereafter, the matrix circuit 29 outputs the color difference signal (R-Y).

(B-Y) and the luminance signal Y, three primary color components R and G are obtained.

Try to find each B.

The above-mentioned dynamic range adjustment section of the embodiment that constitutes such an image signal recording and reproducing section is required to process the image signal required from the solid-state image sensor 1 or to use a mass storage section. It is sufficient to incorporate a switch circuit 30 for switching whether or not to process the image signal read out from 25.

According to such an embodiment, the high dynamic range image signal input as described above is processed with good quality in the form of its luminance signal Y and color difference signals (R-Y) and (B-Y). It can be stored and stored in the mass storage unit 25.

Then, it becomes possible to effectively adjust the dynamic range of the recorded and saved image signal with a high dynamic range and to display the image on an image monitor.

Further, in each of the embodiments described above, the image signal is logarithmically converted in order to control the dynamic range of the image signal, but this logarithmic conversion process is applied to each signal read out from the solid-state image sensor 1. Also good.

That is, in each of the embodiments described above, it is necessary to quantize the noise component of the image signal in order to ensure the dynamic range of the image signal, and the number of quantization bits is about 12 bits. However, the 12-bit high-speed A/D converters currently in use, especially those capable of operating at television signal rates, are very expensive. Moreover, as images become higher in resolution and their frequency bands become wider,
An A/D converter with a quantization precision of about 12 bits may not be able to handle the above-mentioned image processing.

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

Therefore, as shown in FIG. 9, the image signal repeatedly read out from the solid-state image sensor 1 at high speed is input to the video processor 7, and at this point the luminance signal Y and the three primary color components R, G, B
and logarithmically transform each of these signals. After each of the logarithmically transformed signal components is digitally encoded into 8 bits, each of these signal components is written into the frame memories 6a, 6b, 6g, and 8r, respectively, and cumulatively added. This cumulative addition expands the dynamic range of each signal component. Since each signal component whose dynamic range has been expanded becomes, for example, a 12-bit digital signal, these are compressed to 8 bits via bit shifters 14a, 14b, 14g, ]4r, and then the dynamic range described above is compressed to 8 bits. It is used for compression processing of the clean range.

By configuring the signal processing circuit in this way, it becomes possible to handle 8-bit signals in most of the signal systems, making it possible to construct an electronic camera using existing general-purpose image processing circuit components (semiconductor ICs, etc.) as they are. becomes possible. Also A
Although the noise component is greatly amplified by the log amplifier installed before the /D converter, the S/N improvement effect of the cumulative addition works as described above, and the cumulatively added image signal is converted into bits. Since the signal is shifted, it is possible to suppress the noise component to a very small level. As a result, S/H
This makes it possible to display a good image.

Next, another embodiment for reducing the number of quantization bits of the A/D converter will be shown below. In this embodiment, for example, prior predictive coding is employed, and desired digital conversion is performed on the image signal using an A/D converter with a smaller number of quantization bits than the required number of quantization bits. Specifically, the three-dimensional array of image data is divided into blocks into matrix regions of a predetermined size, and each of these blocks is converted into three-dimensional orthogonal transform (DCT) coefficient data. Then, the image data is digitally converted by predictive coding from the origin position in each block.

FIG. 11 is a schematic diagram of a digital conversion circuit employing previous value predictive coding, which realizes 12-bit digital coding using an 8-bit A/D converter. This digital conversion circuit uses an analog subtracter 31 to find the difference between the current input analog signal and the signal generated by one data previous in the decoding circuit 32, and uses this as a predicted signal. This predicted signal is subjected to non-linear conversion in a non-linear conversion section 23, and the output thereof is converted into a high-speed digital signal using an 8-bit high-speed operation type A/D converter 34. Since the predicted signal obtained by the analog subtracter 31 concentrates around zero, the nonlinear converter 33 uses a nonlinear converter, for example, as shown in FIG. Conversion characteristics are set.

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

The decoding circuit 32 linearly converts the 8-bit digital signal using a linear converter 35 having input/output characteristics opposite to those of the non-linear converter 33. This linear conversion equalizes the quantization precision of the 8-bit digital signal. A digital adder 36 inputting this linearly converted digital signal 41 sequentially adds the data to the value outputted one data before (previous value) and outputs it 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 multiplier 38. Note that the coefficient γ is often given as a value close to [1]. Further, when [γ=11], the coefficient multiplier 38 is unnecessary.

By feeding back the previous value (output value of one data previous) output from this coefficient unit 38 to the digital adder 36, a predicted value at the current data timing is added to the output value of one data previous. is output. At the same time, the previous value (output value of one data previous) outputted from the coefficient unit 38 is D
The signal is converted into an analog signal via the /A converter 39 and provided to the analog subtracter 31.

In this way, the digital conversion circuit shown in FIG. 11 calculates the difference between the signal obtained by analog conversion of the digital conversion result of one data sample before and the analog input signal at the current data timing as a predicted signal, and converts this predicted signal into a predicted signal. After non-linear conversion, an 8-bit A/D converter 24 is used to perform high-speed digital conversion. The desired number of quantization bits (
It is designed to obtain a 12-bit) digital signal.

As a result, a general-purpose 8-bit A that can operate at high speed and is inexpensive.
By effectively using the /D converter 24, a digital conversion result with a quantization bit number can be obtained, and image processing in each of the embodiments described above can be easily realized.

In this case, the predictive coding is used as the previous value prediction within a frame, but even if interframe predictive coding, three-dimensional predictive coding, or various planar predictive coding other than the previous value prediction are adopted as appropriate, As described above, by using the inexpensive high-speed 8-bit A/D converter 24, it is possible to realize digital conversion processing with a desired number of quantization bits, such as obtaining a 12-bit digital signal, for example.

It should be noted that the present invention is not limited to each of the embodiments described above. For example, in each embodiment, the image signal is divided into three primary color components R, G,
Although the dynamic range was adjusted by converting it to B, the dynamic range could also be adjusted by separating it into three complementary color components (yellow, magenta, and cyan). Further, the dynamic range may be adjusted for the color difference signals (R-Y) and (B-Y). however,
In this case, the color difference signals (R-Y) and (B-Y) have positive and negative polarities, so a log amplifier for logarithmically converting these should have characteristics as shown in Figure 10, for example. There is a need. In addition, the number of times the image signal is repeatedly read out from the solid-state image sensor 1, the means for adjusting the dynamic range, etc. can be modified in various ways according to the specifications.In short, the present invention can be modified in various ways without departing from the gist thereof. It can be implemented.

[Effects of the Invention] As explained above, according to the present invention, it is possible to very simply and effectively increase the dynamic range of an image signal captured and inputted by a solid-state image sensor, and to achieve a high dynamic range. It becomes possible to effectively image and input the subject. Furthermore, great practical effects can be obtained, such as the ability to improve the S/N ratio.

[Brief explanation of drawings]

The figure shows an electronic camera according to the present invention.
The figure is a schematic configuration diagram showing the first embodiment, Figure 2 is a diagram for explaining the S/N improvement effect by cumulative addition of image signals, and Figure 3 is a diagram showing the dynamic range of the image signal and the dynamic range of the image monitor. FIG. 4 is a diagram showing an example of the configuration of a two-dimensional filter used in the example, FIG. 5 is a diagram showing an example of the configuration of the dynamic range/gain controller used in the example, and FIG. 7 is a main part configuration diagram showing a modification example of the dynamic range and gain controller.
The figure is a diagram for explaining a modification example for dynamic range adjustment. Further, FIG. 8 is a schematic configuration diagram showing a second embodiment of the present invention,
FIG. 9 is a schematic configuration diagram showing the third embodiment of the present invention;
Figure 0 shows the characteristics of the log amplifier used in the fourth embodiment, Figure 11 shows the configuration example of the digital conversion circuit, and Figure 12 shows the characteristics of nonlinear conversion in the digital conversion circuit shown in Figure 11. FIG. ■... Solid-state image sensor (AMI), 2... Preamplifier, 3... Signal processing circuit, 4... A/D converter, 5...
... Adder, 6... Frame memory, 7... Video processor, Dynamic range control circuit, 9b
, 9g, 9r...log amplifier, 11b, 11g, 11
r-...Adder, 12b, 12g, 12r...Reverse log amplifier, 13b, 13g, 13r-D/A
Converter, 14a, 14b, 14g, 14r=...
Bit shifter, 21a, 21b, 21c... memory, 25... mass storage unit, 29... matrix circuit, 31... analog subtracter, 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 (2)

[Claims] (1) In an electronic camera that electronically captures an image of a subject using a solid-state image sensor and displays the image on an image monitor, a solid-state image sensor that can read out the input image signal at a high speed compared to the image display cycle. an element, means for repeatedly performing imaging of a subject by the solid-state imaging device and reading out the image signal thereof at high speed a plurality of times within the image display cycle; and an image signal repeatedly read out from the solid-state imaging device. an electronic camera comprising: means for accumulatively adding over the period of the image display. (2) A solid-state image sensor capable of reading out an input image signal at a high speed compared to the image display cycle; and a solid-state image sensor capable of reading out an image signal inputted at a high speed compared to the image display cycle; means for accumulatively adding image signals repeatedly read out from the solid-state image sensing device over the period of image display; An electronic camera characterized by comprising means for adjusting and outputting the adjusted image to an image monitor.