Abstract: A gamma correction method and system, which performs a gamma correction on an n-bit video signal to thus generate a gamma correction value. At first, a first primary index and a first sub-index are obtained by performing an index mapping on a value of the video signal. Next, a first gamma value is obtained by performing a table lookup on the first primary index and the first sub-index. Next, a second primary index and a second sub-index are obtained by performing the index mapping on the first gamma value. Next, multiple thresholds are obtained by performing the table lookup on the second primary index and the second sub-index. Finally, the value of the video signal and the multiple thresholds are compared to accordingly correct the first gamma value and generate the gamma correction value.

Abstract: An automatic gain controller and the controlling method thereof are disclosed. The automatic gain controller includes a first multiplexer for receiving an input signal and a gain and generating a first output, a second multiplexer for receiving a signal time constant and a gain time constant and generating a second output, a filter electrically connected to the first multiplexer and the second multiplexer for generating one of a signal-energy and an actual gain in response to the first output and the second output, a signal-energy processing device electrically connected to the filter, the first multiplexer and the second multiplexer for generating the gain and the gain time constant in response to the signal-energy, and a multiplier electrically connected to the filter for multiplying the actual gain by the input signal to generate an output signal.

Abstract: A device for the FPN correction of image signals which are generated by image cells of an image sensor comprises a discriminator for determining in which value range out of at least two value ranges a value of an image signal of an image cell is located at a predetermined instant of time. The result determined by the discriminator is feed to a correction device. The correction device selects correction coefficients from a plurality of sets of correction coefficients as a function of the result determined by the discriminator, and a transformation unit calculates the corrected value for the image signal by using the selected correction coefficients.

Abstract: Providing a signal processing method for image synthesis with reduced computation load, a signal processor circuit for image synthesis with reduced computation load which allows manufacturing at a low production cost, and imaging apparatus which uses the signal processing method and the signal processor circuit. The signal processor circuit includes: a table storage area for storing an LUT; a table overwriting section for overwriting an LUT written into the table storage area with another LUT; and an arithmetic operation section for performing arithmetic operation on a first digital signal or a second digital signal based on the LUT written into the table storage area each time an LUT is written into the table storage area and synthesizing the first digital signal and the second digital signal.

Abstract: A photographic image is divided into a central area and a surrounding area, and video signals for the central and surrounding areas are integrated by an area integrator circuit. When an operator of video camera attached to a notebook personal computer is to photograph himself/herself with an imager of the video camera pointing toward the operator, a control microcomputer causes the integration result for the former to be multiplied by a larger weighting before both are summed. The control microcomputer generates exposure information according to the result, and compares the exposure level indicated by this information with the reference level to control an electronic shutter of an imaging device and the gain of an amplifier circuit so that the exposure level matches the reference level. Thus, the exposure of the video camera can be adjusted to an appropriate level. If the imager points towards an object on the opposite side of the operator, exposure control is performed as usual.

Abstract: A gain characteristic correctable dynamic range enhancement system (DRES) receives input signals from an imager device connected to a correlated double sampling (CDS) circuit for receiving the video signal from the CCD imaging device. The dynamic range enhancement system includes a variable gain amplifier (VGA), and a limited bit-width analog-to-digital converter (ADC) which digitizes the analog signal received from the VGA. The output of the ADC is provided to an initial bit range position of a wider bit-width shifter connected to the output of the ADC. The DRES system correctably extends the dynamic range of the imager device, subject to offsets providing linearity corrections at predetermined trip points, subject to determined offset values, to ensure that there are no discontinuities in the system transfer function.

Abstract: Disclosed is an automatic video gain control circuit, which includes an analog to digital converter, an envelope detector and an extreme value detector. The analog to digital converter converts an analog video signal to a digital video signal. The envelope detector detects a baseband amplitude signal according to the digital video signal. The extreme value detector generates an extreme value to control RF signal gain.

Abstract: The present invention provides a gamma-correction circuit, which is capable to decrease the noise in graphic signal or make the noise not clearly sensible while carrying out gamma-correction on the graphic signals. In the circuit, a high-pass filter is used to decrease the noise in a graphic signal, a gamma-correction section is used for carrying out gamma-correction on the noise suppressed graphic signal, meanwhile a threshold handling section is used for threshold treatment on the high frequency component of the graphic signal to decrease noise, and then the output of the threshold handling section is combined with the gamma-corrected graphic signal through an adder.

Abstract: A system, method and medium correcting brightness of an image, and more particularly, a system, method and medium correcting brightness of an acquired image to achieve a target brightness. The system includes an initial brightness sensing unit to sense an initial brightness of the image from an initial exposure, and an image correction unit to correct the brightness of the sensed initial image toward a target brightness using predetermined brightness information corresponding to a sensed brightness environment of the image.

Abstract: Automatic gain control is provided for a confocal imaging system to improve the quality of images produced by the system. The confocal imaging system utilizes an illumination source, such as a laser, to produce illumination which enables imaging of an object. The automatic gain control is provided by an automatic gain controller which receives a raster scan video of two-dimensional frames of images from the confocal imaging system, converts the raster scan video into pixels, where each pixel has a brightness value, and then counts, in each frame, the number of pixels which are too bright, the number of pixels which are too dim, and the total number of pixels.

Abstract: Image signals outputted from a CCD to an image signal processing circuit, which performs A/D conversion, YC signal processing to convert the image signals into video signals of NTSC or the like and outputs video signals after D/A conversion. A microcomputer receives the video signals from the image signal processing circuit and determines a brightness level of the video signals. An EEPROM stores a data table showing the relationship between a correction amount and the brightness level, and the microcomputer obtains the correction amount from the EEPROM. The microcomputer corrects the video signals according to the correction amount before the D/A conversion, and the image signal processing circuit outputs the corrected video signals to a displaying device controlling circuit, and a displaying device displays an image.

Abstract: A processing system for a charge coupled device (CCD) or CMOS imaging system includes a correlated double sample (CDS) circuit for receiving data from an imager, a variable gain amplifier (VGA) having amplifiers of selectable current level to enable reduced data resolution in a preview display, a low power mode analog-to-digital converter (ADC) having a selectable narrow bit-width output and coupled to said VGA circuit, and a gain circuit coupled to said ADC. The single chip low-power analog front end produces digitized CCD data in either 13-bit, 12-bit or 10-bit formats at a first current level and 9-bit, 8-bit, or 6-bit formats at a second current level. The VGA amplifier includes symmetrical subcircuits which are independently actuable to enable full or reduced data resolution levels respectively for still image capture operation and video previewing on a separate preview screen.

Abstract: A method for producing an extended color gamut luminance-chrominance digital image from a captured digital image includes determining an estimate of the colors of the captured digital image of an original scene and further processing to produce an extended range output RGB image value including values outside the range that can be displayed on the output image display device, and producing an extended color gamut luminance-chrominance digital image by transforming the extended range output RGB image values to a luminance-chrominance representation.

Abstract: Automatic control method and system for EBCCD sensor. The invention relates to a novel protective method of operating the Electron Bombarded Charge Coupled Device (EBCCD), a recently developed, high sensitivity, low noise, and expensive focal plane array sensor. In particular, the invention provides a method for operation that automatically controls the EBCCD gain at a very high rate. This allows i) for sensor damage protection from too much light, ii) for extension of sensor service life by reducing gain in periods of non-use, and iii) for automatic gain adjustment to rapidly compensate for variations in scene brightness.

Abstract: An image input system includes a solid state image pickup device and a preprocessor for performing correlated double sampling amplification on an output of the image pickup device and outputting a video signal. The preprocessor has a correlated double sampling amplifier for outputting signal information corresponding to a difference voltage between the black level in a feedthrough period of the image pickup device and a signal level in a charge signal output period; and an offset cancelling circuit for cancelling an offset voltage corresponding to the difference voltage in a state where the image pickup device is optically interrupted to the input terminal of the correlated double sampling amplifier. The correlated double sampling amplifier cancels out the offset voltage and the offset cancelling voltage as signal components of polarities opposite to each other, so that circuits following the correlated double sampling amplifier are not influenced by the offset voltage.

Abstract: A video signal processing circuit converting a color image represented using a plurality of primary color signals into a monocolor image is provided. The video signal processing circuit includes: a chroma adjustment unit adjusting the chroma of the plurality of input primary color signals; a gain correction unit provided for each of the primary color signals, correcting gain on the primary color signals whose chroma is adjusted in the chroma adjustment unit; and a control unit instructing the chroma adjustment unit to adjust the chroma and instructing each of the gain correction units to correct the gain.

Abstract: A digital camera simulates the use of fill flash. The camera takes a series of photographs of a scene at various focus distances. The photographs are stored, along with their corresponding focus distances. The photographs are analyzed to determine the distance to objects at various locations of the scene. Regions of a final photograph are selectively adjusted in brightness based on the distance information to simulate the effect that would have resulted had fill flash been used.

Abstract: An automatic gain control device for an electronic endoscope is provided and comprises a controllable gain amplifier, an A/D converter, a histogram circuit, and a CPU. The controllable gain amplifier amplifies image signals from an imaging device. Amplified image signals from the controllable gain amplifier are input to the A/D converter. A histogram of the amplified image signals from the controllable gain amplifier is produced by the histogram circuit when an image taken in a white-balance test accessory is taken. By using the CPU, the gain of the controllable gain amplifier is adjusted in accordance with the determination of whether a saturated pixel exists for signals in the tolerance range of the A/D converter, so that a linear region of the image signals from the controllable gain amplifier substantially coincides with the tolerance range.

Abstract: The present invention provides an image capturing apparatus, which comprises a plurality of photoelectric converter-containing pixels that are positioned horizontally and vertically and a gain circuit, has a gain controller that can control the gain of the gain circuit in N stages (where N is an integer equal to or greater than 2). The gain circuit outputs each of a plurality of signals given by the product of the output signal from one of the plurality of pixels and the gain in each stage of the N stages.

Abstract: An image-sensing apparatus has an area sensor 1 that outputs image data by logarithmically converting the brightness of light incident thereon, a black-level detector 2 for detecting the black level BL of the image data at which the image data has the lowest signal level, a white-level detector 3 for detecting the white level WL of the image data at which the image data has the highest signal level, a calculation formula determiner 4 for determining, in accordance with the detected black and white levels BL and WL, the formula to be used to convert the signal level of the image data, and a dynamic range converter 5 for converting the signal level of the image data using the calculation formula determined by the calculation formula determiner 4.

Abstract: The objects of the present invention are to provide an electronic camera which is able to precisely evaluate the type of a subject and perform an optimal gray-scale transformation on the image of the subject. The electronic camera comprises: an histogram creation unit for creating an intensity histogram of an image obtained with an image sensor; and a setting unit for setting a gray-scale transformation characteristic to be applied to the image according to the created intensity histogram. Using the created histogram makes it possible to precisely evaluate the type of the subject and set an optimal gray-scale transformation characteristic.

Abstract: For a digital imaging device having automatic gain control, a system and method have been provided for noise compensation in low-light conditions. The method comprises: receiving digital image information; compressing the image information; supplying the compressed image information; monitoring an automatic gain control signal; comparing the monitored gain control signal to a predetermined threshold gain value; in response to monitoring a high gain control signal, selecting a low-light processing algorithm; and, in response to the low-light algorithm, controlling the volume of the supplied compressed image information. Selecting a low-light processing algorithm includes selecting an algorithm that limits decreases in the compression ratio by changing parameters in a compression algorithm. Alternately, the low-light processing algorithm, prior to compressing, filters noise from the received digital image information.

Abstract: The present invention has an object to provide a gradation correcting apparatus for correcting the gradation of the white side of a video luminance signal. The gradation correcting apparatus is provided with a maximum value detector 101 for detecting a maximum value of a luminance signal S101, a white comparator 102 for comparing the luminance signal S101, a maximum luminance value S111 detected by the maximum value detector 101, and a first white threshold value S103, a white linear converter 103 for performing linear conversion on the luminance signal S101 on the basis of the maximum luminance value S111, the first white threshold value S103, and a second white threshold value S104, and a white controller 104 for correcting the luminance signal S101 on the basis of the result of the comparison in the white comparator 102, the output of the white linear converter 103, and the second white threshold value S104.

Abstract: An electronic camera apparatus reads out, from an image sensing device, an image signal which represents a color image constructed by a number of pixels to which predetermined colors are assigned and has pieces of luminance information with analog values representing luminances of the pixels, the luminance information being discrete on a time axis, and generates a desired image from the image signal. The apparatus has a luminance correction section.

Abstract: A method and apparatus for adjusting, on a pixel-by-pixel basis, the gain and offset in an AFE as the pixels are sequentially processed. Although the method can be used for any purpose, it is directed in particular to light source non-linearity, such as edge effects of a scanner. A unique clocking method clocks the gain and offset values into the register at a higher clock rate than the image sampling rate.

Abstract: In performing automatic white balance of a digital image, a signal is obtained from an image sensor, which represents data corresponding to an image. A plurality of channels is obtained from the signal. A mean value for each of the plurality of channels is determined using a histogram. An average dynamic range is determined from the signal using a histogram. A difference or ratio between one or more of the mean values and the average dynamic range is determined, and that difference or ratio defines a white balance correction. The white balance of the image is then adjusted using the white balance correction.

Abstract: The object of the present invention is to improve the quality of picture in the image.

Abstract: The present invention relates to an image processor and an image processing method for compensating gradation by effectively avoiding drop of partial contrast through application to an image processor such as television receiver, video tape recorder, television camera and printer or the like. A domain to which an input image data belongs is judged, for example, with reference to the low frequency element r (i, j) of the pixel value x (i, j) and the signal level x (i, j) of the image data forming an input image VT is compensated on the basis of the result of judgment r(i, j).

Abstract: The invention provides a method and apparatus for reducing image lag in CMOS active pixel sensors at low light levels by controlling the reset level. By ensuring that the reset level is independent of the preceding signal level, the problem of image lag can be avoided. Always resetting a photodiode to a fixed voltage is a hard reset. The maximum signal swing is limited by the reset level and the column readout amplifier. If the column circuits are not modified, using hard reset can reduce the maximum signal swing. However in dark images only a portion of the full scale is used. Therefore the amplifier gain setting can be used to determine whether to use a hard reset or soft reset. This method and apparatus for using hard or soft reset dependent on signal level improves image quality at low light levels without compromising performance at high illumination.

Abstract: A programmable gain amplifier having three separately programmable amplifiers. A programmable transconductance amplifier is followed by a programmable transimpedance amplifier, then a programmable switched capacitor amplifier. In one embodiment, this programmable gain amplifier is implemented in an analog front-end (AFE) circuit. One AFE embodiment provides a coarse pre-gain offset a black reference level sampler, and a fine post-gain offset in the programmable switched capacitor amplifier. In one embodiment, an ADC reference is sampled, and is subtracted directly from the video signal in the switched capacitor amplifier so that the zero level of the video signal is made to correspond to the zero level of the ADC.

Abstract: A digital-signal-processing circuit comprising an LUT memory used for storing a gamma-correction LUT used for carrying out gamma correction on an input digital video signal, and a front-stage signal-processing unit provided at a stage preceding the LUT memory and used for carrying signal processing, such as contrast adjustment, after the input digital video signal having a typical width of 8 bits is subjected to signal processing, such as contrast adjustment, in the signal-processing unit to be transformed into a digital video signal with a width of 11 bits. The 11-bit digital video signal is supplied to the LUT memory having an output bit count of 10 bits, which is smaller than the 11-bit width of the digital video signal supplied to the LUT memory but greater than the 8-bit width of the digital video signal input to the signal-processing unit.

Abstract: The invention is a method and apparatus to extend the signal range of a digital image beyond the nominal sensor or data format range. The method and apparatus automatically acquires a scaled series of source data, applies noise reduction to the source data, and constructs a scaled composite with usable signal ranges greater than that of the individual data sources. Applied to digital images, the invention permits presentation and analysis of all signals from a subject in a single composite or an image resulting from the method and apparatus of the present invention. The present invention overcomes two defects in prior art systems: increased noise in the resultant composite image arising from rescaling of component images and dependence on evaluating image content to determine image scaling. Because this invention can be automated, it can be applied in numerous fields requiring high throughput.

Abstract: An automatic gain controlling circuit controls a gain of a video signal from an imager having an electronic shutter function according to a gain control signal. An average detecting circuit detects an average level of a luminance signal of the video signal. An automatic exposure controlling circuit generates the gain control signal according to the luminance average level in response to a mode signal indicative of the cycles per second of the ac line and generates a timing signal corresponding to the ac line and a shutter speed control signal together with electronic shutter control signal generation circuit at a unit of the voltage variation cycle of the ac line according to the luminance average level such that a shutter interval of the imager is changed stepwise and each of the shutter intervals is an integer times the voltage variation cycle of the ac line.

Abstract: In a CMOS image sensor, it is important to control the exposure time or gain. For varying changes in ambient light, the exposure time of the array must be changed. The present invention describes a method for controlling the exposure time or gain. Each of the intensities of the pixels in a frame is analyzed to provide an indication of the number of pixels having an intensity above or below multiple predetermined thresholds. This information is then used to change the exposure time. The magnitude of change in the exposure time is also determined by the number of pixels having an intensity above or below multiple predetermined thresholds, as the case may be.

Abstract: A method is described for detecting brightness signals from a multiplicity of light-sensitive sensor elements, in particular CCD lines or arrays, in which the brightness signals are amplified in such a way that an A/D converter which digitizes the amplified brightness signals works in its permissible working range. For the brightness signal of a predetermined sensor element, the gain is reduced in steps, preferably in binary steps, from a maximum gain factor down to a working value at which the A/D converter works in the permissible working range. For each following sensor element, the working value of the respective preceding sensor element is used as the maximum gain factor. The number of changeover operations of the amplifier is considerably reduced and thus the detection time is shortened.

Abstract: A digital programmable gain stage for adjusting the gain of an input signal. A fine gain adjustment circuit sets gains between 1 and 2 (0-6 dB). A coarse gain adjustment stage adjusts the gain by multiples of 2. An input signal is multiplied by the fine gain adjustment factor, and then the coarse gain adjustment stage multiplies or divides the result by a multiple of 2. This architecture allows for gain adjustments from −24 dB to +66 dB in steps of 0.006 dB, using 14 bit resolution. Any number of gain ranges and gain resolutions are feasible with the current design by changing the bit width of the individual components.

Abstract: By flexibly coping with both image sensors of a CCD sensor and a CMOS sensor without providing any external circuit, a signal processing is performed. In a sensor selecting switch provided in an image-sensor signal-processing circuit, first and fourth switches are turned on when the CMOS sensor is connected, and second and third switches are turned on when the CCD sensor is connected. The sensor selecting switch is controlled by a control signal generated in a control circuit, based on sensor selection data which is stored in a register and which is data for selecting the CCD or CMOS sensor. By so doing, even if polarity of an output signal of the image sensor is reversed, a normal signal is inputted to both inputs of the CDS amplifier, whereby it is possible to flexibly cope with both of the CCD and CMOS sensors.

Abstract: A digital camera (10) includes a CCD imager (16). A long-time exposure image signal obtained by a long-time exposure of the CCD imager (16) is applied to a terminal (S1) of a switch (SW1), and a short-time exposure image signal obtained by a short-time exposure of the CCD imager (16) and a gain adjustment is applied to a terminal (S2) of a switch (SW2). A CPU (44) controls the switch (SW1) by comparing a Y level of the long-time exposure image signal with a reference value Ys so as to generate a combined image signal. More specifically, the CPU (44) connects the switch (SW1) with the terminal (S1) when a condition of Y level≦Ys is satisfied, and connects the switch (SW1) with the terminal (S2) when a condition of Y level>Ys is satisfied. The CPU (44) detects a color deviation degree of an object prior to generation of the combined image signal and reduces the reference value Ys on the basis of a detection result.

Abstract: An image pickup element including: a plurality of pixels that pick up an object image; a gain variable amplifying circuit that amplifies a signal from the plurality of pixels; and a semiconductor substrate on which the plurality of pixels and the gain variable amplifying circuit are formed, wherein the gain variable amplifying circuit includes a first amplifying circuit that amplifies the signal from the plurality of pixels and a second amplifying circuit that amplifies a signal from the first amplifying circuit and is connected in series with the first amplifying circuit; and wherein a gain of the first amplifying circuit is switched at every first multiple and a gain of the second amplifying circuit is switched at every second multiple different from the first multiple.

Abstract: A method for detecting intensity saturation of a light sensor includes monitoring an electrical signal from a light sensor for detecting an intensity saturation condition of at least one pixel of the light sensor, converting the electrical signal to a digital signal, imposing a reserved bit combination on the digital signal indicating the intensity saturation condition of the pixel, and transmitting a control signal in response to the digital signal to compensate for the intensity saturation condition of the pixel.

Abstract: A display driver for implementing an inversion flicker compensation method is disclosed. The inversion flicker compensation method is applicable to a liquid crystal display device that is operable to emit a luminous output in response to a reception of a voltage drive signal and a voltage reference signal. The display driver is operated in accordance with the method to provide the voltage drive signal to the liquid crystal display device in response to a reception of a voltage data signal having a data voltage level indicative of a gray level of a color component. The display driver includes a gamma lookup table for the voltage drive signal that lists a pair of drive voltage levels for the voltage drive signal that correspond to the gray level as indicated by the data voltage level of the voltage data signal. The drive voltage levels have opposing polarities relative to a reference voltage level of the voltage reference signal.

Abstract: A gain characteristic correctable dynamic range enhancement system (DRES) receives input signals from an imager device connected to a correlated double sampling (CDS) circuit for receiving the video signal from the CCD imaging device. The dynamic range enhancement system includes a variable gain amplifier (VGA), and a limited bit-width analog-to-digital converter (ADC) which digitizes the analog signal received from the VGA. The output of the ADC is provided to an initial bit range position of a wider bit-width shifter connected to the output of the ADC. The DRES system correctably extends the dynamic range of the imager device, subject to offsets providing linearity corrections at predetermined trip points, subject to determined offset values, to ensure that there are no discontinuities in the system transfer function.

Abstract: A system and method for processing digital video. The invention allows for manual level and gain adjustment of the video similar to that used in a histogram based automatic level and gain control system using a cumulative distribution function. Level changes are made by an offset to the existing automatic level and gain. Level changes are first made by applying an offset L and the midscale gray intensity bin on the histogram is located. Gain changes are made by changing the relative gain multiplier (G) which acts on the automatic level and gain algorithm causing the gain to change equally about midscale gray (i.e., midscale gray is maintained). In accordance with the invention, as part of the histogram based manual level and gain algorithm, the local gain is clipped to a predetermined maximum in order to prevent an overly noisy picture when too much gain is applied. The inventive method determines how to prevent a shift in the level when increasing the gain (i.e., G>1) even when clipping is applied.

Abstract: A method and apparatus for adjusting the amplitude and DC bias of a video signal is presented, which may be performed in preparation for analog-to-digital conversion. This is accomplished by first converting a received voltage mode video signal to a current mode video signal. Similarly, a voltage mode bias control signal is converted to a current mode bias control signal. The amplitude of the current mode video signal is then adjusted to produce an amplitude adjusted video signal. Similarly, the amplitude of the current mode bias signal is adjusted to produce an amplitude adjusted bias control signal. The current mode amplitude adjusted signals are then combined to produce a biased adjusted current mode video signal. The biased adjusted current mode video signal is then converted back to a voltage mode signal, which may be provided to an analog-to-digital converter for conversion.

Abstract: An image pickup device has an image sensor generating an image signal, a pulse pattern generator generating a driving signal for the image sensor and an amplifier for amplifying the image signal with a given gain, which can be adjusted by the user.

Abstract: An image sensor controls the gain of a pixel signal on a pixel-by-pixel basis and extends a dynamic range while maintaining a S/N ratio at a favorable level. A column unit in an image sensor is independently detects a level of each pixel signal and independently sets a gain for level of the signal. A photoelectric converting region unit has pixels arranged two-dimensionally with a vertical signal line for each pixel column to output each pixel signal. The column unit is on an output side of the vertical signal line. The column unit for each pixel column has a pixel signal level detecting circuit, a programmable gain control, a sample and hold (S/H) circuit. Gain correction is performed according to a result of a detected level of the pixel signal.

Abstract: A processing system for a charge coupled device (CCD) or CMOS imaging system includes a correlated double sample (CDS) circuit for receiving data from an imager, a variable gain amplifier (VGA) having amplifiers of selectable current level to enable reduced data resolution in a preview display, a low power mode analog-to-digital converter (ADC) having a selectable narrow bit-width output and coupled to said VGA circuit, and a gain circuit coupled to said ADC. The single chip low-power analog front end produces digitized CCD data in either 13-bit, 12-bit or 10-bit formats at a first current level and 9-bit, 8-bit, or 6-bit formats at a second current level. The VGA amplifier includes symmetrical subcircuits which are independently actuable to enable full or reduced data resolution levels respectively for still image capture operation and video previewing on a separate preview screen.

Abstract: A dual analog-to-digital (A/D) converter circuit having two separate channels coupled to receive a single analog input signal, each of the two channels includes a means for converting an analog input signal to a digital signal at respective sample times that are adjustable to be substantially simultaneous; a means for adjusting the gain of the two channels to differ by a predetermined factor; a means for detecting a channel overflow condition in one of the two channels having a higher gain; and a means for merging the two channels into a continuous output stream.

Abstract: An offset level detection method for auto color gain control of analog video signals, which is used to find an optimal offset level for determining the input of the auto color gain control. The method includes at least the following steps: First, a lower limit of the min of analog video signals is determined. The position of the lower limit of the min is set as a first min. An upper limit of the min is searched backwards from the first min. The position of the upper limit of the min is set as a second min. Finally, the first min and the second min are averaged to obtain an optimal offset level.

Abstract: An automatic gain control device for an electronic endoscope is provided and comprises a controllable gain amplifier, an A/D converter, a histogram circuit, and a CPU. The controllable gain amplifier amplifies image signals from an imaging device. Amplified image signals from the controllable gain amplifier are input to the A/D converter. A histogram of the amplified image signals from the controllable gain amplifier is produced by the histogram circuit when an image taken in a white-balance test accessory is taken. By using the CPU, the gain of the controllable gain amplifier is adjusted in accordance with the determination of whether a saturated pixel exists for signals in the tolerance range of the A/D converter, so that a linear region of the image signals from the controllable gain amplifier substantially coincides with the tolerance range.