Abstract: An image processing device calculates a frequency of a pixel value for each block, generates a first histogram formed by N bins, mixes the first histogram of a high luminance block and the first histogram of each block, and thereby generates a second histogram for each block. Based on the second histograms of a block including a target pixel and an adjacent block, a frequency of a pixel value that depends on a pixel position in the block of the target pixel is calculated, and a third histogram is generated for each pixel. A relationship between the pixel value and an output value of the pixel value is generated based on the third histogram such that a maximum cumulative frequency of the third histogram matches a maximum value of the output value of the pixel value, and the output value is calculated from the pixel value of the target pixel.

Abstract: A system for duplicate text recognition includes a first means for dividing an electronic text into a plurality of phrase segments; a second means for converting each of the phrase segments into a unique and fixed-length bit string; a third means for storing a plurality of groups of the bit strings, each group of bit strings (string group) including a plurality of bit strings respectively corresponding to the phrase segments in a particular electronic text; and a fourth means for determining whether a predefined similarity between any two string groups in the third means reaches a first threshold, and for determining the two electronic texts corresponding to the two string groups are duplicate texts if the predefined similarity between the two string groups reaches the first threshold.

Abstract: An information processing apparatus includes: a distinguishing unit which, by using an ensemble classifier, which includes a plurality of weak classifiers outputting weak hypotheses which indicates whether a predetermined subject is shown in an image in response to inputs of a plurality of features extracted from the image, and a plurality of features extracted from an input image, sequentially integrates the weak hypotheses output by the weak classifiers in regard to the plurality of features and distinguishes whether the predetermined subject is shown in the input image based on the integrated value. The weak classifier classifies each of the plurality of features to one of three or more sub-divisions based on threshold values, calculates sum divisions of the sub-divisions of the plurality of features as whole divisions into which the plurality of features is classified, and outputs, as the weak hypothesis, a reliability degree of the whole divisions.

Abstract: A method and system include using a scanner to copy a document containing an original image and an embossment. The method includes first scanning a front face of the document from which the original image is visible to form a first image, wherein the first scanning is conducted with a sensitivity such that the embossment is essentially not visible in the first image; increasing a sensitivity of the scanner; second scanning the document to create a second image, wherein the embossment is visible in the second image; combining the first and second images so as to obtain a reproduction image of the original image containing the embossment.

Abstract: A method performed by a software process executing on a computer system, includes obtaining a digital image having a plurality of pixels encoded in a YUV color space. Each pixel has a luma component of value Y, a blue color-difference component of value U and a red color-difference component of value V. For a specified pixel, the method includes calculating whether U is less than a first threshold and V is greater than a second threshold. The method further includes determining whether the specified pixel potentially depicts an orange hue depending on a result of the calculation.

Abstract: Disclosed is a method of performing contrast enhancement for an image. A mean luminance value is calculated with respect to an image that is read, the type of the image is determined based on the mean luminance value, a contrast reference curve is created by using a hyperbolic tangential function curve according to the type of the image, and the contrast of the image is enhanced by using the contrast reference curve.

Abstract: Crowd source editing of digital images to reduce errors in a digital images includes receiving a proposed modification to a content portion of a digital image. A determination is made as the whether the occurrence of the proposed modification to the content portions meets a modification threshold. Accordingly, the proposed modification to the content portion of the digital image is adopted when the occurrence of the specific modification meets the modification threshold.

Abstract: An image of a negotiable instrument may be taken by an imaging device and provided from a user to a financial institution. The image may be processed using operations such as deskewing the image, dewarping the image, and detecting corners or edges of the check in the image. Brightness correction may then be performed on the image. The brightness correction may be performed on the image using a histogram of the image with an overlaid reference mark. The negotiable instrument may be deposited in a user's account using the brightness corrected image.

Abstract: An image processing apparatus including: a determining processing section which binarizes a pixel value of a target pixel using a threshold; a calculation section which calculates feedback values by multiplying binarized pixel values of adjacent processed pixels by a feedback coefficient; a addition section which adds the feedback values to the pixel value of the target pixel before binarization; a diffusion section which diffuses a difference between the binarized pixel value and the unadded pixel value as an error to adjacent unprocessed pixels; and a subtraction section which subtracts the error from the unadded pixel value of the target pixel, wherein when all pixel values of processed pixels are 0 and an output value of the target pixel is a maximum value, it is determined that the target pixel is an isolated point and an output value of an adjacent pixel is set to a forced output value excluding 0.

Abstract: An imaging apparatus that adjusts focus based on frequency components extracted from an image signal is provided. The apparatus includes a 1st order Infinite Impulse Response (IIR)-filter including a plurality of sample delayers having a plurality of line buffers for buffering and delaying a plurality of samples to sequentially read pixels of the image signal through raster scanning and extracting frequency components of the image signal from the read pixels by using the plurality of sample delayers; and a delay sample number controller for controlling the IIR-filter to match the number of horizontal pixels sequentially read from the image signal through raster scanning to the number of the plurality of samples buffered by the plurality of line buffers.

Abstract: A camera-shake correction apparatus includes an image capturing unit configured to capture an object image, a camera-shake detection unit configured to detect a camera-shake applied to the camera-shake correction apparatus, a correction unit configured to correct the camera-shake of the object image by moving a correction member based on a camera-shake signal detected by the camera-shake detection unit, and a control unit configured to measure an amplitude of the camera-shake or a frequency of the camera-shake, or both the amplitude of the camera-shake and the frequency of the camera-shake, based on the camera-shake signal supplied from the camera-shake detection unit, and the control unit further configured to control to hold the correction member at a latest position if it is determined that the measured amplitude is smaller than a predetermined amplitude or if it is determined that the measured frequency is lower than a predetermined frequency, or if it is determined that the measured amplitude is smaller

Abstract: An apparatus and methods are provided for determining control parameters for image enhancement. In one embodiment a method for determining control parameters includes receiving image data for a first frame and calculating an adaptive threshold value based on the image data. The method includes determining a pixel slope distribution for a pixel window of the image data, wherein the pixel window is selected based on the adaptive threshold value and determining a spectrum estimation coefficient based on the pixel distribution, wherein the spectrum estimation coefficient is determined based on the spectral components of the image data. The method may then include determining one or more control parameters for enhancement of the image data based on the spectrum estimation coefficient, wherein the one or more control parameters relate to filtering parameters for adaptive enhancement of image data.

Abstract: Near infra-red images of natural scenes usually have better contrast and contain rich texture details that may not be perceived in visible light photographs. The contrast and rich texture details form a NIR image corresponding to a visible light image are useful for enhancing the visual quality of the visible light image. To enhance the visual quality of a visible light image using its corresponding near infra-red image, a computer-implemented method computes a weight region mask from the visible light image, transfers contrast data and texture data from the near infra-red image to the visible light image guided by the weighted region mask. The contrast data is computed from the low frequency subbands of the visible light image and corresponding infra-red image after a wavelet transform by matching the histogram of gradient magnitude. The texture data is computed from the high frequency subbands of both images after wavelet transform.

Abstract: An image processing apparatus includes a separating unit, a setting unit, and a determining unit. The separating unit separates an image into types of partial images other than a specific type, which is likely to be erroneously separated. The setting unit makes setting designating whether or not predetermined two types of partial images of the separated partial images are to be easily determined to be partial images of the specific type. The determining unit determines whether or not at least one of the predetermined two types of the partial images is the partial image of the specific type or not based upon the setting.

Abstract: A method for composing a global histogram of the values of the pixels of a hardcopy original includes a division of a detection area, which may be larger than the original, in stripes. For each of the stripes, a local histogram is made, which is added to a candidate histogram. If the decision is made from the values of the local histogram that a stripe belongs to the original, the candidate histogram is added to the global histogram. In this way, a representative histogram of the original is obtained, even if the white pixels from the original are indiscernible from the white pixels from the cover of the scanner. The method is embodied in an electronic component, including an application specific processing unit.

Abstract: An image processor includes a first dither data memory storing a first dither matrix, a second dither data memory storing a second dither matrix, a selecting unit selecting one of the first dither matrix and the second dither matrix, and a converting unit converting multi-value image data to binary data by comparing density of the multi-value image data to the threshold value set in corresponding element of the one of the first dither matrix and the second dither matrix selected by the selecting unit. The second dither matrix is configured of a plurality of sub-dither matrices. Each sub-dither matrix has a plurality of elements each assigned with a threshold value in a range from a maximum threshold value to a minimum threshold value. A set of threshold values from the minimum threshold value to a predetermined intermediate threshold value is assigned to elements in corresponding locations of each of the plurality of sub-dither matrices.

Abstract: The present invention provides a method for an Optical Character Recognition (OCR) system providing recognition of characters that are partly hidden by crossing outs due to for example an imprint of a stamp, handwritten signatures, etc. The method establishes a set of template images of certainly recognized characters from the image of the text being processed by the OCR system, wherein the effect of the crossed out section is modelled into the template images before comparing these images with the image of a visually impaired crossed out character. The modelled template image having the highest similarity with the visually impaired crossed out character is the correct identification for the visually impaired character instance.

Abstract: There are many applications that conduct both generation of contrast or complexity level and motion estimation for video processing. The applications often use a block matching technique. An embedded system such as a personal digital camera is an example of such an application. Additionally, comparison of error differences around the location of minimum error in a motion estimation error table is able to be used to determine low contrast in a scene.

Abstract: A system for inspecting a product that includes a scanner to scan across the product and generate an image of the product, the image including a matrix of pixels each having a grayscale value, and an analyzing device electrically coupled with the scanner to receive and analyze the image of the product, the analyzing device including a microprocessor to calculate a reference grayscale value associated with each of the pixels in the image, wherein the reference grayscale value includes an average of the grayscale values of pixels located adjacent to the each pixel, a memory to store the reference grayscale value associated with each of the pixels and at least one threshold associated with the reference grayscale value, and a comparing module to compare the grayscale value of each of the pixels in the image with the at least one threshold associated with the each pixel.

Abstract: Embodiments of the present invention provide techniques and configurations for error diffusion halftoning of an image including receiving a signal that indicates selection of a first implementation or a second implementation of determining a threshold perturbation value for error diffusion halftoning of an image, and determining the threshold perturbation value using a table of programmable values according to the selected one of the first implementation or the second implementation, wherein the second implementation provides fewer threshold perturbation values for a larger region of the image than the first implementation. Other embodiments may be described and/or claimed.

Abstract: A method for detecting a clear path of travel for a vehicle using an image generated by a camera includes monitoring the image, and utilizing a first patch-based analysis of the image including dividing the image into a plurality of patches, and analyzing each patch to determine a first clear path confidence likelihood for each of the patches of the first patch-based analysis. Each of the patches with the first clear path confidence likelihood greater than a first threshold confidence likelihood is defined as a clear path patch. A second analysis is utilized upon a portion of the patches with the first clear path confidence not greater than the first threshold confidence likelihood to determine a second clear path confidence likelihood for each of the patches of the second analysis. Each of the patches of the second analysis with the second clear path confidence likelihood greater than a second threshold confidence likelihood is defined as a clear path patch.

Abstract: A method of processing video comprising a succession of images of a scene to detect movement of an object in the scene, comprising storing a matrix of bytes each representing the difference in intensity of a respective pixel between temporally adjacent images, creating from those bytes a histogram of the frequency at each of a range of positive and negative values of the intensity difference, locating the limits of a central peak of the frequency distribution in the histogram so as to include in the central peak changes due to illumination change and repetitive motions in the background of the scene, determining the proportion of bytes in the remainder of the distribution that are in tails of the distribution on each side of the central peak, repeating the aforesaid process for each successive pair of temporally adjacent images, and providing an output indicative of a moving object and not indicative of illumination change or repetitive motions, in the event that that proportion meets a predetermined criterio

Abstract: Provided is an image processing apparatus which includes a block histogram generation unit configured to calculate frequency of a pixel value in each block, divide a dynamic range, and generate a first histogram including “N” number of bins, a pixel histogram generation unit configured to calculate frequency of a target pixel in a block based on first histograms of the block including the target pixel and a block adjacent to the block including the target pixel, and generate a second histogram including “N” number of bins for each pixel, and an output value determination unit configured to generate a relation between the pixel value and an output value of the pixel value based on the second histogram so that a maximum cumulative frequency of the second histogram matches a maximum value of the output value, and calculate the output value based on the pixel value of the target pixel.

Abstract: The invention relates to a method of locating a code in an image file, comprising forming an image window from a target comprising a readable code, dividing the image window into sub-windows, analysing for each sub-window whether it constitutes a part of the code by comparing the variation density color of the sub-window with one or more threshold values set for the color, gathering the sub-windows evaluated as constituting a part of the code into a group of sub-windows, and verifying that the gathered group of sub-windows defines a valid code.

Abstract: A system reads a digital image that includes a set of pixels. The system determines a distribution of colors of the pixels of the digital image. Also, the system analyzes the distribution to identify a range of colors of a background of the digital image. Further, the system identifies pixels whose colors are within the identified range, and the system modifies the identified pixels to have a different color.

Abstract: A system and method for enhancing a content file is disclosed. The system comprises a histogram module, a contrast stretching module and a brightness module. The histogram module generates a histogram including data that describes one or more pixel intensities for one or more channels included in a content file. The contrast stretching module adjusts the one or more pixel intensities for the one or more channels included in the content file based at least in part on the histogram. The brightness module is communicatively coupled to the contrast stretching module for determining whether a brightness level for the content file is within a range describing one or more acceptable brightness levels. The brightness module adjusts the brightness level for the content file responsive to determining that the brightness level for the content file is outside the range.

Abstract: A system for processing an image for binarization comprises at least one subsystem that breaks the image into multiple sub-images, at least one subsystem that generates a histogram for each sub-image, and at least one subsystem that determines optimal thresholding values for image binarization by statistical analysis of the histogram for each sub-image.

Abstract: A gradation correction characteristics evaluation device includes: a histogram creation unit that creates a histogram based upon pixel values indicated at pixels constituting an input image; and an evaluation unit that evaluates gradation correction characteristics, which is used to correct gradation of the image, based upon the histogram of the image having been created by the histogram creation unit and the gradation correction characteristics.

Abstract: Aspects of the present invention relate to methods and systems for segmenting a digital image into regions. A frequency-of-occurrence of image values may be determined excluding a portion of pixels in a digital image. An image value associated with a peak in the frequency-of-occurrence of image values may be identified and associated with an image label. Pixel locations may be labeled based on the associated labels and image values. Additionally, unreliable pixels may be determined and labeled based on the associated labels and image values, and an unreliable pixel may be assigned a label after multiple scan passes of a classification map.

Abstract: The present invention relates to a method and apparatus capable of generating frequency-modulation halftone dots in high speed and belongs to the field of the digital image halftone. In the prior art, read-write operation is usually carried out many times in error rows during processing each pixel so that halftone dots are generated in low speed. In the method according to the present invention, the error generated by the current pixel is buffered in a register file and the final accumulated error values are written in the error rows only after all of the relative pixels are processed. Thus, read-write operation is carried out only once in the error rows for processing each pixel. The present invention also provides an apparatus to implement the method. The apparatus comprises an error row memory, an error buffer register file, a gray generation circuit, a threshold comparison circuit, an error generation circuit, an error buffer register file control circuit, and an error row control circuit.

Abstract: A skewed image data detecting and correcting device includes a skew angle detecting module, and an image rotating correction module. A skewed image data detecting and correcting method includes the following steps. Firstly, a binary digitizing operation is performed to obtain a binary image data. The binary image data is rotated by multiple different rotating angles, thereby obtaining multiple rotated binary image data. The pixel numbers of all horizontal rows of the rotated binary image data are totalized, thereby obtaining multiple horizontal pixel number distribution curves. A high-pass filtering procedure is performed to filter off low-frequency noise, thereby obtaining multiple high-frequency signal curves. The square sums of respective high-frequency signal curves are calculated, thereby obtaining multiple index values.

Abstract: A method, performed by a software process executing on a computer system, includes accessing a digital image comprising a plurality of pixels. The method also includes determining whether one or more pixels bounding a first rectangular sub-region of a predetermined size within the digital image satisfy a specified criterion. If a predetermined percentage of bounding pixels satisfy the specified criterion, the method assumes that all pixels within the first rectangular sub-region also satisfy the specified criterion. The method further includes selectively executing an image analysis algorithm on the digital image using the assumption that all pixels within the rectangular sub-region also satisfy the specified criterion.

Abstract: A computerized device for converting a color image data, indicative of a plurality of color image regions defining a two-dimensional color image, into a grayscale image data indicative of a plurality of grayscale image regions defining a two-dimensional grayscale image, with each of the color image regions corresponding to one of the grayscale image regions. A luminance information and a two-dimensional chromatic information is associated with each of the color image regions. The device includes a processor and a memory store. The memory store is adapted to store a program executable by the processor so as to perform the following steps: determining a principal chromatic component of each of the color image regions; determining a first correlation value; and generating the grayscale image data by reference to the first correlation value.

Abstract: A threshold determination method is selected from among a plurality of alternative global thresholding determination methods and, optionally, a local thresholding determination method based on characteristics of a histogram of grayscales values representing an image. When it is determined to use a global thresholding method, a single global binarization threshold value is determined using the selected global thresholding method. Various alternative global binarization threshold values include a predetermined constant, an average value of the two grayscale values, an Otsu method based threshold value, a Newton method based threshold value, and an Otsu method based threshold value based on a truncated version of the histogram. When it is determined to use local thresholding, a plurality of local binarization threshold values are determined corresponding to different non-overlapping blocks of the image.

Abstract: An apparatus, system, and method for image processing are disclosed, each of which obtains a mark from image data, detects additional information in the mark, determines whether the mark is detected in the mark to generate a determination result, and controls processing performed by an image processing apparatus with respect to the image data based on the determination result.

Abstract: A method and apparatus for processing an image are provided that can suppress blur edges at an edge portion of a character so that sharpness and quality of the image can be improved. The apparatus comprises an inside and outside edge discrimination portion for discriminating whether a target pixel to be processed belongs to an inside edge or to an outside edge, a threshold value generating portion for selecting a threshold value from plural threshold values for error diffusion process in accordance with an area discriminated by the inside and outside edge discrimination portion to output the selected threshold value and an error diffusion process portion for performing the error diffusion process for multilevel input data concerning the target pixel by utilizing the threshold value generated by the threshold value generating portion so as to produce output data whose gradation steps are reduced.

Abstract: A display device includes a scene conversion detecting module to detect whether a scene is converted in an input image, and a brightness compensating module to determine an image category of the input image when a scene conversion is generated in the input image, and compensating for the brightness of the input image by calculating a weighted mean value of a tone increase value corresponding to the determined image category and a tone increase value corresponding to an image category of a previous image.

Abstract: A process for extracting iris data for biometric identification includes a thresholding method where the thresholds are selected according to a nonparametric approach that considers the grey scale and does not require classifying pixels as edge or non-edge pixels. An eye image is first acquired, where the eye image has component images including an iris image with an inner boundary and an outer boundary. The eye image has a distribution of grey levels. Component images, such as an iris image or a pupil image, from the eye image are segmented according to the distribution of grey levels. The inner boundary and outer boundary of the iris image are determined from the component images. The iris image within the inner boundary and outer boundary is processed for biometric identification. The component images may be segmented by creating an eye histogram of pixel intensities from the distribution of grey levels.

Abstract: A test pattern containing plurality of patches recorded using small dot patterns and large dot patterns is printed. The dot sizes arranged in the patches are different between patches. Then the test patterns are read. The detection rate and average density of additional information embedded in each large dot pattern are obtained. A large dot pattern whose detection rate and average density fall within a reference range and are closest to ideal values is determined. The average density of each small dot pattern is obtained. A small dot pattern whose average density falls within a reference range and is closest to the average density of the determined large dot pattern is determined. A copy-forgery-inhibited pattern image is generated using these dot patterns and combined with a print target image.

Abstract: A method for estimating a physical property of a porous material from a sample of the material includes making a three dimensional tomographic image of the sample of the material, segmenting the image into pixels each representing pore space or rock grain, and estimating at least one physical property from the segmented image.

Abstract: A technique is disclosed for reducing noise in a medical image, wherein plural anisotropic areas continuous with a pixel-of-interest contained in the medical image are set with the pixel-of-interest being centered a statistical amount of pixel values of pixels constituting each anisotropic area is calculated with respect to each of the plural anisotropic areas, and either an anisotropic area having the minimum statistical amount out of the plural anisotropic areas is determined and an anisotropic shape filter in the same direction as the anisotropic area concerned is constructed, or an anisotropic area having the maximum statistical amount out of the plural anisotropic areas is determined and an anisotropic shape filter is constructed by clockwise or counterclockwise rotating the anisotropic area concerned around the pixel-of-interest by 90° .

Abstract: Segments of interest within video footage are identified automatically. Such segments of interest include portions of the footage which were taken using a hand held camera and which show a static subject, portions which track the motion of a moving subject, and portions which show an abrupt event. Methods are presented for identifying such segments, based on motion and/or color analysis of the video footage or based on observations of discontinuities in the video footage following a period of stability.

Abstract: A histogram preparer reads image data scanned from an original sheet by the line, preparing a histogram of pixel numbers of respective background densities of a read line, a background density estimator estimates a background density of the read line as a density at a local maximal value in view of a highlight end of the histogram, a background removal reference value setter sets up a background removal reference value as a reference margin based on a pixel number normalized on the estimated background density, a background removal threshold determiner increments the estimated background density by the background removal reference value to set a provisional background removal threshold of the read line, and determines a background removal threshold of the read line as a weighting combination of the provisional background removal threshold and a background removal threshold of a previous line, and a background remover removes a background of the read line based on the determined background removal threshold.

Abstract: An image processing apparatus communicates with an image acquisition apparatus provided with an image acquisition region comprising light-shielded pixels and effective pixels. Data of an image are acquired based on output signals from the effective pixels. An edge of an object is extracted in the acquired image data using a preset edge threshold, and the object is recognized based on the extracted edge. Output signals are acquired from the light-shielded pixels and a degree of variations in noise contained in the output signals from the effective pixels is estimated based on the output signals acquired. The edge threshold is set based on the degree of variations in noise which is estimated, such that the noise having a level which exceeds the edge threshold occurs at a probability lower than a preset value.

Abstract: When retrieving an image from an archive of stored images that is similar to an inputted image, an image-processing apparatus (200) extracts more than one characteristic point from the inputted image (S504), computes a characteristic amount for the characteristic points thus extracted (S505), and evaluates the fluctuation in the characteristic amount when a prescribed alteration is applied to the inputted image (S506). The image-processing apparatus selects a characteristic point from among the characteristic points thus extracted from the inputted image, and retrieves (S508) a stored image that is similar to the inputted image, in accordance with the characteristic amount of the characteristic point thus selected.

Abstract: Converting images to binary image representations is part of an Optical Character Recognition program in a computer system. The method and system is using a relative threshold level to convert the image to its binary image representation.

Abstract: In an example embodiment, a system for creating a display from multiple projectors receives as an input a source pixel derived from an image to be displayed. The system generates a scalar-adjusted pixel by applying a scalar for an adjustment range to each channel value in the source pixel, where the scalar depends on whether the source pixel is gray or color. The system modifies each channel value in the scalar-adjusted pixel according to a luminance adjustment curve for a projector, where the luminance adjustment curve depends on whether the source pixel is gray or color. The system generates the luminance adjustment curve from captured calibration images by: (1) creating an interpolated response curve; and (2) generating and inverting a median difference curve based on the interpolated response curve for the projector and the interpolated response curves for the other projectors in the system.

Abstract: An electronic visual aid is provided that includes an evaluating unit, which is supplied with a recording of an information carrier on which information standing out visibly from the background is displayed. The evaluating unit determines a brightness distribution of the recording and derives from the brightness distribution a brightness threshold value lying in the transition zone between a zone of the brightness distribution associated with the background and a zone of the brightness distribution associated with the information. The visual aid also includes an image processing unit which generates from the recording a binary image having only two different, predetermined brightness values, by respectively assigning to the pixels of the binary image the first of the two brightness values when the brightness of the corresponding pixel of the recording is below the brightness threshold value, and otherwise assigning the second brightness value.

Abstract: A plurality of images inputted in an image signal input portion are divided into a plurality of regions by an image dividing portion, and a feature value in each of the plurality of regions is calculated by a feature value calculation portion and divided into a plurality of subsets by a subset generation portion. On the other hand, a cluster classifying portion classifies a plurality of clusters generated in a feature space into any one of a plurality of classes on the basis of the feature value and occurrence frequency of the feature value. And a classification criterion calculation portion calculates a criterion of classification for classifying images included in one subset on the basis of a distribution state of the feature value in the feature space of each of the images included in the one subset.

Abstract: A projection display unit includes: a light modulation panel which modulates light from a light source in accordance with a given image signal; an iris diaphragm which regulates, by changing a diaphragm diameter, a transmission amount of light modulated by the light modulation panel; a histogram creator which creates a histogram of a luminance signal distribution of the image signal; a histogram analyzer which analyzes the created histogram to specify high-luminance and low-luminance reference values in the histogram; a reference value derivation section which derives a single reference value from both the high-luminance reference value and the low-luminance reference value specified by the histogram analyzer; and an iris controller which determines the diaphragm diameter of the iris diaphragm for the light modulated by the light modulation panel in accordance with the image signal on the basis of the single reference value specified by the reference value derivation section.