Abstract: Provided are a method of controlling a focus lens to be moved to a target location by generating a normalized focus graph by use of relative values of a plurality of focus values obtained by using a plurality of filters each having different cut-off frequencies, and predicting a target position of the focus lens according to the normalized focus graph, an apparatus operating by using the method, and a recording medium for recording the method. According to the present invention, in terms of performing an auto-focusing function, by optimizing the motion line of the focus lens, wasteful power consumption can be prevented and a scanning time of the focus lens can be shortened.

Abstract: A digital photographing apparatus capable of automatically determining whether a macro mode is an appropriate mode, a methods of controlling the same, and a computer readable recording medium storing instructions for executing the method(s) is disclosed A lens position determining unit is disclosed that determines whether an auto-focusing lens position is within the lens position range corresponding to a macro mode, according to the position relationship between a lens position point corresponding to a maximum value of the plurality of auto-focus values obtained by an auto-focus value obtaining unit and other lens position points corresponding to other auto-focus lens values.

Abstract: A method for automatically focusing a camera including the steps of (A) recording a first topology and a second topology, where the second topology occurs temporally after the first topology, and (B) comparing the first topology with the second topology. A focus of the camera is automatically adjusted based upon one or more similarities between the first topology and the second topology.

Abstract: A focus control apparatus and method capable of shortening a focus adjustment time in focus control. The method includes extracting a first high frequency component depending upon a first cutoff frequency and a second high frequency component depending upon a second cutoff frequency higher than the first cutoff frequency from a video signal, generating first and second contrast signals of the video signal respectively based on the first and second high frequency components, using a quotient obtained by dividing a value of the first contrast signal by that of the second contrast signal as a parameter, exercising focus control based on the parameter, and setting the first and second cutoff frequencies so as to cause a value of the parameter to assume a peak when a focus lens in an image pickup apparatus is located in a position at a predetermined distance from an in-focus position.

Abstract: A focus adjustment apparatus includes an imaging unit configured to capture an object image input via a focus lens to output image data, a focus adjustment unit configured to perform focus adjustment by controlling a position of the focus lens based on the image data, a motion detection unit configured to detect a motion of the object image based on the image data, and a control unit configured to control the focus adjustment unit to perform a first focus adjustment operation if motion of the object image is not detected by the motion detection unit, and to control the focus adjustment unit to perform a second focus adjustment operation different from the first focus adjustment operation if motion of the object image is detected by the motion detection unit.

Abstract: An image is focused onto an image sensor array by efficient movement of an adjustable focus lens by a lens focus motor. A minimum of three focus positions is required to determine an estimated best focus position of the lens focus motor. After which a sweep of the focus positions surrounding the estimated best focus position is performed to verify and determine the best actual focus position of the lens focus motor. A sharpness value of the image being focused comprising a Sobel edge detection or other detections means provide sharpness data to evaluate image sharpness at various lens focus motor positions.

Abstract: An auto focus (AF) apparatus and method for a camera that improves the AF action by reducing the number of time and steps required of a conventional apparatus and method. An encoder initial value is detected by measuring an initial position of a lens unit by means of an encoder; matching the measured encoder initial value to an initial position value to which the lens unit is to move while performing the auto focus; performing the auto focus starting from the matched initial position value, and dividing a distance that the lens unit is to cover into sections corresponding to a preset number of steps; detecting an edge value which shows a brightness change for a contour of a subject for as many as the number of the preset steps. The AF is completed by moving the lens unit to a position corresponding to a maximum edge value selected from among the detected edge values.

Abstract: A method for automatically focusing a camera including the steps of (A) recording a first topology and a second topology, where the second topology occurs temporally after the first topology, and (B) comparing the first topology with the second topology. A focus of the camera is automatically adjusted based upon one or more similarities between the first topology and the second topology.

Abstract: A focus evaluation value representing a focusing state of a taking lens is repeatedly calculated on the basis of an image signal output from an imaging section of a digital camera, a change in the focus evaluation value generated by the movement of the taking lens is detected, when a predetermined change in the focus evaluation value is detected in manual focusing, at least one of a first mode for continuing manual focusing and a second mode for making the transition to auto-focusing, in which the taking lens is automatically moved, is selected, when the predetermined change in the focus evaluation value is detected in the case in which the second mode is selected, the focusing operation is automatically switched to auto-focusing, whereby the taking lens is automatically moved such that the focus evaluation value is the peak value.

Abstract: An imaging apparatus comprises a focusing unit configured to focus an object to be shot by an imaging unit, a first shooting control unit configured to control the imaging unit in order to continuously shooting at first time intervals upon detecting a shooting instruction, a determining unit configured to determine whether the object moves in a distance direction during a control operation of the first shooting control unit, and a second shooting control unit configured to control the imaging unit in order to continuously shoot at second time intervals and to control the focusing unit in order to focus the object when the determining unit determines that the object moves in the distance direction.

Abstract: A focus adjustment apparatus or an image capturing apparatus is provided with a system controller. The system controller calculates a correlation value between an image in a focus detection area when a focusing lens is located at a lens position apart by a predetermined distance from a lens position where a focus evaluation value reaches a peak value, to a close end side, and an image in a focus detection area when a focusing lens is located at a lens position apart by a predetermined distance from a lens position where a focus evaluation value reaches a peak value, to an infinity side, and determines a lens position corresponding to a peak value to be a focused lens position, when a correlation value calculated by the correlation value calculation unit is over a predetermined value.

Abstract: An imaging device includes a capturing module with at least one lens for capturing an image from a scene, a driving module for driving the at least one lens to different focusing positions using different driving steps, a flat-scene judging module, and a step-judging module. The flat-scene judging module divides the image into a central area and a plurality of peripheral areas, and determines whether the captured scene is a flat scene according to the divided image. The step-judging module determines whether the driving steps corresponding to a maximum focusing value of the central area of the image are same as driving steps corresponding to respective maximum focusing values of the peripheral areas of image, and changes the driving steps corresponding to the maximum focusing value of the central area to the driving steps corresponding to the greatest one of the maximum focusing values of the peripheral areas.

Abstract: A method applies fast and accurate autofocusing (AF) by using a contrast AF method in a digital photographing apparatus. In the digital photographing apparatus, when AF peaks of a subject of a central multi-point and a subject of a nearest multi-point are detected, further scanning is not performed. In addition, scanning is not performed on a region from which it is difficult to detect a peak, so that fast and accurate AF may be performed.

Abstract: An image-pickup apparatus 100 includes a focus detecting part 7 that detects focus information indicating a focus state of an image-pickup optical system, a color measuring part 14a, 14b, and 15 that detects color measurement information related to a color of an object, a controlling part 6 that generates controlling information used in focus control using the focus information and the color measurement information, and a memory 9 that stores the color measurement information.

Abstract: A video camera constructed according to one aspect of the focus adjustment device moves a focus lens forward and backward and detects peak values of an AF evaluation value of the focus lens in the forward moving direction and in the backward moving direction. The video camera calculates a correction value based on a difference between the peak value of the evaluation value detected in the forward motion of the lens and the peak value of the evaluation value detected in the backward motion of the lens. The video camera corrects the AF evaluation value with the calculated correction value and detects a focused position of the lens based on the corrected AF evaluation value in moving the lens.

Abstract: An autofocus searching method includes the following procedures. First, focus values of images, which are acquired during the movement of the object lens, are calculated, in which the focus value includes at least the intensity value of the image derived from the intensities of the pixels of the image. Next, focus searching is based on a first focus-searching step constant and a first focus-searching direction, in which the first focus-searching step constant is a function, e.g., the multiplication, of the focus value and a focus-searching step size. If the focus searching position moves across a peak of the focus values, it is then amended to be based on a second focus-searching direction and a second focus-searching step constant, in which the second focus-searching step constant is smaller than the first focus-searching step constant, and the second focus-searching direction is opposite to the first focus-searching direction.

Abstract: A photographing apparatus includes a drive portion driving a focus lens included in a photographing optical system in a focus adjustment direction when a shutter button is pressed, a photographing portion continuously and sequentially outputting images of an object formed on an image forming surface through the photographing optical system as the shutter button is pressed once, as image data corresponding to the number of all pixels, an in-focus position detection portion detecting an in-focus position of the focus lens based on the image data sequentially output from the photographing portion, an in-focus control portion maintaining the focus lens at the in-focus position by controlling the drive portion based on a result of the detection by the in-focus position detecting portion, and a recording portion sequentially recording the image data output from the photographing portion during which the focus lens is maintained at the in-focus position after the shutter button is pressed.

Abstract: A lens apparatus capable of carrying out a suitable AF control operation even when text or character information is superimposed on a video signal is provided. The lens apparatus is configured to generate first and second AF evaluation values from a video signal obtained from an imaging unit of a camera apparatus, and to perform focusing control based on the second AF evaluation value. In the lens apparatus, the first AF evaluation value is selectively output to a second AF evaluation value generating unit for every scanning line of the video signal.

Abstract: In an imaging device according to one aspect of the invention, an amplitude demand Ac is specified according to a wobbling amplitude Ai required for detection of a hill-climbing direction based on an F value and a wobbling amplitude Ag required for detection of the hill-climbing direction based on an AGC gain. An allowable amplitude Am set for preventing a potential image shake caused by a magnification change with a position shift of a compensator lens in wobbling is specified corresponding to a zoom position and an object distance. When Ac>Am, the control procedure restricts the wobbling amplitude to Am and increases a sampling number of AF evaluation values to be detected at respective positions in wobbling, in order to ensure the sufficient detection performance of the hill-climbing direction. When Ac?Am on the other hand, the control procedure sets Ac to the wobbling amplitude.

Abstract: An automatic focus adjustment device has an image sensing element for converting an object optical image into an electrical signal, and outputting an image signal, a filter for extracting high-frequency components of the image signal obtained by the image sensing element, an integrator for integrating the high-frequency components extracted by the filter and outputting an integrated value, a peak hold circuit for detecting and outputting a peak value of the high-frequency components extracted by the filter, a discrimination unit for discriminating the luminance distribution of the object optical image, and a focus adjustment unit for making focus adjustment using one of the integrated value output from the integrator and the peak value output from the peak hold circuit in accordance with the discrimination result.

Abstract: A novel imaging apparatus capable of correcting a focus state by an AF detection value both simply and surely has been disclosed. The imaging apparatus comprises an auto-focus drive section for moving a lens, an AF processing section for calculating an AF detection value indicating the focus state from imaging data, a luminance processing section for calculating a luminance value from the imaging data, a correction section for calculating a corrected AF detection value by correcting the calculated AF detection value by the calculated luminance value, and a control section for controlling the auto-focus drive section based on the calculated corrected AF detection value. The imaging data is data not having been subjected to auto-exposure processing.

Abstract: An imaging device includes an imaging unit that obtains an image signal relating to a subject, a driving unit that drives a focus lens, a first detecting unit that performs focus detection based on a contrast detection method to detect an in-focus position of the focus lens, a second detecting unit that performs focus detection based on a phase difference detection method, while the focus lens is being driven toward the in-focus position, to detect a provisional in-focus position of the focus lens, and an in-focus control unit that controls the driving unit to drive the focus lens to pass through the provisional in-focus position and then return to the in-focus position. Focus detection information is obtained at least for a given range of positions, and is stored in a predetermined storage unit. The in-focus position is detected based on the stored focus detection information.

Abstract: An electronic still camera includes a finder optical system for viewing a subject image. An imaging section obtains the subject image. A display section displays the subject image based on image data associated with the subject image obtained by the imaging section. A mode selecting section selects either a first mode in which the electronic still camera performs imaging operation using the imaging section while a user views the subject image through the finder optical system or a second mode in which the electronic still camera performs imaging operation using the imaging section while the user views the subject image on the display section. A first focus detection circuit performs a first focus detecting operation when the first mode is selected by the mode selecting section. A second focus detection circuit performs a second focus detecting operation when the second mode is selected by the mode selecting section.

Abstract: A digital camera includes: an evaluation value calculation unit that calculates a focal point evaluation value that changes in correspondence to a position assumed by a focus lens based upon image signals; a focal adjustment unit that executes an AF search by detecting a focus match position based upon resulting focal point evaluation values and driving the focus lens to the focus match position; a face recognition unit that recognizes a face of a person in an image by analyzing the image signals; a distance calculation unit that determines an approximate distance to the face based upon the recognized face size; and a lens position determining unit that determines a focus lens position to be set as a start point of the AF search by the focal adjustment unit based upon the approximate distance to the face having been determined by the distance calculation unit.

Abstract: A digital still camera includes an image-capturing unit capturing a subject image via an image-capturing lens to create an image, a focus detecting unit detecting focus in accordance with the image created by the image-capturing unit, an image-capturing lens driving unit driving the image-capturing lens in accordance with a result of the focus detection provided by the focus detecting unit, and a receiving unit receiving an instruction to initiate image capture by the image-capturing unit. When the receiving unit receives the instruction to initiate image capture, the image-capturing unit captures the subject image successively to create a plurality of images, while the image-capturing lens driving unit drives the image-capturing lens successively. Accordingly, it is possible to provide an image in a high in-focus state while shortening the time required until an image is actually captured after an instruction is provided to initiate the capture of the image.

Abstract: A method for determining the quality of focus of a digital image of a biological specimen includes obtaining a digital image of a specimen using a specimen imaging apparatus. A measure of image texture is calculated at two different scales, and the measurements are compared to determine how much high-resolution data the image contains compared to low-resolution data. The texture measurement may, for example, be a Brenner auto-focus score calculated from the means of adjacent pairs of pixels for the high-resolution measurement and from the means of adjacent triples of pixels for the low-resolution measurement. A score indicative of the quality of focus is then established based on a function of the low-resolution and high-resolution measurements. This score may be used by an automated imaging device to verify that image quality is acceptable. The device may adjust the focus and acquire new images to replace any that are deemed unacceptable.

Abstract: This invention allows focus detection devices to be smoothly and quickly switched even if different image capturing frame counts or image capturing field counts are set in accordance with image capturing purposes. An AF system selection unit switches focus detection methods based on a direct distance measurement AF unit and captured signal AF detection unit in accordance with the frame count or field count of a captured signal.

Abstract: An automatic focusing method for a camera, including scanning in a macro mode, scanning in a normal mode, and additional scanning. In the scanning in the macro mode, a region within a first distance is scanned if the macro mode is set by a user. In the scanning in the normal mode, a region beyond the first distance is scanned if the normal mode is set by the user. In the additional scanning, the scanning in the normal mode is performed additionally if it is determined that the position of the focus lens found in the scanning in the macro mode does not have the largest focus value, and the scanning in the macro mode is performed additionally if it is determined that the position of the focus lens found in the scanning in the normal mode does not have the largest focus value.

Abstract: There is disclosed a digital camera which detects a focus of a lens unit by a method selected from a plurality of focus detection methods based on information on the lens unit taken from the lens unit attached to the digital camera. As an example of a focus detection method, there is a method by a phase difference system or a contrast system, but the method is not limited to this example.

Abstract: A method, apparatus, and system are disclosed for selecting quality images from multiple captured images. One embodiment is an image capturing system. The system includes hardware for capturing a plurality of consecutive images and a processor for determining a quality indication for the consecutive images and for selecting one of the consecutive images based on the quality indication.

Abstract: An imaging device is provided. The imaging device can maintain a constant angle of view even if a focal distance of an entire lens system changes as a focusing lens moves. The imaging device includes an image sensor, a focusing lens, a lens driver, an image generator, a magnification changing rate obtaining unit, and a size changer. The image sensor shoots a snap shot of an object, and the focusing lens performs focusing on the object. The lens driver drives the focusing lens to a plurality of focal points for the object, and the image generator generates an image on the basis of a photograph signal from the image sensor. The magnification changing rate obtaining unit obtains a magnification changing rate for each focal point such that an angle of view for each image photographed at each focal point of the focusing lens is maintained constant. The size changer changes the size of the image on the basis of the magnification changing rate.

Abstract: In order to carry out relatively accurate AF control while eliminating the adverse effect on a reproduced moving picture, a subject is imaged every 1/30 seconds, so that subject images are obtained. Image data representing the subject images respectively corresponding to odd-numbered frames are recorded on a memory card as image data representing the moving picture. At timing where the subject images respectively corresponding to even-numbered frames are obtained by the imaging, auxiliary light is irradiated onto the subject. A high-frequency component is extracted from the image data representing each of the subject images respectively corresponding to even-numbered frames, so that focusing data representing the degree of focusing of the subject image is obtained. Since the subject image used for focusing control is bright, focusing control can be carried out relatively accurately.

Abstract: A photography device has an AF mechanism including: a CCD; an analog signal processing section; an image input controller; an AF processing section; a CPU; and a focusing lens driving section. The AF mechanism operates to focus an imaging lens on a subject. If an image represented by output from the CCD does not include a specific low contrast subject, image data representing the image is passed through a first high frequency filter that transmits components having frequencies greater than or equal to a first cutoff frequency, and a focus evaluation value is determined based on the transmitted components. If the image includes the specific subject, the image data is passed through a second high frequency filter that transmits components having frequencies greater than or equal to a second cutoff frequency, lower than the first cutoff frequency, and a focus evaluation value is determined based on the transmitted components.

Abstract: A CPU 11 in a digital camera 1 determines that the photography environment is dark and includes a spot light source, in the case where the number of pixels that have a higher luminosity than a first threshold to the total number of pixels in the focus area exceeds a first certain proportion and the number of pixels that have a lower luminosity than a second threshold to the total number of pixels in the focus area exceeds a second certain proportion, on the basis of a luminosity signal Y which has been acquired. Subsequently, the CPU 11 reads out a coefficient value of a cut-off frequency from a memory 110, inputs it to an HPF 9 thereby setting the cut-off frequency fc higher.

Abstract: The embodiments of the invention relate to automatic focusing methods and apparatus suitable for use in digital imaging devices. The proposed methods and apparatus evaluate the focus condition of the optical system by evaluating the digitized image, without requiring additional hardware besides the digital image-capture signal flow path. A method for computing the appropriate direction and magnitude of optical system adjustment, based on the evaluated focus condition, is provided. The computed quantities are communicated to the lens driving apparatus to reposition and adjust the optical system and to incrementally obtain a better focus. Upon reaching a desired focus quality, the device is prevented from controlling the lens driving apparatus.

Abstract: There is a problem that a delay is caused in signal processing by exercising control so as to cause amplitude peaks in a transmission signal to fall in a prescribed range. A transmission apparatus for conducting wireless communication makes a decision whether a specific pattern which causes a peak exceeding a predetermined amplitude range to be generated in frequency characteristics of a transmission signal is included in a transmission code sequence for forming the transmission signal. And the transmission apparatus selects filter coefficients which prescribe a band limiting factor for the frequency characteristics of the transmission signal, on the basis of a result of the decision, and conducts filtering on the transmission code sequence by using the selected filter coefficients.

Abstract: In an image pickup apparatus, information of a distance to an object is acquired according to an image pickup direction such as panning or tilting under a condition where focusing can be conducted, an image pickup direction is detected at a present position due to a panning angle and a tilting angle in the case where focusing cannot be conducted at a low illumination level, the information of distance to an object corresponding to the detected image pickup direction is read out from the memory, and a focus lens is driven at the read position, thereby making it possible to take a photograph even under a condition where the object cannot be focused.

Abstract: An automatic focusing apparatus includes an image pickup optical system; an image pickup device for converting an optical image formed by the image pickup optical system into an electric image signal at a predetermined cycle and outputting the electric signal; a focusing device; an optical flow calculation device for calculating optical flows in accordance with the image signals in a first image plane at a first time and a second image plane at a second time different from the first time, and for calculating an average of magnitudes and directions of the optical flows; and a judgment device for determining whether or not the focusing device is to be driven in accordance with calculated average of the magnitudes and the directions of the optical flows.

Abstract: A focus detection apparatus includes a lens drive mechanism for moving a focusing lens group, and a controller for detecting a contrast value of the object image and moving the focusing lens group. The controller calculates a difference between maximum and minimum contrast values detected at the different positions of the focusing lens group; compares contrast values at two adjacent lens positions to determine whether the contrast value increases successively and subsequently decreases successively; detects a maximum contrast value, if the contrast value increases successively and subsequently decreases successively; calculates the maximum contrast value via a point of intersection between straight lines of two linear approximation expressions if the difference is equal to or greater than a predetermined value; calculates the maximum contrast value from a quadratic approximation expression, if the difference is smaller than the predetermined value.

Abstract: Evaluation values are extracted at first timings with respect to a movement of a focus lens, and evaluation values are extracted at second timings having higher frequency than the first timings on the basis of the evaluation values extracted at the first timings. Then, even if the evaluation values have been extracted at the second timings in such a way, the focus lens is moved on the basis of the evaluation values extracted at the first timings. Thereby, the fast and suitable movement of AF can be implemented.

Abstract: A focus detection apparatus includes a focusing lens group, and a controller. The controller establishes a first predetermined number and a first criterial value if a maximum contrast value and/or minimum contrast value is outside a predetermined range, and a second predetermined number and second criterial value if the maximum and minimum contrast values are within the predetermined range; compares contrast values detected at adjacent positions to determine whether the contrast value of the object image increases once and subsequently decreases by the first or second predetermined number of times; detects a maximum contrast value if the contrast value of the object image increases once and subsequently decreases by the first or second predetermined number of times; determines a difference between the maximum contrast value and a detected contrast value; and selects the maximum contrast value if the difference exceeds the first/second criterial value.

Abstract: A video camera includes a gate circuit for extracting a sharpness signal relative to an area which is set in a portion of a picture, a focus adjusting device for performing focus adjustment on the basis of the sharpness signal relative to the area, and an area selecting circuit for controlling the gate circuit to vary the area in size and determining a size of the area during a driving of a variator lens in accordance with a size of the area and a focal length used before the driving of the variator lens.

Abstract: An output from an auto focus sensor is converted into a digital signal by an A/D converting section, and an output from the A/C converting section is stored in a memory section. Further, a second AF arithmetic section is used to concurrently execute a plurality of focus detection arithmetic operations based on data in the memory section.

Abstract: Provided are an automatic focusing method in which a photograph region is brought into focus through automatic movement of a focal lens to a focal position, in response to a photographing-command signal, and a digital photographing apparatus using the method. The method includes dividing the photograph region into a plurality of sub-regions, focusing on the sub-regions and obtaining focal position values DSFOC, calculating an average focal position value ADSFOC of the focal position values DSFOC, selecting focal position values DSFOC whose differences from the average focal position value ADSFOC are equal to or less than a threshold value DTH, and moving the focal lens to a focal position corresponding to the focal position value DSFOC having the shortest focal distance among the selected focal position values DSFOC.

Abstract: A storage unit is configured to store beforehand a table that shows a relation between spread parameters and command values supplied to a control unit to acquire a focused image of an object, and information that designates a command value corresponding to an inflection point on an approximated curve showing the relation that the spread parameters have with the command values, the control unit being configured to control a state of an optical system in accordance with an input command value. The luminance information about the object that lies at a distance falling within a range over which focusing should be detected is acquired, at the position of the optical system, which is obtained by the command value corresponding to the inflection point shown in the table.

Abstract: A focus adjustment apparatus, which attains focus adjustment by extracting, as a focal point voltage, a predetermined frequency component of a video signal obtained from an image sensor upon sensing an image of an object, and moving a focus adjustment member in an optical axis direction using a moving unit to maximize the focal point voltage, has a detector that detects a half-stroke state of a shutter button, and a full-stroke state which is set via the half-stroke state, and a controller that executes focus adjustment control for the half-stroke state upon detection of the half-stroke state, and selectively enables or disables the focus adjustment control for the half-stroke state in accordance with a time elapsed from detection of the half-stroke state until detection of the full-stroke state, upon detection of the full-stroke state.

Abstract: Methods, software, and apparatus for focusing an image in biological instrument are disclosed. Focusing elements are moved to various focus positions within a focus element travel range, and sample images are captured at the various focus positions. The sample images are resolved into subregions and an optimal focus position is determined based on the image intensity statistical dispersions within the identified subregions.

Abstract: A method for focus adjusting through which a subject image formed with a photographic optical system is captured by an image-capturing device and a focus match position for the photographic optical system is calculated based upon focus evaluation values calculated by using image-capturing signals includes steps for: obtaining focus evaluation values over first sampling increments in a focus adjustment range of the photographic optical system; making a decision as to whether or not a sampling position corresponding to a largest value among the focus evaluation values obtained over the first sampling increments is substantially at an end point of the focus adjustment range; obtaining focus adjustment values over second sampling increments smaller than the first sampling increments in a range that contains the end point and is smaller than the focus adjustment range if the sampling position corresponding to the largest value among the focus evaluation values is at the end point of the focus adjustment range; and

Abstract: The autofocus apparatus determines a focus position according to a result of sampling an AF evaluated value and drives a lens system to the focus position. This autofocus apparatus further performs a flash in synchronism with a sampling timing of an AF evaluated value.

Abstract: Systems and method for determining, based on a gray scale image, focus of an imaging system. A method of this invention includes the steps of: a) acquiring a gray scale image of a test target, b) binarizing the acquired gray scale image, c) analyzing the binarized acquired image, d) adjusting focus of acquisition optics of the imaging system, and e) repeating steps a) through d) until a substantially maximum number of line pairs of a number of groups of line pairs of the test target is obtained, wherein each group from the number of groups of line pairs has a predetermined spatial frequency.