Showing papers on "Depth of field published in 2003"

Materials and methods for simulating focal shifts in viewers using large depth of focus displays

Abstract: A large depth of focus (DOF) display provides an image in which the apparent focus plane is adjusted to track an accommodation (focus) of a viewer's eye(s) to more effectively convey depth in the image. A device is employed to repeatedly determine accommodation as a viewer's gaze within the image changes. In response, an image that includes an apparent focus plane corresponding to the level of accommodation of the viewer is provided on the large DOF display. Objects that are not at the apparent focus plane are made to appear blurred. The images can be rendered in real-time, or can be pre-rendered and stored in an array. The dimensions of the array can each correspond to a different variable. The images can alternatively be provided by a computer controlled, adjustable focus video camera in real-time.

Enhanced three-dimensional integral imaging system by use of double display devices

Abstract: We propose an enhanced three-dimensional (3D) integral imaging system using multiple display devices. Experimental results with double devices prove the improvement in the image depth for a given image quality. We present experiments on an enhanced 3D integral imaging system using double display devices, in which two 3D subimages that cover different depth ranges are separately generated in each device, and then they are combined with a beam splitter to reconstruct the whole 3D image with an enhanced depth of view. In a similar manner, the double-device system can also be used to obtain a wider viewing angle by combining two images with different viewing angle ranges. We discuss the possibility of 3D integral imaging systems using multiple display devices as extensions of the system with double display devices.

Computationally efficient algorithm for multifocus image reconstruction

Abstract: A method for synthesizing enhanced depth of field digital still camera pictures using multiple differently focused images is presented This technique exploits only spatial image gradients in the initial decision process The image gradient as a focus measure has been shown to be experimentally valid and theoretically sound under weak assumptions with respect to unimodality and monotonicity Subsequent majority filtering corroborates decisions with those of neighboring pixels, while the use of soft decisions enables smooth transitions across region boundaries Furthermore, these last two steps add algorithmic robustness for coping with both sensor noise and optics-related effects, such as misregistration or optical flow, and minor intensity fluctuations The dependence of these optical effects on several optical parameters is analyzed and potential remedies that can allay their impact with regard to the technique's limitations are discussed Several examples of image synthesis using the algorithm are presented Finally, leveraging the increasing functionality and emerging processing capabilities of digital still cameras, the method is shown to entail modest hardware requirements and is implementable using a parallel or general purpose processor

All optical extended “depth-of field” imaging system

Abstract: The instant invention is an optical imaging system that produces images of acceptable quality of objects which are located at a wide variety of distances from the optical imaging system. A preferred embodiment of the optical imaging system includes an object (10), an auxiliary lens (12), a composite phase marsk (14) and a detector (18) arranged along an optical axis (20). Light from the object (10) is focused by the auxiliary lens (12) in tandem with the composite phase mark (14), producing an image (16) which is incident th detector (18).

Extended depth of field using a logarithmic asphere

Abstract: Imaging systems are described which use a logarithmic asphere and image processing in order to increase the depth of field substantially beyond classical limits. A nonparaxial form of the diffraction theory integral for an impulse response is derived and evaluated in order to establish a precise expression for the transmission function of this asphere. This nonparaxial physical optics formulation provides results of fractional wavelength accuracy that enable one immediately to complete the design and fabrication of the optical system. Circularly symmetric aspherical lenses, either for single-lens cameras or blurring phase filters for use with commercial photographic lenses, have been fabricated using advanced grinding and finishing machines. Computer simulation studies are presented to show that a logarithmic asphere is capable of diffraction-limited performance over an extended depth of field. Experimental imaging results including digital processing by an inverse filter show a tenfold increase in the depth of field.

Compound camera and methods for implementing auto-focus, depth-of-field and high-resolution functions

Abstract: A compound camera system for generating an enhanced virtual image having a large depth-of-field. The compound camera system comprises a plurality of component cameras for generating image data of an object and a data processor for generating the enhanced virtual image from the image data. The data processor generates the enhanced virtual image by generating a first component virtual image at a first depth plane, generating a second component virtual image at a second depth plane, and inserting first selected pixels from the first component virtual image into enhanced the virtual image and inserting second selected pixels from the second component virtual image into the enhanced virtual image.

Computational imaging with the logarithmic asphere: theory

Abstract: A theory for an integrated system is described that combines a logarithmic aspheric imaging lens with maximum-entropy digital processing to extend the depth of field ten times over that of a conventional lens and to provide near-diffraction-limited resolution. Two types of logarithmic aspheres are derived that are circularly symmetric lenses with controlled continuous radial variation of focal length. The details of an iterative maximum-entropy algorithm are also presented. The properties of convergence and speed of the algorithm are greatly improved by introducing a metric parameter to adjust the weight of different pixel values of the recovered picture in each loop properly.

Methods and systems for reducing depth of field of hybrid imaging systems

Abstract: An imaging system for imaging an object onto an image plane. An optical arrangement forms an intermediate image of the object at an intermediate plane with a first value of axial resolution. The imaging system also includes a digital processor configured to process the intermediate image to form a final image of the object at the image plane. The imaging system further includes a specially designed optical element that cooperates with the optical arrangement and the digital processor to define a second value of axial resolution that is greater than the first value.

Method and apparatus for controlling the depth of field using multiple user interface markers

Abstract: A digital imaging device that allows the user to mark multiple objects with UI markers is disclosed. The digital imaging device automatically adjusts the focus and aperture to include the marked objects in the depth of field of the digital imaging device.

Imaging optical code reader having selectable depths of field

Abstract: Several optical systems for imaging engines of imaging optical code readers are disclosed. Each optical system includes the abilities to change the depth of field of the imaging field and to adjust a focus quality of the imaging field. The disclosed structures for changing the depth of field of the disclosed optical systems allow for the automatic or manual selection of one of a plurality of depths of field.

Image pickup apparatus

Abstract: The present invention relates to a compact and low-cost image pickup apparatus that is capable of photographing a high-quality image comparable to silver halide photographs even when the image is enlarged to 8x10'' size or larger and that enables the depth of field to be controlled with an aperture number exceeding F4. In the image pickup apparatus, an image of an object produced by an optical system (10) is formed on an electronic image pickup device (20), thereby obtaining image information concerning the object. The optical system (10) has a structure capable of obtaining an aperture number equal to or larger than F4 by reducing the beam diameter. Performance required for the optical system (10) is such that the size of the diameter of 90% encircled energy of the point spread function by amplitude is allowed to be up to about 8 times larger than the pixel pitch corresponding to the resolvable pixel unit. The pixel pitch of the image pickup device (20) is not larger than about 5 micrometers. The number of pixels is not less than about 2.5 million, which meets the resolvable pixel unit.

Improved digital SEM of cancellous bone: scanning direction of detection, through focus for in-focus and sample orientation.

Abstract: Three-dimensional (3D) study of cancellous bone tissue organization is necessary to understand how modelling and remodelling processes regulate bone structure and connectivity. It requires imaging methods that have both sufficient resolution power and width and depth of field. Since clinical imaging methods fall far short of the first requirement, we can only study prepared tissue in isolation from the body. Scanning electron microscopy (SEM) of macerated plane parallel slices is the most productive method, but we meet special technical problems in imaging porous bone because samples need to be relatively thick to maintain both continuity and context. Problems due to charging under the electron beam can be controlled by imaging with only high-energy backscattered electrons (BSE). This gives an important additional benefit that the direction of apparent illumination can be manipulated by positioning the detector, and multiple detector positions can be employed strategically to generate images in which colour is used to help in coding surface morphology. However, we next confront the difficulty of the limited depth of field. This can be improved by taking series of images, moving the sample along the electron optic axis, and combining these to generate a single extended-focus image. SEM imaging geometry gives a change in magnification with change of working distance, and it is shown that this must be corrected for each image of the through-focus sequence. Colour coding the lighting direction and increasing the depth of field are approaches that can be combined, and are well matched to the possibilities offered by communication by digital data projection. Finally, the latter means also offer another powerful technique for 3D representation through the display of through tilt image sequences. The novel routines considered here are generally applicable to all classes of microanatomical SEM sample.

Methods and apparatus for rendering an image with depth-of-field display

Abstract: A depth of field rendering apparatus, method and program displays a sense of distance using a Z buffer to establish a depth direction of objects in an image and generating an image in a just-in-focus state while writing a Z value of each of dots in the image into the Z-buffer. A blurred image is produced from the just-in-focus image and portions of the blurred image are selectively overwritten on the just-in-focus image by comparing a preset Z value to the Z value of each of the data in the Z buffer.

Depth-of-field micron resolution velocimetry with pulsed images of injected solid particles

Abstract: Method and apparatus for measuring fluid motion with micron scale spatial resolution, in which fluorescent particles are injected into a fluid body in a test device, the test device is broadly illuminated with pulses of light at the excitation frequency of the fluorescent particles, the fluorescent light is collected by a microscope objective lens, and the light thus collected is relayed through a fluorescent filter to an image recording device, the depth of field of the objective lens defining the thickness of a two-dimensional measurement plane.

Whiteboard view camera

Abstract: A whiteboard view camera, which in one embodiment is mounted on a boom, which is fixed above the whiteboard. However, the whiteboard view camera can also be wall or table mounted. The whiteboard view camera differs from an ordinary camera by allowing the lens to tilt with respect to the sensor plane, and shift with respect to the central ray. When the tilt angle α is zero, then the resolution of whiteboard is uniform (e.g., the top and bottom of the whiteboard have the same resolution). In addition, the focus plane is equal to the whiteboard plane, so depth of field issues are not a problem (e.g., a large aperture can be used). Hence, no image noise is introduced. A key contribution of the whiteboard view camera configuration according to the invention is the use of a view camera to capture whiteboard images at uniform resolutions. One embodiment of the whiteboard view camera employs a microphone array of the invention and uses a computer to optimize the image data and audio signals.

Device for contactless optical acquisition of biometric characteristics of at least one body part

Abstract: A device for contactless optical acquisition of biometric characteristics of at least one body part with at least one camera having a lens system and an image sensor. The device acquires a surface image of body part which is positionable in an object plane. The lens system provides distortion-free imaging in the entire image field and has a depth of field which at least corresponds to the maximum topographic extension of the surface contour of the surface of the body part, which surface is acquirable from one direction by the camera. The device has a positioning assistance device which generates directions to a user in order to provide contactless positioning of the surface of the body part to be imaged in the object plane.

Image pickup device, image data generating device, image data processor, and image data processing program

Abstract: PROBLEM TO BE SOLVED: To flexibly correct the distance in focus regarding the photographed image. SOLUTION: The image pickup device 1 photographs images with the same field angle and different distances in focus by one release operation. It can falsely generate the image in the case of changing the distance in focus on the basis of the images and lens information after the photographing. Accordingly, it is possible to flexibly change the distance in focus such as moving the focus forward and backward ex post and changing the depth of field in the photographed images. COPYRIGHT: (C)2005,JPO&NCIPI

Accurate preview for digital cameras

Abstract: A digital camera and method that embodies a preview image that shows what the final image will look like, including depth of field and shutter speed temporal effects (blur). Preview images are displayed as a series of stop-action still images rather than as continuous video. Overlays or picture-in picture can be used to show live action video simultaneously for framing.

Extended depth of field using the logarithmic asphere

Abstract: Transmission functions are derived for a novel logarithmic aspheric lens that provides an extended depth-of-field when used in an integrated digital processing system. Diffraction-theory equations valid in the non-paraxial case are presented together with a comparative study of two designs. This lens can be used either singly or in conjunction with a standard photographic lens. A tenfold increase in the depth-of-field has been obtained.

Image pickup device provided with distance image measurement function and endoscopic apparatus

Abstract: PROBLEM TO BE SOLVED: To display a scale for measuring the actual size of an object on an image since perspective is lost and the absolute size of the object is not recognized because focusing is made in a wide range in the case that the depth of field is large. SOLUTION: The size of the object is measured by obtaining distance images to the individual parts of the object by using a range image sensor and overwriting isometric distribution contour within a plane where the object is projected on a two-dimensional image as a mesh-like scale from a geometrical relation by using the distance in the depth direction. COPYRIGHT: (C)2005,JPO&NCIPI

Camera with indication of measure of focus as a function of focal distance

Abstract: A camera includes software to compute a measure of focus at a plurality of focal distances The camera includes an indicator of the measure of focus as a function of focal distance The camera may also include an indication of present focal position The camera may also include an indication of present depth of field

Two methods for increasing the depth of focus of imaging systems

Abstract: In this paper we describe two approaches for extending the depth of field in incoherent imaging system. The first one, a hybrid opto-digital incoherent imaging system, relies on an optical setup whereby the image is deliberately distorted, followed by a digital restoration stage. The second, an all-optical incoherent imaging system is based on a spatially code multiplexed multiple Fresnel lens mask, poisitioned in the lens aperture. Both provide a relatively high optical throughput and small contrast reduction, for an extremely wide range misfocus positions. For both cases, design considerations for an extended depth of field will be described. It is important to mention that both approaches are able to provide results in real time, thus enabling their usage in practical systems; yet the all-optical system presents a remarkable simplification.

Calibration of curvature of field for depth from focus

Abstract: A method for accurate depth measurement in depth from focus is presented With depth from focus the 3D shape of objects can be measured To do so, an image series with different distances between camera and object is evaluated to extract focused parts Combining the results of an edge detection filter with the distance information at which the images have been acquired provides a depth image of the object The focus information is influenced by optical aberrations Especially the curvature of field leads to a significant error in the depth image This error can be seen by measuring the depth information of a planar object with depth from focus The error in the depth image is approximated by fitting a second order surface to the depth image To overcome the influence of outliers in the depth image a robust least-squares fitting with suppression of outliers is used The second order surface is then used to correct depth images, which reduces the influence of the curvature of field on the depth data and leads to more accurate 3D measurements

Phase control and measurement in digital microscopy

Abstract: The ongoing merger of the digital and optical components of the modern microscope is creating opportunities for new measurement techniques, along with new challenges for optical modelling. This thesis investigates several such opportunities and challenges which are particularly relevant to biomedical imaging. Fourier optics is used throughout the thesis as the underlying conceptual model, with a particular emphasis on three–dimensional Fourier optics. A new challenge for optical modelling provided by digital microscopy is the relaxation of traditional symmetry constraints on optical design. An extension of optical transfer function theory to deal with arbitrary lens pupil functions is presented in this thesis. This is used to chart the 3D vectorial structure of the spatial frequency spectrum of the intensity in the focal region of a high aperture lens when illuminated by linearly polarised beam. Wavefront coding has been used successfully in paraxial imaging systems to extend the depth of field. This is achieved by controlling the pupil phase with a cubic phase mask, and thereby balancing optical behaviour with digital processing. In this thesis I present a high aperture vectorial model for focusing with a cubic phase mask, and compare it with results calculated using the paraxial approximation. The effect of a refractive index change is also explored. High aperture measurements of the point spread function are reported, along with experimental confirmation of high aperture extended depth of field imaging of a biological specimen. Differential interference contrast is a popular method for imaging phase changes in otherwise transparent biological specimens. In this thesis I report on a new isotropic algorithm for retrieving the phase from differential interference contrast images of the phase gradient, using phase shifting, two directions of shear, and non–iterative Fourier phase integration incorporating a modified spiral phase transform. This method does not assume that the specimen has a constant amplitude. A simulation is presented which demonstrates good agreement between the retrieved phase and the phase of the simulated object, with excellent immunity to imaging noise.

Ultrasonic imaging with spot focused waves

Abstract: The invention is a system that was developed for medical imaging, with particular attention to breast imaging applications. Spot focused architecture enables very high resolution imaging using very large aperture transducer arrays, where depth of field and focal length cause a small focused spot at a pre-set depth for each transmit-receive operation. Scanning depends on rapid movement of the focus spot throughout an intended object space, so transmit-receive events are overlapped in time. Coded signals are used to suppress interference caused by such overlap. Selection of codes by pre-set correlation is simple, where a correlator channel produces a single image data sample for each spot. Coded signals are compensated for frequency dependent attenuation by the medium to enable wide bandwidth effects. Attenuation leveling and fixed paths to spots enable prediction and compensation for frequency dependent attenuation to enable broad band effects. The architecture provides for bistatic operation of sparse arrays, with hybrid electronic beamformers. It also uses mechanical scanning. Transducer elements are constructed by cutting strips from thin cards of piezo-electric material.

System for extending depth of field

Abstract: PROBLEM TO BE SOLVED: To obtain an image which has ghost removed and the depth of field extended. SOLUTION: Respective image data D 1 and D 2 of intermediate images I 1 and I 2 are acquired by rotating a pupil modulating device 3 at rotation angles 0° and 180°, and arithmetic processing for the sum and difference between these intermediate image data D 1 and D 2 is performed to obtain an image which has ghost removed and the depth of field extended in real time. COPYRIGHT: (C)2005,JPO&NCIPI

Depth of Field Control in Incoherent Hybrid Imaging Systems

Abstract: A hybrid imaging system combines a modified optical imaging system and a digital post-processing step. We define a new metric to quantify the blurring of a defocused image that is more suitable than the defocus parameter for hybrid imaging systems.

Apparatus for OCT imaging with axial line focus for improved resolution and depth of field

Abstract: An apparatus for performing low coherence ranging of a sample with high transverse resolution and large depth of focus, comprising an optical ranging system comprising a light source, a means for directing light from the light source to the sample, a means for directing reflected light from the sample to a detector, at least one detector, a means for processing light data received by the detector and which generates an image and an optical element having a transverse resolution defined as DELTAris less than or equal to about 5microm, and a depth of focus DELTAz of at least about 50 microm.

Picture management system and picture management method, and computer program

Abstract: PROBLEM TO BE SOLVED: To provide a picture management system and a picture management method, and a computer program capable of facilitating management of pictures by recognizing an object shown in a photographed picture and coupling the photographed picture to the object shown in the picture. SOLUTION: The picture management system acquires a position of a camera, a direction of a lens, a focal distance, a field angle, and an aperture in the case of photographing a picture, calculates a photographing space comprising a focal plane and a depth of field on the basis of the values above, recognizes an object by collating the photographing space with a position on a map, ranks a plurality of photographing objects by measuring a distance from a photographing center, a measurement error of the camera position, and a measurement error in the lens direction, and a photographer deletes and edits recognition results to practically carry out recognition of the object. COPYRIGHT: (C)2005,JPO&NCIPI