Showing papers on "Lens (optics) published in 2001"

Simultaneous linear estimation of multiple view geometry and lens distortion

Abstract: A problem in uncalibrated stereo reconstruction is that cameras which deviate from the pinhole model have to be pre-calibrated in order to correct for nonlinear lens distortion. If they are not, and point correspondence is attempted using the uncorrected images, the matching constraints provided by the fundamental matrix must be set so loose that point matching is significantly hampered. This paper shows how linear estimation of the fundamental matrix from two-view point correspondences may be augmented to include one term of radial lens distortion. This is achieved by (1) changing from the standard radial-lens model to another which (as we show) has equivalent power, but which takes a simpler form in homogeneous coordinates, and (2) expressing fundamental matrix estimation as a quadratic eigenvalue problem (QEP), for which efficient algorithms are well known. I derive the new estimator, and compare its performance against bundle-adjusted calibration-grid data. The new estimator is fast enough to be included in a RANSAC-based matching loop, and we show cases of matching being rendered possible by its use. I show how the same lens can be calibrated in a natural scene where the lack of straight lines precludes most previous techniques. The modification when the multi-view relation is a planar homography or trifocal tensor is described.

Reduced area imaging device incorporated within wireless endoscopic devices

Abstract: A reduced area imaging device is provided for use in medical or dental instruments such as an endoscope. In a first embodiment of the endoscope, connections between imaging device elements and between a video display is achieved by hard-wired connections. In a second embodiment of the endoscope, wireless transmission is used for communications between imaging device components, and/or for transferring video ready signals to a video display. In one configuration of the imaging device, the image sensor is placed remote from the remaining circuitry. In another configuration, all of the circuitry to include the image sensor is placed in a stacked fashion at the same location. The entire imaging device can be placed at the distal tip of an endoscope. Alternatively, the image sensor can be placed remote from the remaining circuitry according to the first configuration, and control box is used which communicates with the image sensor and is placed remotely from the endoscope. Further alternatively, the imaging device can be incorporated in the housing of a standard medical camera which is adapted for use with traditional rod lens endoscopes. In any of the configurations or arrangements, the image sensor may be placed alone on a first circuit board, or timing and control circuits may be included on the first circuit board containing the image sensor. The timing and control circuits and one or more video processing boards can be placed adjacent the image sensor in a tubular portion of the endoscope, in other areas within the endoscope, in the control box, or in combinations of these location.

Calcitic microlenses as part of the photoreceptor system in brittlestars

Abstract: Photosensitivity in most echinoderms has been attributed to 'diffuse' dermal receptors. Here we report that certain single calcite crystals used by brittlestars for skeletal construction are also a component of specialized photosensory organs, conceivably with the function of a compound eye. The analysis of arm ossicles in Ophiocoma showed that in light-sensitive species, the periphery of the labyrinthic calcitic skeleton extends into a regular array of spherical microstructures that have a characteristic double-lens design. These structures are absent in light-indifferent species. Photolithographic experiments in which a photoresist film was illuminated through the lens array showed selective exposure of the photoresist under the lens centres. These results provide experimental evidence that the microlenses are optical elements that guide and focus the light inside the tissue. The estimated focal distance (4-7 micrometer below the lenses) coincides with the location of nerve bundles-the presumed primary photoreceptors. The lens array is designed to minimize spherical aberration and birefringence and to detect light from a particular direction. The optical performance is further optimized by phototropic chromatophores that regulate the dose of illumination reaching the receptors. These structures represent an example of a multifunctional biomaterial that fulfills both mechanical and optical functions.

Power vector analysis of the optical outcome of refractive surgery

Abstract: Purpose To demonstrate the power vector method of representing and analyzing spherocylindrical refractive errors. Setting School of Optometry, Indiana University, Bloomington, Indiana, USA. Methods Manifest and keratometric refractive errors were expressed as power vectors suitable for plotting as points in a 3-dimensional dioptric space. The 3 Cartesian coordinates ( x , y , z ) of each power vector correspond to the powers of 3 lenses that, in combination, fulfill a refractive prescription: a spherical lens of power M , a Jackson crossed cylinder of power J 0 with axes at 90 degrees and 180 degrees, and a Jackson crossed cylinder of power J 45 with axes at 45 degrees and 135 degrees. The Pythagorean length of the power vector, B , is a measure of overall blurring strength of a spherocylindrical lens or refractive error. Changes in refractive error due to surgery were computed by the ordinary rules of vector subtraction. Results Frequency distributions of blur strength ( B ) clearly demonstrate the effectiveness of refractive surgery in reducing the overall blurring effect of uncorrected refractive error. Power vector analysis also revealed a reduction in the astigmatic component of these refractive errors. Paired comparisons revealed that the change in manifest astigmatism due to surgery was well correlated with the change in keratometric astigmatism. Conclusions Power vectors aid the visualization of complex changes in refractive error by tracing a trajectory in a uniform dioptric space. The Cartesian components of a power vector are mutually independent, which simplifies mathematical and statistical analysis of refractive errors. Power vectors also provide a natural link to a more comprehensive optical description of ocular refractive imperfections in terms of wavefront aberration functions and their description by Zernike polynomials.

Plastic lens system for vehicle imaging system

Abstract: An optical or lens system for use with an imaging system of a vehicle includes a plurality of optical elements. The optical elements include less than five optical elements and, preferably, include four optical elements. Each of the optical elements is formed of a plastic material. At least two of the optical elements include a diffractive element. Preferably, a diffractive element is formed on an outer surface of two of the optical elements. The optical system provides and focuses a field of view of a targeted area of at least approximately 100 degrees to an imaging plane. The imaging plane is at an imaging sensor or camera or other imaging device operable to receive the image from the optical system. The optical system further includes an aperture stop between two of the optical elements.

Interferometeric imaging with a grating based phase control optical delay line

Abstract: An apparatus for performing high speed scanning of an optical delay and its application for performing optical interferometry, ranging, and imaging, including cross sectional imaging using optical coherence tomography, is disclosed The apparatus achieves optical delay scanning by using diffractive optical elements in conjunction with imaging optics In one embodiment a diffraction grating disperses an optical beam into different spectral frequency or wavelength components which are collimated by a lens A mirror is placed one focal length away from the lens and the alteration of the grating groove density, the grating input angle, the grating output angle, and/or the mirror tilt produce a change in optical group and phase delay This apparatus permits the optical group and phase delay to be scanned by scanning the angle of the mirror In other embodiments, this device permits optical delay scanning without the use of moving parts

A general imaging model and a method for finding its parameters

Abstract: Linear perspective projection has served as the dominant imaging model in computer vision. Recent developments in image sensing make the perspective model highly restrictive. This paper presents a general imaging model that can be used to represent an arbitrary imaging system. It is observed that all imaging systems perform a mapping from incoming scene rays to photo-sensitive elements on the image detector. This mapping can be conveniently described using a set of virtual sensing elements called raxels. Raxels include geometric, radiometric and optical properties. We present a novel calibration method that uses structured light patterns to extract the raxel parameters of an arbitrary imaging system. Experimental results for perspective as well as ion-perspective imaging systems are included.

Rearview mirror assembly with information display

Abstract: An interior rearview mirror assembly provides a display system for displaying light or information to a driver of a vehicle. The display includes a refractive light directing element, which may include a prismatic display lens which refracts and directs the light of the display message downwardly and/or sidewardly toward a driver of the vehicle for improved viewing of the display message by the driver of the vehicle. The display system is mountable to a printed circuit board positioned within the case of the mirror assembly. The printed circuit board may also be connected to a pair of illumination sources positioned at a lower portion of a casing of the mirror assembly.

Refractive acoustic devices for airborne sound.

Abstract: We show that a sonic crystal made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. It is demonstrated that, in the long-wave regime, the crystal has low impedance and the sound is transmitted at subsonic velocities. Here, the fabrication and characterization of a convergent lens are presented. Also, an example of a Fabry-Perot interferometer based on this crystal is analyzed. It is concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems.

Methods of obtaining ophthalmic lenses providing the eye with reduced aberrations

Abstract: The present invention discloses methods of obtaining ophthalmic lens capable of reducing the aberrations of the eye comprising the steps of characterizing at least one corneal surface as a mathematical model, calculating the resulting aberrations of said corneal surface(s) by employing said mathematical model, selecting the optical power of the intraocular lens. From this information, an ophthalmic lens is modeled so a wavefront arriving from an optical system comprising said lens and corneal model obtains reduced aberrations in the eye. Also disclosed are ophthalmic lenses as obtained by the methods which are capable reducing aberrations of the eye.

Exposure apparatus and exposure method capable of controlling illumination distribution

Abstract: An exposure apparatus radiates an exposure light beam from an exposure light source onto a reticle via an illumination optical system including a first fly's eye lens, a second fly's eye lens, a lens system, a blind, and a condenser lens system, and it projects an image of a pattern on the reticle onto a wafer via a projection optical system. An illumination characteristic is measured by using an evaluation mark plate on a reticle stage and a spatial image-measuring system provided for a wafer stage. The states of the second fly's eye lens and the lens system are adjusted by the aid of a driving unit on the basis of the measured value. A concentration filter plate, which is formed with a pattern of a predetermined transmittance distribution, is rotatably arranged in the vicinity of a conjugate plane with respect to an image plane between the second lens system and the blind. The angle of rotation of the concentration filter plate 51 is controlled so that the uneven illuminance is corrected. The illumination optical system can be adjusted correctly for a short period of time. It is possible to improve the uniformity of the exposure amount distribution.

Intraocular lenses with fixated haptics

Abstract: Intraocular lenses (50) for implanting within the natural capsular bag of the human eye having features on the outer ends (54, 114, 136, 128) or portions of the lenses to fixate the lens within the natural capsular bag following implantation.

Image sensing apparatus

Abstract: An image sensing apparatus has an image sensing element which accumulates received light as a charge, a mechanical shutter which travels to shield the image sensing element, and a scan unit which makes a scan for starting charge accumulation. The image sensing apparatus executes the scan for starting charge accumulation prior to traveling of the mechanical shutter and controls the scan for starting charge accumulation and traveling of the shutter to serve as a front curtain and a rear curtain of a shutter. Note that a scan pattern setting unit (113b) sets the scan pattern of the charge accumulation start scan based on information associated with a mounted photographing lens.

Design and characterization of single- and multiple-beam mm-wave circularly polarized substrate lens antennas for wireless communications

Abstract: Single- and multiple-beam circularly polarized ellipsoidal substrate lenses suitable for millimeter-wave wireless communications have been designed, implemented, and experimentally characterized at 30 GHz. The lenses are made out of low-cost low-permittivity Rexolite material. The single-beam lens achieves a directivity of 25.9 dB, a front-to-back ratio of 30 dB, and an axial ratio of 0.5 dB is maintained within the main lobe. The measured impedance bandwidth is 12.5% within a SWR/spl les/1.8:1. The single-beam antenna is well suited for broad-band wireless point-to-point links. On the other hand, the multiple-beam lens launches 31 beams with a minimum 3-dB overlapping level among adjacent beams. The coverage of the lens antenna system has been optimized through the utilization of a hexagonal patch arrangement leading to a scan coverage of 45.4/spl deg/ with a maximum loss in directivity of 1.8 dB due to multiple reflections. The multiple-beam lens antenna is suitable for indoor point-to-multipoint wireless communications such as a broad-band local area network or as a switched beam smart antenna. During the proposed design process, some fundamental issues pertaining to substrate lens antennas are discussed and clarified. This includes the depolarization properties of the lenses, the effect of multiple internal reflections on the far-field patterns and the directivity, the nature of the far-field patterns, the estimation of the lens system F/B ratio, and the off-axis characteristics of ellipsoidal lenses.

Head mounted display with full field of view and high resolution

Abstract: A head mounted virtual environment display with high visual resolution and a full field of view is disclosed The display uses an optical system in which the video displays and corresponding lenses are positioned tangent to hemispheres with centers located at the centers of rotation of a user's eyes Centering the optical system on the center of rotation of the eye allows both a full field of view and high fidelity visual resolution, without compromising visual resolution A multi-panel video wall design for the video displays allows each lens facet to image a miniature flat panel display at optical infinity The flat panel displays are centered on the optical axes of the lens facets A parallel graphics architecture uses data from high resolution and accuracy head trackers and built-in eye trackers to generate high detail 3D models at high frame rates with minimal perceptible lag Resolution for central vision is optimized with a roaming high level of detail window, and slip artifacts associated with rapid head movements are eliminated using freeze-frame

The thickness of the aging human lens obtained from corrected Scheimpflug images.

Abstract: Commonly, measurements of lens thickness are performed using A-scan ultrasonography or slitlamp Scheimpflug photography. Both techniques have their drawbacks in the study of presbyopia: ultrasonography requires the velocity of sound in the lens which may change with age, whereas Scheimpflug photography requires knowing the refractive index of the lens to enable correction of the photographs for the distortion due to the refraction of the cornea and lens. By combining Scheimpflug photography and axial optical eye-length measurements, we were able to individually correct the Scheimpflug images for distortion and calculate the refractive index and thickness of the human lens. Lens thickness of 90 subjects ranging in age between 16 and 65 years was measured, and an average increase of 24 μm/year was found. This value is consistent with ultrasonographic measurements assuming an age-independent velocity of sound in the lens of 1641 m/s. The posterior lens surface recedes from the cornea with age, and this backward movement does not differ significantly from the forward movement of the anterior lens surface.

Electronic imaging using a logarithmic asphere.

Abstract: Transmission functions are derived that are valid in the nonparaxial case for a class of lenses that will image a continuum of points along an optical axis to a single image point This lens, which we call a logarithmic asphere, is then used in a digital camera The resolution of the camera is limited by the pixel size of the CCD; ie, it is not diffraction limited Digital processing is used to recover the image, and image-plane processing is used for speed We find a tenfold increase in the depth of field over that for the diffraction-limited case

Scanning single-mode fiber optic catheter-endoscope for optical coherence tomography

Abstract: We describe a new optical coherence tomography catheter-endoscope for micrometer-scale, cross-sectional imaging in internal organ systems. The catheter-endoscope uses single-mode fiber optics with a novel transverse scanning design. The distal end of the catheter-endoscope uses a gradient-index lens with a microprism to emit and collect a single spatial-mode optical beam with specific focusing characteristics. The beam is scanned in a circumferential pattern and can image transverse cross sections through the structure into which it is inserted. A device with a diameter as small as 1.1 mm has been achieved, and imaging of in vitro human venous morphology is demonstrated.

Active array lens antenna using CTS space feed for reduced antenna depth

Abstract: A space-fed active array lens antenna system has an active array lens with a first array of radiating elements defining a front antenna aperture which transmits and receives RF energy from free space, a second array of radiating elements defining a rear antenna aperture which transmits and receives RF energy from a feed aperture, and an array of transmit/receive (T/R) modules sandwiched between the front aperture and rear aperture. The T/R modules include a phase control circuit and an amplitude control circuit which provide phase and amplitude control for RF signals passing through the modules. The feed aperture includes a wide band CTS aperture which produces a plane wave in the near field.

Coplanar camera scanning system

Abstract: A system for scanning objects having a linear array sensor, adapted to detect light input signals, is provided. A lens is optically connected to the linear array sensor, and is adapted to receive and transmit an optical image located in a field of view along a lens axis to the linear array sensor. A light source which generates an illumination stripe in general linear alignment with the lens axis is provided. A cylindrical lens is positioned between the light source and an object to be scanned. The cylindrical lens adapted to collect, transmit and focus light from the light source to form the illumination stripe.

Image stabilizer for a microcamera module of a handheld device, and method for stabilizing a microcamera module of a handheld device

Abstract: A method and a handheld device for stabilizing an image captured by an optical lens of a micro camera integral with the handheld device, which may, for example, be a mobile phone. Motion sensors sense motion of the device and are used to cause movement of the micro camera to substantially compensate for the sensed movement so as to maintain a steady, focussed image to be displayed by a display on the handheld device or elsewhere, such as a remote display. The micro camera is moved by one or more motion actuators which move the camera in a horizontal plane substantially perpendicular to an axis of the lens of the camera and/or move the camera so as to pivot the lens axis.

Integrated optical micro-electromechanical systems and methods of fabricating and operating the same

Abstract: An apparatus and method of fabricating and operating a micro-electromechanical systems (MEMS) integrated optical structure is disclosed. Micro-optics is integrated with MEMS actuators to provide a building block for a micro-optical communication device. Such micro-optical communication device may realize a variety of optical communication systems including optical interconnects, laser communications, or fiber optic switches. In accordance with one aspect of the present invention, a micro-optical element such as a micro-lens is advantageously integrated with an actuator such as MEMS comb drive actuator to form a MEMS lens assembly. The MEMS lens assembly is further coupled to an optical source which may provide a MEMS integrated micro-optical communication device. This integration substantially obviates the generally needed external or manual positioning of the micro-optical element to align a light beam or an optical signal being emitted from the optical source. The MEMS comb drive actuator, responsive to an actuation force, selectively positions the micro-optical element. By appropriately micro positioning a micro-optical element such as a micro-lens relative to an optical source, such as an input optical fiber or a laser diode, a focused light beam or an optical signal may be coupled to a respective optical fiber or a detector. In one embodiment, a commonly used flip chip module assembly technique may be adapted for bonding the MEMS lens assembly to a carrier substrate, which preferably receives the optical source. The carrier substrate is generally disposed on a host assembly. A flip chip based passive alignment of the MEMS lens assembly could be provided. Additionally, an active alignment of the light beam or optical signal with an optical detector may be provided, which can be maintained through a feedback loop.

Integrated ic chip package for electronic image sensor die

Abstract: An IC chip package for an image sensitive, integrated circuit semiconductor die incorporates all the components typically found in an imaging module of an electronic camera. The IC chip package (80) consists of a plastic substrate base (83) for holding an image sensor die and a separate, plastic upper cover (81) for encapsulating the image sensor die and holding a filter glass (87), an optical lens (89), and providing an aperture for the optical lens. The upper cover (81) has a lower shelf (109) for holding the optical lens (89) in alignment with the aperture opening over the image sensor die, and has an upper shelf (107) for holding the filter glass (87) over the optical lens (89). The lens is attached to the lower shelf using UV cure adhesive, and its focal distance to the image sensor die is determined by first electrically activating the image sensor die, adjusting the lens position to identify the optimal focus sharpness, and then applying UV light to activate the UV cure adhesive and hold the lens in focus.

Projection optical system and exposure apparatus having the projection optical system

Abstract: A projection optical system according to the present invention whose image side numerical aperture is greater than or equal to 0.75, and which forms an image of a first object upon a second object using light of a predetermined wavelength less than or equal to 300 nm, comprises: a first lens group G 1 of positive refractive power; a second lens group G 2 of negative refractive power; a third lens group G 3 of positive refractive power; and a fourth lens group G 4 of positive refractive power, and: the first lens group G 1, the second lens group G 2, the third lens group G 3 and the fourth lens group G 4 are arranged in order from a side of the first object; and a distance D in mm along an optical axis between an optical surface of the fourth lens group G 4 closest to the second object, and the second object, satisfies a condition of 0.1

GRIN fiber lenses

Abstract: A GRIN fiber lens has a silica-glass core whose refractive index has a radial profile. The profile has a radial second derivative whose average magnitude in the core is less than about 1.7×10 −6 microns −2 times the value of the refractive index on the axis of the GRIN fiber lens.

Solid-state image pickup device

Abstract: PROBLEM TO BE SOLVED: To provide a solid-state image pickup device adaptive to a change in a size of a lens. SOLUTION: In the solid-state image pickup device 10 that is provided with a printed circuit board 11 with an opening 11a, a solid-state image pickup element 18 with a light receiving face 18a, a sensor package 12 containing them, and an optical unit 15 with a lens 14, the sensor package 12 and the optical unit 15 are placed so as to ensure an optical path through which a light made incident on the lens 14 passes the opening 11a and arrives in the light receiving face 18a on the other side. The area of the printed circuit board can effectively be utilized by mounting components on both sides of the printed circuit board and the size of the printed circuit board 11 in a horizontal direction can be reduced. Since the optical unit 15 is mounted on the printed circuit board 11, even when the bright lens 14 with a large diameter is in use, the solid-state image pickup device can cope with the lens 14 without increasing the opening 11a and without the need for increasing the size of the solid-state image pickup device 10. COPYRIGHT: (C)2002,JPO

Digital eye camera

Abstract: A digital camera that combines the functions of the retinal camera and corneal camera into one, single small, easy to use instrument. The single camera can acquire digital images of a retinal region (9) of an eye, and digital images of a corneal region of the eye. The camera includes a first combination of optical elements for making the corneal digital images. A portion of these elements are shared elements including a first objective element (12) of an objective lens combination, a digital image sensor (18) and at least one eyepiece for viewing either the retina or the cornea. The retinal combination also includes a first changeable element of the objective lens system for focusing, in combination with the first objective element, portions or all of the retinal region at or approximately at a common image plane. The retinal combination also includes a retinal illuminating light source (27), an aperture within the frame and positioned within the first combination to form an effective retinal aperture located at or approximately at the lens of the eye defining an effective retinal aperture position, an infrared camera (34) for determining eye position, and an aperture adjustment for adjusting the effective retinal aperture based on position signals from said infrared camera. The cornea combination of elements includes a second changeable element of the objective lens system for focusing, in combination with the first objective element, portions of all or the cornea region at or approximately at a common image plane.