Showing papers on "Depth of field published in 1986"

Pseudo-random point sampling techniques in computer graphics

Abstract: A computer database contains visual and other information of an object scene from which a television monitor or film display is created by electronically sampling points of the object scene information in the computer memory. Undesirable effects of aliasing are significantly reduced and substantially eliminated by pseudo-randomly distributing, in a particular manner, the occurrence of the point samples in space and time. Realistic depth of field is obtained in the images, corresponding to what is observed through a camera lens, by altering the sample point locations to simulate passing them through an optical aperture in a pseudo-random distribution thereacross. Further, effects of illumination, shadows, object reflection and object refraction are made more realistic by causing each sample point to pseudo-randomly select one of a predetermined number of possible ray directions.

Focus warning system for a manually-focused still video camera having an electronic viewfinder

Abstract: A manually-focused video camera provides a movie image for an electronic viewfinder and a still image for recording apparatus. A diaphragm in the optical section of the camera determines the optical aperture presented to incoming image light, which coincidentally establishes the depth of field in which the subject remains in focus. When the aperture necessary for a still image exceeds the aperture used for the movie image by, e.g., three aperture stops, a warning system in the camera produces a control signal. The existence of this signal indicates a potential focusing problem due to the disparity between aperture values and the reduced depth of field in the corresponding still image. The signal is used, e.g., to illuminate a warning element in the viewfinder or to insert a neutral density filter into the path of incoming light, in the latter case forcing the movie aperture to approach the still aperture and thereby causing the movie depth of field to approach the still depth of field.

Method and apparatus for processing analog optical wave signals

Abstract: Discrete segments of an analog optical wave signal are collected in individual waveguides of a waveguide array. In the waveguide array, the optical signal is processed to provide an analysis of the signal or to control the signal. The signal can be analyzed by Mach-Zehnder interferometers which can provide an indication of the distance of a subject from the array. By controlling the dielectric constants of the waveguides electronically, the array can serve as an aberration free focusing lens or as an aberration compensation lens. Rapid electronic control of the focal length of the lens makes the lens particularly applicable to automatic focusing systems, systems which view only objects within a selected range of distances from the array, and the compiling of in focus segments to form a wide depth of field image.

Automatic focus and exposure controlled camera

Abstract: An electrically operated camera is operated automatically from between far-focus and near-focus lens settings responsively to ambient light sensings. The far-focus lens setting is less than infinity. Under strong lighting conditions, the aperture is automatically set between a range of values, the largest of which is no greater than the hyperfocal aperture value corresponding to the far-focus setting of the lens, thereby setting the outer boundary of the depth of field at infinity. In weak light, a flash system is automatically enabled, the lens is set to a near-focus position, and the aperture is automatically set at its maximum value. Timed energization of a single electrically operated solenoid is used to establish all settings in both modes. An additional macrofocus setting is provided for setting the lens at a focusing distance much shorter than the near-focus setting, and the aperture is automatically set at its minimum value in flash mode, or over a range of values according to ambient sensings when bright lighting conditions prevail.

Filtering Effects In Far-Field In-Line Holography

Abstract: A nonblocked zero-frequency filtering technique is used to improve the in-line holographic recording of small objects at extended distances from the hologram. Since the filter is coated on the relay lens, the irradiance distributions in three planes (i.e., in projected images, diffraction patterns, and reconstructed images) are calculated. Influences of filter diameter, filter transmittance, and exposure level of holograms are considered in discussing fringe visibility, image forms, and image contrast.

Optical sensors for range and depth measurements

Abstract: A new type of optical range sensor is being developed which makes use of the shallow depth of field of a type II confocal scanning optical microscope. The range resolution is of the order of 2 μm at a 10-20 cm distance from the lens. We have shown that the system works well on rough surfaces, although with a much decreased output signal. In another set of experiments employing microscope lenses, various versions of the system are being used to measure the thickness of transparent films with a thickness of the order of 100 nm to 5 μm with good accuracy and with transverse resolutions in the 150-500 nm range. We can scan the beam electronically with a Bragg cell, or mechanically, to measure the profiles of objects.A new type of optical range sensor is being developed which makes use of the shallow depth of field of a type II confocal scanning optical microscope. The range resolution is of the order of 2 μm at a 10-20 cm distance from the lens. We have shown that the system works well on rough surfaces, although with a much decreased output signal. In another set of experiments employing microscope lenses, various versions of the system are being used to measure the thickness of transparent films with a thickness of the order of 100 nm to 5 μm with good accuracy and with transverse resolutions in the 150-500 nm range. We can scan the beam electronically with a Bragg cell, or mechanically, to measure the profiles of objects.

Body information processor

Abstract: PURPOSE:To reduce misses of measurement by increasing the aperture ratio of an object which forms an optical path and decreasing depth of field, calculating the differential value of the brightness signal of a formed image, and comparing a distribution of points where the differential value exceeds a specific value. CONSTITUTION:Lenses 1 and 2 which form an environmental image on photosensor arrays 3 and 4 are held by a frame 5 and coupled together mechanically, and moved forth and back by a motor 5 as shown by an arrow 6. Then, the lenses 1 and 2 have large aperture ratios and are made relatively small in depth of field. The lenses 1 and 2 are moved by a moving means 28 for focusing and synchronized with a driving circuit 5 for the photosensors 3 and 4 so that a time period longer than, for example, a distance calculation time is obtained. An output image signal is differentiated by differentiation circuits 6 and 7 with time and a distribution of points where the differential value exceeds the specific value is compared. Consequently, the distance distribution is measured within a practical time and misses of measurements resulting from an erroneous assumption of corresponding points of a right and left images are reduced greatly.

Calculation and Measurement of Image Formation, Spatial Resolution, and Effective Depth of Focus for a Scanning Microscope with Confined Electromagnetic Waves

Abstract: The resolution of scanning microscopes with confined waves is mainly determined by the diameter of the confinement region instead of by the wavelength. The ‘effective depth of focus’, i.e. the tolerable distance between the plane of minimum confinement of waves and the object plane is about one-quarter of the diameter of the confinement cross-section.

Camera with fixed photographic lens having depth of field maximized corresponding to iso sensitivity of film

Abstract: PURPOSE:To utilize the depth of field of a photographic lens effectively at a maximum by putting parallel plane glass whose thickness corresponding to a stop between the photographic lens and a film at right angles to an optical axis, and shortening the distance between the lens and film substantially. CONSTITUTION:The photographic lens of a fixed lens camera focuses an image normally when the distance to a subject is 2.5-3M. The depth of focus increases according to an aperture value F as shown by the solid line in a figure, but is increase beyond when the lens is stopped down to F>=11 and becomes fruitless. For the purpose, the focal length is set to 1.045M to eliminate the futility of the depth of focus and when the lens is stopped to other values, the parallel plane glass is interposed between the lens and film at right angles to the optical axis. Its thickness is set to 0.326X3mm when F is 16, 0.587X3mm when 11, or 0.75X3mm when 8 or 5.6. A multiplier 3 is the reciprocal of the equivalent shortening ratio of the glass. Consequently, the futility of the depth of focus is eliminated for all aperture values and short-range photography is performed.

Method for correlating depth of photographic field with maximum useable lens aperture setting

Abstract: Presented is a method for use by a photographer to determine the maximum useable lens aperture setting of a camera for any given depth of field. A formula has been developed that results in the indication of the minimum useable aperture number when easily available parameters are used in the formula.

Method and apparatus for forming electrical signal of video image frame

Abstract: A computer database contains visual and other information of an object scene from which a television monitor or film display is created by electronically sampling points of the object scene information in the computer memory. Undesirable effects of aliasing are significantly reduced and substantially eliminated by pseudo-randomly distributing, in a particular manner, the occurrence of the point samples in space and time. Realistic depth of field is obtained in the images, corresponding to what is observed through a camera lens, by altering the sample point locations to simulate passing them through an optical aperture in a pseudo-random distribution thereacross. Further, effects of illumination, shadows, object reflection and object refraction are made more realistic by causing each sample point to pseudo-randomly select one of a predetermined number of possible ray directions.

Ultrasonic imaging apparatus

Abstract: An ultrasonic imaging apparatus comprising an electronically adjustable mechanical lens (18) for ultrasonic array and phased array imaging having strip-like electrodes in the longitudinal direction of the array Electronic delays are applied to signals going to or coming from the electrodes in both the transverse plane and the longitudinal plane to correct for phase errors which would normally occur when the mechanical lens is out of focus This results in increased depth of field for the transducer lens