Showing papers on "Pixel published in 1975"

Apparatus for image manipulation

Abstract: An image can be represented by an M × N array I(*,*) of image points, where each point I(i,j) over the ranges 0≦i

Decision-directed recursive image enhancement

Abstract: A nonlinear method of estimating pictorial data from noisy observations is considered. The data is assumed to be composed of an object with one texture in the background. An edge detection technique using likelihood functions is used to decide if an incoming picture element is a member of the object or the background. Then, the picture element is directed to one of the two Kalman filters designed based upon the statistics of the object or the background accordingly.

Digital Computer Simulation Study of a Real-Time Collection, Post-Processing Synthetic Focusing Ultrasound Cardiac Camera

Abstract: High resolution ultrasound images (90% of Rayleigh limit at all depths) were obtained by computer analysis of digitized (at 10 and 20 points per microsecond, 8 bits per point) signals detected with a 32 element lead zirconium titanate 3.0 MHz array. Every sixth element was used as a transmitter and pulsed 31 times while the signals from the remaining 31 elements were addressed sequentially by an analog switch and their signals digitized and recorded. Each pixel in the cross-sectional image was produced by calculating the inner product of a specific window function and the ensemble of digitized signals. Thus the array is mathematically focused optimally for each pixel in the image. The acquisition and storage of all received signals allows subsequent approximate calculation of spatial distributions of such parameters as reflection, index of refraction, attenuation, etc. The extension of these techniques through the use of a fast analog and digital computer interface to obtain realtime and stop-action imaging is treated. Examples of images produced by these algorithms, the time requirements of various algorithms as determined by the computation speeds of present and anticipated digital and analog processing hardware is presented. Supported in part by NIH research grants HT-4-2904, RR-7, and HL-04664. Also supported in part by a contract from the Office of Naval Research to E. M. Eyring, with whom S. A. Johnson was a part-time research associate.

Estimating proportions of objects from multispectral scanner data

Abstract: Progress is reported in developing and testing methods of estimating, from multispectral scanner data, proportions of target classes in a scene when there are a significiant number of boundary pixels. Procedures were developed to exploit: (1) prior information concerning the number of object classes normally occurring in a pixel, and (2) spectral information extracted from signals of adjoining pixels. Two algorithms, LIMMIX and nine-point mixtures, are described along with supporting processing techniques. An important by-product of the procedures, in contrast to the previous method, is that they are often appropriate when the number of spectral bands is small. Preliminary tests on LANDSAT data sets, where target classes were (1) lakes and ponds, and (2) agricultural crops were encouraging.

Silicon diode array vidicons at the telescope: observational experience.

Abstract: We have used silicon vidicon tubes in a two-dimensional integrating imaging device at the telescope to obtain photometric images of astronomical objects. In this article we report on the performance of the imaging system we have experienced under actual observing conditions. The imaging system and the procedures we have devised to use it are described. Exposures reproduce to better than 0.05% of full scale intensity for each picture element. The response of the entire imaging system is linear with gamma = 1 for at least nearly 5 orders of magnitude to within at least 0.44% of full scale intensity and probably much better. Images made through the telescope of extended sources agree photometrically with photomultiplier measurements to about 1%. Photometry of stars reproduces to better than 0.5%.

Picture image information band compression and transmission system

Abstract: A picture image information band compression and transmission process includes the steps of providing one set of three scanning lines making information of the first scanning line of each one set as an estimation scanning line, estimating a picture element to be estimated by four consecutive picture elements, preparing estimated picture image informations, and translating the estimation reference scanning line and two estimated picture image information into run length codes and into mode codes, respectively, and compressing and transmitting the run length codes.

A Comparison Of Hardware Implementations Of The Hadamard Transform For Real-Time Image Coding

Abstract: Several different hardware configurations for implementing the Hadamard transform in real-time are discussed. The discussion is referenced to a 64 point (8 x 8) transform that is used in image coding for bandwidth reduction. A successive implementation of two 8 point transformations with intermediate random access memory using the straight forward N2 computation is compared to implementations of the Fast Hadamard Transform (FHT). The speed of computing transform coefficients is compared to the hardware requirements of the various techniques. The relationship between computational speed and the resolution and frame rate of television imagery that may be transform encoded using the different methods is illustrated. It is shown that for picture element (pixel) rates up to 5 MHz the N2 computation is the more economical to implement.

Real Time Television Image Bandwidth Reduction Using Charge Transfer Devices

Abstract: Recent advances in analog semiconductor technology have made possible the direct sensing and processing of television images. By combining a charge transfer device (CTD) imager and a CTD transversal filter, real time image sensing and encoding have been achieved with low power integrated circuits so that digital transmission and bit rate reduction are made possible using differential pulse code modulation (DPCM). Good mean square error performance and freedom from DPCM artifacts are possible in a hybrid intraframe image encoder. The hybrid transform encoder performs a discrete cosine transform (DCT) on each line of the television image as it is scanned. This compacts the variance into low frequency coefficients and the DPCM encodes the corresponding DCT coefficients between successive lines. Computer simulation of this hybrid coding technique has shown good performance on 256 x 256 pixel images at 0.5 bits/pixel and channel bit error rates of 10-2. An experimental system using a low resolution General Electric 100 x 100 charge injection device camera and a Texas Instruments bucket brigade transversal filter as part of the DCT processor has been constructed and provides good low resolution image quality at 1 bit/pixel and bit error rates of 10-3. A high resolution vidicon compatible system is also being constructed.

A Dual Mode Nonlinear Interpolative Compressor For SAR Images

Abstract: A dual mode nonlinear interpolative compressor is described which compresses synthetic aperture radar images. The compression algorithm takes advantage of (1) the strong contrast between the target and the background, (2) the small percentage of target area compared with the total SAR image. The algorithm operates in two modes, i.e., an exact data transmission mode and an interpolative mode. The image is first segmented into small sub-blocks. The compressor then selects one of two modes according to the pixel values inside the block. If any pixel inside the block is above a predetermined threshold all pixels in this block are transmitted. On the other hand, if all pixels inside the block are below the threshold only one pixel is transmitted. At the receiver a two dimensional interpolation is then conducted to estimate the entire pixels in the block. Under the stationary assumption of the background information a second order statistic of the SAR image is used to derive the interpolative scheme. The compressor not only offers a high degree of exact target recovery but also offers a good recovery of the background information. Computer simulation results indicate that a good quality reconstruction can be accomplished with 1.5 bits per pixel.© (1975) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.