Eastman-kodak Company

William K Hickok

Hans-Peter Baumeister

Robert C Wheeler

Matthew DiPietro

Robert P Collette

Lenard M Metzger

Lawrence J Bernstein

Gerald J Kosarko

William Thomas Hochreiter

John M Riley

A calibration utility 22 for electronically-generated images decouples tone scale and color corrections by completing tone scale and color balance corrections upon separate RGB image signals (representative of intensity) and hue and saturation corrections upon combinations of RGB signals (representative of chrominance). An operator adjusts tone scale controls 32 and color controles 34, which provide values for calibrating separate RGB tone scale look-up tables 49a, 49b, and 49c and a color matrix 48 in a printer 14. To decouple the corrections, the tone scale look-up tables 49a, 49b, 49c are adjusted until the brightness of a predetermined number of image levels is accurately rendered. If the resultant image signal contains coloration in neutral areas, the values in the particular look-up table(s) for the color(s) producing the color cast in the neutral areas is adjusted, thereby producing a neutrally-adjusted image signal substantially free of neutral coloration. The hue and saturation of the image can then be adjusted by modifying terms in the color matrix 48 without affecting the tone scale reproduction.

Printer calibration method using electronically-decoupled color and tone

A skip-field guard-bandless video tape recorder records and plays back adjacent tracks on a video tape with two closely adjacent heads of opposing head gap azimuth angles (to suppress cross-talk), only during alternate (odd) half-rotations of the head drum. Unavoidable cross-talk of synchronization pulses from adjacent tracks does not create visible interference or timing errors during playback by virtue of a special offset angle .theta..sub.1, between the adjacent recording heads, proportional to the linear offset distance between adjacent tracks. During playback, skipped fields are 'filled-in' by a repetition of each recorded field through a second (duplicate) pair of closely adjacent heads of opposing azimuth positioned to retrace the recorded tracks during the other alternate (even) half-rotations of the head drum. An offset angle .theta..sub.2 between the two head pairs (i.e., between opposing heads of like azimuth) corresponds to a half horizontal video line and provides for precise self-interlacing of the repeated fields.

Zero guard-band skip-field video cassette recorder

A pair of oppositely-disposed stabilizer devices support opposed magnetic heads for interfacing with opposite sides of a rotating magnetic disk. Each stabilizer device includes a block with an opening through which the magnetic head protrudes for engagement with a respective side of the disk. A flat, circumferential air bearing surface on each block surrounds the opening adjacent the disk for generating coupling forces that deform the disk out of its nominal plane on opposite sides thereof and into intimate contact with the transducing gaps on the respective heads. The stabilizer devices are positioned in relation to separate radii depending from the center of the drive spindle so that a circumferential offset is established that permits substantially separate interaction of the air bearing surfaces with the disk.

Magnetic recording device using circumferentially offset heads with

In a time division multiplex video reproducing apparatus, a dual purpose memory serves to (a) perform time compression for time division multiplexing and (b) perform as a variable delay line for time base error correction. Seemingly unavoidable conflicts in the allocation of memory space (between multiplexing operations and time base error correction operations) are eliminated by performing the time base error correction operations during a memory idle time inherent in the time division multiplexing process. As a result, time base error correction in this invention requires little additional hardware and no additional space in the memory beyond that required for time division multiplexing.

Dual purpose memory for time division multiplexing and time base error

A time division multiplex video tape recorder has a channel for receiving the main portion of an incoming video signal, comprising the luminance signal and horizontal synchronization pulse, and a separate channel for receiving the modulated sub-carrier portion of the video signal, comprising the chrominance signal. The luminance channel includes a signal processor for separating the luminance signal and horizontal synchronization pulse from one another. The signal processor removes the horizontal synchronization pulse from the luminance channel and inserts it into the chrominance channel. The luminance signal of each horizontal video line is time-compressed by itself into a first time segment, while the horizontal sync pulse and the chrominance signal of the same horizontal line are time-compressed together into a second time segment, the two segments being recorded serially within the space of one horizontal line scan period. The removal of the horizontal sync pulse from the luminance channel facilitates a decrease in the time compression ratio of the luminance signal and of the time-compressed luminance bandwidth so as to avoid the magnetic tape-to-head interaction cut-off frequency, thereby providing an improvement in overall image quality.

Time division multiplex video recorder with high resolution

A time division multiplex video recording system records every other one of the two chrominance signals (I and Q or R-Y and B-Y) of successive video fields and records the luminance signal (Y) of every field in separate time division segments. During odd fields, it records the luminance signal and the I chrominance signal of every horizontal line and during even fields it records the luminance signal with the Q chrominance signal of every horizontal line. During playback, a field store memory receives and stores the previously recorded chrominance signal of each field for repetition during the next to fill in for the unrecorded chrominance signal. In another embodiment, a helical scan four-head video playback system repeats every field during playback of the next field by playing back the adjacent tape tracks of both fields simultaneously, to fill in for the unrecorded chrominance signal (thereby eliminating the requirement for a field store memory). The invention represents a dramatic improvement because it achieves at least twice the vertical chrominance sampling rate of known time division multiplex video recording techniques.

Time division multiplex video recorder with enhanced vertical

Timing in a time division multiplex video cassette recorder is improved and skew jump error is virtually eliminated by recording video signals with a superimposed pilot signal synchronized to--but having a frequency greater than--the incoming horizontal sync pulse frequency. During playback, a local pilot signal--similar to the previously recorded superimposed pilot signal--and a local horizontal sync signal control the de-multiplexing process and timing. The local pilot and horizontal sync signals are controlled by a three-tiered feedback timing control loop: a phase lock loop varies a local clock signal in order to correct very fine time differences between the recorded and local pilot signals; a digital loop changes the frequency ratio between the clock signal and the local pilot signal to correct larger time differences between the recorded and local horizontal sync pulse signals; and a look-ahead up/down counter counts and stores the net cumulative change in the pulse repetition frequency ratio. The ratio is changed by the entire cumulative amount during (or just prior to) the first horizontal line (only) of each video field as a very large automatic correction which anticipates skew jump error. The phase lock loop is virtually unaffected by interruption of the digital control loop (due to temporary drop-outs of the imcoming horizontal sync pulse signal), and the systm timing is therefore impervious to dropouts or noise.

Noise-impervious video timing recovery and automatic skew compensation

A peripheral memory controller controls a helical scan magnetic tape recorder so as to record and play back data files in parallel tracks on a magnetic tape. The tape is contained in a cassette having a magnetic disk fixably mounted on one reel of the cassette so that the movement of the tape and rotation of the disk are simultaneous. The peripheral memory controller refers to a file allocation table stored in one (or more) tracks on the disk, in order to correlate data file descriptions with track locations on the tape. A disk head rapidly scans the file allocation table disk track(s) within just one (or a few) revolutions of the disk while transmitting the contents of the table to the peripheral memory controller. The controller deduces therefrom the tape track location of a particular data file and commands the tape to be transported to that location in order to access that file. In another embodiment, sub-file allocation tables, each describing the tape track location of each sub-file within a given data file, are recorded in other disk tracks whose locations are recorded, in turn, in the file allocation table disk track. In order to take advantage of the co-movement of the tape and the disk, each sub-file allocation table stores the names of sub-files whose tape track locations fall within a length of tape covered during one rotation of the reel and disk, so that each sub-file allocation table disk track may be scanned completely while maintaining the position of the tape within the tape location range of the corresponding sub-file allocation table.

Tape memory with integral disk index on reel

Method and apparatus for the processing of color video signals in which the two fields of a color video frame are compressed into a single field without appreciable loss of picture resolution and without image disturbance and degradation. The compressed signal may be recorded on a single track of a VCR and played back in a still-frame mode without picture jitter, color loss, or image degradation. According to the invention, first and second color video signals of a predetermined time period (such as a field period) are compressed into a time-division-multiplexed (TDM) signal of a single time period. The luminance components of the first and second signals are summed to produce a sum luminance signal and subtracted to produce a difference luminance signal, the sum signal having a greater bandwidth than the difference signal. A chrominance signal is produced which is a function of the chrominance components of the first and second signals. The luminance signals and chrominance signal are compressed and arranged sequentially to form a TDM signal of a single time period.

Method and apparatus for combining two color video signals

A camera includes a photographic film having a given film speed which decreases when the film is exposed to light which varies from a given illumination level. A camera shutter is controlled by a timing circuit adapted to produce an exposure which is adjusted to compensate for the decreased film speed.

Exposure control apparatus with compensation for film reciprocity failure

Magnetic head positioning and playback apparatus is provided for use with a helical scan tape recorder to accurately position a playback head with respect to a magnetic track. The playback head has a split face portion dividing the playback gap substantially in half. Reproduce signals from the corresponding portions are simultaneously processed to provide an indication of positional error and summed to provide a playback signal. In one form, by differencing the reproduce signals from the corresponding portions and by multiplying the difference and sum signals together, a usable correction signal is provided to a servo circuit for simultaneously centering the head on the track while reproducing a playback signal -- this being accomplished without the use of a separate control track. By further comparing the correction signal with a reference level, momentary disturbances in the track are detected as they occur; this information is used to determine which portion of the head provided the disturbance and to prevent that portion's signal from summing into the playback signal.

Magnetic head positioning and playback apparatus utilizing a split head

The present invention departs from conventional concepts, involving the use of magnetic tape or the like, of color video signal recording by providing video signal recording and reproducing apparatus in which preferential dropout compensation is obtained without the use of special dropout compensation circuitry. A color video signal is down-converted in frequency to produce a video signal of a recordable frequency range with picture information at relatively low frequencies and color and sound information at relatively higher frequencies, respectively. Dropouts, therefore, affect the sound information first, the color information second, and the picture information last, as is preferable. In accordance with another aspect of the invention, time base error correction is obtained without the use of time base error correction circuitry by separating the luminance and chrominance signals and so down-converting each signal to a recordable frequency range that the luminance carrier and the chrominance carrier have the same frequency. Upon recording and playing back, time base variations, as may be caused by tape flutter, will then affect both carriers equally. After up-converting and recombining the luminance and chrominance signals to form the original video signal, the frequency spacing between the luminance carrier and the chrominance carrier will be independent of time base variations in the recording process and, therefore, have the same frequency spacing as the original video signal.

Color video signal recording and reproducing apparatus providing

A color video recorder/reproducer records wide bandwidth luminance information alternately with narrow bandwidth luminance information plus chrominance information for the transmitted lines of a television picture frame. Before recording, the chrominance information is frequency converted to occupy a frequency band substantially adjacent to the frequency band occupied by the narrow bandwidth luminance information. Upon playback, the frequency converted chrominance information is separated from the narrow bandwidth luminance information and converted to its originally occupied frequency band. A video signal is then reconstructed by combining the signal recorded for a given line with a complementary portion of the signal recorded for the preceding line. Upon display of a picture thus produced, an artifact pattern is observed. The present invention recognizes the source of this artifact pattern to be the imperfect separation of the narrow bandwidth luminance information from the chrominance information. Rather than employ expensive and complicated filtering devices to better separate the two signals, the present invention permits the small portion of chrominance information to stay in the luminance channel but compensates therefor by so frequency converting the chrominance information before recording that the artifacts thus produced in one line of the picture frame are 180.degree. out of phase with the artifacts in an adjacent line and thus are effectively cancelled out by the integrating characteristics of the eye.

Growing community of inventors

Rochester, NY, United States of America

William K Hickok