Analog to digital converter for two-dimensional radiant energy array computers in which the converter stage derives a bit array of digital radiant energy signals representative of the amplitudes of an input radiant energy analog signal array and derives an output radiant energy analog signal array to serve as an input to succeeding stages. The converter stage includes a digital radiant energy array device which contains radiant energy array positions so that the analog array is less than a predetermined threshold level and which doesn't contain radiant energy at array positions where the input analog array exceeds the threshold level. A scaling device amplifies the radiant energy signal levels of the input array and the digital array so that the radiant energy signal level carried by the digital array corresponds to the threshold level. An adder device adds the signals of the scaled input and digital arrays at corresponding array positions to form the output analog array.

This invention relates to the production of a printing block or form of the kind in which at least one original is scanned optoelectronically to obtain image signals being mixed to generate a composite signal and is recorded as the printing block or form, one of the image signal which is to be mixed being modulated by a control signal and the other image signal being modulated by the amplitude-inverted control signal and the modulated image signals being summated to obtain said desired composite signal, said control signal determining a mixing range and the mixing characteristic within said mixing range. According to the invention, the said control signal is derived from the color information of a colored control mask by scanning said mask or from the image content of the original.

A continuous-tone image, which can be in full color, is scanned to produce color-separation images in halftone dots. Edges of features in the scanned image are sensed, and the positions and shapes of the halftone dots that define corresponding edges in the halftone reproductions are adjusted so that they conform better to the feature edges. This reduces or eliminates the apparent serrations or roughness of feature edges in the halftone reproductions otherwise caused by misalignment of the halftone dots with the feature edges and improves image definition.

A fiber optic delay line filter receives light energy input signals repretative of any form of temporally varying signals such as electrical or acoustical, for example. A plurality of fiber optic light paths each having a determinably variant optical propagation delay, receives and transmits the light energy signals. A photo responsive means receives the delayed output light energy signals transmitted by the plurality of fiber optic light paths and produces a single electrical output signal as a function of the sum of the delayed output light energy signals, thus performing a filtering or correlation function. In a preferred embodiment, an injection laser or light emitting diode may be employed as the means for converting the temporally varying input signals to commensurate light energy signals. In a variant embodiment, a single fiber optic light path, having a partially reflective surface at each end, gives effect to multiple reflective transmissions along the length of the fiber optic light path which are then detected by a photo responsive device, providing a narrowband filter output as a function of the length and number of multiple reflective transmissions.

Contrast is increased when reproducing originals, by using a first correcting signal for continuous-tone areas in the original and a second correcting signal which affects only line elements (narrow lines) in it. To generate a picture signal and a surrounding-area signal, an opto-electronic scanning member having a picture-point aperture and a surrounding-area aperture is provided. The diameter of the picture-point aperture is approximately equal to the width of the line elements in the original which are to be corrected. The first correcting signal is obtained from the picture signal and the surrounding area signal in a difference stage, and a selectable proportion of it is superimposed on the picture signal to increase sharpness. The difference stage is followed by a threshold circuit which allows positive parts of the first correcting signal lying above a first threshold and negative parts of the first correcting signal lying below a second threshold value to pass through, the parts which are allowed to pass through being superimposed on the picture signal as a second correcting signal, to increase sharpness for line elements. With the arrangement, the reproduction of line elements can be optimized and the increase of contrast in continuous-tone areas can be selected so that no unsightly seams occur at jumps in tonal values.