Halftone Dots Research Articles

オフセット印刷とその用紙

It appears to be of great significance to discuss about the reproduction of halftone dots in offset printing, because offset process is most prevailing in Japan according to the statistics based on the investigation of each printing process.If dots reproduction is evaluated using various paper types under the controlled plate-preparing conditions, there would be a considerable difference between coated and uncoated paper. For example, when used uncoated paper, dot-gains from highlight to shadow area are observed on the whole, lowering the density in solid area. Whereas, in the case of coated paper, halftone dots tend to he reproduced closer to the reproduction curve of original plate.For the purpose to see how the final print quality (dots reproduction) is affected by the properties of paper, a simulation has been made using data obtained from following items :1) The relationship between surface properties of paper and printing ink.2) An inference from ink absorption into paper and amounts of ink remained on the surface.3) The relationship between brightness of paper and print reproduction. Finally, some troubles which might occur in printing operation are considered statistically on both sheet and web offsed process.

Measurement of histograms of halftone images

We present theory and experiments for two optical methods for measuring histograms of halftone images. In both methods, the histogram is obtained by spatial filtering of the halftone object. In the first method, we used a phase filter with a comb-type point spread function. In the second method, the filter matched one kind of the differentiated halftone dots. Experiments show that the first method works fast and gives fairly accurate results (errors were about 10%), whereas the second method requires more experimental efforts, but the results are more accurate in this case (errors were about 0.9%).

Yule-Nielsen effect in printing: a physical analysis

The Yule-Nielsen curve-fitting parameter n is derived in terms of the point spread function describing the scattering of light in paper substrates upon which are printed halftone dot or line patterns. The value of n is shown not to depend strongly on either screen frequency or area coverage at low area coverages or highlight regions. However, when the shadow regions are considered, n becomes increasingly dependent on both of these parameters. This dependence is not explicitly allowed for by the Yule-Nielsen equation. It is analytically shown that the value of n approaches 1.0 as the substrate approaches a specular surface and approaches 2.0 as the substrate becomes a perfect diffuser. The value of this analysis is the following. First, it indicates that the Yule-Nielsen equation is physically adequate in highlight and medium shadow regions. Second, an accurate determination of n at any screen frequency can be made from a single measurement of n at any other frequency using an inferred scattering length. Third, this analysis shows that the empirical (Yule-Nielsen) determination of n from dot density and fractional area coverages is valid only in the regions below about 50% area coverage.

Analysis of halftone dot profile and aliasing in the discrete binary representation of images*

Screening techniques are widely used in the binary display of continuous-tone images by digital output devices. The quality of the halftone image resulting from such a nonlinear transformation is dependent on the dot profile employed. In the Fourier domain, aliasing degrades the halftone image. The relationship between image quality and dot profile is studied from this point of view. For a well-known dot profile, it is shown analytically how aliasing is suppressed, and that quantization contouring may be eliminated without an appreciable increase in aliasing.

Halftone method with edge enhancement and Moiré suppression

A method has been found for separating control of high and low spatial frequencies in a continuous-tone image during conversion to a halftone (binary) form for printing. This method allows edge enhancement, while simultaneously limiting creation of spurious Moiré patterns due to image frequencies near the halftone screen frequency. Macroscopic grey scale control is achieved by determination of average grey level by low-pass filtering of the image. This information is used to set halftone dot size. Microscopic or detail contrast is controlled as in the ordinary halftone process, that is, by screen shape and screen modulation, which therefore affects partial dot structure. In the absence of detail, the results of this process match ordinary halftones. In detailed areas, however, the low-frequency control limits generation of spurious low-frequency Moiré patterns, while free choice of screen modulation allows enhancement of edges up to the common limit where image noise becomes dominant.

Half tone dot reproduction as a means of lens testing

A simple relationship was sought between lens MTF and the results of photographing half-tone dot patterns. Qualitative understanding was more important than quantitative accuracy, and therefore emphasis was laid on developing an inexact but helpful model. This was successful and has thrown useful light on the results which had been observed.

Three-dimensional computerized display of physiologic models and data

Three-dimensional images of physiologic data or models of data can be projected on a conventional oscilloscope by a computerized technique. The computer directs the X and Y deflections of the electron beam to a designated location on the oscilloscope face and modulates the beam intensity at that position to create a half-tone dot. By moving the beam in a programmed, incremental fashion, with appropriate changes of intensity, known patterns with varying shades of gray can be used to create a three-dimensional impression. We have used this method and data from orthogonal roentgen videoangiograms to generate simulated three-dimensional images of the left-ventricular chamber at end-systole and end-diastole, and to display scintigraphic patterns of pulmonary blood flow obtained from experimental animals after injections of radioactive microspheres into the circulation during exposure to normal and increased gravitational-inertial force.

Generation of Halftones by Computer-Controlled Microfilm Recorder

Computers, in conjunction with microfilm recording equipment, are capable of generating pictures with a reasonable number of gray levels and good resolution. A method is described for producing pictures by means of halftone dot patterns using such equipment. The method is relatively insensitive to variations in hardware performance and adjustments.

Electronic halftones

To derive the greatest advantage from automation in the production of newspapers and books the present optical method of producing halftone dot patterns must be replaced by an electronic method. This article discusses developmental electronic-halftone techniques that use a high-resolution cathode-ray tube as the display device.

Studies on the Reproduction of Halftone Dots in Deep-Etch Plate-Making

Studies on the Reproduction of Halftone Dots in Deep-Etch Plate-Making

The Study of Halftone Dot by Powderless Etching Process

The Study of Halftone Dot by Powderless Etching Process

A Method for Determining the Density Distribution of Halftone Dots

AbstractAn area of the dots to be measured is cemented to an area of large dots (very small holes) of the same spacing, so that a large moire pattern results. The moire “dots” are in effect enlargements of the dots under test, and their density contours are obtained by contact-printing the combination together with a step wedge on sheets of a suitable photographic material, using various exposures. In each print the density printed through is indicated by the step wedge, while the corresponding contour is indicated by the innermost row of small dots which have just printed. A contour map is then obtained by placing the prints in the negative carrier of an enlarger and tracing the isopaques on a sheet of paper on the easel.

Book Review: How Halftone Dots Make Pictures

Book Review: How Halftone Dots Make Pictures