We present algorithms for predicting the usefulness and naturalness of color reproductions of natural scenes. The algorithms are based on a computational model of the stages that lead to an observer's impression of the usefulness and naturalness of an image. These stages are (1) the perception, or internal quantification, of color; (2) the construction of a memory standard for an object's color based on its color as observed in the past; and (3) matching of observed object colors with memory standards. In the first of the above stages, the internal quantification of color, the concept of (partially) flexible metrics plays a central role. To test the usefulness algorithm, it was used to predict the discrimination of detail in black and white images of which the contrast was manipulated by applying an s-shaped transform on CIE 1976 lightness L^*. The naturalness algorithm was tested by using it to predict the naturalness of the grass, skin, or sky areas of images of which the color was manipulated by shifting CIE 1976 hue angle h_uv and scaling CIE 1976 saturation s_uv of the grass, skin, or sky areas of the images. The predictions produced in these tests correspond quite well to experimentally obtained judgments of human subjects.

In laser thermal transfer printing using a dye sublimation type medium, a high definition and continuous tone image can be obtained easily because a laser light focuses on a small spot, and its heat energy can be controlled by pulse width modulation. In this study, we investigated dye transfer depth from the ink layer to elucidate the mechanism of dye transfer. Ink donor sheets composed of a laser light absorbing layer and several color sublimation dye layers were prepared. The results confirmed that the dye was transferred from the surface ink layer in contact with the receiving layer, and also from the bulk of the ink layer in the range of low and high recording energy, respectively. By microscopic measurement after laser irradiation, we find that dye transfer from the bulk of the ink layer corresponds to the creation of a small hole at the ink's surface. Temperature transition in the ink layer by numerical calculation was different depending on the contact condition with the receiving sheet and the spot size of the laser light.

The effects of adding a thin layer of an energetic polymer such as nitrocellulose (NC) to laser photothermal imaging media are investigated. Photothermal media are used which are model systems for computer-to-plate or computer-to-press imaging. The media consist of a substrate, a thin absorbing metallic absorbing layer and a silicone rubber imaging layer. An energetic polymer can be added between the substrate and the absorber. With 10 μs duration near-IR exposure pulses, the energetic layer has no discernable effect. With 110 ns imaging pulses, exposed spots in imaging media with energetic underlayers can be more than three times larger. The improvement due to energetic polymers results from confining the hot gas-phase thermochemical decomposition products under the silicone layer, as shown by time-resolved microscopy. The force exerted by the expanding bubble tears the neck of the bubble away from the substrate, increasing the imaged spot size. These rather complicated processes cannot be described by previously used simple exposure threshold models. An exposure parameter is introduced which deals with this problem. In some cases energetic material underlayers can improve the sensitivity of the media by a factor of three. This work is believed to be the first where a substantial sensitivity improvement in laser threshold for photothermal imaging is obtained with energetic polymers.

The authors are actively involved in the development of Elgraphy: a novel image acquiring system that combines electrophotography and liquid crystal technology. The intermediate medium for image storage in Elgraphy (image receptor) consists of an organic photosensor layer (Elgraphic photosensor) and a liquid-crystal layer. The Elgraphic photosensor, through which a dark current of several μA/cm² flows when a voltage of 10 V/μm is applied at room temperature, exhibits marked photocurrent amplification: exposure to light yields a photocurrent greater than the number of photons absorbed. Upon exposure to light, the quantum yield rises very fast and exceeds unity within about 30 msec. The ionization potential of the charge transfer material (CTM) are shown to be related to photocurrent amplification. The state of space charges trapped in the photoconductive layer is probably affected by the diffusion of the CTM into the charge generation layer (CGL). It has been found that several types of deep traps with a trap depth of more than 1 eV play an important role in this phenomenon. The authors propose that these traps capture electrons generated near the electrode/photoconductive layer interface, thus lowering the barrier to hole injection.

Recently the surface state model of tribocharging has been used to determine the relative work functions of toners. The approach consists of examining the correlation between charge-to-mass data for a series of toners measured using several carriers of differing charging ability and the charge-to-mass of a reference toner measured using the same carriers. In this article this method has been used to analyze published data on the charging behavior of toners containing carbon blacks with different contact potentials. An excellent correlation was found between the relative work functions estimated from the triboelectric data and direct contact potential measurements. The results confirm that relative work functions of toners can be accurately estimated using the surface state model. The analysis also shows that in general these materials follow the high-density limit of the surface state model.

An image analyzer that employed neural networks was used to classify prints according to whether they were laser printed or photocopies of the laser prints. The prints analyzed were monochrome images of squares, the text character ‘a’ and a circle. Each image was reproduced in a range of tones. The image analysis system produced raw image data from the prints and a pre-processing program was used to extract features from this raw image data. Neural networks employed the features to find classification models for the three different sets of images. In the analysis a classification rate of 100% was achieved for the squares, 95% for the letter ‘a’ and 93% for the circle.

A traditional method to reconstruct a 3-D shape from shading is to structure an objective functional H(X), over surface normal distribution X, which is a weighted average of the regularization terms representing smoothness constraints and data term representing the image-irradiance equation; the reconstruction is then to find the surface normal distribution X, which minimizes H. However, there is a prominent weakness in that it is difficult to recover discontinuities in the surface normal at edges. In order to overcome this drawback, we propose a new method of shape from shading by using a concave-type regularization term for reconstruction of a 3-D shape with edges for non-Lambertian surface. We theoretically prove that the algorithm is convergent and effective for recovery of a 3-D shape with edges. We also provide experimental comparison of the proposed method with the existing method by using both numerical and real images. Experimental results show that our recovery is more accurate.

An intercomparison of visual diffuse transmission density measurements of photographic and x-ray film step tablets was completed by two national metrology institutes, the National Institute of Standards and Technology, USA, and the Physikalisch-Technische Bundesanstalt, Germany. The samples were measured by three reference densitometers according to procedures described in international documentary standards. The instruments are well characterized with estimates of their measurement uncertainties. The systematic differences between the density measurements were less than 0.010 for the photographic films and 0.015 for the x-ray films for densities as great as 3.3.

A thiol compound with a long hydrocarbon chain was introduced into the developing solution for a silver chloride DTR printing plate. It was found that the hydrophobicity of physically developed silver area could be greatly improved. The higher the silver density and thiol concentration were, the greater the hydrophobicity of the silver surface was. Raman and XPS study revealed that hydrophobization was caused by adsorption of the thiol compound on physically developed silver particles on the plate.

The interaction between two kinds of photographic gelatin and chemical sensitizers was studied by X-ray Photoelectron Spectroscopy. After the gelatin samples were immersed into the chloroauric acid solution for 5 min, methionine and methionine sulfoxide in gelatins were oxidized to methionine sulfone, reducing most parts of Au³⁺ to Au which was coordinated by gelatin macromolecule. According to the ratio of Au³⁺ to Au in gelatins, it is shown that the reducing power of Rousselot gelatin is stronger than that of Baotou gelatin. When sodium thiosulfate was added to gelatins, methionine sulfoxide was reduced to methionine. Sodium thiosulfate, which is a reductant stronger than both methionine and methionine sulfone, could coexist steadily with methionine and methionine sulfone in the gelatin. Two kinds of photographic gelatins added with sodium thiosulfate could reduce Au³⁺ to colloid gold. In this redox reaction, the main reductant is sodium thiosulfate, but not methionine in the gelatin. The addition of sodium thiosulfate enhanced the reducing power of the photographic gelatin.