Dual‐color mixing for fused deposition modeling printers

In this work we detail a method that leverages the two color heads of recent low‐end fused deposition modeling (FDM) 3D printers to produce continuous tone imagery. The challenge behind producing such two‐tone imagery is how to finely interleave the two colors while minimizing the switching between print heads, making each color printed span as long and continuous as possible to avoid artifacts associated with printing short segments. The key insight behind our work is that by applying small geometric offsets, tone can be varied without the need to switch color print heads within a single layer. We can now effectively print (two‐tone) texture mapped models capturing both geometric and color information in our output 3D prints.     

中国木版年画的画版处理技术研究

为了对中国木板年画进行数字化保护,本文以套色印刷的朱仙镇木板年画为例, 采用图像处理技术从年画中提取出线版和色版。处理流程分为前处理、线版提取、色版提取和 后处理四个部分。以像素的RGB 和CMY 颜色分量比率计算灰度值,将图中大部分彩色转化为 白色,依此对年画进行去色处理;再经过阈值处理、形态学处理和线条光滑获得年画的黑色线 版。主要利用K-均值聚类方法获取年画的色版。本文的处理结果很好地表现了年画的画版原貌, 所提出的处理框架对于中国木板年画的数字化保护具有较高的实用价值。     

Texture Mapping Real‐World Objects with Hydrographics

In the digital world, assigning arbitrary colors to an object is a simple operation thanks to texture mapping. However, in the real world, the same basic function of applying colors onto an object is far from trivial. One can specify colors during the fabrication process using a color 3D printer, but this does not apply to already existing objects. Paint and decals can be used during post‐fabrication, but they are challenging to apply on complex shapes. In this paper, we develop a method to enable texture mapping of physical objects, that is, we allow one to map an arbitrary color image onto a three‐dimensional object. Our approach builds upon hydrographics, a technique to transfer pigments printed on a sheet of polymer onto curved surfaces. We first describe a setup that makes the traditional water transfer printing process more accurate and consistent across prints. We then simulate the transfer process using a specialized parameterization to estimate the mapping between the planar color map and the object surface. We demonstrate that our approach enables the application of detailed color maps onto complex shapes such as 3D models of faces and anatomical casts.     

Relating halftone dot quality to paper surface topography

Most printed material is produced by printing halftone dot patterns. One of the key issues that determine the attainable print quality is the structure of the paper surface, but the relation is non-deterministic in nature. We examine the halftone print quality and study the statistical dependence between the defects in printed dots and the topography measurement of the unprinted paper. The work concerns SC paper samples printed by an IGT gravure test printer. We have small-scale 2D measurements of the unprinted paper surface topography and the reflectance of the print result. The measurements before and after printing are aligned with subpixel resolution, and individual printed dots are detected. First, the quality of the printed dots is studied using Self Organizing Map and clustering and the properties of the corresponding areas in the unprinted topography are examined. The printed dots are divided into high and low print quality. Features from the unprinted paper surface topography are then used to classify the corresponding paper areas using Support Vector Machine classification. The results show that the topography of the paper can explain some of the print defects. However, there are many other factors that affect the print quality, and the topography alone is not adequate to predict the print quality.     

Nozzle condition monitoring in 3D printing

3D printing and particularly fused filament fabrication is widely used for prototyping and fabricating low-cost customized parts. However, current fused filament fabrication 3D printers have limited nozzle condition monitoring techniques to minimize nozzle clogging errors. Nozzle clogging is one of the most significant process errors in current fused filament fabrication 3D printers, and it affects the quality of the prototyped parts in terms of geometry tolerance, surface roughness, and mechanical properties. This paper proposes a nozzle condition monitoring technique in fused filament fabrication 3D printing using a vibration sensor, which is briefly described as follows. First, a bar mount that supports the liquefier in fused filament fabrication extruder was modeled as a beam excited by a system of process forces. The boundary conditions were identified, and the applied forces were analyzed for Direct and Bowden types of fused filament fabrication extruders. Second, a new 3D printer with a fixed extruder and a moving platform was designed and built for conducting nozzle condition monitoring experiments. Third, nozzle clogging was simulated by reducing the nozzle extrusion temperature, which caused partial solidification of the filament around inner walls of the nozzle. Fourth, sets of experiments were performed by measuring the vibrations of a bar mount during extrusion of polylactic acid, acrylonitrile butadiene styrene, and SemiFlex filaments via Direct and Bowden types of fused filament fabrication extruders. Findings of the current study show that nozzle clogging in fused filament fabrication 3D printers can be monitored using an accelerometer sensor by measuring extruder’s bar mount vibrations. The proposed technique can be used efficiently for monitoring nozzle clogging in fused filament fabrication 3D printers as it is based on the fundamental process modeling.     

熔丝沉积制造中稳固低耗支撑结构生成

熔丝沉积制造(Fused deposition modeling, FDM)是利用熔融塑料丝的一种3D打印技术,热塑料由喷嘴喷出逐层堆积完成打印.由于熔丝只能沉积在已存在物体的上层,因此需要构造支撑结构以支撑悬空部分.针对现有支撑结构生成算法中存在的或结构不稳固或耗材多的缺陷,提出一种以熔丝为支撑单位的树形稀疏支撑结构.与传统算法计算模型表面支撑区域不同,本算法计算每段熔丝需要支撑的区域,使支撑结构更契合熔丝沉积特点.算法还将支撑结构分为三类,将多约束优化问题分解,降低算法复杂度.实验结果表明,本文算法生成的支撑结构算法耗材少、支撑稳定.     

Economic approximate-K color printing algorithm

This article describes a novel scheme to save the usage of ink or toner by an approximate-K algorithm for color printers. Existing printers use the mixtures of three color toners (Cyan, Magenta and Yellow) to print all the pixels for color images, and it makes color printing 4–4.5 times more expensive than monochromic printing. Since human eyes are not sensitive to distinguish neighboring colors in the color space, we can use the K (blackK) toner to replace the colors close to gray-scale. We can then reduce the ink usage without affecting the image visual qualities. We use the saturation in the HSV (hue, saturation, value) color model to discover the near gray-scale pixels and transform those pixels to gray level. We then evaluate the objective image quality using the PSNR (Peak Signal Noise Ratio) and use the DSCQS (Double Stimulus Continuous Quality Scale) as the subjective evaluation method. From our experimental results, printing a color image using our algorithm needs only 84 % of the original price in average.     

Determination of color changes of inks on the uncoated paper with the offset printing during drying using artificial neural networks

This study attempts to determinate color changes based on time in inks applied on the surface of wood-free uncoated paper with offset printing during drying. This study consists of two main cases: (1) Experimental analysis: By preparing a test page according to the 12647-2 principle with an offset printing system, test prints were applied to 120 g/m² wood-free uncoated paper using an ECI 2002 CMYK test chart. Each press was measured being subject to process every 15 min in the first 2 h, then hour by hour between 2 and 12 h, then 4–4 h between 12 and 24 h, and then 6–6 h between 24 and 48 h. CIELAB and reflectance values between 380 and 720 nm of the target, 1,485 colors of the test chart were obtained. To see the drying and color changes of the ink on paper, changes were determined by printing on the paper and applying artificial neural network (ANN) to spectrophotometer data at the stated time intervals. (2) Empirical analysis: The use of the ANN has been proposed as numerical approach to get of empirical equations of color changes in inks applied on the surface of wood-free uncoated paper with offset printing during drying. Based on the outputs of the study, ANN model can be used to estimate the effects of digital proofing systems used in color management on print quality with high confidence with the use of the acquired equations without experimental study. In the study, as colors are defined in terms of wave length, in case, all wave lengths are taken into consideration, certain wave length changes have been taken into consideration.     

基于机器视觉的印刷质量检测研究（英文）

为了实现对物品印刷质量的高效检测,通过机器视觉技术,采用图像处理的方法来实现印刷品质量的检测。根据印刷检测的功能需求,设计了三个具体的功能模块,并在VS2008和OpenCV1.0平台下实现了印刷质量检测的功能,支持印刷品图像的输入、人机交互处理、划痕和偏色检测、结果输出等功能。与传统采用的手工方法相比,提高了印刷质量检测的效率,检测速度快,准确率高,检测结果客观,能够迅速而精确地检测出目标印刷品的外观缺陷程度。     

Automatic Generation of Virtual Woodblocks and Multicolor Woodblock Printing

In this paper, we study a method to synthesize a multicolor virtual woodblock print by using several virtual woodblocks. It consists of two sections: carving and printing, to synthesize a virtual print. In the carving section, virtual woodblocks are generated by a user with supporting of an automatically carving method based on feature extraction of a gray value image. And woodblocks are also generated automatically by using a full-color image as a draft. In the printing section, a "paper sheet", a "printing brush" and "ink" are prepared in addition to the "woodblock" in the virtual space and the user synthesizes a woodblock print interactively. As the printing factors, a color of ink, a moisture value and a grain change the finish of the print. Using several virtual woodblocks and printing to a paper sheet in succession, a printing image of each woodblock is combined based on the printing factors and a multicolor virtual prints is synthesized.     

A computational model of print-quality perception

A system has been developed that can simulate human print quality assessments for simple prints. It consists of an image analysis system and a neural network trained in differentiating between different quality prints. Humans were used to assess the print quality of a series of images of different tones, produced by a variety of printing processes. An image analysis system was employed to collect and pre-process raw image data from the prints. A neural network employing supervised learning was then used to produce computer models of the assessments. The image analysis system and neural network models were subsequently employed to predict the observer assessments for a further set of prints that had not undergone the supervised learning procedure. In the prediction trial, the system correctly classified 23 out of 24 prints.     

Watercolor Woodblock Printing with Image Analysis

Watercolor paintings have a unique look that mixes subtle color gradients and sophisticated diffusion patterns. This makes them immediately recognizable and gives them a unique appeal. Creating such paintings requires advanced skills that are beyond the reach of most people. Even for trained artists, producing several copies of a painting is a tedious task. One can resort to scanning an existing painting and printing replicas, but these are all identical and have lost an essential characteristic of a painting, its uniqueness. We address these two issues with a technique to fabricate woodblocks that we later use to create watercolor prints. The woodblocks can be reused to produce multiple copies but each print is unique due to the physical process that we introduce. We also design an image processing pipeline that helps users to create the woodblocks and describe a protocol that produces prints by carefully controlling the interplay between the paper, ink pigments, and water so that the final piece depicts the desired scene while exhibiting the distinctive features of watercolor. Our technique enables anyone with the resources to produce watercolor prints.     

Super‐high‐resolution transfer printing for full‐color OLED display patterning

Abstract— A transfer‐printing method for the patterning of thin polymer layers is described. A hard stamp with a raised feature is brought into contact with a spin‐coated organic film under elevated pressure and temperature to break the films. The patterned film is then transfer printed onto the devices. This method is used to print red/green/blue subpixel arrays with a pattern size as small as 12 μm at a resolution of 530 ppi to demonstrate its ability for full‐color organic light‐emitting‐display fabrication. Devices with printed organic layers have similar performance to spin‐coated controls under optimized printing temperature and pressure settings. The critical physical parameters include a soft intermediate plate for the sharp breaking of edge patterns, control of surface energies, and printing at moderate temperature and pressure to achieve intimate contact between the printed layer and the underlying substrate.     

Automated quality control of printed flasks and bottles

The paper faces the quality control problem for printed flasks, bottles and cans, used as containers for drugs and beverages. The control is mainly aimed at identifying ink spots and faded prints produced by a serigraphic process, but the approach is generically applicable to any kind of printing and printed cylindrical surface. Differently from the existing systems, based on the acquisition of good printed samples, the automatic control is based on the original digital image feeded to the printing system. Therefore, the control takes place directly between the ideal model and the result of a complex printing process including a number of distortion and noise sources. Problems related to image acquisition, reconstruction and alignment are investigated; a novel technique for image-model verification, based on adaptive local deformation, is also proposed and tested over a significant set of samples. A complete prototype system designed for such quality control is finally described and its operating capability on the field is discussed.     

A mathematical model to predict surface roughness and pattern thickness in roll-to-roll gravure printed electronics

The roll-to-roll printing processes have recently been applied for the manufacturing of printed electronics due to their advantages, such as their high-throughput capabilities and low associated costs. In a roll-to-roll printing machine, a web or substrate is moved from an unwinding roll to a winding roll. During printing, the operating tension is important for correct substrate handling to prevent substrate defects, such as wrinkles, scratches and breaks. Accordingly, the operating conditions of the moving web can affect the quality of the printed pattern. In this study, a mathematical model has been developed to predict the thickness and surface roughness of printed patterns. Because the dynamics of roll-to-roll printing systems are complicated and non-linear, a statistical model is preferred. A full factorial method has been used with four independent variables: operating tension, print speed, ink viscosity and theoretical transfer volume. This model accurately predicted the surface roughness and thickness of the printed pattern.     

A randomized algorithm for natural object colorization

Natural objects often contain vivid color distribution with wide variety of colors. Conventional colorization techniques, on the other hand, produce colors that are relatively flat with little color variation. In this paper, we introduce a randomized algorithm which considers not only the value of target color but also the distribution of target color. In essence, our algorithm paints a color distribution to a region which synthesizes color distribution of a natural object. Our approach models the correlation between intensity and color in HSV color space in terms of H – S, H – V and S – V joint histogram. During the colorization process, we randomly swap and reassign color of a pixel to minimize a cost function that measures color consistency to its neighborhood and intensity‐to‐color correlation captured in the joint histogram. We tested our algorithm extensively on many natural objects and our user study confirms that our results are more vivid and natural compared to results from previous techniques.     

Color laser printer forensic based on noisy feature and support vector machine classifier

Digital forensics in the ubiquitous era can enhance and protect the reliability of multimedia content where this content is accessed, manipulated, and distributed using high quality computer devices. Color laser printer forensics is a kind of digital forensics which identifies the printing source of color printed materials such as fine arts, money, and document and helps to catch a criminal. This paper present a new color laser printer forensic algorithm based on noisy texture analysis and support vector machine classifier that can detect which color laser printer was used to print the unknown images. Since each printer vender uses their own printing process, printed documents from different venders have a little invisible difference looks like noise. In our identification scheme, the invisible noises are estimated with the wiener-filter and the 2D Discrete Wavelet Transform (DWT) filter. Then, a gray level co-occurrence matrix (GLCM) is calculated to analyze the texture of the noise. From the GLCM, 384 statistical features are extracted and applied to train and test the support vector machine classifier for identifying the color laser printers. In the experiment, a total of 4,800 images from 8 color laser printer models were used, where half of the image is for training and the other half is for classification. Results prove that the presented algorithm performs well by achieving 99.3%, 97.4% and 88.7% accuracy for the brand, toner and model identification respectively.     

VB打印技术研究

提出两种技术可提高打印开发的速度和质量.通过程序自动识别窗体上文本框、标签和图片框等控件,并按以上控件对应打印程序进行输出,实现打印的自动化;介绍一种打印预览实用技术,可实现复杂格式的输出.     

基于视觉选择性注意机制的目标检测的研究

视觉选择性注意模型的应用是当今认知信息处理领域的研究热点。根据人类视觉感知理论,在介绍具有代表性的视觉注意模型（Itti模型）的基础上,在特征提取的初级阶段引入新的低层视觉特征,形成一种新的引导注意的显著图,从而实现较为准确的目标检测。结果证明该方法在一定程度上避免了漏检测现象的发生,使得注意区域更能接近生物视觉系统的实际。     

全彩3D打印颜色再现方法

全彩3D打印具有快速再现彩色原型的优势, 已经开始广泛应用于医疗、工业、食品等多个领域. 这些领域对3D打印产品的颜色再现精度要求越来越高, 如何提高全彩3D打印产品的颜色再现质量成为研究热点问题之一. 本文对全彩3D打印的颜色再现方法进行了较为全面的论述. 在对全彩3D打印实现方式分类的基础上, 重点对全彩3D打印颜色再现中的颜色转换和打印输出模型两种核心技术进行分析, 探讨现有方法的优势与不足, 在此基础上论述了全彩3D打印的发展趋势.