Taufiq Widjanarko - Academia.edu (original) (raw)

Papers by Taufiq Widjanarko

Optics and Laser Technology, Jun 1, 2002

In this paper, we propose a post-processing technique to obtain optical microscope images with ex... more In this paper, we propose a post-processing technique to obtain optical microscope images with extended depth of focus using a conventional microscope. With the proposed technique, we collect a sequence of images focused at di erent depths. We then combine the in-focus regions of each acquired frame to compose a single all-in-focus image. That is, a new image with extended depth of focus is obtained. The key to such an algorithm is in selecting the "in-focus" regions from each frame. In this paper, we describe the technique used to identify the in-focus region on every depth slice. Quantitative simulation results are presented where mean absolute error is used as a metric to assess the algorithm performance. Results using real imagery are also presented for subjective evaluation. Based on subjective evaluation and the quantitative simulation results, we believe that the proposed algorithm provides useful depth of focus extension. ?

Journal of the Optical Society of America, Aug 19, 2020

Metal powder bed fusion (PBF) methods need in-process measurement methods to increase user confid... more Metal powder bed fusion (PBF) methods need in-process measurement methods to increase user confidence and encourage further adoption in high-value manufacturing sectors. In this paper, a novel measurement method for PBF systems is proposed that uses multi-view fringe projection to acquire high-resolution surface topography information of the powder bed. Measurements were made using a mock-up of a commercial PBF system to assess the system's accuracy and precision in comparison to conventional single-view fringe projection techniques for the same application. Results show that the multi-view system is more accurate, but less precise, than single-view fringe projection on a point-by-point basis. The multi-view system also achieves a high degree of surface coverage by using alternate views to access areas not measured by a single camera.

Augmented and Mixed Reality promises another leap forward in productivity and lifestyle, offering... more Augmented and Mixed Reality promises another leap forward in productivity and lifestyle, offering benefits with a magnitude and impact matching that of the introduction of smartphones. However, to enable this, many significant technical challenges must be overcome. Here we review the state of the art, identifying key challenges established in the literature to consumer-wearable devices. In particular, we discuss: vergence-accommodation conflict (the detrimental effect of overlays that are optically inconsistent with the real-world objects they augment), the need to present overlays visible against the vast dynamic range that the human eye can process, and constraints surrounding the scalability and cost of manufacture of optics. We demonstrate that digital holography as a display mechanism not only provides an effective solution to the aforementioned challenges, but also that various hardware requirements become far less stringent. By operating in the Fourier Domain, holographic dis...

To support the manufacture of next-generation high-value products, increased reliance will be pla... more To support the manufacture of next-generation high-value products, increased reliance will be placed on metrology. This article will discuss an approach to metrology that, in our opinion, has the potential to significantly enhance the metrology capability in advanced manufacturing. First, let us briefly review the need for metrology in manufacturing. Lord Kelvin said: “If you cannot measure it, you cannot improve it”, and this simple statement captures a great deal about why measurement is an essential part of manufacturing. The following are some of the primary reasons why we put so much effort into measuring what we manufacture:

Journal of the Society for Information Display, 2021

Journal of the Optical Society of America A, 2020

2014 13th International Conference on Control Automation Robotics & Vision (ICARCV), 2014

ABSTRACT Recent advances in automation and sensor technology have enabled the use of industrial r... more ABSTRACT Recent advances in automation and sensor technology have enabled the use of industrial robots for complex tasks that require intelligent decision making. Vision sensors have been the most successfully used sensor in many high value industrial applications. Over the recent years, weld seam tracking has been a topic of interest, as most of the existing robotic welding systems operate on basis of pre-programmed instructions. Such automated systems are incapable of adapting to unexpected variations in the seam trajectory or part fit-up. Applications such as tungsten inert gas (TIG) welding of aerospace components require high tolerances and needs intelligent decision making. Such decision making procedure has to be based on the weld groove geometry at any instance. In this study, a novel algorithm along with an automated system was developed for estimating the joint profile and path tracking of a three dimensional (3D) weld groove. A real-time position based closed-loop system was developed with a six axis industrial robot and a laser triangulation based sensor. The system was capable of finding the 3D weld joint profile and position in real-time, and make intelligent decisions accordingly. Raw data from a vision sensor was processed through a novel algorithm to obtain X and Z co-ordinates at an accuracy of 8.3μm and 43μm respectively at an acquisition speed of 2.5 profiles per second. The algorithm was also capable of measuring the weld gaps with an accuracy of 28μm. Finally, the developed system was successfully used for three dimensional seam tracking, and demonstrates an accuracy of ±0.5mm at a tracking a speed of 2mm/s.

Optics & Laser Technology, 2002

The literature search shows there are at least three mainstreams in optical data encryption and d... more The literature search shows there are at least three mainstreams in optical data encryption and decryption technique. First, which dominates the publications in the field, is the random mask encoded method initiated by research group from EE Dept Univ. of Connecticut lead by ...

Abstract-In this report two binary image thresholding methods are briefly described. Both methods... more Abstract-In this report two binary image thresholding methods are briefly described. Both methods assume that the image consists only two major parts: object (foreground) and background. First method is Otsu method. Threshold value in this method is calculated by minimizing the ...

Abstract-In this paper a study on implementation of reinforcement learning (RL) method for an obj... more Abstract-In this paper a study on implementation of reinforcement learning (RL) method for an object recognition system is presented. The learning method is implemented by neuro-dynamic programming (NDP) structure featured by the presence of the critic and action networks. ...

Page 1. First year Report Taufiq Widjanarko Research student (starting date: April 2006) Supervis... more Page 1. First year Report Taufiq Widjanarko Research student (starting date: April 2006) Supervisors: Prof. Jonathan M. Huntley Dr. Pablo D. Ruiz Director of Research: Dr. Ian Ashcroft Wolfson School of Mechanical and Manufacturing Engineering Loughborough University ...

2004 IEEE International Joint Conference on Neural Networks (IEEE Cat. No.04CH37541)

In this work, we propose an adaptive automatic target recognition (ATR) technique that exploits r... more In this work, we propose an adaptive automatic target recognition (ATR) technique that exploits reinforcement learning (RL) for multiresolution object recognition. The RL structure is the implementation of neuro-dynamic programming (NDP) for the critic and action networks. The critic network calculates the cost-to-go function J* based on a simplistic ATR plant that involves multiresolution images as the input state variable. The calculation of this function, J* includes the role of the reinforcement signal in the critic network. Output of this critic stage is fed back to update the weights of both action and critic networks respectively. Our simulation results suggest that RL may be successfully integrated into an adaptive multiresolution ATR framework.

In this paper, a brief survey on three-dimensional display technologies is reported. The survey s... more In this paper, a brief survey on three-dimensional display technologies is reported. The survey starts from the basic consideration on how a human visual system can perceive depth, as the missing dimensional component, from two-dimensional planar images. As these visual depth cues have been identified, efforts are directed to construct displays that are able accommodate as many cues as possible. Numerous displays have been built in this respect, however, only two are presented in this paper: lenticular sheet and parallax barrier. This approach, however, does not comprehensively solve the problem since these apparatus can not reproduce the original object wavefront that contains phase of the wave within which the information of object’s spatial location is embodied. Holography, conceived for the first time in 1948, is able to fulfill this necessity, and it is the main reason up to now holography remains considered as the only true threedimensional display. The remaining part of this ...

Laser (profile) scanners (LS) have been widely used in industry for 3D shape measurement. However... more Laser (profile) scanners (LS) have been widely used in industry for 3D shape measurement. However, commercially available scanners are costly. They are also less flexible as the components of the device are permanently fixed in a sealed housing, whereas altering setup geometry can improve the device’s height resolution. This paper describes the design and construction of a LS setup from generic off-the-shelf components; a digital camera, laser line module, optical bandpass filter and a machine vision library software for image to 3D point cloud conversion. The performance of the setup is assessed by measuring a set of step height samples ranging from 50 μm to 1 mm. LS measurement performance is determined by comparing measurements of the step heights with those taken from a Coordinate Measurement Machine (CMM). Average measurement difference between the setup and CMM is 20.29 μm with repeatability of 0.60 μm. The highest percentage error for the smallest tested step height suggests ...

A new approach to the absolute measurement of two-dimensional optical path differences is present... more A new approach to the absolute measurement of two-dimensional optical path differences is presented in this thesis. The method, which incorporates a white light interferometer and a hyperspectral imaging system, is referred to as Hyperspectral Interferometry. A prototype of the Hyperspectral Interferometry (HSI) system has been designed, constructed and tested for two types of measurement: for surface profilometry and for depth-resolved displacement measurement, both of which have been implemented so as to achieve single shot data acquisition. The prototype has been shown to be capable of performing a single-shot 3-D shape measurement of an optically-flat step-height sample, with less than 5% difference from the result obtained by a standard optical (microscope) based method. The HSI prototype has been demonstrated to be able to perform single-shot measurement with an unambiguous 352 (m depth range and a rms measurement error of around 80 nm. The prototype has also been tested to pe...

Symmetry

The authors would like to make the following addenda and correction to their paper [...]