Cameron H. G. Wright

Computer-assisted laser photocoagulation of the retina—a hybrid tracking approach

A system for robotically assisted retinal surgery has been developed to rapidly and safely place lesions on the retina for photocoagulation therapy. This system provides real-time, motion stabilized lesion placement for typical irradiation times of 100 ms. The system consists of three main subsystems: a digital-based global tracking subsystem; a fast, analog local tracking subsystem; and a confocal reflectance subsystem to control lesion parameters dynamically. We have reported previously on these individual subsystems. This paper concentrates on the development of a second hybrid system prototype. Considerable progress has been made toward reducing the footprint of the optical system, simplifying the user interface, fully characterizing the analog tracking system, using measurable lesion reflectance parameters to develop a noninvasive method to infer lesion depth, and integrating the subsystems into a seamless hybrid system. These system improvements and progress toward a clinically significant system are covered in detail within this paper. The tracking algorithms and concepts developed for this project have considerable potential for application in many other areas of biomedical engineering.

Initial in vivo results of a hybrid retinal photocoagulation system

We describe initial in vivo experimental results of a new hybrid digital and analog design for retinal tracking and laser beam control. An overview of the design is given. The results show in vivo tracking rates which exceed the equivalent of 38 degrees/s in the eye. A robotically assisted lesion pattern is created for laser surgery to treat conditions such as diabetic retinopathy and retinal breaks.

A systematic model for teaching DSP

While many DSP topics are difficult for undergraduates to internalize, appropriate demonstrations and laboratory experiences have been shown to be very helpful. This paper describes a highly successful pedagogical model the authors have developed which includes theory, demos, lab exercises, and real-time DSP experience using MATLAB and the Texas Instruments C6711 digital signal processing starter kit.

Computer-aided retinal photocoagulation system

Researchers at the University of Texas at Austins Biomedical Engineering Laser Laboratory and the U. S. Air Force Academy’s Department of Electrical Engineering are developing a computer-assisted prototype retinal photocoagulation system. The project goal is to rapidly and precisely automatically place laser lesions in the retina for the treatment of disorders such as diabetic retinopathy and retinal tears while dynamically controlling the extent of the lesion. Separate prototype subsystems have been developed to control lesion parameters (diameter or depth) using lesion reflectance feedback and lesion placement using retinal vessels as tracking landmarks. Successful subsystem testing results in vivo on pigmented rabbits using an argon continuous wave laser are presented. A prototype integrated system design to simultaneously control lesion parameters and placement at clinically significant speeds is provided.

Teaching DSP concepts using MATLAB and the TMS320C31 DSK

A graphically-oriented MATLAB program written by the authors facilitates teaching real-world digital signal processing concepts such as quantization of digital filter coefficients that occur in fixed-point processors, for example the widely used TMS320C5x. While many universities have or plan to buy the inexpensive floating-point TMS320C31 DSKs for pedagogical reasons, this MATLAB program simulates certain fixed-point effects on these floating-point devices and eliminates the need to purchase expensive specialized software programs or extra hardware. The program described in this paper provides an interactive graphical user interface which communicates directly with the DSK, and demonstrates in real-time how coefficient quantization adversely affects filter performance, without the need for tedious programming of the TMS320C31.

Hybrid approach to retinal tracking and laser aiming for photocoagulation

The initial experimental results of a new hybrid digital and analog design for retinal tracking and laser beam control are described. The results demonstrate tracking rates that exceed the equivalent of 60 deg per second in the eye, with automatic creation of lesion patterns and robust loss of lock detection. Robotically assisted laser surgery to treat conditions such as diabetic retinopathy and retinal tears can soon be realized under clinical conditions with requisite safety using standard video hardware and inexpensive optical components.

A Multiaperture Bioinspired Sensor With Hyperacuity

We have developed a multiaperture sensor based on the visual system of the common housefly (Musca domestica). The Musca domestica insect has compound eyes, which have been shown to exhibit the ability to detect object motion much finer than their photoreceptor spacing suggests, a phenomenon often called motion hyperacuity. We describe how such motion hyperacuity can be achieved through a controlled preblurring of an optical imaging system. We used this method to develop a software model of a new fly eye sensor and to optimize its motion hyperacuity. Finally, we compare the completed sensor to previously developed fly eye sensors. The new design shows a threefold improvement in signal-to-noise ratio and motion acuity.

Using DSP hardware to teach modem design and analysis techniques

While many communication topics are difficult for undergraduate students to internalize, demonstrations and laboratory experiences have been shown to stimulate the learning process greatly. The paper describes a highly successful combination of theory, demonstrations, lab exercises, and real-time DSP experiences using Matlab and the Texas Instruments C6711 digital signal processing starter kit (DSK). A digital communication transmitter capability has been added to a software tool (winDSK6) which controls the DSK. This approach, when also combined with state-of-the-art measurement equipment, has proven highly successful in reinforcing modem design and analysis techniques.

COMMFSK: a Hardware Approach to Teaching FSK

Many communication topics are difficult for undergraduate students to internalize, but demonstrations and laboratory experiences have been shown to help a great deal. This paper describes how we teach the concept of frequency shift keying by using a highly successful combination of theory, demonstrations, lab exercises, and real-time DSP experiences that incorporate MATLAB and the Texas Instruments C67x digital signal processing starter kit

Motion Detection: A Biomimetic Vision Sensor Versus a CCD Camera Sensor

We compare a traditional CCD imaging sensor with a biomimetic vision sensor (based on Musca domestica, the common house fly) with regard to detecting small moving objects at various speeds and levels of contrast. The patent-pending biomimetic vision sensor described is shown to be capable of reliable object detection in spite of challenging movement and low contrast conditions in which a typical commercial CCD camera sensor failed to properly detect the object.