In this thesis, an existing non-contact dermatoscope will be further developed on the basis of knowledge and experience, and established as a new prototype for dermatoscopy at the Hannover Institute of Optical Technologies (HOT).In this system, the light generated by a white LED is collimated and polarized by a lens system, and generates a homogeneous light spot at a distance of 60cm. By cross polarization, the light reflected directly onto the skin surface can be suppressed, so that only light reflected in deeper skin layers can pass through the analyzer, and contributes to the image information. Due to the difficult handling of the original device, the further developed (advanced) system was compactified and automated, taking into account the basic principle of non-contact dermatoscopy. The illumination unit used in the original non-contact dermatoscope was replaced with a newly constructed reflector in order to improve the brightness, and the homogeneity of the light spot in the target area. These two reflectors were measured with a near field goniophotometer to characterize the illuminance distribution. The conducted tests included the definition of an ideal setup of the lens system, both in practice, and in optical systems simulations by using Zemax. It could be shown that the reflectors improve the illuminance, and generates a homogeneous light spot in the target area, which homogeneously illuminates the image area of the camera. Furthermore, this system has been completely automated by providing automatic focus as well as adjustment of one of the polarizers (analyzer) used. For this purpose, a automatic focus lens was integrated on the existing objective and a mid range infrared distance sensor was installed into the system. By various tests, such as the determination of the resolution with the modulation transfer function, the new camera system was characterized. Based on this tests, the highest possible resolution was determined and the work area could be defined. In this work area structures of 30 μm can be resolved sharply. In addition to the automation of the focus, a stepper motor has been installed to control the analyzer. A program was written in LabVIEW, which controls all components, automates the image acquisition, and provides the possibility of image processing (blood contrast enhancement). Subsequently, the entire system has been mounted on a variably adjustable swivel arm, in order to improve the handling for the dermatologist.
Inhaltsverzeichnis (Table of Contents)
- Abstract
- 1 Introduction
- 2 State of the Art
- 3 Design and Construction of the Illumination Unit
- 3.1 Introduction
- 3.2 Reflector Design
- 3.2.1 Reflector Measurement with Goniophotometer
- 3.2.2 Simulation of the Reflector in Zemax
- 3.3 Lens System Design
- 3.3.1 Lens System Design and Optimization in Zemax
- 3.3.2 Homogeneity of the Illumination
- 3.4 Automatic Focus and Analyzer Adjustment
- 3.4.1 Automatic Focus
- 3.4.2 Automatic Analyzer Adjustment
- 3.5 Camera System Characterization
- 3.5.1 Modulation Transfer Function (MTF) Measurement
- 3.5.2 Resolution Test with USAF-1951 Test Chart
- 3.6 Integration of the System
- 3.6.1 Swivel Arm
- 3.6.2 Software Development in LabVIEW
- 4 Discussion
- 5 Conclusion
- 6 References
Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)
This Master's thesis focuses on the development and construction of a new prototype for non-contact dermatoscopy, building upon an existing device. The main objective is to improve the performance, usability, and automation of the system for improved skin cancer detection and analysis.
- Development of a new illumination unit with enhanced brightness and homogeneity
- Optimization of the lens system and reflector design using simulation software
- Implementation of automatic focus and analyzer adjustment for ease of use
- Characterization of the camera system for resolution and performance evaluation
- Integration of the components into a compact and user-friendly system
Zusammenfassung der Kapitel (Chapter Summaries)
- Chapter 1: Introduction This chapter provides an overview of the background and motivation for the project, highlighting the importance of non-contact dermatoscopy for early skin cancer detection. It introduces the existing system and its limitations, setting the stage for the development of a new prototype.
- Chapter 2: State of the Art This chapter explores the current technologies and research related to non-contact dermatoscopy, providing a comprehensive review of existing techniques and their advantages and disadvantages. It sets the context for the proposed design and construction of the new illumination unit.
- Chapter 3: Design and Construction of the Illumination Unit This chapter delves into the detailed design and construction process of the new illumination unit. It describes the development of the reflector, lens system, and automatic focus and analyzer adjustment mechanisms. It also discusses the characterization of the camera system and the integration of all components into a functional system.
Schlüsselwörter (Keywords)
Non-contact dermatoscopy, illumination unit, reflector design, lens system optimization, automatic focus, analyzer adjustment, camera system characterization, image processing, skin cancer detection, early diagnosis, medical technology.
- Quote paper
- Thomas Hildebrandt (Author), 2018, Design, simulation, and construction of an illumination unit for non-contact dermatoscopy, Munich, GRIN Verlag, https://www.grin.com/document/442621
