VGA급 캡슐형 내시경을 위한 영상 신호 비압축 실시간 전송 = Real-Time and Non-Compression Wireless Transmission Method of Image Signal for VGA Capsule Endoscope

다국어 초록 (Multilingual Abstract)

In order to overcome the weakness of CIF capsule endoscope and furnish doctors a high quality image for accurate diagnosis or therapy, a VGA capsule endoscope system was proposed and implemented in this paper. For transmission of VGA digital image, the new encoding and transmission method without compression was proposed. The bandwidth of encoded image signal is limited by a simple pulse shaping circuit which can be loaded within the miniaturized capsule, and this bandwidth-limited signal is transmitted to external receiver using BFSK modulation. Finally, the transmitted signal is demodulated and restored in receiver part, and reconstructed so that the endoscopes' images can be displayed in the personal computer.
Using the proposed method, a VGA capsule endoscope which has the data rate of 20 Mbps was implemented. The capsule which has the shape of cylinder is composed of a VGA image sensor, a CPLD module for signal encoding, a transmitter with a pulse shaping circuit, a transmitting antenna, a optical lens, and a battery. The external device for receiving the images transmitted by the capsule consists of a RF receiver with a receiving antenna, a pulse shaping circuit for restoration of pulse signal, a CPLD module for signal decoding, a data acquisition board, and a personal computer with a display unit.
The CPLD encoder in the capsule adds a specified bit stream to original image data, and this encoded data is transmitted using the asynchronous BFSK method. The received signal is restored to original pulse train using a pulse shaping circuit. And the pulse train is separated into the synchronization code and endoscopes' image data by the CPLD decoder. Then, the processed data is transmitted to the data acquisition board for the reconstruction of endoscopes' images.
The frequency for transmitting data was selected as 1.2 GHz considering the attenuation due to the human body and the size of transmitting antenna. The output power was -6 dBm with reference to the international regulation for maximum permeable exposure.
In order to confirm the operation of the implemented VGA capsule endoscope, several fundamental test and experiment for data transmission was accomplished. Through the results, it was verified that the implemented capsule could have the enough efficiency and operation performance. From the in-vivo experiment using an animal, it was confirmed that the implemented VGA capsule endoscope can transmit the high-quality VGA image at the rate of 1.4 frames per second.
The encoding method for transmitting images without compression proposed in this paper has three advantages. Firstly, this encoding method doesn't increase the transmission data and doesn't use any compression method, but the implemented capsule can transmit the image data in real-time using a simple timing control method. Secondly, the high frequency component in the abrupt transition of pulse signal is blocked using a pulse shaping circuit, but no loss of information is occurred when the transmitted signal is reconstructed in the pulse shaping circuit of an external receiver. Finally, since this method uses a simple circuit with a miniaturized analog device, the easy implementation in a capsule endoscope system is possible as simple hybrid form.
The VGA capsule endoscope implemented in this paper can transmit the higher quality images in real-time than CIF capsule. Therefore, it is expected that the proposed method for high data rate transmission of VGA image signal can be applied to various biomedical fields for more accurate diagnosis and therapy.

목차 (Table of Contents)

• I. 서 론 1
• Ⅱ. 캡슐형 내시경 시스템과 그 원리 7
• 2.1 소화관의 구조와 생리 7
• 2.2 캡슐형 내시경 시스템 10
• 2.2.1 M2A 10
• 2.2.2 Norika-V3 13
• 2.2.3 MiRO 15
• 2.3 기존의 디지털 통신 방법 17
• 2.3.1 기본적인 디지털 변복조 방식 18
• 2.3.2 기타 변복조 방식 20
• 2.3.3 디지털 영상 전송 방법 23
• Ⅲ. 제안한 영상 인코딩 및 전송 방법 25
• 3.1 디지털 영상 센서와 영상 신호 인코딩 25
• 3.1.1 영상 센서의 선정 25
• 3.1.2 제안한 영상 신호 인코딩 방법 29
• 3.2 VGA 영상 전송 방법 35
• 3.2.1 대역폭 제한 35
• 3.2.2 제안한 대역폭 제한 방법 40
• Ⅳ. VGA급 캡슐형 내시경의 구현 47
• 4.1 송신 주파수 및 송신 전력 결정 49
• 4.2 초소형 FSK 송신기 설계 및 구현 55
• 4.3 VGA급 캡슐형 내시경 제작 67
• 4.4 수신부 구현 및 영상 신호 복원 69
• 4.5 영상 복원 71
• Ⅴ. 실험 및 결과 74
• 5.1 온도 변화에 따른 송수신 주파수 변화 관찰 74
• 5.2 공기 중에서의 데이터 전송 실험 75
• 5.3 동물 실험 78
• 5.4 고찰 81
• Ⅵ. 결 론 83
• 참 고 문 헌 85
• 영 문 초 록 95