We describe a novel method based on optical coherence tomography (OCT) for the accurate measurement of the refractive index of in vitro human teeth. We obtain the refractive indices of enamel, dentin, and cementum to be 1.631±0.007, 1.540±0.013, and 1.582±0.010, respectively. The profile of the refractive index is readily obtained via an OCT B scan across a tooth. This method can be used to study the refractive index changes caused by dental decay and therefore has great potential for the clinical diagnosis of early dental caries.
Region-of-interest (ROI) image coding is an interesting feature in JPEG2000, which allows for encoding the ROIs in an image with better quality than the background (BG). Considering the limitations of two standard ROI coding methods, a new ROI coding method called generalized partial bitplanes shift (GPBShift) is presented in this paper. To control the relative importance between ROI and BG, the method divides the bitplanes of ROI and BG coefficients into two parts by using scaling values S1 and S2, respectively. Instead of shifting the bitplanes all at once by the same scaling value S in the standard methods, GPBShift shifts part of them on the basis of the bitplane shifting scheme. The GPBShift not only can code arbitrarily shaped ROI without explicitly transmitting any shape information to the decoder, but also flexibly select the scaling values to adjust relative compression quality in ROI and BG. Additionally, the method can efficiently code multiple ROI with different priorities in an image. Experimental results show that the GPBShift method can provide significantly better visual quality than the Maxshift method at low bit rates, and higher coding efficiency than the general scaling based method.
An inspection system has been developed for on-line detection of film defects, which bases on combination of photoelectric imaging and digital image processing. The system runs in high speed of maximum 60m/min. Moving film is illuminated by LED array which emits even infrared (peak wavelength λp=940nm), and infrared images are obtained with a high quality and high speed CCD camera. The
application software based on Visual C++6.0 under Windows processes images in real time by means of such algorithms as median filter, edge detection and projection, etc. The system is made up of four modules, which are introduced in detail in the paper. On-line experiment results shows that the inspection system can recognize
defects precisely in high speed and run reliably in practical application.