Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 1150474

Scanning tooth surface reflectometer.

H Gabathuler
View original source ↗Export metadata ↓

Abstract

A method for tooth surface lustre measurements with a scanning reflectance sensor system is described. A fiber optic light beam of high intensity is projected onto the labial tooth surface. The reflected light at position X is conducted through the same fiber optic to a photodiode, amplified and recorded on an X-Y recorder. Position X is measured by a potentiometer in the rotation center of a rod to which the fiber optic head is attached and which can be moved parallel to the arcade of anterior teeth to be measured. The experimental system allows the assessment of differences in light reflection caused by light scattering resulting from roughened enamel surfaces and by stains.

Explore related subjects

ElectronicsFiber Optic TechnologyHumansLightOptical FibersSurface PropertiesToothJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

H Gabathuler. 1975. Scanning tooth surface reflectometer.. https://pubmed.ncbi.nlm.nih.gov/1150474/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1992

A new superbright LED stimulator: photodiode-feedback design for linearizing and stabilizing emitted light.

A new, reliable LED photic generator is described for analog stimulus presentation in vision research. A "superbright" red-emitting diode is controlled via optical feedback using a PIN-photodiode. A Maxwellian-view stimulator developed this way has been proven capable of covering intensities of retinal illuminance of over 26,000 td with a linear dynamic range of 3.7 log units. The device also has outstanding properties in linearity (distortion less than 0.12% at 100 Hz), frequency characteristics (d.c. to 2 kHz full-modulation bandwidth), stability (0.0002% fluctuation), and noise (S/N ratio greater than 76 dB).

Electronics↗
PubMed1992

Spectral feature enhancement for people with sensorineural hearing impairment: effects on speech intelligibility and quality.

People with sensorineural hearing loss often have difficulty understanding speech in background noise at speech-to-noise ratios (0 to +6 dB) for which normally hearing people have little difficulty. Spectral analysis of speech in noise at these ratios typically shows that the major spectral prominences in the speech (formants) are well represented, but the spectral valleys between the formants are filled with noise. Hearing impaired people have a reduced ability to pick out the spectral prominences, and are more affected by the noise filling in the valleys, partly because of their reduced frequency selectivity. This paper describes a 16-channel bandpass filter bank, implemented in analog electronics, that attempts to enhance spectral features of speech in noise to improve intelligibility for the hearing impaired. Each channel generates an 'activity function' that is proportional to the magnitude of the signal envelope in that channel, averaged over a short period of time. A positively weighted activity function from the nth channel is combined with negatively weighted functions from channels n-2, n-1, n+1, and n+2, giving a correction signal used to control the gain of the bandpass signal in the nth channel. Recombining the bandpass signals results in an enhancement of spectral features of the speech in noise. Two different experiments are described here, one using the activity function as described, and the other using a non-linear transform of the activity function. In both experiments, several different weighting patterns were used in calculating the correction signal. The intelligibility of speech in noise processed by the system was measured for subjects with moderate sensorineural hearing loss. In both experiments, no improvement in intelligibility was found. However, subjective ratings of the stimuli used in Experiment 2 indicated that some subjects judged the processed stimuli to have both higher quality and higher intelligibility than unprocessed stimuli.

Electronics↗