| 摘要 |
<p>A biometric sensor comprises: an illumination means; an SBG device further comprising transparent substrates sandwiching an array of selectively switchable SBG elements, the substrates and SBG array together providing a fust TIR light guide; means for coupling illumination light into the light guide; and an optical wave guiding structure sandwiched between a first cladding layer facing the SBG device and a second cladding layer, the cladding layers providing a second TIR light guide. An SBG element in a diffracting state diffracts incident light into the second TIR light guide to provide second TIR light. The sensor further comprises means for coupling the second TIR light into the wave- guiding structure; a means for coupling light out of the wave-guiding structure onto a detector element. External pressure at a point on the outer side of the second cladding layer causes the propagation of the second TIR light to be frustrated.</p> |
