Abstract

Spectroscopic imaging is useful technique in applications such as coloring-matter identification in old paintings or textiles, chemical-state analysis in biological or medical diagnosis, etc. An optical system, in which two-dimen- sional images for different wavelengths are taken in turn by using wavelength filters, is not good at detection of continuous spectra. Another system, where wavelength of light source is scanned, can not be applied for luminescence or wavelength-shift case. Fourier transform spectroscopic imaging technique requires complex optics and data conver- sion. On the other hand, a compact and handy system is strongly desired in application to in situ analysis or in vivo diagnosis. A thin film grating lens¹⁻⁴⁾ is very attractive in system miniaturization since wavelength dispersion function and lens function can be achieved by a single component. Besides it, the grating can be fabricated by using planar fabrication processes with high productivity. However, a grating lens is not good at wide-view-angle imaging, because large aberration arises when the grating is used with neither designed incident wavefront nor designed wavelength. Specially designed systems^{5, 6)} are therefore required for suppressing aberration down to practical level. In this paper, we discuss a new compact optical device capable of two-dimensional mapping of continuous spectra, and report the fabrication and experimental results of the grating lens.

© 2002 Optical Society of America