We present a method of quantitatively acquiring a large complex field, containing not only amplitude information but also phase information, based on single-shot phase imaging with a coded aperture (SPICA). In SPICA, the propagating field from an object illuminated by partially coherent visible light is sieved by a coded mask, and the sieved field propagates to an image sensor, where it is captured. The sieved field is recovered from the single captured intensity image via a phase retrieval algorithm with an amplitude support constraint using the mask pattern, and then the object's complex field is reconstructed from the recovered sieved field by an algorithm employing a sparsity constraint based on compressive sensing. The system model and the theoretical bounds of SPICA are derived. We also verified the concept with numerical demonstrations.

No abstract

We report on experimental verification of optical trapping using multiple beams generated by a vertical-cavity surface-emitting laser (VCSEL) array. Control of the spatial and temporal emission of a VCSEL array provides flexibility for manipulation of microscopic objects with compact hardware. Simultaneous capture of multiple objects and translation of an object without mechanical movement are demonstrated by an experimental system equipped with 8 x 8 VCSEL array sources. Features and applicability of the method are also discussed.

No abstract

We report on the wavelength-multiplexing diffractive phase element (WMDPE) capable of generating independent spot patterns for different wavelengths. The iterative method proposed by Bengtsson [Appl. Opt. 37, 1998] for designing a kinoform that produces different patterns for two wavelengths is extended to the WMDPE for multiple wavelengths (more than two wavelengths). Effectiveness of the design algorithm is verified by design and computer simulations on the WMDPE's for four and nine wavelengths. The WMDPE for three wavelengths (441.6, 543.5, and 633 nm) is designed with five phase levels and is fabricated by electron-beam lithography. We observed that the individual spot patterns are reconstructed for the design wavelengths correctly. Performance of the WMDPE is evaluated by computer simulations on the uniformity error, the light efficiency, and the contrast. On the basis of the results, the characteristics of the WMDPE's are discussed in terms of various conditions of fabrication and usage.