Compressive Sensing refers to the acquisition in compressed form of sparse signals. One of the CS applications is the Single Pixel Camera that rethinks the conventional imaging systems. The key part of the camera is a Spatial Light Modulator (SLM), which provides the mechanism for taking arbitrary measurements of the scene. The non-uniform sampling (NUS) scenario offers a simple procedure to select random samples from the scene, instead of taking random projections. This paper analyses the Single Pixel Camera performance using NUS in the case of two categories of samples: randomly distributed over the scene and selected from the contours vicinity. The NUS is compared, in terms of reconstructed images, with measurements obtained by projection on a random selection from the S-Transform basis. The results are given on simulated data and on real images obtained with the experimental model of a Single Pixel Camera. The comparison of reconstructed images in the three cases of measurements shows that, in terms of PSNR, the NUS with contour pixels is equivalent with the S-transform based measurement.

Single Pixel Camera (SPC) is an alternative architecture for imaging systems that emerged as an application of Compressive Sensing theory. The SPC distinctive feature is the single detector that measures linear combinations of pixels instead of pixels as in imaging array cameras. The measurements are obtained by projecting the scene on a Spatial Light Modulator (SLM), the other distinctive component of the SPC architecture. This paper discusses the problem of resolution in SPC. We show that in terms of Point Spread Function (PSF), the resolution model is similar to that of an imaging array camera except the fact that the role of the imaging array is taken over by the SLM. This reduces the contribution of the optics to the SPC resolution comparing with the CCD cameras. Relying on an existing method, we develop a procedure that uses a circular chart to measure the camera PSF. Our procedure has as additional facilities the correction of chart tilt and the capability to work with non-circular apertures. At low noise, tilts up to 15 degrees are practically removed.

A grating interferometer that uses the high diffraction orders in conjunction with a Twyman–Green commercial interferometer is used for the measurement of in plane movement of gratings. The high diffraction orders ensures the amplification of the measurement precision with a factor equal to the diffraction order of the measurement in principle, because no imaging of features marking the beginning and the end of the measured length feature is necessary, and therefore the resolution limits associated with microscope imaging are eliminated.