Showing papers on "Image conversion published in 1977"
21 Jun 1977
TL;DR: In this article, a time-domain technique is presented for the analysis of mixers, yielding values for their optimum impedance conditions and expressions for the conversion coefficients for all small-signal first-order conversion products.
Abstract: A time-domain technique is presented for the analysis of mixers. Three simple circuit models using "ideal diodes" have been analyzed exactly, yielding values for their optimum impedance conditions and expressions for the conversion coefficients for all small-signal first-order conversion products. Some new physical insights are obtained. Without image rejection, 3.92 dB conversion loss is the minimum for an untuned mixer, 3.36 dB with single-stub tuning, and 3.0 dB with resonator tuning. For the optimum bias level and IF impedance, no image signal is generated in any of these cases. With an image band-stop filter, lower conversion loss is predicted when the impedances are changed, but, the improvement predicted is small unless the conversion loss without the image filter can approach 3.0 dB.
3 citations
01 Jan 1977
TL;DR: In this paper, a two-step process is proposed for speckle reduction in coherent imaging, in which an image is first recorded in coherent light and then spatially filtered in incoherent light.
Abstract: A new method for speckle reduction in coherent imaging is presented. The method is based on a two-step process in which an image is first recorded in coherent light and then spatially filtered in incoherent light. This two-step process, which does not use moving parts, is shown to be mathematically equivalent to the well-known moving aperture technique. Also a real-time version of the two-step process is presented, where a liquid crystal cell provides the necessary coherent-to-incoherent image conversion. Finally, it is shown that the spatial filtering effect of a single small aperture can also be achieved by a large-aperture phase plate.
1 citations
12 Jan 1977
TL;DR: In this article, the real-time light modulators for the input plane of coherent optical processors are presented. But the modulators are not suitable for the real time processing of optical sensors.
Abstract: In recent years it has become possible to read out electronic image sensors by means of deformable membrane mirror arrays1'2"'"5. Similar techniques have also been explored for use with scanned electron beams6'7. The principal motivation for this work has been "real-time" light modulators for the input plane of coherent optical processors.