Single-pixel imaging has become a topic of intense interest amongst theoreticians and experimentalists in recent years, and is still attracting great attention due to its potential applications in biomedical imaging, remote sensing, defence monitoring, etc. Two main fields should be involved in single-pixel imaging scheme: single-pixel camera and computational quantum imaging, which are proposed in the year 2006 and 2008, respectively. Although these two single-pixel imaging schemes belong to different research fields, they are nearly identical in the realization setup and using the similar image recovering algorithm. The single-pixel camera scheme is mainly based on compressive sensing algorithms, which can recover the image with about 30 percent measurements of its total pixels (raster scan method), but need the prior knowledge of the image. While the computational quantum imaging method usually recovers the image by using the second-order correlation function, which is computational fast but need more measurements to retrieve a high quality image. Thus, both the methods mentioned above are time consuming. In this paper, a single-pixel imaging scheme based on Walsh-Hadamard transform is proposed and is demonstrated both theoretically and experimentally. The retrieving times of different algorithms are discussed and compared with each other. An image of 10241024 pixels can be acquired around 1 second with our method while it will take 8 seconds by using TVAL3 algorithm on the general computer in our numerical simulation experiment. It is also experimentally demonstrated that the nature targets from 500 meters to 5000 meters away are acquired, with pixels of 128128 and in the waveband of 350-900 nm, and the speed of the imaging frame rate is achieved at 0.5 frame per second. The differences and commons between single-pixel imaging and computational quantum imaging are also discussed in this article. It is found that the Walsh-Hadamard transform we proposed is stable and can be sufficiently saving the imaging time of the single-pixel imaging schemes while maintaining a high imaging quality. Moreover, the single-pixel remote imaging scheme can be used in other wave band such as infrared and micro wave imaging, or will be useful in the case when the array detector technique is difficult to meet the requirements such as the sensitivity or the volume. And our scheme proposed here can make the single-pixel imaging technique step further toward its real applications.

Design, fabrication and characterizations of GaN-based blue micro light emitting diode (LED) arrays are reported. The GaN micro-LED array consists of 320 × 256 pixels with a pitch size of 30μm. Each pixel is 25 × 25 μm2 in size, which is designed for backside emission and high density flip-chip packaging. The selected LED pixels being tested exhibit good uniformity in terms of turn-on voltage and reverse leakage current. The efficiency droop behavior and reliability behavior under high forward current stress are also studied. The micro-LED pixel shows improved reliability, which is likely caused by enhanced heat dissipation.

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