We propose a new diffraction phase microscope (DPM), in which a photon counting (PC)-based single-pixel imaging (SPI) technique is introduced for obtaining two-dimensional quantitative phase images (QPIs) of transparent objects. The introduction of the SPI technique is promising for alleviating the sensitivity problem in DPM. This is because a highsensitive single-channel photodetector such as a photomultiplier tube can be used and the spatial multiplex advantage in the signal-to-noise ratio (SNR) can be expected. Furthermore, the employment of the PC technique solves the dynamic range problem inherent to the SPI. As a proof-of-principle experiment, we measured the QPI of a 125-nm thickness ITO layer coated on a silica-glass substrate, demonstrating the superiority of the PC-based SPI-DPM over SPI-DPM in SNR.
Dual comb spectroscopy (DCS) is based on the combination of Fourier transform spectroscopy with an optical frequency comb (OFC), and has a spectral resolution of MHz order over a spectral range of several tens THz. Furthermore, nonmechanical time-delay scanning enables the rapid data acquisition. While DCS imaging is required for hyperspectral imaging, an imaging sensor cannot be used for DCS imaging because of a slow response time compared to the temporal evolution of interferogram signal. Therefore, it is essential to acquire the interferogram signal by use of a single-channel detector while scanning the sample position or the focal point. If DCS imaging can be achieved without the need for such scanning, the application field of the DCS imaging will be largely expanded. One promising method to achieve the scanless imaging is a single-pixel imaging (SPI). SPI enables scan-less imaging by use of optical spatial coding on the sample with a single-channel detector. Also, the spatial averaging effect improves an image quality.
In this paper, we present combination of DCS with SPI, namely a DCS-SPI. DCS-SPI provides 12,000 mode-resolved hyperspectral images in both amplitude and phase at a spatial resolution of 46 μm without the need for mechanical scanning. Furthermore, we determined thickness of a chromium layer from a phase image in the near-infrared wavelength region.
Dual comb spectroscopy (DCS) is based on the combination of Fourier transform spectroscopy with an optical frequency comb (OFC), and has a spectral resolution below MHz order over a spectral range over several tens THz. Furthermore, non-mechanical time-delay scanning enables the rapid data acquisition. However, in order to expand DCS into spectral imaging, a CCD or a CMOS camera cannot be used because a high-speed, point detector is indispensable to acquire the fast interferogram signal in DCS. Therefore, the first demonstration of DCS imaging was based on the mechanical scanning of the sample position. If DCS imaging can be achieved without the need for mechanical scanning, the application field of the DCS imaging will be largely expanded. One promising method to achieve the scan-less 2D imaging is a single-pixel imaging (SPI), enabling scan-less 2D imaging by use of pattern illumination on the sample and a point detector. Also, the accumulation effect in the random pattern illumination increases a signal-to-noise ratio. In this paper, we present combination of DCS with SPI, namely a scan-less DCS imaging. Spectral imaging of a sample indicated the effectiveness and potential of scan-less DCS imaging.
In this paper, we report on comparisons of single-pixel imagings using Hadamard Transform (HT) and the ghost imaging (GI) in the view point of the visibility under weak light conditions. For comparing the two methods, we have discussed about qualities of images based on experimental results and numerical analysis. To detect images by the TH method, we have illuminated the Hadamard-pattern mask and calculated by orthogonal transform. On the other hand, the GH method can detect images by illuminating random patterns and a correlation measurement. For comparing two methods under weak light intensity, we have controlled illuminated intensities of a DMD projector about 0.1 in signal-to-noise ratio. Though a process speed of the HT image was faster then an image via the GI, the GI method has an advantage of detection under weak light condition. An essential difference between the HT and the GI method is discussed about reconstruction process. Finally, we also show a typical application of the single-pixel imaging such as hyperspectral images by using dual-optical frequency combs. An optical setup consists of two fiber lasers, spatial light modulated for generating patten illumination, and a single pixel detector. We are successful to detect hyperspectrul images in a range from 1545 to 1555 nm at 0.01nm resolution.
In this paper, we present experimental results concerning the reduction effect of the accumulated number of computational ghost imaging (CGI) under different light intensities. By using circulatory illumination pattern, the CGI is possible to directly reduce the accumulated number. In addition, for improvement of the spatial resolution of CGI, the illumination pattern scale is reduced illumination to the object by applying microscopic illumination system. Thereby, the propose method can be achieved high spatial resolution imaging that permitted image of microscopic object. Moreover, the proposed method provided image of the biological cell by fluorescence signal detection. As a result, we demonstrated the potential of CGI for applying measurements field of the cell biology.