Segmented Planar Imaging is an advanced technology for ultra-thin, high-resolution imaging with photonic integrated circuit (PIC). In this paper, a segmented planar imager with a novel hierarchical multistage sampling lens array is proposed, which can effectively improve the sampling of low and medium frequency information. Based on the novel lens array architecture, a full-chain signal level model of the segmented planar imaging system is established, considering the fill factor of lens array and the wavelength spacing of the arrayed waveguide grating in PICs. The simulation results show that the imaging quality of the segmented planar imaging system with the hierarchical multi-level sampling lens array is significantly improved, compared with the original segmented planar imaging system. Moreover, the error range and optimization options of some parameters are given based on the full-chain modeling. There is almost no influence on the system imaging results when the error of the lens array fill factor is within 5%. The imaging quality of the system is enhanced as the wavelength spacing of the arrayed waveguide grating is reduced, and arrayed waveguide grating with wavelength spacing of 10 nm is the optimal choice for the system. The results will be helpful for the optimal design of segmented planar integrated optical imaging systems.

Considering the limited pixel number and large pixel size of common display panel, the captured elemental images (EIs) array of high density pixels cannot be reconstructed sufficiently in the display process of integral imaging, because of matched display requirement. To solve this problem, this paper presents a novel approach to improve integral imaging resolution by designing a coded sub-pixel mask on common display panel. Specifically, multi-pixels in the captured EIs are displayed in a pixel in the common display panel with time multiplexing along with the corresponding aperture switched on/off of the coded sub-pixel mask periodically, in which the resolution of the reconstructed image is determined by the coded aperture size of the sub-pixel mask rather than the pixel size of the display panel. Then, the mapping relationship between the displayed pixel and the position of the switched on aperture of the coded sub-pixel mask is established theoretically. Computational reconstruction and optical experimental results show that this method can match the pixel number of the captured EIs with that of the display panel and the resolution of integral imaging can be improved significantly.

Building a wide-area, high-efficiency, and accurate detection technology for air targets has become a new challenge for the construction of space situational awareness. Firstly, based on the space-based optical detection requirements for aircraft plume, the method of integrated modeling for sea/cloud background radiation characteristics based on coupling of remote sensing data and physical model is proposed, which can effectively deduce the background radiation field distribution under any environmental conditions. Specifically, combined with meteorological satellite sensor data, such as cloud top temperature, cloud type and cloud top height, three-dimensional atmospheric transmittance and atmospheric path thermal radiation texture are generated for different cloud heights and cloud phase conditions. Then, a coupled sea/cloud bidirectional reflectance model matched to the sampling of space-based detectors is established. Further, the accurate prediction model for multi-spectral imaging features of aircraft plume is built by considering the space-based full imaging chains including the complex coupling of aircraft plume, sea/cloud background, environmental atmosphere, optical system, and imaging detector. Finally, combined with the diffraction effect of the optical system, the multi-spectral imaging features of the aircraft plume are simulated under various spectral bands, flying heights, sea/cloud backgrounds, and detection angles, and the detection performances are analyzed and discussed by using the signal-to-clutter ratio (SCR). Research results show that the detection capability in the narrow band of 2.65–2.90µm and 4.25–4.50µm is better than the wide band of 3–5µm. When the aircraft flying height is greater than 5km, the aircraft plume can be detected in both narrow bands. It is more reliable to use the multispectral joint-band to detect aircraft plume in different backgrounds.

The non-uniformity of the lens array in the segmented planar integrated optical imaging system has not been studied. We design an inhomogeneous multistage sampling lens array based on a hierarchical multistage sampling lens array of the segmented planar integrated optical imaging system by changing the radius of the lenslet for frequency-selective sampling to optimize the design of the UV spatial frequency distribution. The signal transfer model of the proposed imaging system was established considering the radius of the lenslet and key waveguide parameters. Simulation results show that the proposed system produces better imaging quality owing to the selective sampling of frequency. Compared with the homogeneous multistage sampling lens array (radius of 1.8 mm), the optimal radius parameters of the inhomogeneous multistage sampling lens array are given for the same longest lens array length. Detailed calculations of the parameters of the waveguide connected to the lens array were performed. Our results provide a theoretical basis for the optimal design and process of a new segmented planar integrated optical imaging system.

In view of the optical detection requirements of wide-area and continuous surveillance of air targets, the detection ability of an infrared imaging system in geostationary orbit for aircraft plumes is studied. The point spread model of the subpixel imaging of the full chain, including the aircraft plume, the sea surface, the environmental atmosphere, the optical system, and the imaging detector is established. The detection ability of the typical imaging system in geostationary orbit is analyzed from the signal-to-noise ratio (SNR) and the detection range in combination with the effect of the point spread function (PSF) of the optical system. Meanwhile, the optimal coupling condition of the PSF to the spatial resolution is discussed. The imaging characteristics of the aircraft target on the focal plane of the infrared imaging system under different spatial sampling rates are simulated and verified. Research shows that the SNR of the system first increases, and then decreases gradually with an increase of the spatial sampling rate. The detectable range covered by the pixel footprint decreases as the detector size increases. When the detector size is 15, 20, and 30 μm, the target can be detected with a spatial resolution of 200–700, 300–700, and 400–600 m, respectively.

We propose an interpolation method to effectively improve the visual quality of the reconstructed integral image. Specifically, the dot-pattern output plane image (OPI) is first generated based on the pickup EIs by using pixel-to-pixel mapping. Then all the zero pixels in the dot-pattern OPI are interpolated by utilizing a non-zero-pixel derivation technique, and the final reconstructed integral image is obtained. To confirm the feasibility of this method, some computational experiments were carried out for test plane images with different depths. Quantitative experimental analysis shows that our proposed method has good robustness and can largely enhance the viewing quality of the reconstructed integral image compared to the plane-by-plane reconstruction technique and the conventional pixel-to-pixel mapping and interpolation technique.