We present a high throughput crop physiology condition monitoring system and corresponding monitoring method. The monitoring system can perform large-area chlorophyll fluorescence imaging and multispectral imaging. The monitoring method can determine the crop current condition continuously and non-destructively. We choose chlorophyll fluorescence parameters and relative reflectance of multispectral as the indicators of crop physiological status. Using tomato as experiment subject, the typical crop physiological stress, such as drought, nutrition deficiency and plant disease can be distinguished by the monitoring method. Furthermore, we have studied the correlation between the physiological indicators and the degree of stress. Besides realizing the continuous monitoring of crop physiology, the monitoring system and method provide the possibility of machine automatic diagnosis of the plant physiology. Highlights: A newly designed high throughput crop physiology monitoring system and the corresponding monitoring method are described in this study. Different types of stress can induce distinct fluorescence and spectral characteristics, which can be used to evaluate the physiological status of plants.

We propose a highly efficient waveguide display based on space-variant volume holographic gratings (SVVHGs). The local period and slant angle of the SVVHG vary along the tangential direction, enabling variant incident angles to satisfy the Bragg condition of the local gratings. As a result, we enlarge the field of view (FOV) without using the conventional multiplexing scheme, while achieving high efficiency and large FOV at the same time. We experimentally record the SVVHGs on Bayfol HX200 films. We demonstrate that the proposed display can achieve 31.9% system efficiency for a broadband light source and 52.3% for a coherent light source, 20° FOV, and high brightness uniformity, making it a promising candidate for widespread applications in the augmented reality (AR) industry.

This paper proposes a 360-deg large-scale multiprojection light-field 3D display system, which can reconstruct the light field of models in real space. The reconstructed contents can be observed by multiple viewers from different angles and positions simultaneously. In this system, 360 projectors project images onto a cylindrical light-field diffusion screen whose height is 1.8 m and diameter is 3 m. When moving around the system, viewers can see 3D scenes with smooth-motion parallax, and the frame rate can reach 30 fps and above. To achieve a large-scale display, we design a wide-field lens with cylindrical lenses to enlarge the projection image. To promote efficiency of data transmission and render 3D contents in real time, we apply computers equipped with multiple graphic cards, and display data are divided by field programmable gate array. Finally, a 360-deg light-field autocalibration method based on CCD and multiview sampling is proposed, whose calibration effect is strongly confirmed by experiment results.

We develop a compact full-color augmented reality near-eye display system with a multicolor holographic optical combiner and a freeform relay system. The digital image is produced by a full-color micro organic light-emitting diode (Micro-OLED) display module. The freeform relay system includes four freeform optics and a holographic optical mirror, which are employed to correct both the monochromatic and chromatic aberrations caused by the holographic optical combiner. The two multicolor holographic mirrors have a three-layer laminated structure and are delicately fabricated to yield an improved diffractive efficiency and a reduced efficiency difference for red, green, and blue colors. The high degrees of freedom of freeform optics, and the thin and light nature of the holographic optical combiner yield a compact form factor near-eye display system with a diagonal field of view (FOV) of 20° and the eye-box of 5 mm × 5 mm. Two prototypes are built to demonstrate the feasibility of the proposed display system.

Both multiview and light-field reconstructions are proposed for a multiple-projector 3D display system. To compare the performance of the reconstruction algorithms in the same system, an optimized multiview reconstruction algorithm with sub-view-zones (SVZs) is proposed. The algorithm divided the conventional view zones in multiview display into several SVZs and allocates more view images. The optimized reconstruction algorithm unifies the conventional multiview reconstruction and light-field reconstruction algorithms, which can indicate the difference in performance when multiview reconstruction is changed to light-field reconstruction. A prototype consisting of 60 projectors with an arc diffuser as its screen is constructed to verify the algorithms. Comparison of different configurations of SVZs shows that light-field reconstruction provides large-scale 3D images with the smoothest motion parallax; thus it may provide better overall performance for large-scale 360° display than multiview reconstruction.

This paper presents a distortion correction method for designing a wide field of view (FOV) lens for an imaging system. The lens is composed of two aspheric surfaces and several spheres. In the preliminary design, profiles of the aspheric surfaces can be obtained according to aplanatism, refraction law, and polynomial fitting methods, where the numeric computation, the differential geometry computation, and the polynomial fitting algorithm are stated in detail. Then the lens is optimized by the damped least squares method. Theoretically, this method cannot eliminate aberrations absolutely but can balance some kinds of aberrations to the image well. Furthermore, a projector lens with a wide FOV, low distortion, and low throw ratio [TR = (projection distance)/(image diagonal size)] is designed successfully by this method.