Fig. 1. Illustration of the architecture and working principle of the proposed system. (a) Architecture of the proposed system. (b) Schematic diagram of solar energy collection. (c) Schematic diagram of solar power supply. (d) Schematic diagram of near-eye display.

Fig. 2. Specific design parameters of the optical combiner. (a) Near-eye display module. (b) Solar energy collection module.

Fig. 3. Results of the optical combiner. (a) Prototype of the optical combiner. HOE-1 is located on the front surface, and HOE-2 and HOE-3 are located on the back surface. (b) Collected light emitted from the edge of the waveguide. (c) Comparison of transmitted light spectrum without and with the optical combiner. The pink area and orange solid line respectively represent the transmitted light spectrum without and with the optical combiner. The brown dashed line represents the difference, which is collected by the optical combiner. (d) Full-color near-eye display effect. (e) Comparison of near-eye display without and with HOE-1.

Fig. 4. Results of collection characteristic analysis. (a) Definition of vertical incident angle. The range of 0°–90°of vertical incident angle is defined as the change from incidence perpendicular to the waveguide to parallel to the waveguide. (b) The collected light results on the upper and lower edges of the waveguide at different vertical incident angles. (c) The relationship between the vertical incident angle and the center collection wavelength. HOE-1 is divided into four partitions, and the results of different partitions are represented by different colors. (d) Secondary diffraction phenomenon on thick substrates without partitioning HOE. (e) Secondary diffraction phenomenon on thin substrates with partitioning HOE. (f) Elimination of secondary diffraction phenomenon on thick substrates with partitioning HOE.

Fig. 5. Measurement of power supply efficiency under sunlight. (a) Device for measuring power supply efficiency. (b) The collected light on the bottom solar cell. (c) The charging capacity of the bottom solar cell in half an hour. (d) The collected light on the top solar cell. (e) The charging capacity of the top solar cell in half an hour.

Fig. 6. Schematic diagram of the reason and elimination of secondary diffraction effect. (a) HOE without partition design. (b) The effective area of HOE without partitioning. The light incident on the effective area shown by the green square can be successfully collected to the edge of the waveguide. (c) The invalid area of HOE without partitioning. The light incident on the invalid area shown by the gray square cannot be collected to the edge of the waveguide, but is diffracted for the second time into the transmitted light shown by the red line. (d) HOE with partition design. (e) Elimination of secondary diffraction. The light shown by the blue line is no longer diffracted a second time at point C2 due to the mismatch of Bragg condition.

Fig. 7. Analysis of collection angle. (a) Wavelength mismatch at the recording angle. (b) Variable wavelength reconstruction at different angles. (c) Horizontal and vertical selection angles of HOE.

Fig. 8. Holographic exposure system based on right-angle prism for fabricating HOE-1.

Fig. 9. Holographic exposure system based on equilateral prism for fabricating HOE-2 and HOE-3.