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This paper presents an instantaneous analysis shadow moire method for dynamic out-of-plane displacement measurement. The shadow moire method is widely applied to the measurement of the out-of-plane displacement, such as the deformation or warpage on the surface of the objects. Generally, the method of phase shifting is used to analyze the phases of the shadow moire fringes and to obtain the out-of-plane displacement. To generate accurate phase shifting, the grating must be moved step by step precisely. However, the step motion provided by the conventional mechanical device is neither accurate nor prompt. In this study, a novel stair-structured plate consisting of a series of 4-step-height sets is designed to produce shadow moire fringes with the quadrature phase. The quadrature-phase fringes are utilized to extract instantaneously the shadow moire phase for measurement of the dynamic out-of-plane displacement of an object. Experiments show that our method can effectively detect the dynamic out-of-plane displacement with a micrometric scale resolution and is capable of suppressing the discrepancy of displacement to 0.83 $$\%$$ . The proposed measurement method of the out-plane displacement is suitable for the pressure sensing or application of the tactile sensor.

A light-mixing module consisting of a compound parabolic concentrator (CPC) and a light-mixing tube is proposed herein to realize a uniform and efficient solar-lighting system. In this lighting system, the sunlight collected into a fiber and then guided to an indoor destination is the principal light source, while an auxiliary light source including multiple red, green, blue, and white (RGBW) light-emitting diodes (LEDs) is controlled by an auto-compensating module. To mix the principal and the auxiliary sources and to realize the uniform illumination, the light-mixing tube was coated with BaSO4 and optimized as a cylindrical tube. The design of the light-mixing tube is described and discussed in this article. According to the simulated results, the uniformity and the optical efficiency of the designed light-mixing tube are 82.9% and 85.7%, respectively, while from the experimental results, the uniformity of 85.9% and the optical efficiency of 83.3% have been obtained. In terms of the common indoor-lighting standards and the specifications of commercial components used in lighting systems, the proposed light-mixing module has demonstrated the high uniformity and acceptable optical efficiency. Additionally, since the main components of the light-mixing module can be designed as plastic optics, a cost-effective light-mixing module and a profitable lighting system can be realized. Thus, the performance and the price of the proposed light-mixing module fit the demands of the illumination market, while the proposed system shows the potential for indoor solar-lighting applications.

A light-mixing module consisting of a compound parabolic concentrator (CPC) and a fiber for mixing light from red, green, blue, and white (RGBW) LEDs was proposed. The design principle was investigated and a design prototype was demonstrated in a simulation. The simulated results showed that the chromatic nonuniformity was reduced to 1/10 when the fiber length was 40 times the core width, and the module efficiencies were more than 80% and more than 60% when the fiber lengths were 350 mm and 5 m, respectively. The proposed module is suitable for solar lighting compensation or indoor lighting, such as plant-factory lighting.