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Tartary buckwheat is rich in flavonoids. However, the health‐promoting effect of these flavonoids has not been adequately studied. In the present study, we investigated the impact of rutin, quercetin, and Tartary buckwheat on the lipid metabolism of rats on a high‐fat diet. Quercetin could significantly reduce body weight, serum triacylglycerol, low‐density lipoprotein cholesterol, TNF‐α, insulin, and ameliorate glucose tolerance. It was surprising that Tartary buckwheat significantly increased the weight of the rats. Rutin, quercetin, and Tartary buckwheat tended to decreased fat deposition in the liver of rats but have little effect on short‐chain fatty acid production. The changes in the structure and diversity of the microbiota were found to be modulated by these diets. It was concluded that quercetin could attenuate high‐fat diet‐induced obesity, rutin, quercetin, and Tartary buckwheat can shape the specific structure of gut microbiota. Mechanism of Tartary buckwheat on lipid metabolism needs further systematic research.

Head-mounted display (HMD) has been widely used in many fields, and most existing HMDs are complex and typically non-aesthetically pleasing. In this paper, a novel compact, lightweight and wearable off-axis HMD with freeform surface is reported. It is challenging to achieve large field of view (FOV) and maintain compact structure simultaneously for this type system. In this design, the compact off-axis HMD consists of a tilted ellipsoid combiner and a four pieces relay lenses. It offers a diagonal FOV of 30°, and an exit pupil diameter of 7 mm. No diffractive surfaces are used, thus avoiding the effect of stray light and ghost image in previous designs. The x-y polynomial freeform surface is adopted in the relay lens for improving the image quality and minimizing the structure size. Analytical expressions to determine the initial structure of HMD has been given, while structure constrains, optimization strategy and tolerance analysis are also described in details. The optical system is easy to manufacture by ordinary method which is beneficial for mass production. Further, a prototype of this compact HMD is successfully implemented with good imaging performance. The compact structure of HMD makes it well suited for integrating a normal glass, significantly advancing the application of HMD in people's daily life.

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