The invention relates to a solar water heater device, which comprises a thermoelectric conversion module, a heat collector, a heat exchanger, an optical focusing plate and a power supply system.

一种太阳能热水器装置，其包括热电转换模块、集热器、热交换器、光聚焦板及电源系统。

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The optical writing object lens of the laser direct writing device must be focused in spots by a focusing-servo mechanism.

在激光直接写入设备中需要有高分辨力的调焦伺服机构对光刻物镜进行调焦伺服。

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Studying the theory of optical pickup head unit (OPU) and how to pickup the signal on the disk. Based on these theories, it analyse the structure of the focusing and tracking device.

研究光学拾取头的基本原理和光盘信号拾取原理，简要分析了实际的光学头聚焦伺服和循迹伺服的机械结构。

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