一種包括一個透鏡單元陣列及一個受塑膠外殼之影像讀取裝置，該透鏡單元陣列包括一陣列的分布折射率塑膠柱面透鏡元件及一對塑膠板，而這些分佈折射率塑膠柱面透鏡元件被黏固在塑膠板之間。該透鏡單元陣列被固定在塑膠外殼內。塑膠外殼及透鏡單元陣列之塑膠板二者之熱膨漲係數相差5.0×10^(-5)cm/cm/C或以下。或者更理想地，相差3.0×10^(-5)cm/cm/C或以下。塑膠外殼係以縱向的排列將多個由由噴射鑄造法製造法製成之外殼片段相連接而成。
An image-reading device comprises a lens Unit array comprising an array of distributed refractive index plastic cylinderical lens elements and plastic plates, cylindrical lens elements there betweene, and a plastic case containing and holding the lens unit array. The difference in the thermal expansion coefficients of the plates of the lens unit array and the plastic case is 5.(superscript *) 10^(-5)cm/cm/C or below, or more preferably, 3.0(superscript *) 10^(-5)cm/cm/C or below, in a longitudinal arrangement, a plurality of case segments formed by an injection molding.
