| 摘要 |
PURPOSE:To prevent the rugged pattern working faces of Fresnel lenses from being damaged or deformed by arranging two transparent bases on which micro- Fresnel lenses are formed respectively on both front and rear faces of an image device so that the faces forming the micro-Fresnel lenses are turned to the inside of the device. CONSTITUTION:The image deice is provided with at least two transparent bases 10, 20 obtained by forming many micro-Fresnel lenses on one face of each base. These two transparent bases 10, 20 are arranged on the front and rear faces of the image device so that the faces forming the micro-Fresnel lenses, i.e. the rugged pattern working faces, are turned to the inside of the image device. The optical axes of the corresponding micro-Fresnel lenses on the front and rear faces coincide with each other. Consequently, the rugged pattern faces can be previously prevented from damage or dirt adhesion or damage for deformation due to other physical and chemical factors, so that the optical characteristics of the micro-Fresnel lenses can be maintained almost at constant values.
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