| 摘要 |
PURPOSE:To display various information without shading the visual field though an optical system has a short overall length and is small-sized, by forming an Albada reflecting face as a rear reflecting face on the object-side lens surface of a prescribed lens and bringing a visual field frame image due to the eyepiece lens-side surface of the prescribed lens for the visual field frame image due to the Albada reflecting face to the outside of the focal depth of eyes. CONSTITUTION:The object-side surface of a single lens L1 is formed as the Albada reflecting face, and a visual field frame E is provided in an eyepiece lens L2 having a positive refracting power. The visual field frame E is illuminated with the luminous flux from an object, and the luminous flux passing the eyepiece lens L2 from the visual field frame to the object side is reflected on said Albada reflecting face A and passes an eyepiece lens-side surface of the single lens L1 and passes the eyepiece lens L2 again and reaches observing eyes. Rays of light form the visual field frame E are indicated by solid lines, and the position of the virtual image is indicated by dotted lines. Rays of light in the Albada optical system are indicated by S, and rays of light in the Albada optical system is indicated by S' if the Albada reflecting face is formed as the front reflecting face.
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