| 摘要 |
An optical spyglass of a compact dimension to be mounted in a house door or the like for providing to an interior viewer a substantially 180 DEG wide-angle outdoor view. Its optical system comprises a wide-angle lens having a convex surface of a large radius curvature and an opposing convex surface of a small radius curvature for converging incoming light of substantially 180 DEG outdoor sight at a large rate, an objective having a concave surface and butted coaxially on the side of the concave surface of the lens for collimating the converged light to be of a small confined diameter, an eyepiece having a convex surface disposed coaxially with the objective and spaced therefrom for magnifying the collimated light to be of a normal view of the outdoor sight. Such optical system is secured in a substantially tubular barrel body disposed closely around the collimated light of the confined diameter. The barrel body of the spyglass is inserted in a through hole made in the door or the like and is secured thereto by means of a cylinder member engaged onto the barrel body holding the door or the like between opposing flanges provided on the barrel body and cylinder member.
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