How to measure the focal length of a convex lens

Abstract

The invention relates to a method for measuring the focal distance of a convex lens, comprising the following steps: setting a laser, a hole shield, a convex lens, a plane mirror and an adjusting common axis, wherein the laser light emitted by the laser can pass through a small hole on the hole shield; adjusting the vertical position of the convex lens so as to have a certain distance from a shaft; adjusting the position of the plane mirror, so that the laser light emitted from the small hole of the hole shield is refracted through a lens and then reflected through the plane mirror, and the light is then refracted through the convex lens to return into the small hole on the hole shield so as to form closed light; and calculating to obtain the focal distance of the convex lens by using the distance between the hole shield and the convex lens as an object distance or an image distance and using the distance between the plane mirror and the convex lens. According to the method for measuring the focal distance of the convex lens provided by the invention, artificial errors are eliminated well, and the result of the focal distance of the convex lens obtained through the calculation is very accurate since the object distance and the image distance determined by the hole shield and the plane mirror are both accurate.

Description

technical field [0001] The invention relates to the technical field of measuring the property parameters of a convex lens, in particular to a method for measuring the focal length of a convex lens. Background technique [0002] Convex lens is the most commonly used optical element and is the basis of optical instruments such as microscopes and telescopes. The focal length is an important parameter to characterize the imaging properties of the lens. Determining the focal length is not only a product inspection task, but more importantly, it provides a basis for the design of the optical system. [0003] The most commonly used focal length measurement methods are mostly designed according to the relationship between the object and the image, such as the object distance and image distance method. Specifically, this method is based on the fact that the light emitted by the object will form a real image on the other side after being converged by a convex lens, and then in the li...

AI Technical Summary

Problems solved by technology

[0004] The disadvantage of the method for measuring the focal length of the lens is that the object distance and the image distance are not easy to measure accurately.

First of all, it is difficult to determine that the position of the optical bench that fixes the two lasers is the intersection point of the reverse extension of the two laser beams, so the measurement of the object distance is inaccurate; in addition, the laser spot on the whiteboard is very large. It is difficult to judge whether the two laser beams are irradiated on the same point of the whiteboard, resulting in very inaccurate measurement of image distance

Therefore, there is a large error in the lens focal length calculated from the object distance and image distance obtained according to the above technical solution.

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