SU1216698A1 - Method of measuring operational section of optical system - Google Patents

Abstract

The invention relates to a measurement technique and allows to simplify the measurement process. A parallel beam of light, passing through the optical system under study, is focused by it in focus. On the way of the converging homocentric beam, there are two photodetectors that are displaced relative to the axis of the optical system so as not to hinder the rays from falling on them. The photocurrent is measured from a light source placed at a point with a known distance from the top of the last surface of the optical system to this point, and at a second point located at a certain distance from the first. The calculation formula for calculating the working length is given. 3 il. SL C 3 35: oh

Description

The invention relates to a measurement technique and can be used to measure the size of the working section of the optical system.

The goal of fi3o6peTeHMe is to simplify the process of measuring the working section of the optical system,

Fig. 1 shows the scheme in which the method for measuring the working segment of the optical system 3 of a converging beam is carried out; in fig. 2 — skip method in a divergent beam; Fig. 3 shows a device for measuring a working segment.

The method of measuring the working section of the optical system is to create an optical system converging at the focus of the light beam and measuring the photocurrent at two points located at a known distance from the last surface of the optical system (Fig. 1 and 2).

A device for carrying out the method (Fig. 3) contains successively fixed on base 1 the illuminator 2, the optical system 3 under investigation, the photodetectors F. and F., which are on either side of the optical axis of the system.

The device works in the following manner.

The lighter 2 projects a parallel beam of light onto the optical system 3 under study, which focuses the light at the F focus, two photodetectors F and F, which are displaced relative to the optical axis of the system in such a way that the photoreceiver F I did not interfere with the incident beam on photodetector F., the photosensitive areas of the photodetectors being oriented perpendicular to the optical axis of the systems.

At point b (fig. 2) there is a point source of light with the power of light fa J, Illumination E of area 3, (formed by a solid angle: located at a distance c - „d, from the light source according to the law of quad -) distance is equal to

- jl

U - 2

If we successively measure the photocurrent C, the photodetector F, set at a distance of r. From the source of light, and the photocurrent Eg, the photoreleiver. (fJj set to ras2166982

d V from the installation point of the first photodetector F, and at a distance G from the light source, then

E, ir-, g

F7

25

thirty

35

40

50

With t;) jpepMH geometrical optics rays have the property of reversibility, i.e. an image may be considered a subject. If pad 5 is an element of the optical system that has focus at point F (where the point source of light is located), then the length of the working segment, 5 of this optical system, will be

J

where Hm is the installation distance from the top of the last surface of the optical system to the nearest photodetector,. Substituting the value

we find

Dg

 + 4G + g,

In accordance with the rule of signs, the focus r will be valid if Р „5 has a + sign, and imaginary if

PCI

with, has a sign

The greater the difference of the photocurrent t, and Eg, the more accurately the working segment is determined.

This device is conveniently used to monitor commercially manufactured optical systems, since the choice of the distance between the photodetectors tie will determine the difference between the photocurrents E, and E.

Since the photodetectors are not located on the optical axis of the system, but are displaced from it on opposite sides, then when accurate measurements are necessary to take into account the cosine of the angle between the perpendicular to the photosensitive area of the photoreceiver and the direction of propagation, the cosine tends to unity.

The implementation of the method can be carried out by means of a device, which includes one phototechnical device mounted on a moving mechanism with a known length

With t;) jpepMH geometrical optics rays have the property of reversibility, i.e. an image may be considered a subject. If pad 5 is an element of the optical system that has focus at point F (where the point source of light is located), then the length of the working segment, 5 of this optical system, will be

J

where Hm is the installation distance from the top of the last surface of the optical system to the nearest photodetector,. Substituting the value

we find

Dg

 + 4G + g,

thirty

In accordance with the rule of signs, the focus r will be valid if Р „5 has a + sign, and imaginary if

PCI

with, has a sign

The greater the difference of the photocurrent t, and Eg, the more accurately the working segment is determined.

This device is conveniently used to monitor commercially manufactured optical systems, since the choice of the distance between the photodetectors tie will determine the difference between the photocurrents E, and E.

Since the photodetectors are not located on the optical axis of the system, but are displaced from it on opposite sides, then when accurate measurements are necessary to take into account the cosine of the angle between the perpendicular to the photosensitive area of the photoreceiver and the direction of propagation, the cosine tends to unity.

The implementation of the method can be carried out by means of a device, which includes one phototechnical device mounted on a moving mechanism with a known size.

standing between its two extreme positions.

The illuminator projects a parallel beam of light onto the optical system under study, which focuses the light at the G focus, light hits the photodetector F when the displacement mechanism is in one extreme position, which produces the photocurrent E.

The movement mechanism takes the photodetector F to another extreme position, where the latter produces a photocurrent E,.

Knowing the distance lg between the two extreme positions of the moving mechanism and knowing the adjusting distance g of the moving mechanism to the top of the last surface of the optical system, calculate the length of the working segment using the formula

year

yg

pdS

4-DG t PM

13

1Eg / E, This device has one photodetector located on the optical axis of the system, therefore its photosensitive area is located perpendicular to the direction of propagation of the flow, i.e. the accuracy of determining the length of the working segment is maximum.

To measure the working segment with the same accuracy at different focal lengths of optical systems.

the movement mechanism can be equipped with a reading device.

In the devices described, photodetectors can be installed both in 5 converging and diverging homocentric beams. In the latter case, it is convenient to measure small working lengths.

ten

Claims (1)

Invention Formula A method of measuring the working section of the optical system, which consists in creating a light beam by the optical system, measuring the photocurrent at a point with a known distance,. from the top of the last surface of the optical system to this point, about the t, which is due to the fact that to simplify the measurement process, the photocurrent is additionally measured at a second point located at a distance from the first point, with both measuring points arranged in a converging or diverging light beam and the working segment is calculated by the formula t Ы f g a j where is e , - photocurrent, measured at a point at the installation distance - NII.; 2 photocurrent measured at a point at a distance of fо a g 1 FIG. g 7777777777777777777 //. Ft Editor T, Kugrysheva Compiled by M. Rytov Tehred Z.Pa.lny Proofreader T, Kolb Order 995 / 54Tira x778Subscription VNSHSHI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Branch PPT1 Patent, Uzhgorod, ul "Project, 4