SU1500920A1 - Apparatus for measuring coefficient of mirror reflection - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the specular reflection coefficient of optical surfaces by an absolute method without using a reference standard. The aim of the invention is to increase the measurement speed. For this, a device for measuring the mirror reflection coefficient, containing a radiation source, an optical channel, containing a diaphragm arranged successively along the radiation path, an optical system, a rotary mirror reflector made with the ability to switch between two extreme positions, a focusing lens and a photodetector, an additional optical mirror is inserted a channel containing a series of additional diaphragms along the course of the radiation, an optical system common to both channels, still Mirror reflector, the reflecting surface of which is located in the same plane with the reflecting surface of the rotary mirror reflector in one of its extreme positions, an additional focusing lens, an additional photodetector and an electric signal divider connected to the photodetector outputs, one of the photodetectors being configured to adjust the transmission coefficient . The device allows to increase the measurement speed by simultaneously measuring signals that are proportional to the radiation incident on the sample and reflected from the sample. This excludes an error due to the instability of the radiation source. 1 il.

Description

one

(21) 4192214 / 24-25

(22) 11.02.87

(46) 08/15/89. Bksh. No. 30

(72) S.A. Vorobev, A.A.Gruzdev,

S.V.Pechenkin and MDSterin

(53) 535.242 (088.8)

(56) USSR Copyright Certificate No. 411356, cl. G 01 N 21/55, 1971.

USSR author's certificate j№ 723390, glue G 01 J 1/04, 1978.

(54) DEVICE FOR MEASURING THE MIRROR REFLECTION COEFFICIENT

(57) The invention relates to a measurement technique and can be used to measure the specular reflection coefficient of optical surfaces by an absolute method without using a reference standard. The aim of the invention is to increase the measurement speed. For this purpose, a device for measuring the mirror reflection coefficient, containing a radiation source, an optical channel, containing a diaphragm, an optical system, a rotating mirror reflector, successively switchable between two extreme positions, a focusing lens and a photodetector, arranged along the radiation path, an additional optical channel containing in series along the course of the radiation an additional diaphragm, an optical system common to both channels, not a moving mirror reflector, the reflecting surface of which is located in the same plane with the reflecting surface of the rotary mirror reflector in one of its extreme positions, an additional focusing lens, an additional photoreceiver and an SI1 electric divider connected to the outputs of photodetectors, one of the photoreceivers made with possibility of adjusting the transfer ratio. The device makes it possible to increase the measurement performance by simultaneously measuring signals that are proportional to the radiation incident on the sample and reflected from the sample. This excludes an error due to the instability of the radiation source. 1 il.

cl

with

Isd

The invention relates to a measurement technique, more specifically to photometric devices, and can be used to measure the reflection coefficient of mirror surfaces by an absolute method without using a reference standard.

The aim of the invention is to increase the measurement speed.

The drawing shows a diagram of the proposed device.

The device consists of source 1, primary and secondary apertures 2 and 3, optical system 4, rotating and fixed mirror reflectors 5 and 6, primary and secondary focusing lenses 7 and 8, primary and secondary photoelectric receivers 9 and 10, dividing device 11. The sample to be measured is marked 12 in the drawing.

The angle of incidence of the axial beam in the beam onto sample 12 is indicated by i. The AC lies in the plane of the axial beam incident on the sample and lies between the point of axial beam impact on the mirror reflector 5 in its initial - A position and the intersection point of the reflector 5 plane with the normal to the sample surface 12. Section A С is similar for switched - А

that reflector 5

Mali to sample 12 is

both ways from nor90 + i

-.

The device works by following the position of the reflector 5. The angle of the photodetectors will be equal to one.

In position A of the rotary reflector 5 (shown in dotted lines in the drawing), the output signal of the photoelectric receiver 9 is determined by the formula, which also includes the coefficient proportional to the specular reflection coefficient of the sample 12, i.e.

and, .K ,,. K.5, (3) Thus, if we calculate from 20

25

at once.

The rotary reflector 5 is set to the initial position A and the signals are aligned in the two channels. Then, the rotary reflector 5 is set to the switched (operating) position A and measurements are taken. When the rotary reflector 5 is installed in the initial position A (shown in solid lines), the radiation from the light source 1 through the diaphragm 2 and the optical system 4 falls. On the reflector 5, In position A this reflector reflects the beam to the focusing lens 7, through which it enters, at the input of the photoelectric receiver 9. Similarly, the beam passing through the diaphragm 3 and the optical system 4 is directed by a fixed reflector 6 through the focusing lens 8 to the second photoelectric receiver 10

The signal U, at the output of the photoelectric receiver 9 is equal to

and, В-К, .К4.КуК, -К5, (1) where В is the brightness of the light source 1}

K - coefficient determining the part of the flow that passed through the diaphragm 2

K - coefficient of light transmission of the optical system 4

K - reflector reflection coefficient 5j

signals and and and then

one

it

wearing equals

Y - Bj KfK 4-Koir -Kj-KTK 2 and yy

and and.

(four)

Since the alignment of the photoelectric output signals 35

40

H-l 1

and,

that

yi

UT

45

chesky receivers K.

B.}.

When the photoelectric receivers are connected to the ratio meter, the latter measures the value of the specular reflection coefficient of the sample, z Kfff.

The mirror reflector 5 rotates around an axis C, perpendicular to the plane of the drawing. Since LASO LA CO (along the OS side and the corners adjacent to it), the CA CA, i.e. points A and A on the reflector 5 are the same. Since the angles of rotation of the reflector are 90

l am

+

t

a LOAC g: SLA i CAB

Lca b

90 ° - i

then in this case

K - coefficient of light transmission lenses 7i

K - photoelectric receiver transmission coefficient 9. Signal and. at the output of the second photoelectric receiver 10 is equal to Ua B-Ki-K.-KfKj.K,., (2)

where coefficients K, K, K Kg, K are similar respectively to coefficients K, K

4 s

I. ,, Kg for shape

ly (1).

Since at least one of the photoelectric receivers is configured to control the transmission coefficient, the signals at the outputs of both photodetectors are equal.

When connecting the outputs of both photodetectors to the ratio meter at its output, the ratio of the signals with

signals and and and then

one

it

wearing equals

Y - Bj KfK 4-Koir -Kj-KTK 2 and yy

and and.

(four)

Since the alignment of the photoelectric output signals

five

0

H-l 1

and,

that

yi

UT

five

chesky receivers K.

B.}.

When the photoelectric receivers are connected to the ratio meter, the latter measures the value of the specular reflection coefficient of the sample, z Kfff.

The mirror reflector 5 rotates around an axis C, perpendicular to the plane of the drawing. Since LASO LA CO (along the OS side and the corners adjacent to it), the CA CA, i.e. points A and A on the reflector 5 are the same. Since the angles of rotation of the reflector are 90

l am

+

t

a LOAC g: SLA i CAB

Lca b

90 ° - i

five

then in this case

.

The tABC is ABC 90, which means that the axial rays in the two positions A and A of the reflector are reflected not only from one point of the reflector, but also propagate after reflecting one by one

same direction.

The optical scheme is designed in such a way that the diameters of the images of diaphragms 2 and 3 on lenses 7 and 8 are equal and this equality is maintained at both positions of the rotary reflector 5, whereby the light beams from the optical system U to lines 7 and 8 propagate in the light tubes same cross section. This causes the same image sizes on the photodetector 10 and on the photodetector 9 (at both positions of the reflector 5).

To eliminate the effect of wrapping bridges in front of photodetectors, light-scattering filters are installed,

Thus, the light beam is reflected by the same part of the reflector 5 at both its positions, falls on the photodetector 9 from the same direction and illuminates the same part of the photoreceiver, which in combination with the diffusing light. A filter that eliminates the influence of the beam rotation due to reflection from the sample eliminates the dependence of measurements on the angle of incidence of the beam on the photodetector, as well as on possible surface irregularity of the photodetector properties.

Similarly, the light beam falls on the photodetector 10 at the same angle, from the same direction, and illuminates the same portion of the photodetector 10 as the photodetector 9.

In addition, both photodetectors are located next to each other (therefore, are in the same thermal mode), the optical path of the rays from the radiation source to the main photodetector 9 in the initial position and the additional photodetector 10 are the same, the elements of the optical channels, paired with one and the other photodetectors are almost identical, which improves the accuracy of the device. The described optical scheme allows creating a small-sized device, convenient for operating in a superimposed way, which can be used when measuring the specular reflection coefficient of large-size optical reflectors.

The optical scheme provides the possibility of creating structures with a wide range of angles of incidence of light on the sample (almost from the angles.

Q

five

0 5 o

five

p with Q

close to O, to angles close to 90),

If necessary, change yrnt. In addition to turning the light source block, the incidence of the light beam on the sample should also move the reflectors 5 and 6, setting the appropriate distance from the axis of rotation of the mirror reflector to the test sample. This distance is easily determined by solving the AOB and Lion triangles and is equal to

1 h-Fl - H-I il} i} siS-i.1 cos i

where h is 80,

To measure the specular reflection coefficient at a single point by the indicated method (with switching the specular reflector) a time of 15 s is required.

If one works with the same device without switching the mirror, then one measurement takes s5 time. However, this results in a measurement error due to time instability of the radiation source, as well as instantaneous changes in the source brightness, since the optical design of the device is single-channel.

The proposed solution makes it possible to shorten the measurement time of the specular reflection coefficient by approximately 10 s at each point. The error due to the instability of the measurement source is excluded, Uchitsha, that to control the reflection coefficient: only the aspherical reflectors of the CM-265 need to be made in the order of 50,000 measurements, the proposed technical solution has a significant effect.

Formula

and 3

gaining

A device for measuring the specular reflection coefficient, comprising a radiation source, an optical channel, a diaphragm arranged successively along the radiation path, an optical system, a tilting reflector made with the possibility of switching between two extreme positions, a focusing lens and a photodetector, characterized in that , in order to increase speed, an additional optical channel was inserted into the device, which contains successively located along the radiation path The aperture, an optical system common to both channels, a fixed mirror reflection zhatel, the reflective surface is disposed in one plane

with a reflective surface of the swivel transmission coefficient

a mirror reflector in one of its extreme positions, an additional focusing lens, an additional photodetector and an electrical signal divider connected to the photodetector outputs, and made of photodetectors with the possibility of adjusting the fO fl

Claims (1)

Claim A device for measuring the specular reflection coefficient, comprising a radiation source, an optical channel, comprising a diaphragm sequentially arranged along the radiation, an optical system, a rotary mirror reflector configured to switch between two extreme positions, a focusing lens and a photodetector, characterized in that, for the purpose of to improve performance, an additional optical channel is introduced into the device, containing an additional diaphragm sequentially located along the radiation a gma, an optical system common to both channels, a fixed mirror reflector, the reflective surface of which is located in the same plane as the reflective surface of the rotary mirror reflector in one of its extreme positions, an additional focusing lens, an additional photodetector and an electric signal splitter connected to the outputs of the photodetectors, moreover, one of the photodetectors is configured to adjust the transmission coefficient. G 40 I Compiled By, Kotenev Editor T. Parfenova Tehred L. Oliinyk Proofreader T. Kolb Order 4858/38 Circulation 789 Subscription VNIIIPI State 113035, Committee for Inventions and Discoveries under the USSR SCST Moscow, Zh-35, Raushskaya nab., D. 4/5 Production and Publishing Plant Patent, Uzhgorod, st. Gagarina, 10