SU1437823A1 - Variable optical attenuator - Google Patents

Abstract

The invention relates to means of controlling parameters of optical radiation and can be used for calibrated attenuation of optical radiation while increasing the accuracy of the attenuation coefficient and simultaneously expanding the spectral range. The attenuator contains two reflective elements 1 and 2 installed in series along the radiation path, each having one Frenrel surface area 3 and 4, respectively, which are oriented mutually in parallel, and the normals are equal to the optical axis, but counter-polar; ; software sign angles c. Elements 1 and 2 are installed at the kinks 7, the optical axis of the attenuator with the possibility of changing the angles ((while preserving them (C (L 4 o 00 h 00 12 n

Description

Fig.Z

mutual equality by rotating around a single axis 5, perpendicular to the plane containing the 2-axis or the optical axis. Element 2 is fixed in relation to the axis of rotation 5 of the retroreflective element 6, the input and output apertures of element 6 are separated in the direction of the axis of rotation 5 and aligned with the apertures of elements 1 and 2. In order to increase the range of variation of the attenuation coefficient in the device A second retroreflective element 7 is used, fixedly mounted with respect to the axis of rotation 5 behind element 1 in the direction of radiation. The input aperture of element 7 is matched through elements 2 and 1 with the output aperture of element 6, and the output aperture of element 7 is spaced with its input aperture in the direction of the axis

5 revolutions. A beam of radiation 25 after fourfold reflection from elements 1 and 2, twice from an element

6 and once from element 7 exits the device weakened. Due to the well-known relationship between the reflection coefficient of radiation from Fresnel surfaces 3 and 4 and the variable angle M of the radiation incident on these surfaces, the attenuation coefficient of the beam 25 emerging from the device is strictly calibrated. 1 hp ff. 3 il.

one

The invention relates to the field of means for controlling parameters of optical radiation and can be used for calibrated attenuation of the intensity of optical radiation, for example, when certifying and measuring parameters of photosensitive elements and photodetectors, in medical research and laser therapy, surgery.

The scope of the invention is an increase in the accuracy of the attenuation coefficient with simultaneous expansion of the spectral range, as well as an increase in the range of the attenuation coefficient.

Figure 1 shows the attenuator with one retroreflective element; Fig. 2 shows a view of the latter in section j; an attenuator with two retroreflectors.

The controlled optical attenuator contains two reflective elements 1 and 2 arranged in series along the radiation path, each having one Fresnel reflecting surface 3 and 4, which are respectively oriented mutually in parallel, and the normals to which the optical attenuator is equal in strength to the optical axis, but opposite angles of H. Elements 1 and 2 are set

ten

at the break points of the E-prefab optical axis of the attenuator with the possibility of changing the angles (f while maintaining their mutual equality by rotating the circle around the single axis 5, perpendicular to the plane containing the Z-shaped optical axis. Behind the element 2 along the course of the radiation is set stationary relative to axis 5 rotation of the light-rotating element 6, and the input and output apertures of the element 6 are separated in the direction of the axis of rotation 5 and aligned with the apertures of the elements 1 and 2. In the second embodiment (Fig. 3) a second light-rotating is used Element 7 is also fixed with respect to the axis of rotation 5 behind element 1. Along the course of radiation, the input aperture of element 7 is matched through elements 2 and 1 with the output aperture 6, and the output aperture of element 7 is separated from its input aperture in the direction of axis 5

25 rotations

The specific structural implementation of the attenuator is reduced to the following. Reflective elements 1 and 2, made, for example, in the form of plane-parallel plates or wedges made of K-108 glass, are mechanically coupled (interconnected) to each other, for example, mounted on a common rotary platform 8 having an axis of rotation 5, which

15

20

thirty

is in the plane of the reflecting face 3 of the element 1.

In order to eliminate the effect of reflections from the face of elements 1 and 2 not participating in the formation of a beam of attenuated radiation, all faces of elements 1 and 2, except mutually parallel reflective faces 3 and 4 facing each other, are covered, for example, with a layer of black paint absorbing radiation.

The turntable 8 is mechanically connected with the actuator 9, for example, containing a stepper motor of the type SCHDR-711-, as well as with a sensor 10 of the type

radiation reflecting surface 3 elements 1 year angle c, value

ten

which is determined by the angular orientation of the reflected element 1 relative to the incident beam 17, the beam 18 reflected from the surface of element 1 falls on the reflected surface A of element 2 Since the reflecting surfaces 3 and 4 of elements 1.2 are parallel, the angle of incidence on the second reflecting element is also equal to t /, and

beam 13 reflected by element 2 is parallel to incident beam 17.

The change of the angle ip is carried out by supplying the control voltage to the actuator 9 of the rotary stage 8 with the help of the SHDR-711 stepper motor.

The change in angle i-p is made.

angle is a code using, for example, a gear.

The retroreflective element 6 is extruded in the form of two reflecting elements, for example, within 3080 °. The magnitudes of 11.12 are reflecting planes that are at an angle (f is determined using perpendicularly oriented angle 10 sensor type 10. Power is relative to the other and the line of the beam of attenuated radiation section perpendicular to axis 5 the second reflecting element and the optical axis of the attenuator; the Light 25 is defined as the tovoltage element 6 can also be made in the form of an AP-90 rectangular prism,

The turntable 8, the drive 9, the sensor 10 angle - code, as well as the retroreflective element 6 are fixed on the base 13 of the attenuator, Additional Ro, (c /) - K2 (F

thirty

where R, (c,) is the reflection coefficient of the elements 1,2, respectively.

For radiation, the polarization plane of which is parallel to the axis of rotation 5 of the rotary stage 8, the reflection coefficient of elements 1,2, for example, of K-108 (, 52) full glass, is) H2 (H) iO, 07 with and R, (t /) R ((f) at (f 80 °.

The body retroreflective element 7 is fixed at the base of the attenuator 13 and spatially offset from the first light reflector element 6 in the direction of the axis 5 by an amount where d is the beam diameter of the attenuated radiation, which provides spatial separation of the radiation beam reflected by element 7 relative to the original beam.

Structurally, the retroreflective element 7 is made similar to the light returning element 6. FIG. 3 shows a variant of the light of the returning element 7 in the form of two flat mirrors 14, 15,

Reference numeral 16 in FIG. 3 denotes a attenuated radiation consumer, such as a certified photodetector or a mirror, which directs the attenuated radiation in the desired direction.

The device operates as follows: about 55 beams with reflecting edges of elements.

at once.

A beam of radiation 17, having a power PO, falls on the first along

radiation reflecting surface 3 elements 1 year angle c, value

which is determined by the angular orientation of the reflected element 1 relative to the incident beam 17, the beam 18 reflected from the surface of element 1 falls on the reflected surface A of element 2 Since the reflecting surfaces 3 and 4 of elements 1.2 are parallel, the angle of incidence on the second reflecting element is also equal to t /, and

beam 13 reflected by element 2 is parallel to incident beam 17.

The change of the angle ip is carried out by supplying the control voltage to the actuator 9 of the rotary stage 8 with the help of the SCHDR-711 stepper motor.

The change in angle i-p is made.

for example, within 3080 °. The magnitude of the angle (f is determined by an angle-code sensor 10. The power of the beam of attenuated radiation at the output of the second reflecting element is defined as

imer within 30gr (f is determined by ik 10 of the type - the angle - of the beam of the weakened output of the second reflection is defined as

, (s /) - K2 (F

thirty

35

40

where R, (c,) is the reflection coefficient of the elements 1,2, respectively.

For radiation, the polarization plane of which is parallel to the axis of rotation 5 of the rotary stage 8, the reflection coefficient of elements 1,2, for example, of K-108 (, 52) full glass, is) H2 (H) iO, 07 with and R, (t /) R ((f) at (f 80 °.

For radiation whose polarization plane is perpendicular to the axis of rotation 5, the reflection coefficient of elements 1,2 in this case is Ri (v) R2 (t) x; 0.04 when Lf 30 and Rj (Lf) R2 (4) -: i 0.25 at.

Thus, the power of the light beam 19 at the output of the second reflecting element 2 varies with the angle 1 (within P g (, nt ,, g Z (0.005-i-0.3) Poi .i (0.0016 - 50 - 0.0625) Po for radiation, the polarization plane of which is respectively parallel and perpendicular to the axis of rotation 5.

After reflection first in the process

45

1.2 pzgchook 19 of radiation is fed to the input of the retroreflective element 6, which inverts (rotates) the direction of propagation of this beam.

The radiation beam 20 reflected by surfaces 11 and 12 of element 6 is parallel to the incident beam 19, has a direction of propagation opposite to this beam and is shifted relative to it in the direction 4U 2Y., Which is determined by the value of the coordinate of Ur of the beam relative to the line of intersection of the planes 11,12 of element 6 ,

After passing through the retroreflective element 6, the beam 20 of attenuated radiation passes backward relative to the beam 17 in the direction, successively reflected by the first faces of elements 2 (beam 21) and 1 (beam 22) along the beam.

The output beam 22 of the attenuated radiation reflected by element 1 is parallel to the incoming cable 17, is shifted relative to it in the direction of the axis 5 by the value of / dY and has a power

out

P (g)) - P (l /). R, B Po.

where RCB is the reflection coefficient of the light-return element 6. The reflection coefficient Rg of the light-returning element 6 is determined by the reflection coefficient R about the radiation by the surfaces of the elements 11 and 12 Reg R and is, for example, Rce2; 0.99 when performing elements 11 and 12 in the form of dielectric mirrors, RCB - iO, 8-0.9 in the performance of these elements in the form of metallized mirrors and R (-g-0.95 in the fulfillment of lights in the form of a reflective element 6 we.

The value of R is constant and does not change when the angle of rotation of the pad 8 changes.

The limits of change in the power Pjyy of the output beam of radiation, Pd, Pd, ks using, for example, reflecting elements 1.2 made of K-108 glass, are for the case of polarizing light in a plane parallel to the axis of rotation:

Thus, the dynamic range of the attenuator operation is

M - | - 2.4 10, MWH

t „eo about 30 dBo

With this value of the attenuation coefficient

Kcc. () -R (C) Rcv

is determined entirely by calculation based on the calculation of the values of R / t /) and R (tj) with the value of the angle (/, determined with the help of a 6 "sensor

The accuracy of setting the required value of the attenuation coefficient is determined by the accuracy of setting the angle value (/ and is, for example, with the angle setting error if (equal to the angle line and the values of ff -DAO dKoc./

five

corner

80

-2; 0.3% for radii0

five

COSA

Nor With a known state of polarization.

When the device according to FIG. 3 is executed, the work of the attenuator proceeds similarly. The attenuated radiation beam 19, reflected by the retroreflective element 6, re-passes the second 2 and first 1 reflecting elements, falls on the second retroreflective element 7,

Reflecting from the element 7 of light rotation, the beam of attenuated radiation 23 is spatially displaced in the direction of the axis 5 by an amount of 4 ° 2Y, where Y is the height of the beam 2R relative to the intersection line of the reflecting elements 7 (or the equivalent line of intersection of the cathode faces of a rectangular prism).

After reflection from the element 7, the beam 23 of attenuated radiation passes through the elements 1 and 2 for the third time. At the same time, the power of the beam 24 is equal to

five

Tj3

, (tf)

0

five

element 2

R5 (/).

After passing the weakened beam of elements 1 and 2 three times, the beam 24 is again reflected by the light reflecting element 6, simultaneously shifting in the direction of the axis 5.

The repeated reflection of the retroreflective element 6 is the beam of attenuated radiation for the fourth time passes the elements 2 and 1 of the reflection and sent to the consumer 16. The power Pftux of the beam 25 after a four-fold passage through the elements 1 and 2 is PBj, R (tc) R (i /) Rce Po. The limits of power variation are different, for example, in the case of elements 1 and 2 of brand glass, the polarization of light in a plane parallel to the axis of rotation of elements 1,2, and the use of retroreflective elements with dielectric coatings providing Q; 0.99

 BWx.iWHH

Bfclx MdnC 6, 25 when

 l 3

 at

about when Dynamic range attenuator

YU

is at

Ptfcl. Mai

m

% s. min

v.6 60 dB.

with accuracy

dKpCA

TO".

weakening

, 0.6%

Thus, the introduction of the second retroreflective element 7 allows the dynamic range of the attenuator to be expanded to 60 dB while maintaining the spectral range of operation and the accuracy characteristics of the device. In addition to the position of the consumer 16 shown in FIG. 3, located in the cross section of the radiation beam, four times passing through the reflection elements of the device, the consumer 16 can be located (by moving in the direction of the axis 5) in the radiation beam transmitted 6.8 ... 2n ... times through elements 1 and 2, which increases the dynamic range of the device, which in this case is M ZOP dB due to additional radiation passes through the reflected elements.

A controlled optical attenuator is interfaced with a computer using an angle-code drive on a stepper motor and a digital sensor and can be part of specialized model complexes and stands that allow solving problems of metrology and alignment in various fields of science.

g

five

0

five

0

five

0

five

0

Claims (2)

1. A controlled optical attenuator containing two successively arranged along the radiation of the reflecting element, to the Fresnel reflecting surfaces of which the optical attenuator axis is equal in magnitude but opposite in sign to the angles, and the reflecting elements are installed with the ability to measure the specified angles while maintaining i-rx mutual equality by rotating these elements, distinguished by the fact that, in order to improve the accuracy of setting the attenuation coefficient while expanding with an optical-rotating element is inserted into it, the reflecting elements each have one Fresnel reflecting surface, which are oriented mutually in parallel, and are installed at the break points of the Z-shaped optical axis of the attenuator with the possibility of rotation around a single axis perpendicular to the plane containing the Z- figurative optical axis, and the rear-reflective element is mounted stationary relative to the axis of rotation of the reflecting elements behind the second one along the optical axis, with the input and output apertures of the light locomotive rotating element spaced in the direction of the axis of rotation of the reflecting elements and consistent with the apertures of the latter. 2. An attenuator in accordance with claim 1, characterized in that, in order to increase the range of variation of the attenuation coefficient, a second retroreflective element is inserted fixedly relative to the axis of rotation of the reflecting elements behind the first one along the optical axis, and the input aperture of the second retroreflective element is matched through the second and first reflecting elements with the output aperture of the first retroreflective element and the output aperture of the second retroreflective element with the input aperture raenessenl with its input aperture in the direction the axis of rotation of the reflecting elements. U Uk, ro ; / fi $ .1 20 6 j2 ./ wel