CN101788719B - Method for obtaining continuous luminous energy attenuation ratio smaller than polaroid extinction ratio and attenuator - Google Patents

Abstract

The invention discloses a method for obtaining continuous luminous energy attenuation ratio smaller than polaroid extinction ratio and an attenuator, relating to the field of luminous energy attenuation, in particular to a method for obtaining continuous luminous energy attenuation ratio smaller than polaroid extinction ratio and an attenuator using the method. The attenuation ratio (luminous energy attenuation ratio) of the practical nonideal polaroid attenuator to light beam energy can not be below the extinction ratio thereof. The invention utilizes the attenuator composed of a nonideal polaroid group and an optical filter with fixed luminous energy attenuation ratio to obtain the effect that the luminous energy attenuation ratio is smaller than the extinction ratio of the polaroid group. Meanwhile, the functional relation of the luminous energy attenuation ratio of the nonideal polaroid group to the translucidus shaft included angle theta and transmitted ray amplitude ratio epsilon and the position on which the light transmittance maximum are induced. According to the relation, the luminous energy attenuation ratio of the attenuator is continuously changed by controlling the opportunity for the optical filter to be inserted into a light path. The method utilizes the attenuator composed of the polaroid group of which the extinction ratio is 1*10<-5> and the optical filter of which the luminous energy attenuation ratio is 0.01 to continuously obtain the luminous energy attenuation ratio.

Description

A kind of light rate that declines of obtaining is continuously and less than the method and the attenuator of polaroid extinction ratio

Technical field

The present invention relates to the optical energy attenuation field, be specifically related to a kind of light rate that declines of obtaining continuously and less than the method for polaroid extinction ratio, and use the optical attenuator of said method.

Background technology

Along with the continuous development of modern times simulation and Detection Techniques, more and more higher to the requirement of optoelectronic device simulation parameter.This wherein, system go out light intensity variation range, change the important indicator that precision and continuity often become equipment.For volume and the weight that reduces system, traditional optical filtering membrane type fader should not adopt at this owing to problems such as volume, precision.Based on above consideration, a kind of combination attenuator of normal employing in the optical device based on the polarized light principle.

Polaroid is one of the most frequently used optical device, and it is incident beam to be decomposed into the light beam of two quadrature forms, and a kind of optical component that this two-beam is seen through with varying strength.Since natural light by polaroid after its energy decay to some extent, in optical system engineering, polaroid often is used as the attenuating device of beam energy.Ideal polarizer only allows to see through fully along the linearly polarized light of a certain direction vibration, and this direction is called as light transmission shaft; Direction of vibration another perpendicular linearly polarized light of axle is therewith then all stopped, and claims that the direction of this and light transmission shaft quadrature is an extinction axis.The minimum that polarizer group can the reach light rate that declines is called extinction ratio.

Adopt the decline optical system of light of polarizer group, its light rate minimum that declines is extinction ratio.Lot of documents thinks that the extremely low light rate that declines can not be obtained by polarizer group.(being published in " Chinese laser " the 26th the 1st phase of volume " half-wave plate and the polaroid composite set that are used for accurate decay control " literary composition in 1999) as people such as Cai Xijie.

Summary of the invention

The present invention will have the optical filter and the polarizer group of the light rate that fixedly declines to make up, and enter the opportunity of polarizer group light path by accurate control optical filter, thereby expand the optical range that declines of polaroid, and the continuous variation of the light rate that realized declining.The attenuator of being made up of above-mentioned optical filter and polarizer group is applicable to that needing that light beam is carried out light intensity high-magnitude beam attenuation, the maximum light rate that declines is lower than the intrinsic extinction ratio of polarizer group and the needs realization optical system to continuous, the accurate control of light rate that declines.The following technical scheme of concrete employing:

A kind of light rate that declines of obtaining comprises continuously and less than the method for polaroid extinction ratio:

At first, the polarizer group of being made up of two polaroids is begun to decline continuously photocontrol from initial zero-bit, be about to two polaroids and rotate relatively around the primary optical axis center;

Secondly, when the light transmission shaft that rotates to described two polaroids forms an angle, optical filter is inserted in the light path of described polarizer group;

Then, above-mentioned polarizer group is changed to initial zero-bit again, this moment is the relatively rotatory polarization sheet group photocontrol that declines once more, promptly obtains continuously and less than the light rate that declines of the intrinsic extinction ratio of described polarizer group;

It is characterized in that described certain angle is to make angle when the light rate that declines of polarizer group equals the light rate that declines of described optical filter.

Further, there is following relation in the light rate that declines of described light transmission shaft angle and polarizer group:

$T=\frac{I_2}{I_{\max }}=\frac{{\cos }^2\mathrm{\&theta;}+2\mathrm{\&epsiv;}\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+2{\mathrm{\&epsiv;}}^2{\sin }^2\mathrm{\&theta;}-2{\mathrm{\&epsiv;}}^3\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+{\mathrm{\&epsiv;}}^4{\cos }^2\mathrm{\&theta;}}{1+{\mathrm{\&epsiv;}}^4},$

Wherein, I ₂Be output intensity, I _MaxBe maximum output intensity, ε is the electric vector of polarizer group extinction axis transmitted component and the electric vector amplitude ratio of light transmission shaft transmitted component.

When further, the described initial zero-bit light transmission shaft angle that is defined as two polaroids of polarizer group is pi/2 4.

A kind of attenuator of realizing said method comprises:

Control motor, optical filter and support thereof, polarizer group, driven wheel, and

Gear ring is located on the polarizer group, thereby the control motor meshes the relative rotation that drives described polarizer group by driven wheel and above-mentioned gear ring,

The tooth bar chute is used for holding tooth bar and is inserted into the light path of polarizer group to drive optical filter by its support,

It is characterized in that, rotate to relatively in described polarizer group and insert described optical filter when its light rate that declines equals the transmitance of described optical filter.

Further, there is following relation in the light rate that declines of counterrotating angle of described polarizer group and polarizer group:

$T=\frac{I_2}{I_{\max }}=\frac{{\cos }^2\mathrm{\&theta;}+2\mathrm{\&epsiv;}\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+2{\mathrm{\&epsiv;}}^2{\sin }^2\mathrm{\&theta;}-2{\mathrm{\&epsiv;}}^3\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+{\mathrm{\&epsiv;}}^4{\cos }^2\mathrm{\&theta;}}{1+{\mathrm{\&epsiv;}}^4},$

Wherein, I ₂Be output intensity, I _MaxBe maximum output intensity, ε is the electric vector of polarizer group extinction axis transmitted component and the electric vector amplitude ratio of light transmission shaft transmitted component.

The present invention passes through two polaroid P ₁, P ₂Optical axis begin the relatively rotation photocontrol that declines continuously from a certain relative angle that is in original state (being the logic zero-bit), by the time when the light rate that declines of polarizer group reaches the light rate that declines of optical filter, optical filter and polarizer group are made up, afterwards polarizer group is reset to original state, decay continuously once more, can realize that the light rate that declines of composite set (being attenuator) changes continuously.Like this, be equivalent to carry out the secondary optical filtering, can obtain the attenuation range of high-magnitude.The precision of attenuator luminous energy decay is by the running accuracy control of motor.

Description of drawings

The combination attenuator of Fig. 1 polarizer group and optical filter.

The electric vector of the postrotational relatively imperfect polarizer group emergent light of Fig. 2 is described.

Fig. 3 attenuator structural drawing.

Fig. 4 attenuator rate of change of light rate that decline with angle theta.

The light rate that declines of Fig. 5 attenuator is before wherein optical filter is inserted in Fig. 5 (a) expression, after optical filter is inserted in Fig. 5 (b) expression.

Embodiment

Actual polaroid is nonideal.The difference of itself and ideal polarizer is, after the light beam transmission, the light of extinction axis has remnants, and resulting is not linearly polarized light completely, but partial poolarized light.Therefore, even the light transmission shaft of two polarizers is orthogonal at this moment, transmitted light intensity is also non-vanishing.At this moment the ratio of the minimum transmitted light intensity of polarizer when tested polarizer rotates max transmissive light intensity when parallel to each other with two polarizer light transmission shafts is called extinction ratio.Wherein ε is the electric vector amplitude ratio of polarizer extinction axis transmitted component and light transmission shaft transmitted component, ε=E _y/ E _x, E _xBe the electric vector amplitude of light transmission shaft transmitted component, E _yElectric vector amplitude for the extinction axis transmitted component.The extinction ratio of polaroid can be expressed as ε ²If need to obtain the extremely low light rate that declines in the practical application, the extinction ratio of general polaroid is difficult to reach requirement.The present invention has the optical filter of light rate that fixedly declines by adding one, but has realized the composite set effect of light rate less than intrinsic extinction ratio of polarizer group and stepless control that always decline.

The continuous light that declines of light device mechanism that keeps declining, in the moment that must guarantee to enter at optical filter the decay light path, the light rate that declines in real time of polarizer group is consistent with the fixedly transmitance of optical filter.Promptly need to draw the light rate that declines of imperfect polaroid and the relational expression of its light transmission shaft angle theta.

Polarization fading device such as Fig. 1.Utilize the Jones vector method to analyze the light rate that declines of imperfect polaroid.If polaroid P ₁, P ₂Light transmission shaft be respectively x ₁, x ₂, work as P ₂With respect to P ₁During rotation θ angle, set up electric vector synoptic diagram as shown in Figure 2:

Get and pass through P ₁The electric vector of polarized light be $\left[\begin{array}{c}{A}_1\\ B_1\end{array}\right],$

According to Fig. 2, its two component is at P ₂Projection A on light transmission shaft and the extinction axis _ξ, B _ηCan be expressed as:

A _ξ＝A ₁cosθ+B ₁sinθ

(1)

B _η＝(-A ₁sinθ+B ₁cosθ)·ε

With these two components at x ₁, y ₁Projection again on the axle obtains two component A of emergent light ₂, B ₂, can be expressed as:

A ₂＝A _ξcosθ-B _ηsinθ

(2)

B ₂＝A _ξsinθ+B _ηcosθ

Obtain by (1), (2):

$\left[\begin{array}{c}{A}_2\\ B_2\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \sin \mathrm{\&theta;}& \cos \mathrm{\&theta;}\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\&theta;}& \sin \mathrm{\&theta;}\\ -\mathrm{\&epsiv;}\sin \mathrm{\&theta;}& \mathrm{\&epsiv;}\cos \mathrm{\&theta;}\end{array}\right]\left[\begin{array}{c}{A}_1\\ B_1\end{array}\right]=U\left[\begin{array}{c}{A}_1\\ B_1\end{array}\right]---\left(3\right)$

(3) U is P in the formula ₁, P ₂The Jones matrix expression formula of imperfect polaroid when the light transmission shaft angle is θ:

$U=\left[\begin{array}{cc}{\cos }^2\mathrm{\&theta;}+\mathrm{\&epsiv;}{\sin }^2\mathrm{\&theta;}& (1-\mathrm{\&epsiv;})\sin \mathrm{\&theta;}\cos \mathrm{\&theta;}\\ (1-\mathrm{\&epsiv;})\sin \mathrm{\&theta;}\cos \mathrm{\&theta;}& {\sin }^2\mathrm{\&theta;}+\mathrm{\&epsiv;}{\cos }^2\mathrm{\&theta;}\end{array}\right]---\left(4\right)$

By the light vector behind first polaroid be:

$E_1=\left[\begin{array}{c}1\\ \mathrm{\&epsiv;}\end{array}\right]---\left(5\right)$

Behind second polaroid, the expression formula of its Jones vector is:

$E_2={\mathrm{UE}}_1$

$=\left[\begin{array}{c}{\cos }^2\mathrm{\&theta;}+\mathrm{\&epsiv;}{\sin }^2\mathrm{\&theta;}+\mathrm{\&epsiv;}(\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}-\mathrm{\&epsiv;}\sin \mathrm{\&theta;}\cos \mathrm{\&theta;})\\ (1-\mathrm{\&epsiv;})\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+\mathrm{\&epsiv;}({\sin }^2\mathrm{\&theta;}+\mathrm{\&epsiv;}{\cos }^2\mathrm{\&theta;})\end{array}\right]---\left(6\right)$

By formula (6) as can be known, the light intensity I of this partial poolarized light after through second polaroid ₂Can be expressed as the function of two polaroid light transmission shaft angle theta, that is:

I ₂＝|e ₂| ²

＝[cos ²θ+εsin ²θ+ε(1-ε)cosθsinθ] ²+[(1-ε)cosθsinθ+ε(sin ²θ+εcos ²θ)] ²

When θ=arctan ε, I ₂Maximal value is 1+ ε ⁴, i.e. the largest light intensity I of emergent light _MaxThe light rate that declines of polarizer group is defined as output intensity I ₂With maximum output intensity I _MaxRatio.Can obtain the light rate function that declines thus:

$T=\frac{I_2}{I_{\max }}=\frac{{\cos }^2\mathrm{\&theta;}+2\mathrm{\&epsiv;}\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+2{\mathrm{\&epsiv;}}^2{\sin }^2\mathrm{\&theta;}-2{\mathrm{\&epsiv;}}^3\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+{\mathrm{\&epsiv;}}^4{\cos }^2\mathrm{\&theta;}}{1+{\mathrm{\&epsiv;}}^4}---\left(7\right)$

Analyze this function its maximum of T as can be known _MaxWith minimum value T _MinBe not:

T _max＝1 T _min＝ε ² (8)

As seen from the above analysis, the combination of two polaroids, the variation range of its light rate that declines is 1～ε ²Obtain the littler light rate that declines value, outside the polaroid combination, add a tablet filter, and adopt Electric Machine Control to insert in the decay light path.The light rate that declines of optical filter is a fixed value.When polarizer group is rotated relatively, its light rate T that declines reaches the light rate that the declines T of optical filter ₁The time, optical filter is inserted in the light path, simultaneously polaroid is returned back to logic zero-bit place.This moment, the rotatory polarization sheet carried out work once more, because optical filter is in the light path of polaroid combination, this moment, the light rate that always declines by the attenuator that polarizer group and optical filter are formed can become TT ₁, the light rate that declines variation range is T ₁～ε ²T ₁Through two photoreduction processes that decline, the light rate that the declines variation range of this attenuator is 1～ε ²T ₁More than analyze as can be seen, the luminous energy power that declines that this method is utilized optical filter further reduces T with the decline minimum value of light rate of polarizer group ₁Doubly, improved the luminous energy power that declines, and the light continuity that declines can be controlled accurately.

As shown in Figure 3, attenuator comprises as lower member:

Control motor 1, optical filter 2, gear ring 3, driven wheel 4, polarizer group 5, integral support 6 and tooth bar chute.Gear ring 3 is located on the polarizer group 4, thereby control motor 1 drives the relative rotation of described polarizer group 4 by driven wheel 4 and above-mentioned gear ring 3 engagements.The tooth bar chute is used for holding tooth bar to drive the light path that optical filter 2 is inserted into polarizer group 5.

In the present embodiment, the light rate demand that declines is And the extinction ratio of general polaroid is all greater than this value.The only a few polaroid can reach this requirement, but cost is very high, and extremely low when declining the light rate because various errors, precision is lower.Use the light method that declines of the present invention, the extinction ratio of polarizer group and optical filter decline the light rate long-pending should less than

According to the common parameter of each major company's product, the actual conditions when having contrasted various combination, we select extinction ratio is 1 * 10 ^-5Polarizer group P1, P2, bore is Φ 20mm, the light transmission shaft transmitance reaches 99.99%.Optical filter F clear aperture is Φ 25.4mm, and the light rate that fixedly declines is 0.01.Adopt method of the present invention, the maximum of the above-mentioned combination of devices luminous energy Li Keda 1 * 10 that declines ^-7

At this moment,, make the light rate that the declines T=0.01 of polarizer group in the formula (4), calculate two polaroid light transmission shaft angle theta in the polarizer group=84.4 ° when optical filter declines the light rate when being 0.01.The attenuation accuracy of attenuator is by the running accuracy control of waiing upon the clothes motor, so the angular deflection amount in per step of mechanical speed-control device servomotor has determined the control accuracy of attenuating device.The light rate that the declines T of polarizer group is dT/d θ with the rate of change of θ, the curve of variation as shown in Figure 3, and can draw in θ=45.8 ° the time, dT/d θ minimalization, this minimal value (dT/d θ) _Min=-1.As long as determined minimum control accuracy Δ T ₀, then wait upon the angular deflection amount Δ θ in clothes per step of motor _StepAvailable formula (9) is obtained:

Δθ _step＜|ΔT ₀/(dT/dθ) _min| (9)

The minimum precision of device requirement is Δ T ₀=0.1%, because Δ T ₀/ (dT/d θ) _Min=-1, so as long as make Δ θ _Step＜1mrad (1 milliradian) just can meet the demands, promptly the per step minimum of motor pass by 3.4 '.

The motor movement parameter is 2500step/360 °, about 8.6 '/step, selecting ratio of gear is 1: 7, actual stepping angle is 8.6/7=1.2 '/step, satisfies the high-precision requirement of system.

Because the light rate that declines of system's actual demand in the present embodiment

Greater than the actual maximum that can reach of the selected device light rate (1 * 10 that declines ^-7), when starting working, can get the light rate that declines and be not 1 angle is the logic zero-bit, the described function rectilinearity of whole like this photoreduction processes that decline is better relatively.We get optical axis included angle be pi/2 4 as the logic zero-bit, the polarizer group light rate that declines of this moment is T ', needs the light rate that declines is transferred to 0.01 before inserting optical filter.Electric rotating machine recalls to the logic zero-bit with the polaroid of rotation after inserting optical filter, continues rotatory polarization sheet to the combination light rate that declines again and is the logic zero-bit light rate that declines

Be

Because the stepping deviation of motor, it is the most approaching to get the light rate that declines

Step number, making this light rate that declines is T ".According to motor and gear parameter, two polaroid light transmission shaft angle theta can be divided into 2500 * 7/4=4375 step by stepping between 0-90 °, calculate the corresponding light rate that declines value of each step, above several crucial numerical value are listed below with table 1 form:

Table 1 operation terminal and the corresponding light rate that declines

Can find out that from table 1 attenuator can be finished

The light rate that declines, and inserting the breakpoint of optical filter, it is continuous that the light rate that declines changes.Fig. 4 is the contrast of experimental data and theoretical curve.The deviation of measured value and theoretical value is in 1%, and is better with theory-compliant.

Claims (5)

1. one kind is obtained the light rate that declines continuously and less than the method for polaroid extinction ratio, comprising:

At first, the polarizer group of being made up of two polaroids is begun to decline continuously photocontrol from initial zero-bit, be about to two polaroids and rotate relatively around the primary optical axis center;

Secondly, when the light transmission shaft that rotates to described two polaroids forms an angle, optical filter is inserted in the light path of described polarizer group;

Then, above-mentioned polarizer group is changed to initial zero-bit again, this moment is the relatively rotatory polarization sheet group photocontrol that declines once more, promptly obtains continuously and less than the light rate that declines of the intrinsic extinction ratio of described polarizer group;

It is characterized in that described certain angle is to make angle when the light rate that declines of polarizer group equals the light rate that declines of described optical filter; There is following relation in the light rate that declines of described light transmission shaft angle theta and polarizer group:

$T=\frac{I_2}{I_{\max }}=\frac{{\cos }^2\mathrm{\&theta;}+2\mathrm{\&epsiv;}\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+{2\mathrm{\&epsiv;}}^2{\sin }^2\mathrm{\&theta;}-{2\mathrm{\&epsiv;}}^3\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+{\mathrm{\&epsiv;}}^4{\cos }^2\mathrm{\&theta;}}{1+{\mathrm{\&epsiv;}}^4},$

Wherein, I ₂Be output intensity, I _MaxBe maximum output intensity, ε is the electric vector of polarizer group extinction axis transmitted component and the electric vector amplitude ratio of light transmission shaft transmitted component.

2. method according to claim 1 is characterized in that, described maximum output intensity I _MaxObtain during ε at described angle theta=arctan.

3. according to each described method among the claim 1-2, it is characterized in that, when the light transmission shaft angle that described initial zero-bit is defined as two polaroids of polarizer group is pi/2 4.

4. attenuator of realizing each described method of claim 1-3 comprises:

Control motor (1), optical filter (2), gear ring (3), driven wheel (4), polarizer group (5), integral support (6) and tooth bar chute, gear ring (3) is located on the polarizer group (5), control motor (1) by driven wheel (4) with above-mentioned gear ring (3) thus mesh the relative rotation drive described polarizer group (5), the tooth bar chute is used for holding tooth bar is inserted into polarizer group (5) with driving optical filter (2) light path

It is characterized in that, rotate to relatively in described polarizer group and to insert described optical filter when its light rate that declines equals the light rate that declines of described optical filter, when described polarizer group was rotated relatively, there was following relation in the light rate that declines of the angle theta that light transmission shaft became of described two polaroids and polarizer group:

$T=\frac{I_2}{I_{\max }}=\frac{{\cos }^2\mathrm{\&theta;}+2\mathrm{\&epsiv;}\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+{2\mathrm{\&epsiv;}}^2{\sin }^2\mathrm{\&theta;}-{2\mathrm{\&epsiv;}}^3\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}+{\mathrm{\&epsiv;}}^4{\cos }^2\mathrm{\&theta;}}{1+{\mathrm{\&epsiv;}}^4},$

Wherein, I ₂Be output intensity, I _MaxBe maximum output intensity, ε is the electric vector amplitude ratio of polarizer group extinction axis transmitted component and light transmission shaft transmitted component.

5. attenuator according to claim 4 is characterized in that, described maximum output intensity I _MaxObtain during ε at described angle theta=arctan.

Images