CN204405027U - The measurement mechanism of ahrens prism gummed error - Google Patents

Abstract

The utility model discloses the measurement mechanism of a kind of ahrens prism gummed error, this device comprises lighting point light source, beam-expanding collimation system and ccd detector, beam-expanding collimation system is between lighting point light source and ahrens prism, the natural light that lighting point light source sends impinges perpendicularly on ahrens prism after beam-expanding collimation system beam-expanding collimation, described ccd detector is positioned at the exit direction of ahrens prism reflected light, and ccd detector is connected with computing machine.This device obtains the distribution pattern of reflecting interference striped light intensity by above-mentioned ccd detector and computer acquisition, and the distribution pattern according to interference fringe light intensity draws fringe spacing, and utilizes following formula to calculate gummed error: the utility model can realize the Measurement accuracy of prism cementing error.

Description

The measurement mechanism of ahrens prism gummed error

Technical field

The utility model relates to a kind of measurement mechanism of Crystal polarizing prism design parameters, especially relates to the measurement mechanism of a kind of ahrens prism gummed error.

Background technology

Direction of vibration is asymmetric relative to the direction of propagation, and this phenomenon is called polarization, and polarization is specific to shear wave, is also that shear wave is different from of compressional wave and the most significantly indicates.And light wave is as a kind of shear wave, therefore also there is polarizability.Light can be divided into natural light according to polarizability, polarized light and partial poolarized light.The light beam of occurring in nature, its direction of vibration is all symmetrical relative to the direction of propagation, is called natural light.Polarized light can be divided into linearly polarized light, elliptically polarized light etc.And natural light is converted into polarized light, just need by polarizing device.Such as, polaroid, glass stack etc., ahrens prism plays very important role wherein.

Air-gap type prism is generally glued together by two pieces of triangle crystal to form.Utilize the birefringent phenomenon of polarisation crystal, realize natural light to be converted into polarized light.And in the process of gummed, whether air-gap is parallel, and the transmittance for prism light intensity has very large impact.Angle between uneven air-gap two interface is called gummed error.Be subject to the restriction of actual environment and production technology, the existence of gummed error is inevitable.In general application, the impact of gluing together error should be avoided, but, in the situation that some are special, certain special optical phenomena can be realized by gummed error.Therefore, measuring prism gummed error has very strong practical application meaning.

In prior art, number of patent application be 201310257381.7 Chinese patent disclose a kind of air-gap type ahrens prism gummed error measuring method, the interference fringe that the method utilizes emergent light to be formed, sets up itself and the relation of gummed error, measures gummed error.But the apparatus structure of this kind of method is comparatively complicated, in experimentation, the adjustment difficulty of light path is larger.

Utility model content

Based on above-mentioned technical matters, the utility model provides a kind of ahrens prism to glue together the measurement mechanism of error.

The technical solution that the utility model adopts is:

A kind of measurement mechanism of ahrens prism gummed error, comprise lighting point light source, beam-expanding collimation system and ccd detector, beam-expanding collimation system is between lighting point light source and ahrens prism, the natural light that lighting point light source sends impinges perpendicularly on ahrens prism after beam-expanding collimation system beam-expanding collimation, described ccd detector is positioned at the exit direction of ahrens prism reflected light, and ccd detector is connected with computing machine.

Preferably, described ahrens prism is Glan type ahrens prism, as Taylor prism, Glan pay section's prism etc.

Advantageous Effects of the present utility model is:

Between theory derives interference fringe that reflected light formed interval and gummed error to be measured relation basis on, this device obtains the distribution relation curve of reflecting interference striped light intensity by ccd detector and computer acquisition, and then calculates the gummed error amount of prism; This measurement mechanism simple structure, the reflecting interference striped of formation clearly, is convenient to observe, and compared to the interference fringe measured emergent light and formed, adopts this device to carry out measuring more simple and convenient; The Measurement accuracy of prism cementing error can be realized through experimental verification the utility model.

Accompanying drawing explanation

Below in conjunction with accompanying drawing and embodiment, the utility model is described in further detail:

Fig. 1 is the structural representation of the utility model measurement mechanism;

Fig. 2 is the principle of interference simplified schematic diagram of light at cementing layer;

Fig. 3 is that the utility model experimental example surveys the reflecting interference fringe distribution pattern drawn.

In figure: 1-beam expander colimated light system, 2-CCD detector, 3-ahrens prism, 4-cementing layer, I, II-crystal.

Embodiment

As shown in Figure 1, a kind of measurement mechanism of ahrens prism gummed error, comprises lighting point light source S, beam expander colimated light system 1 and ccd detector 2.Beam expander colimated light system 1 is between lighting point light source S and ahrens prism 3, the natural light that lighting point light source S sends impinges perpendicularly on ahrens prism 3 after beam-expanding collimation system 1 beam-expanding collimation, described ccd detector 2 is positioned at the exit direction of ahrens prism 3 reflected light, and ccd detector 2 is connected with computing machine.

Above-mentioned ahrens prism 3 pays section's prism for Taylor prism or Glan.

Utilize said apparatus to carry out the method for ahrens prism gummed error measure, specifically comprise the following steps:

A places beam expander colimated light system 1 between lighting point light source S and ahrens prism 3, and the natural light that lighting point light source sends impinges perpendicularly on ahrens prism after beam expander colimated light system 1 beam-expanding collimation.

B places ccd detector 2 in the exit direction of ahrens prism reflected light, and ccd detector 2 is connected with computing machine.

C obtains the distribution pattern of reflecting interference striped light intensity by above-mentioned ccd detector and computer acquisition, and the distribution pattern according to interference fringe light intensity draws fringe spacing, and utilizes following formula to calculate gummed error;

$\mathrm{\α}=\mathrm{arc}\mathrm{}\cot (\frac{2\mathrm{\Δx}\sqrt{{n_o}^2-{n_e}^2{\sin }^{2}s}}{\mathrm{\ϵ\λ}}+\tan r)$

$r=\arcsin \left(\frac{n_e\sin s}{n_o}\right)$

In formula, α is gummed error angle to be measured, and λ is optical wavelength, and s is the structure angle of prism, and ε is the scale-up factor relevant with prism structure, and computing formula is r is the refraction angle of light beam in prism cementing layer, n _ofor the refractive index of air, n _efor the refractive index of the corresponding incident beam of prism, Δ x is for recording fringe spacing.

The interference fringe that the utility model utilizes reflected light to be formed, sets up bright fringe or the numerical relation between dark fringe separation delta x and gummed error alpha.Brief description is carried out to theoretical foundation of the present utility model below.

As shown in Figure 2, light beam imports in cementing layer by crystal I, reflects, meet refraction law at A point:

n _esini＝n _osinr

Light is in the process propagated, and the optical path difference that reflection ray and refracted ray produce is:

δ＝n _o(AB+BC)-n _eAD+λ/2

Suppose that at the thickness of B place cementing layer be e, because the thickness of cementing layer is very little, substantially can regard the consistency of thickness of cementing layer near this position as, AB, BC, AD all can be represented by e obviously, so the formula of reduction obtained, namely

$\mathrm{\δ}=2e\sqrt{({n_o}^2-{n_e}^2{\sin }^{2}i)}+\mathrm{\λ}/2$

Here λ/2 are half-wave losses that light produces when entering optically denser medium by optically thinner medium.

During beam orthogonal entrance crystal, cementing layer is incident angle i equals structure angle s.Set up a coordinate system x along cementing layer, in the optical path difference of coordinate x position be

$\mathrm{\δ}\left(x\right)=2(e+\frac{x}{\cot \mathrm{\α}-\tan r})\sqrt{({n_o}^2-{n_e}^2{\sin }^{2}s)}+\mathrm{\λ}/2$

Wherein α is the gummed error of cementing layer, and r is the refraction angle of light beam at prism cementing layer.

As optical path difference δ (x)=k λ, meet the condition that k rank bright fringe produces.

The position of k rank bright fringe is obtained after conversion:

$x=(\frac{\mathrm{k\λ}-\mathrm{\λ}/2}{2\sqrt{({n_o}^2-{n_e}^2{\sin }^{2}s)}}-e)(\cot \mathrm{\α}-\tan r)$

Deduct bright fringe position, k rank with bright fringe position, k+1 rank, namely obtain bright fringe interval:

${\mathrm{\Δx}}^{\′}=\frac{\mathrm{\λ}(\cot \mathrm{\α}-\tan r)}{2\sqrt{({n_o}^2-{n_e}^2{\sin }^{2}s)}}$

As shown in Figure 1, consider that light beam also has a refraction when the side outgoing of prism, the fringe spacing Δ x ' of actual outgoing and have a transformational relation between the fringe spacing Δ x of crystals

$\mathrm{\Δx}=\frac{{\cos \mathrm{\θ}}_2}{{\cos \mathrm{\θ}}_1}{\mathrm{\Δx}}^{\′}=\frac{\sqrt{1-{n_o}^2{\cos }^2\left(2s\right)}}{\sin \left(2s\right)}{\mathrm{\Δx}}^{\′}$

Order $\frac{\sqrt{1-{n_o}^2{\cos }^2\left(2s\right)}}{\sin \left(2s\right)}=\mathrm{\ϵ},$ Then above formula becomes

$\mathrm{\Δx}=\frac{\mathrm{\ϵ\λ}(\cot \mathrm{\α}-\tan r)}{2\sqrt{({n_o}^2-{n_e}^2{\sin }^{2}s)}}$

Then error angle can be expressed as

$\mathrm{\α}=\mathrm{arc}\mathrm{}\cot (\frac{2\mathrm{\Δx}\sqrt{{n_o}^2-{n_e}^2{\sin }^{2}s}}{\mathrm{\ϵ\λ}}+\tan r)$

$r=\arcsin \left(\frac{n_e\sin s}{n_o}\right)$

Wherein, α is gummed error angle to be measured, and λ is optical wavelength, and s is the structure angle of prism, for the scale-up factor relevant with prism structure, r is the refraction angle of light beam in prism cementing layer, n ₀for the refractive index of air, n _efor the refractive index of the corresponding incident beam of prism, Δ x is for recording bright fringe interval.Therefore, go out reflecting interference striped bright fringe interval by ccd detector and computer measurement, namely can solve the size of gummed error angle easily.

Specific experiment example

For Glan-Taylor's ahrens prism, the error angle required when the Light transmission that can realize prism stablizes output is α >=0.5 °, the reflecting interference fringe distribution pattern utilizing the utility model to survey as shown in Figure 3, can show that from Fig. 3 the bright fringe that output intensity distributes is spaced apart Δ x=0.10mm, and to utilize above formula to can be calculated gummed error angle be α=0.6825 °, with need for fluctuate gummed error angle alpha >=0.5 that suppresses of Light transmission ° consistent.

Above-mentioned experiment shows, the utility model can realize the Measurement accuracy of prism cementing error.

The relevant technologies content do not addressed in aforesaid way is taked or uses for reference prior art to realize.

It should be noted that, under the instruction of this instructions, any equivalents done by those skilled in the art, or obvious variant, all should within protection domain of the present utility model.

Claims (2)

1. the measurement mechanism of an ahrens prism gummed error, it is characterized in that: comprise lighting point light source, beam-expanding collimation system and ccd detector, beam-expanding collimation system is between lighting point light source and ahrens prism, the natural light that lighting point light source sends impinges perpendicularly on ahrens prism after beam-expanding collimation system beam-expanding collimation, described ccd detector is positioned at the exit direction of ahrens prism reflected light, and ccd detector is connected with computing machine.

2. the measurement mechanism of a kind of ahrens prism gummed error according to claim 1, is characterized in that: described ahrens prism is Glan type ahrens prism.