CN1071004A - Super thin transparent medium membrane thickness measured method - Google Patents

Abstract

The present invention relates to a kind of super thin transparent medium membrane thickness measured method, belong to the length metering technical field.The optical routing light source that this measuring method adopts, reflecting prism, microscope and photo-detector are formed, and reflecting prism places on the tested transparent dielectric film.The incident light that light source sends returns reflecting prism after entering catoptron and transparent dielectric film, enters microscope through the reflecting prism light reflected, enters photo-detector subsequently.The each point intensity of reflected light that photo-detector obtains and the medium thickness of this point have certain funtcional relationship, thereby can calculate the thickness of this transparent dielectric film according to the each point intensity of reflected light.

Description

Super thin transparent medium membrane thickness measured method

The present invention relates to a kind of super thin transparent medium membrane thickness measured method, belong to the length metering technical field.

In prior art, utilize Total reflection method to measure contact area.Because its intuitive measurement results is reliable, precision, has become the conventional means of measuring contact area, the light total reflection ratio juris can be illustrated with the experimental provision of Archard.As shown in Figure 1, measured surface 1 be pressed under the effect of load truncate prism 2 on the plane, the light source of incident light 3 is a mercury vapor lamp, incident light enters total reflection light 4 takes place on the prism base plane behind the prism.At the prism upper surface, if come in contact with measured surface, then part light enters measured surface; If do not contact with measured surface, then light is all reflected.According to geometric optical theory, when light when optically denser medium (prism) propagates into optically thinner medium (air or oil), if incident angle surpasses a certain critical angle, whole reflected back first media of incident light then, this phenomenon is called total reflection.When object (measured surface among Fig. 1) and prism surface came in contact, the light total reflection condition was destroyed, and the distribution of intensity of reflected light has reflected contact area, and promptly when observing reflected light, the contact region has been represented in the dark space, and relief area is represented in the clear zone.The logical area of measuring the dark space just can be known contact area.Total reflection method that Here it is is measured the principle of contact area.IKe slides and does not slide and real contact area when loading and not loading with the measurement device of Fig. 2.5 is microscopes among the figure, the 6th, and camera, the 7th, light source.Also having a kind of device is that the contact plane of prism tilt to be placed so that the microscope that is used to observe can be placed by the normal position, and shown in Figure 3 is this schematic representation of apparatus.The shortcoming of prior art is the distance between can't surface measurements or the thickness of transparent dielectric film.

The objective of the invention is to utilize the principle of light total reflection, design a kind of method of measuring the super thin transparent medium film thickness.On the angle of wave optics, under total reflection condition light wave be not utterly on the interface by whole reflected back first media (optically denser medium), but return first medium after penetrating the very little degree of depth of second medium (optically thinner medium), so in Fig. 1 between body surface and the prism even without coming in contact but distance very hour, body surface will absorb the energy of a part of light wave, and reflected light is died down.Utilize this characteristic, just can measure the thickness of super thin transparent medium film.

Content of the present invention is a super thin transparent medium membrane thickness measured method, and the optical routing light source of employing, reflecting prism, microscope and photo-detector are formed, and reflecting prism places on the tested transparent dielectric film.The incident light that light source sends returns reflecting prism after entering reflecting prism and transparent dielectric film, enters microscope through the reflecting prism light reflected, enters photo-detector subsequently.Because the medium thickness of each point intensity of reflected light and this point has certain funtcional relationship,, can obtain the thickness of each point transparent dielectric film from photo-detector as long as therefore the each point intensity of reflected light that will obtain is calculated.

Description of drawings:

Fig. 1～Fig. 3 is a prior art measuring principle synoptic diagram.

Fig. 4 measures computing formula symbol diagram.

Fig. 5 is a principle of the invention synoptic diagram.

Below in conjunction with accompanying drawing, introduce computing formula of the present invention and measuring process in detail.Among Fig. 4,8 is first media, and 9 is second media, and 10 is the 3rd media.The funtcional relationship of transparent medium film thickness and intensity of reflected light is shown below:

$\mathrm{R=1-}\frac{\sqrt{{\sin }^2{\theta }_i{\mathrm{-（\epsilon }}_3{\mathrm{/\epsilon }}_1）}}{{\mathrm{cos\theta }}_i}｜\frac{T_{\mathrm{12}}{T}_{\mathrm{23}}{e}^{\mathrm{-\alpha h}}}{{\mathrm{1-R}}_{\mathrm{21}}{R}_{\mathrm{23}}{e}^{\mathrm{-2\alpha h}}}{｜}^2$ (5)

Wherein:

R reflectivity, the i.e. ratio of reflective light intensity and incident intensity

H transparent medium film thickness

ε ₁, ε ₃The specific inductive capacity of the first, three medium

θ ₁The light wave incident angle

T ₁₂The transmission coefficient of light wave from first medium to second medium

T ₂₃Light wave is from the transmission coefficient of second medium to the, three media

R ₂₁The reflection coefficient of light wave from second medium to first medium

R ₂₃Light wave is from the reflection coefficient of second medium to the, three media

α $\frac{2}{{\lambda }_0}\sqrt{n{}^2{}_1\sin {}^2{\theta }_i\mathrm{-n}{}^2{}_2}$

λ ₀Light wave wavelength in a vacuum

n ₁, n ₂The refractive index of first and second medium

For a concrete measurement mechanism, except that R and h, above-mentioned parameter all can obtain by tabling look-up or surveying, and therefore, according to formula (1), as long as measure the reflectivity of a certain position, can extrapolate the thickness of respective point.

For the content of this measuring method is described, introduced below in conjunction with specific embodiment.As shown in Figure 5,11 is metal solids among the figure, the 12nd, and oil film, the 13rd, microscope, the 14th, photo-detector, the 15th, light source, transparent solid are prism (first medium), and transparent dielectric film 12 is an oil (second medium), and the 3rd medium is a metal solid.Light enters prism 15 after being sent by light source 16, and total reflection takes place the interface between oil and prism.Light wave still can penetrate very little degree of depth in the oil reservoir under total reflection condition is arranged, when the distance of metal surface and prism surface very little, be that oil film thickness is when very little, the metal surface will absorb the light-wave energy that a part penetrates oil reservoir, reflected light is weakened, oil film thickness is more little, and then reflected light is weak more, and the quantitative relationship between them is determined by formula (1).Applications of photo-detectors 14 is gathered the reflective light intensity of each point in the measurement field, and the input computing machine, carries out the distribution that computing promptly obtains oil film thickness according to formula (1).

Claims (1)

1, a kind of super thin transparent medium membrane thickness measured method is characterized in that optical routing light source, reflecting prism, microscope and photo-detector composition that measuring method adopts, and described reflecting prism places on the tested transparent dielectric film; The incident light that described light source sends returns reflecting prism after entering reflecting prism and transparent dielectric film, enters microscope through the reflecting prism light reflected, enters described photo-detector subsequently.

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