Sodium Doublet on Fabry-Perot

The image below shows the appearance of the interference fringes of the sodium doublet produced by Fabry-Perot optics. This is the appearance at one position. As the micrometer is adjusted to increase the mirror spacing, the appearance changes as the fringes merge together.

If the micrometer is advanced until the fringes look the same again, then you have advanced one of the fringe sets one full order with respect to the other. This allows you to calculate the wavelength difference. The button below displays a movie of the progression from the appearance at left through a cycle and back to that appearance. 如果将显微镜推进直到条纹看起来再次相同，那么你就将一个条纹组相对于另一个条纹组推进了一个完整的周期。这允许你计算波长差。下面的按钮显示了从左侧出现开始，经过一个周期，再回到该出现的全过程。 Load movie 加载电影

Fabry-Perot Calculation

A high-resolution interferometer, the Fabry-Perot has a resolvance of

=	for r = = reflectance d = mm = etalon separation m = = order of interference. 当 r = 时，反射率为 d = mm 为埃他隆间距，m = 为干涉级次。 中文译文中的待填/计算数值依次对应：1：r 2：d 3：m。实际数值以上方原输入框为准。

which means that the least separation of two spectral lines is given by

这意味着两条谱线的最小分离度由

= = nm = = 纳米 中文译文中的待填/计算数值依次对应：1：dwa 2：dw。实际数值以上方原输入框为准。

for λ = = nm 对于 λ = 0 nm 中文译文中的待填/计算数值依次对应：1：wa 2：w。实际数值以上方原输入框为准。

The interferometer can also be characterized by its free spectral range, the change in wavelength necessary to shift the fringe system by one fringe:

干涉仪也可以通过其自由谱宽来表征，即使干涉条纹系统移动一个条纹所需的波长变化：

Free spectral range: 自由光谱范围：

= = nm = = 纳米 中文译文中的待填/计算数值依次对应：1：sra 2：sr。实际数值以上方原输入框为准。

Fabry-Perot Resolution

A high-resolution interferometer, the Fabry-Perot Interferometer has a resolvance of

which means that the least separation of two spectral lines is given by

Resolvance examples 分辨力示例

Calculation 计算

This separation means that the two wavelengths satisfy the Rayleigh criterion. The interferometer can also be characterized by its free spectral range, the change in wavelength necessary to shift the fringe system by one fringe: