# DIY IR spectrometry - stray light (higher orders diffraction maxima)

Context: homemade IR spectrometer with diffraction grating.

Since

$$m \lambda = d \sin \Theta _{m}$$

diffraction maxima of higher orders from shorter wavelengths will be mixed with lower order maxima for longer wavelengths. For example order 2 for $$\frac{\lambda}{2}$$ with order 1 for $$\lambda$$.

This means I cannot simply associate given $$\Theta$$ with one wavelength.

How can I solve this problem using DIY methods?

• Usually one uses monochromatic light, so there's only one $\lambda$ to be concerned about. As for DIY methods, I'm not sure but I imagine there are filters you could purchase. – Kyle Kanos Jan 14 at 11:10
• You set up the geometry of the given grating and detector so that you don't have significant overlap of orders across the spectrum of interest. – Jon Custer Jan 14 at 14:12