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I want to set up an optical system as shown in the figure. enter image description here A laser beam passes through a diffraction grating, then a beam splitter, through a 35mm focal length lens to the object, and then is reflected back, passing through the beam splitter, through a len with a 50mm focal length, and finally reaching the CCD. I will investigate the changes in the position of the outermost beam spot compared to the central beam when moving the object. Let u be the distance between the position of the outermost beam spot and the central beam spot. The theoretical result, when the distance between the 35mm focal length lens and the object is 35mm, is u=1.567mm. However, when I use a real lens to simulate and take the H2 plane (shown below) as the reference plane, the distance I get is 0.93mm. Where did I go wrong? The principal planes of the lens

Fig.2.The principal planes of the lens

The distances in the simulation system

Fig.3.The distances in the simulation system

[The positions of the 3 beam spots when using a ray4

Fig.4.The positions of the 3 beam spots when using a ray

Reference: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/priplan.html

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  • $\begingroup$ Please provide more info. How far are you moving the source spot? How big isthe source aperture? It appears from your drawing that the beam is diverging from the pinhole.. Given an object at 175 mm , so the lensmaker's formula suggests the focal plane is at 43.75 mm. Next, how did you determine the location of the principal plane(s) of your physical lens? $\endgroup$
    – Carl Witthoft
    Commented Jul 4 at 18:53
  • $\begingroup$ I am just simulating and determining the principal plane using formulas, then entering the distances into the software. I plan to move the sample (object) around from -1mm to 1mm. The laser beam diameter is 2mm. Additionally, I intend to place the sample at the focal plane of the lens so that the central beam converges, rather than having all three beams meet. I use the data from the two lenses below for calculations. 35: edmundoptics.com/p/37814/38894 50: edmundoptics.com/p/… $\endgroup$
    – Yuu
    Commented 2 days ago

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