Lens grating lens spectrometer #156
Replies: 3 comments 6 replies
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Hi @chalongratken, Ray-optics follows the typical convention imaging optical software uses which is that light propagates in the negative Z direction after an odd number of reflections. In your model, you entered the doublet following the grating as if light was propagating in the +Z direction. If you look closely at the lens layout you can see the rays go through surface 6 to 8 "backwards", as seen in the image
You can fix this by scaling the relevant interfaces and gaps by -1. Since you entered the airspace thicknesses 5 and 8 as negative values, these don't need to be scaled.
I wrote a function that takes the surface range and does the scaling. For this case, it would be invoked as: Hope this helps. Mike Hayford |
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Hi Michael, |
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Now I want to adapt the above lens-grating-lens spectrometer into a lens-grism-lens conflagration, in which a couple of wedge prisms were added before and after the grating as shown in the attached image. This configuration will give an in-line spectrometer. But I still have no idea about adding prism. Could you please help me on how to add a wedge prism? Thanks in advance. |
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Hello @chalongratken, This should be possible. Here's an example with made-up data. Use the recently released v0.9.2 ray-optics to get the rendering to look right. %matplotlib inlinefrom rayoptics.environment import *from rayoptics.elem.layout import RayFanBundle
def create_ray_fan_vs_wvl(fig, opt_model, num_rays=21):
ray_fan_bundles = []
system_length, start_offset = fig.sl_so
fov = opt_model['optical_spec']['fov']
fi = 0
fld = fov.fields[fi]
fld_label = fov.index_labels[fi]
wvls = opt_model['optical_spec']['wvls']
for wl, clr in zip(wvls.wavelengths, wvls.render_colors):
rayfan = RayFan(opt_model, f=fld, wl=wl, xyfan='y', num_rays=num_rays,
label=fld_label, color=clr)
rb = RayFanBundle(opt_model, rayfan, start_offset)
ray_fan_bundles.append(rb)
return ray_fan_bundlesopm = OpticalModel()
sm = opm['seq_model']
osp = opm['optical_spec']
pm = opm['parax_model']
em = opm['ele_model']
pt = opm['part_tree']
ar = opm['analysis_results']
osp['pupil'] = PupilSpec(osp, key=['object', 'epd'], value=25.4)
osp['fov'] = FieldSpec(osp, key=['object', 'height'], flds=[0.0], is_relative=False)
osp['wvls'] = WvlSpec([(400, 0.5), (600, 1.0), (800, 0.5)], ref_wl=1)
opm.radius_mode = True
sm.do_apertures = False
sm.gaps[0].thi = 39
# Add Collimator Lens
sm.add_surface([34.9, 9.0, 'N-BAF10','Schott'], sd=15)
sm.add_surface([-28.8, 3.5, 'N-SF6','Schott'])
sm.add_surface([-137.5, 15, 'air'])
sm.set_stop()Enter the first prism.It is best to use the "dec and return" or "decenter and return" decenter type for this. In this case, only the first surface needs to be tilted. # Pick a prism angle
prism_angle = 15
# prism #1
sm.add_surface([0, 8, 'N-BAF10','Schott'], sd=15)
sm.ifcs[sm.cur_surface].decenter = srf.DecenterData('dec and return', alpha=prism_angle)
sm.add_surface([0, 3.5, 'N-BAF10','Schott'])
sm.add_surface([0, 4, 'air'])Add the grating to the exiting surface of the substrate.The ray trace relies on the interact_mode of the surface to determine whether to transmit or reflect the diffrated rays. grating_surface = sm.cur_surface
grating600lp = DiffractionGrating('600L/mm grating', grating_lpmm=600, order=1)
sm.ifcs[grating_surface].phase_element = grating600lpEnter prism #2 and the focusor lens.Again, a decenter and return surface, tilted the opposite direction, is used on the exiting surface of the second prism assembly. sm.add_surface([0, 3.5, 'N-BAF10','Schott'], sd=15)
sm.add_surface([0, 8, 'N-BAF10','Schott'])
sm.add_surface([0, 15, 'air'])
sm.ifcs[sm.cur_surface].decenter = srf.DecenterData('dec and return', alpha=-prism_angle)
# Add Focusor Lens
sm.add_surface([34.9, 9.0, 'N-BAF10','Schott'], sd=15)
sm.add_surface([-28.8, 3.5, 'N-SF6','Schott'])
sm.add_surface([-137.5, 0, 'air'])
sm.gaps[-1].thi = 50
opm.update_model()
sm.list_model()entity_factory = create_ray_fan_vs_wvl, (opm,), {'num_rays': 3}
eflist = [entity_factory]layout_plt1 = plt.figure(FigureClass=InteractiveLayout, opt_model=opm, do_draw_rays=False,
do_draw_beams=False, do_draw_edge_rays=False, entity_factory_list=eflist).plot()
The list_sg method includes the decenter data in the surface listing.sm.list_sg() |
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Thanks Michael! this is really wonderful. However, when I incorporated the code to visualize the spot diagram of the optical system, it gave me the following error: ValueError: zero-size array to reduction operation maximum which has no identity. My added code is: It seems that spot diagram fail to plot when using a grating. |
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This is a problem with the clear apertures set on the surfaces. If you look at the sm.list_model() output, there are a number of surfaces that have a sd (semi-diameter) of 1. This is clipping all the rays when doing a spot diagram. You can quickly set them to the same value this way: When this is done, the spot diagram works correctly. It was failing because no rays got through and that made it unhappy :-( Hope this helps. Mike Hayford |
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Hi Michael, I tried what you suggested and got the spot diagram worked, thanks.
Import RayFanBudle for multiwavelength plot Create optical model Add optical component Add Collimator Lens Add Prism 1 Add transmission plate Add Grating to the existing surface Add Prism 2 Add Focuser Lens Add detector Plot Layout and Rays Plot Spot Diagram And here is the result: Now, the question are:
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Hello @chalongratken, |
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Thanks Michael!
Now I think SiO2 material works for me. Regards, |
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Recently, I am trying to use the rayoptics to model a lens grating lens spectrometer which is basically consisted of a doublet collimator lens, a reflective grating, and a doublet focuser lenses. I followed the suggestion in #147 to create a ray trace with a collimator lens and a grating which is ok. However, when I tried to add the focuser lens after the grating, the rays seems to be discontinuous and they are diverged instead of focusing as seen in the attached image. Here is my code:
from rayoptics.environment import *
opm = OpticalModel()
sm = opm['seq_model']
osp = opm['optical_spec']
pm = opm['parax_model']
em = opm['ele_model']
pt = opm['part_tree']
ar = opm['analysis_results']
osp['pupil'] = PupilSpec(osp, key=['object', 'epd'], value=25.4)
osp['fov'] = FieldSpec(osp, key=['object', 'height'], flds=[0.0], is_relative=False)
osp['wvls'] = WvlSpec([(400, 0.5), (600, 1.0), (800, 0.5)], ref_wl=1)
opm.radius_mode = True
sm.gaps[0].thi = 39
Add Collimator Lens
sm.add_surface([34.9, 9.0, 'N-BAF10','Schott'], aperture_type='circular', aperture_value=25.0)
sm.add_surface([-28.8, 3.5, 'N-SF6','Schott'])
sm.add_surface([-137.5, 0, 'air'])
sm.gaps[-1].thi = 70.0
Add grating
sm.add_surface([.0, -70., 'refl'])
grating_surface = sm.cur_surface
sm.ifcs[grating_surface].decenter = srf.DecenterData('bend', alpha=40)
grating600lp = DiffractionGrating('600L/mm grating', grating_lpmm=600, order=1)
sm.ifcs[grating_surface].phase_element = grating600lp
grating_tilt = 40
total_angle = 60
sm.cur_surface = grating_surface
sm.ifcs[sm.cur_surface].decenter = srf.DecenterData('dec and return', alpha=grating_tilt)
sm.gaps[sm.cur_surface].thi = .0
sm.add_surface([.0, -70.])
sm.ifcs[sm.cur_surface].interact_mode = 'dummy'
sm.ifcs[sm.cur_surface].decenter = srf.DecenterData('decenter', alpha=total_angle)
sm.gaps[-1].thi = -70
Add Focusor Lens
sm.set_stop()
sm.add_surface([34.9, 9.0, 'N-BAF10','Schott'], aperture_type='circular', aperture_value=25.0)
sm.add_surface([-28.8, 3.5, 'N-SF6','Schott'])
sm.add_surface([-137.5, 0, 'air'])
sm.gaps[-1].thi = -50
opm.update_model()
from rayoptics.elem.layout import RayFanBundle
def create_ray_fan_vs_wvl(fig, opt_model, num_rays=21):
ray_fan_bundles = []
system_length, start_offset = fig.sl_so
fov = opt_model['optical_spec']['fov']
fi = 0
fld = fov.fields[fi]
fld_label = fov.index_labels[fi]
wvls = opt_model['optical_spec']['wvls']
for wl, clr in zip(wvls.wavelengths, wvls.render_colors):
rayfan = RayFan(opt_model, f=fld, wl=wl, xyfan='y', num_rays=num_rays,
label=fld_label, color=clr)
rb = RayFanBundle(opt_model, rayfan, start_offset)
ray_fan_bundles.append(rb)
return ray_fan_bundles
entity_factory = create_ray_fan_vs_wvl, (opm,), {'num_rays': 3}
eflist = [entity_factory]
layout_plt3 = plt.figure(FigureClass=InteractiveLayout, opt_model=opm, do_draw_rays=False,
do_draw_beams=False, do_draw_edge_rays=False, entity_factory_list=eflist).plot()
I am still not very clear how to add the optical element after a grating after which the the system coordinate has rotated. Please help me on this issue. Thanks
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