Diffractive Surfaces

Script: 0_hello_deeplens_hsi.py

The DOE is the optical encoder: its wavelength-dependent PSF is what carries spectral information into the RGB capture. DeepLens Hyperspectral Imaging ships three DiffractiveSurface parameterizations, each interchangeable through the lens-config JSON. This example renders each DOE's phase map and its PSF at 400, 500, 600 and 700 nm (point source at 1 m). The PSF changing shape with wavelength is the spectral cue the reconstruction network learns to decode.

Run

# Render the DOE phase map + spectral PSF for every encoder
python 0_hello_deeplens_hsi.py

# ...or just one encoder
python 0_hello_deeplens_hsi.py pixel2d

Key code

from src.hsi_camera import HSICamera

# DOE name -> lens file to visualize
DOES = {
    "pixel2d":              "./lenses/paraxiallens/doelens_hsi.json",
    "diffracted_rotation":  "./lenses/paraxiallens/doelens_diffracted_rotation.json",
    "rotational_symmetric": "./lenses/paraxiallens/doelens_rotational_symmetric.json",
}

for name, lens_file in DOES.items():
    cam = HSICamera(lens_file=lens_file, sensor_file="./sensors/flir/BFS-U3-200S7C-C.json")
    cam.vis_doe()                                                  # phase map (2D + 3D)
    cam.vis_psf(wvln_spectral=[0.4, 0.5, 0.6, 0.7], psf_ks=512, depth=-1000)

Pixel2D — freeform

A free per-pixel height map (doelens_hsi.json). Every pixel is an independent learnable height, giving the most expressive — but highest-dimensional — encoder. It is the default encoder used in the HSI Reconstruction example.

Phase	Spectral PSF (400–700 nm)

DiffractedRotation (Jeon et al. 2019)

An analytic DOE built from blazed Fresnel sectors (here three, num_wings: 3). Its PSF is a sharp lobe that rotates to a different angle at each wavelength, giving a well-conditioned spectral code. It is fixed-form (its only continuous parameter is the focal length), so it is used as a fixed encoder, not an end-to-end design target.

Phase	Spectral PSF (400–700 nm)

RotationallySymmetric (Dun et al. 2020)

A rotationally-symmetric achromat defined by a 1-D radial profile (initialized as a Fresnel lens). The PSF is a set of concentric rings whose scale shifts with wavelength. The radial profile is learnable, so this encoder can be designed end-to-end.

Phase	Spectral PSF (400–700 nm)

Choosing an encoder

DOE	Learnable	Use as
Pixel2D	full height map	freeform fixed encoder, or end-to-end design target
DiffractedRotation	focal length only	fixed analytic encoder
RotationallySymmetric	radial profile	achromat; end-to-end design target

Next steps

• HSI Reconstruction — train a network against a fixed encoder
• End-to-End Design — design the encoder jointly with the network