def double_phase_amplitude_coding(target_phase,
target_amp,
prop_dist,
wavelength,
feature_size,
prop_model='ASM',
propagator=None,
dtype=torch.float32,
precomputed_H=None):
"""
Use a single propagation and converts amplitude and phase to double phase coding
Input
-----
:param target_phase: The phase at the target image plane
:param target_amp: A tensor, (B,C,H,W), the amplitude at the target image plane.
:param prop_dist: propagation distance, in m.
:param wavelength: wavelength, in m.
:param feature_size: The SLM pixel pitch, in meters.
:param prop_model: The light propagation model to use for prop from target plane to slm plane
:param propagator: propagation_ASM
:param dtype: torch datatype for computation at different precision.
:param precomputed_H: pre-computed kernel - to make it faster over multiple iteration/images - calculate it once
Output
------
:return: a tensor, the optimized phase pattern at the SLM plane, in the shape of (1,1,H,W)
"""
real, imag = utils.polar_to_rect(target_amp, target_phase)
target_field = torch.complex(real, imag)
slm_field = utils.propagate_field(target_field, propagator, prop_dist,
wavelength, feature_size, prop_model,
dtype, precomputed_H)
slm_phase = double_phase(slm_field, three_pi=False, mean_adjust=True)
return slm_phase
recon_amp = []
# for each channel, propagate wave from the SLM plane to the image plane and get the reconstructed image.
for c in chs:
# load and invert phase (our SLM setup)
phase_filename = os.path.join(opt.root_path, chan_strs[c], f'{target_idx}.png')
slm_phase = skimage.io.imread(phase_filename) / 255.
slm_phase = torch.tensor((1 - slm_phase) * 2 * np.pi - np.pi, dtype=dtype).reshape(1, 1, *slm_res).to(device)
# propagate field
real, imag = utils.polar_to_rect(torch.ones_like(slm_phase), slm_phase)
slm_field = torch.complex(real, imag)
if opt.prop_model.upper() == 'MODEL':
propagator = propagators[c] # Select CITL-calibrated models for each channel
recon_field = utils.propagate_field(slm_field, propagator, prop_dists[c], wavelengths[c], feature_size,
opt.prop_model, dtype)
# cartesian to polar coordinate
recon_amp_c = recon_field.abs()
# crop to ROI
recon_amp_c = utils.crop_image(recon_amp_c, target_shape=roi_res, stacked_complex=False)
# append to list
recon_amp.append(recon_amp_c)
# list to tensor, scaling
recon_amp = torch.cat(recon_amp, dim=1)
recon_amp *= (torch.sum(recon_amp * target_amp, (-2, -1), keepdim=True)
/ torch.sum(recon_amp * recon_amp, (-2, -1), keepdim=True))
def stochastic_gradient_descent(init_phase,
target_amp,
num_iters,
prop_dist,
wavelength,
feature_size,
roi_res=None,
phase_path=None,
prop_model='ASM',
propagator=None,
loss=nn.MSELoss(),
lr=0.01,
lr_s=0.003,
s0=1.0,
citl=False,
camera_prop=None,
writer=None,
dtype=torch.float32,
precomputed_H=None):
"""
Given the initial guess, run the SGD algorithm to calculate the optimal phase pattern of spatial light modulator.
Input
------
:param init_phase: a tensor, in the shape of (1,1,H,W), initial guess for the phase.
:param target_amp: a tensor, in the shape of (1,1,H,W), the amplitude of the target image.
:param num_iters: the number of iterations to run the SGD.
:param prop_dist: propagation distance in m.
:param wavelength: wavelength in m.
:param feature_size: the SLM pixel pitch, in meters, default 6.4e-6
:param roi_res: a tuple of integer, region of interest, like (880, 1600)
:param phase_path: a string, for saving intermediate phases
:param prop_model: a string, that indicates the propagation model. ('ASM' or 'MODEL')
:param propagator: predefined function or model instance for the propagation.
:param loss: loss function, default L2
:param lr: learning rate for optimization variables
:param lr_s: learning rate for learnable scale
:param s0: initial scale
:param writer: Tensorboard writer instance
:param dtype: default torch.float32
:param precomputed_H: A Pytorch complex64 tensor, pre-computed kernel shape of (1,1,2H,2W) for fast computation.
Output
------
:return: a tensor, the optimized phase pattern at the SLM plane, in the shape of (1,1,H,W)
"""
device = init_phase.device
s = torch.tensor(s0, requires_grad=True, device=device)
# phase at the slm plane
slm_phase = init_phase.requires_grad_(True)
# optimization variables and adam optimizer
optvars = [{'params': slm_phase}]
if lr_s > 0:
optvars += [{'params': s, 'lr': lr_s}]
optimizer = optim.Adam(optvars, lr=lr)
# crop target roi
target_amp = utils.crop_image(target_amp, roi_res, stacked_complex=False)
# run the iterative algorithm
for k in range(num_iters):
optimizer.zero_grad()
# forward propagation from the SLM plane to the target plane
real, imag = utils.polar_to_rect(torch.ones_like(slm_phase), slm_phase)
slm_field = torch.complex(real, imag)
recon_field = utils.propagate_field(slm_field, propagator, prop_dist,
wavelength, feature_size,
prop_model, dtype, precomputed_H)
# get amplitude
recon_amp = recon_field.abs()
# crop roi
recon_amp = utils.crop_image(recon_amp,
target_shape=roi_res,
stacked_complex=False)
# camera-in-the-loop technique
if citl:
captured_amp = camera_prop(slm_phase)
# use the gradient of proxy, replacing the amplitudes
# captured_amp is assumed that its size already matches that of recon_amp
out_amp = recon_amp + (captured_amp - recon_amp).detach()
else:
out_amp = recon_amp
# calculate loss and backprop
lossValue = loss(s * out_amp, target_amp)
lossValue.backward()
optimizer.step()
# write to tensorboard / write phase image
# Note that it takes 0.~ s for writing it to tensorboard
with torch.no_grad():
if k % 50 == 0:
print(k)
utils.write_sgd_summary(slm_phase,
out_amp,
target_amp,
k,
writer=writer,
path=phase_path,
s=s,
prefix='test')
return slm_phase
def gerchberg_saxton(init_phase,
target_amp,
num_iters,
prop_dist,
wavelength,
feature_size=6.4e-6,
phase_path=None,
prop_model='ASM',
propagator=None,
writer=None,
dtype=torch.float32,
precomputed_H_f=None,
precomputed_H_b=None):
"""
Given the initial guess, run the SGD algorithm to calculate the optimal phase pattern of spatial light modulator
:param init_phase: a tensor, in the shape of (1,1,H,W), initial guess for the phase.
:param target_amp: a tensor, in the shape of (1,1,H,W), the amplitude of the target image.
:param num_iters: the number of iterations to run the GS.
:param prop_dist: propagation distance in m.
:param wavelength: wavelength in m.
:param feature_size: the SLM pixel pitch, in meters, default 6.4e-6
:param phase_path: path to save the results.
:param prop_model: string indicating the light transport model, default 'ASM'. ex) 'ASM', 'fresnel', 'model'
:param propagator: predefined function or model instance for the propagation.
:param writer: tensorboard writer
:param dtype: torch datatype for computation at different precision, default torch.float32.
:param precomputed_H_f: A Pytorch complex64 tensor, pre-computed kernel for forward prop (SLM to image)
:param precomputed_H_b: A Pytorch complex64 tensor, pre-computed kernel for backward propagation (image to SLM)
Output
------
:return: a tensor, the optimized phase pattern at the SLM plane, in the shape of (1,1,H,W)
"""
# initial guess; random phase
real, imag = utils.polar_to_rect(torch.ones_like(init_phase), init_phase)
slm_field = torch.complex(real, imag)
# run the GS algorithm
for k in range(num_iters):
# SLM plane to image plane
recon_field = utils.propagate_field(slm_field, propagator, prop_dist,
wavelength, feature_size,
prop_model, dtype, precomputed_H_f)
# write to tensorboard / write phase image
# Note that it takes 0.~ s for writing it to tensorboard
if k > 0 and k % 10 == 0:
print(k)
utils.write_gs_summary(slm_field,
recon_field,
target_amp,
k,
writer,
prefix='test')
# replace amplitude at the image plane
recon_field = utils.replace_amplitude(recon_field, target_amp)
# image plane to SLM plane
slm_field = utils.propagate_field(recon_field, propagator, -prop_dist,
wavelength, feature_size, prop_model,
dtype, precomputed_H_b)
# amplitude constraint at the SLM plane
slm_field = utils.replace_amplitude(slm_field,
torch.ones_like(target_amp))
# return phases
return slm_field.angle()