def test_lsst_y_focus():
# Check that applying reasonable focus depth (from O'Connor++06) indeed leads to smaller spot
# size for LSST y-band.
rng = galsim.BaseDeviate(9876543210)
bandpass = galsim.Bandpass("LSST_y.dat", wave_type='nm')
sed = galsim.SED("1", wave_type='nm', flux_type='flambda')
obj = galsim.Gaussian(fwhm=1e-5)
oversampling = 32
photon_ops0 = [
galsim.WavelengthSampler(sed, bandpass, rng=rng),
galsim.FRatioAngles(1.234, 0.606, rng=rng),
galsim.FocusDepth(0.0),
galsim.Refraction(3.9)
]
img0 = obj.drawImage(
sensor=galsim.SiliconSensor(),
method='phot',
n_photons=100000,
photon_ops=photon_ops0,
scale=0.2/oversampling,
nx=32*oversampling,
ny=32*oversampling,
rng=rng
)
T0 = img0.calculateMomentRadius()
T0 *= 10*oversampling/0.2 # arcsec => microns
# O'Connor finds minimum spot size when the focus depth is ~ -12 microns. Our sensor isn't
# necessarily the same as the one there though; our minimum seems to be around -6 microns.
# That could be due to differences in the design of the sensor though. We just use -6 microns
# here, which is still useful to test the sign of the `depth` parameter and the interaction of
# the 4 different surface operators required to produce this effect, and is roughly consistent
# with O'Connor.
depth1 = -6. # microns, negative means surface is intrafocal
depth1 /= 10 # microns => pixels
photon_ops1 = [
galsim.WavelengthSampler(sed, bandpass, rng=rng),
galsim.FRatioAngles(1.234, 0.606, rng=rng),
galsim.FocusDepth(depth1),
galsim.Refraction(3.9)
]
img1 = obj.drawImage(
sensor=galsim.SiliconSensor(),
method='phot',
n_photons=100000,
photon_ops=photon_ops1,
scale=0.2/oversampling,
nx=32*oversampling,
ny=32*oversampling,
rng=rng
)
T1 = img1.calculateMomentRadius()
T1 *= 10*oversampling/0.2 # arcsec => microns
np.testing.assert_array_less(T1, T0)
depths = np.linspace(-25, 25, 41) # microns
obj = galsim.Gaussian(sigma=1e-4)
sed = galsim.SED("1", wave_type='nm', flux_type='flambda')
fig, ax = plt.subplots()
oversampling = 16
for filter in ['g', 'z', 'y']:
bandpass = galsim.Bandpass("LSST_{}.dat".format(filter), wave_type='nm')
Ts = []
for depth in depths:
depth_pix = depth / 10
surface_ops = [
galsim.WavelengthSampler(sed, bandpass, rng=bd),
galsim.FRatioAngles(1.234, 0.606, rng=bd),
galsim.FocusDepth(depth_pix),
galsim.Refraction(3.9) # approx number for Silicon
]
img = obj.drawImage(
sensor=galsim.SiliconSensor(),
method='phot',
n_photons=1_000_000,
surface_ops=surface_ops,
scale=0.2 /
oversampling, # oversample pixels to better resolve PSF size
nx=32 * oversampling, # 6.4 arcsec stamp
ny=32 * oversampling,
)
Ts.append(img.calculateMomentRadius())
Ts = np.array(Ts) / 0.2 * 10 * oversampling # convert arcsec -> micron
ax.scatter(depths, Ts, label=filter)
ax.set_ylim(2, 7)
def test_refract():
ud = galsim.UniformDeviate(57721)
for _ in range(1000):
photon_array = galsim.PhotonArray(1000, flux=1)
ud.generate(photon_array.dxdz)
ud.generate(photon_array.dydz)
photon_array.dxdz *= 1.2 # -0.6 to 0.6
photon_array.dydz *= 1.2
photon_array.dxdz -= 0.6
photon_array.dydz -= 0.6
# copy for testing later
dxdz0 = np.array(photon_array.dxdz)
dydz0 = np.array(photon_array.dydz)
index_ratio = ud() * 4 + 0.25 # 0.25 to 4.25
refract = galsim.Refraction(index_ratio)
refract.applyTo(photon_array)
# Triangle is length 1 in the z direction and length sqrt(dxdz**2+dydz**2)
# in the 'r' direction.
rsqr0 = dxdz0**2 + dydz0**2
sintheta0 = np.sqrt(rsqr0) / np.sqrt(1 + rsqr0)
# See if total internal reflection applies
w = sintheta0 < index_ratio
np.testing.assert_array_equal(photon_array.dxdz[~w], np.nan)
np.testing.assert_array_equal(photon_array.dydz[~w], np.nan)
np.testing.assert_array_equal(photon_array.flux, np.where(w, 1.0, 0.0))
sintheta0 = sintheta0[w]
dxdz0 = dxdz0[w]
dydz0 = dydz0[w]
dxdz1 = photon_array.dxdz[w]
dydz1 = photon_array.dydz[w]
rsqr1 = dxdz1**2 + dydz1**2
sintheta1 = np.sqrt(rsqr1) / np.sqrt(1 + rsqr1)
# Check Snell's law
np.testing.assert_allclose(sintheta0, index_ratio * sintheta1)
# Check azimuthal angle stays constant
phi0 = np.arctan2(dydz0, dxdz0)
phi1 = np.arctan2(dydz1, dxdz1)
np.testing.assert_allclose(phi0, phi1)
# Check plane of refraction is perpendicular to (0,0,1)
np.testing.assert_allclose(np.dot(
np.cross(
np.stack([dxdz0, dydz0, -np.ones(len(dxdz0))], axis=1),
np.stack([dxdz1, dydz1, -np.ones(len(dxdz1))], axis=1),
), [0, 0, 1]),
0.0,
rtol=0,
atol=1e-13)
# Try a wavelength dependent index_ratio
index_ratio = lambda w: np.where(w < 1, 1.1, 2.2)
photon_array = galsim.PhotonArray(100)
ud.generate(photon_array.wavelength)
ud.generate(photon_array.dxdz)
ud.generate(photon_array.dydz)
photon_array.dxdz *= 1.2 # -0.6 to 0.6
photon_array.dydz *= 1.2
photon_array.dxdz -= 0.6
photon_array.dydz -= 0.6
photon_array.wavelength *= 2 # 0 to 2
dxdz0 = photon_array.dxdz.copy()
dydz0 = photon_array.dydz.copy()
refract_func = galsim.Refraction(index_ratio=index_ratio)
refract_func.applyTo(photon_array)
dxdz_func = photon_array.dxdz.copy()
dydz_func = photon_array.dydz.copy()
photon_array.dxdz = dxdz0.copy()
photon_array.dydz = dydz0.copy()
refract11 = galsim.Refraction(index_ratio=1.1)
refract11.applyTo(photon_array)
dxdz11 = photon_array.dxdz.copy()
dydz11 = photon_array.dydz.copy()
photon_array.dxdz = dxdz0.copy()
photon_array.dydz = dydz0.copy()
refract22 = galsim.Refraction(index_ratio=2.2)
refract22.applyTo(photon_array)
dxdz22 = photon_array.dxdz.copy()
dydz22 = photon_array.dydz.copy()
w = photon_array.wavelength < 1
np.testing.assert_allclose(dxdz_func, np.where(w, dxdz11, dxdz22))
np.testing.assert_allclose(dydz_func, np.where(w, dydz11, dydz22))