Extending Lentil#

Subclassing existing planes#

Lentil planes are designed to be subclassed, allowing users to easily modify default behavior. A number of special methods are provided for easy operator overloading:

Customizing plane attributes#

The following methods can be defined to create dynamic plane attributes. These are commonly used when a plane attribute is stateful and needs to be recomputed at the time of attribute access.

object.__amp__(self)#

Called when the plane’s amplitude attribute is accessed. The __amp__() method should return a Numpy array.

object.__mask__(self)#

Called when the plane’s mask attribute is accessed. The __mask__() method should return a Numpy array.

object.__opd__(self)#

Called when the plane’s opd attribute is accessed. The __opd__() method should return a Numpy array.

Below is a simple example implementing a tip/tilt mirror where the plane’s opd attribute depends on the state of the x attribute. The logic for computing the opd attribute is defined by the __opd__() method:

class TipTiltMirror(lentil.Plane):
    def __init__(self):
        amplitude = lentil.circle((256,256),120)

        self.x = np.zeros(2)
        self._tt_basis = lentil.zernike_basis(amplitude, modes=[2,3])

        super().__init__(amplitude=amplitude)

    def __opd__(self):
        return np.einsum('ijk,i->jk', self._tt_basis, self.x)

>>> tt = TipTiltMirror()
>>> tt.x = [1e-6, 3e-6]
>>> plt.imshow(tt.opd, cmap='RdBu_r')
>>> plt.colorbar()
../_images/extend-1.png

Note

Numerical diffraction propagation calculations can repeatedly access the opd, amplitude, and mask attributes. Because these attributes remain fixed during a propagation, it is inefficient to recalculate them each time the attribute is accessed. To mitigate this, the plane’s freeze() method can be used to temporarily cache these attributes. For more information, see Freezing planes with computationally expensive attribute access

Customizing how a plane interacts with a wavefront#

object.__mul__(self, wavefront)#

Called when a plane is multiplied with a wavefront.

Creating new planes#