Table 1 Reconstruction methods considered

From: High-performance and scalable on-chip digital Fourier transform spectroscopy

Method

Problem

Pseudoinverse

y=Ax (Moore–Penrose)

Ridge Regression

\(\mathop {{\min }}_x \left\{ {\left| {\left| {{\bf{y}} - {\bf{Ax}}} \right|} \right|_2^2 + \alpha _2\left| {\left| {\bf{x}} \right|} \right|_2^2} \right\}\)

LASSO

\(\mathop {{\min }}_x \left\{ {\left| {\left| {{\bf{y}} - {\bf{Ax}}} \right|} \right|_2^2 + \alpha _1\left| {\left| {\bf{x}} \right|} \right|_1} \right\}\)

BPDN

\(\mathop {{\min }}_x \left\{ {(1/2)\left| {\left| {{\bf{y}} - {\bf{Ax}}} \right|} \right|_2^2 + \alpha _1\left| {\left| {\bf{x}} \right|} \right|_1} \right\}\)

RBF Network

\(\mathop {{\min }}_c \left\{ {\left| {\left| {{\bf{y}} - {\bf{Ah}}_{\bf{c}}} \right|} \right|_2^2} \right\}\) with \({\bf{h}}_{\bf{c}} = {\bf{Kc}} = \mathop {\sum }\limits_{d = 1}^D c_de^{ - \beta \left| {\lambda - \lambda _d} \right|^2}\)

Elastic-Net

\(\mathop {{\min }}_{x,x > 0} \left\{ {\left| {\left| {{\bf{y}} - {\bf{Ax}}} \right|} \right|_2^2 + \alpha _1\left| {\left| {\bf{x}} \right|} \right|_1 + \alpha _2\left| {\left| {\bf{x}} \right|} \right|_2^2} \right\}\)

Elastic-D1

\(\mathop {{\min }}_{x,x > 0} \left\{ {\left| {\left| {{\bf{y}} - {\bf{Ax}}} \right|} \right|_2^2 + \alpha _1\left| {\left| {\bf{x}} \right|} \right|_1 + \alpha _2\left| {\left| {\bf{x}} \right|} \right|_2^2 + \alpha _3\left| {\left| {{\bf{D}}_1{\bf{x}}} \right|} \right|_2^2} \right\}\)

  1. Spectral reconstruction techniques/methods considered in this work, and the corresponding problem they solve. Depending on the nature of the problem and input vector, various techniques are such as convex optimization and gradient descent are available to solve the problem. The c coefficients for the RBF Network are computed via c=(AK)+y, where K is the kernel matrix \({\mathbf{K}}_{\lambda ,\lambda _d} = e^{ - \beta \left| {\lambda - \lambda _d} \right|^2}\) and λd are the centers of the radial basis functions