Calculation of the spectral lens to obtain a normalized vegetation index

A new dispersive optical system concept is proposed for image formation in narrow spectral channels. This optical system is based on a conventional converging lens combined with a coded aperture and a diffraction grating. A gradient calculation method was developed, and the phase function at the lens's input aperture was calculated to separate wavelengths of 650 nm and 750 nm. The calculation method demonstrated the optical system's ability to transmit spatial frequencies in a high-contrast image of an object. Compared to existing compact spectral systems, the proposed spectral lens is inexpensive and easy to manufacture, making it suitable for various precision agriculture applications.