An imager for multispectral imaging, comprising: an objective lens configured to disperse light reflected from a target object with a high degree of longitudinal chromatic aberrations along an optical axis of the objective lens; a color sensor configured to capture a plurality of substantially complete images of the target object at a plurality of wavelengths, wherein at least one of the objective lens and the sensor is configured to move along the optical axis to enable the sensor to capture the plurality of substantially complete images; and a processor configured to, for each substantially complete image of the plurality of substantially complete images at a corresponding wavelength: obtain a first image by extracting a sharp region from the substantially complete image; for each color pixel of the remaining regions from the substantially complete image calculate a first ratio, K1, of a pixel intensity of a first color to a pixel intensity of a second color and calculate a second ratio, K2, of the pixel intensity of the first color to a pixel intensity of a third color and based on the K1 and K2 ratios determine which pixels are at the correct wavelength; obtain a second image based on extraction of pixels having correct values of the first ratio, K1, and the second ratio, K2; generate a combined image based on a combination of the obtained first image and the second image at the corresponding wavelength; and obtain a multi-spectral image based on the generated combined image for each substantially complete image of the plurality of substantially complete images at the corresponding wavelength. an objective lens configured to disperse light reflected from a target object with a high degree of longitudinal chromatic aberrations along an optical axis of the objective lens; a color sensor configured to capture a plurality of substantially complete images of the target object at a plurality of wavelengths, wherein at least one of the objective lens and the sensor is configured to move along the optical axis to enable the sensor to capture the plurality of substantially complete images; and a processor configured to, for each substantially complete image of the plurality of substantially complete images at a corresponding wavelength: obtain a first image by extracting a sharp region from the substantially complete image; for each color pixel of the remaining regions from the substantially complete image calculate a first ratio, K1, of a pixel intensity of a first color to a pixel intensity of a second color and calculate a second ratio, K2, of the pixel intensity of the first color to a pixel intensity of a third color and based on the K1 and K2 ratios determine which pixels are at the correct wavelength; obtain a second image based on extraction of pixels having correct values of the first ratio, K1, and the second ratio, K2; generate a combined image based on a combination of the obtained first image and the second image at the corresponding wavelength; and obtain a multi-spectral image based on the generated combined image for each substantially complete image of the plurality of substantially complete images at the corresponding wavelength. obtain a first image by extracting a sharp region from the substantially complete image; for each color pixel of the remaining regions from the substantially complete image calculate a first ratio, K1, of a pixel intensity of a first color to a pixel intensity of a second color and calculate a second ratio, K2, of the pixel intensity of the first color to a pixel intensity of a third color and based on the K1 and K2 ratios determine which pixels are at the correct wavelength; obtain a second image based on extraction of pixels having correct values of the first ratio, K1, and the second ratio, K2; generate a combined image based on a combination of the obtained first image and the second image at the corresponding wavelength; and obtain a multi-spectral image based on the generated combined image for each substantially complete image of the plurality of substantially complete images at the corresponding wavelength.