A biometric access system comprising: a biometric sensor comprising: an interface subsystem comprising an interface surface disposed to contact purported tissue of a subject; an illumination subsystem (103a, 103b) disposed to pass source illumination into the purported tissue of a subject via a set of first surface regions (111a, 111b) of the purported tissue; a detector subsystem disposed to acquire a plurality of images corresponding to a plurality of optical imaging conditions, the plurality of images being based on response illumination exiting a set of second surface regions of the purported tissue, the set of second surface regions being different from the set of first surface regions, the response illumination produced by interactions between the source illumination and subsurface characteristics of the purported tissue, wherein the detector subsystem is disposed to acquire the plurality of images corresponding to the plurality of optical imaging conditions, such that each image is acquired under a different combination of illumination wavelength(s) and exposure time(s); and one or more processors configured to direct operation of the illumination subsystem (103a, 103b) and the detector subsystem to pass source illumination of different wavelengths and exposure times into the purported tissue via the set of first surface regions (111a, 111b) and acquire the plurality of images based on response illumination exiting the set of second surface regions produced by interactions between the source illumination of different wavelengths and exposure times and subsurface characteristics of the purported tissue, whereby the one or more processors are configured to combine the plurality of images to generate a combined image (800, 900, 1000); and to process the combined image (800, 900, 1000) to perform a function affecting access to a secure asset. an interface subsystem comprising an interface surface disposed to contact purported tissue of a subject; an illumination subsystem (103a, 103b) disposed to pass source illumination into the purported tissue of a subject via a set of first surface regions (111a, 111b) of the purported tissue; a detector subsystem disposed to acquire a plurality of images corresponding to a plurality of optical imaging conditions, the plurality of images being based on response illumination exiting a set of second surface regions of the purported tissue, the set of second surface regions being different from the set of first surface regions, the response illumination produced by interactions between the source illumination and subsurface characteristics of the purported tissue, wherein the detector subsystem is disposed to acquire the plurality of images corresponding to the plurality of optical imaging conditions, such that each image is acquired under a different combination of illumination wavelength(s) and exposure time(s); and one or more processors configured to direct operation of the illumination subsystem (103a, 103b) and the detector subsystem to pass source illumination of different wavelengths and exposure times into the purported tissue via the set of first surface regions (111a, 111b) and acquire the plurality of images based on response illumination exiting the set of second surface regions produced by interactions between the source illumination of different wavelengths and exposure times and subsurface characteristics of the purported tissue, whereby the one or more processors are configured to combine the plurality of images to generate a combined image (800, 900, 1000); and to process the combined image (800, 900, 1000) to perform a function affecting access to a secure asset.