A gaze-tracking system (100, 200) for use in a head-mounted display apparatus, the gaze-tracking system (100, 200) comprising: - a plurality of illuminators (102, 202) for emitting light pulses to illuminate a user's eye when the head-mounted display apparatus is worn by the user, the plurality of illuminators (102, 202) comprising at least a first illuminator (102A, 202A) and a second illuminator (102B, 202B), a first wavelength of light emitted by the first illuminator (102A, 202A) being longer than a second wavelength of light emitted by the illuminator (102B, 202B); - at least one lens (104, 206) positioned on an optical path of reflections of the light pulses from the user's eye, wherein the at least one lens has no chromatic-aberration correction, whereby a first focal plane of the at least one lens (104, 206) corresponding to the first wavelength is farther away from the at least one lens than a second focal plane of the at least one lens (104, 206) corresponding to the second wavelength; - at least one camera (106, 208) for capturing an image of the reflections of the light pulses, wherein the image is representative of a position of the reflections on an image plane of the at least one camera (106, 208), wherein the at least one camera comprises a plurality of photo-sensitive elements and a plurality of optical filters (1, 2, 208B, 500), an optical filter being implemented per photo-sensitive element, wherein the plurality of optical filters are divided into at least a first group and a second group, optical filters of the first group being configured to substantially allow a first range of wavelengths to pass through, while optical filters of the second group being configured to substantially allow a second range of wavelengths to pass through, and wherein the plurality of optical filters are implemented on a single chip; and - a processor coupled in communication with the plurality of illuminators (102, 202) and the at least one camera (106, 208), wherein the processor is configured to: - control operations of the plurality of illuminators (102, 202) and the at least one camera (106, 208); - process the captured image to detect a gaze direction of the user; and - adjust a spatial arrangement of the optical filters of the first group and of the second group into separate regions of the single chip, and define shapes and/or sizes of the regions based upon an eye geometry and the gaze direction of the user's eye. - a plurality of illuminators (102, 202) for emitting light pulses to illuminate a user's eye when the head-mounted display apparatus is worn by the user, the plurality of illuminators (102, 202) comprising at least a first illuminator (102A, 202A) and a second illuminator (102B, 202B), a first wavelength of light emitted by the first illuminator (102A, 202A) being longer than a second wavelength of light emitted by the illuminator (102B, 202B); - at least one lens (104, 206) positioned on an optical path of reflections of the light pulses from the user's eye, wherein the at least one lens has no chromatic-aberration correction, whereby a first focal plane of the at least one lens (104, 206) corresponding to the first wavelength is farther away from the at least one lens than a second focal plane of the at least one lens (104, 206) corresponding to the second wavelength; - at least one camera (106, 208) for capturing an image of the reflections of the light pulses, wherein the image is representative of a position of the reflections on an image plane of the at least one camera (106, 208), wherein the at least one camera comprises a plurality of photo-sensitive elements and a plurality of optical filters (1, 2, 208B, 500), an optical filter being implemented per photo-sensitive element, wherein the plurality of optical filters are divided into at least a first group and a second group, optical filters of the first group being configured to substantially allow a first range of wavelengths to pass through, while optical filters of the second group being configured to substantially allow a second range of wavelengths to pass through, and wherein the plurality of optical filters are implemented on a single chip; and - a processor coupled in communication with the plurality of illuminators (102, 202) and the at least one camera (106, 208), wherein the processor is configured to: - control operations of the plurality of illuminators (102, 202) and the at least one camera (106, 208); - process the captured image to detect a gaze direction of the user; and - adjust a spatial arrangement of the optical filters of the first group and of the second group into separate regions of the single chip, and define shapes and/or sizes of the regions based upon an eye geometry and the gaze direction of the user's eye. - control operations of the plurality of illuminators (102, 202) and the at least one camera (106, 208); - process the captured image to detect a gaze direction of the user; and - adjust a spatial arrangement of the optical filters of the first group and of the second group into separate regions of the single chip, and define shapes and/or sizes of the regions based upon an eye geometry and the gaze direction of the user's eye.