Apparatus and methods for hyperspectral imaging with on-chip digital time delay and integration

#Embodiments of the present invention generally relate to the field of spectrally resolved imaging systems and, more specifically, to extending the imaging range and/or improving the signal-to-noise ratio of spatially scanning “hyperspectral” imaging systems.

#Accurate measurement of spectral signatures requires sensing an image in many narrow spectral bands, also referred to herein as channels. Since each spectral channel is so narrow, each channel accumulates relatively small signals. The lower the signal levels, the lower the achievable imaging range between object and sensor. Longer imaging range is improved by collecting more signal.

#Most hyperspectral sensors are scanning systems that image an object in one dimension through a narrow slit onto a sensing array while spreading out the spectrum of each point along the slit in a direction orthogonal to the slit using a prism or grating. These slit spectrometers are typically operated in a “pushbroom” scan mode. They operate by continuously scanning a single line of pixels across the scene. The light is passed through the slit and dispersed into its constituent colors by either a diffraction grating or prism within the optical spectrometer. Exposure time (i.e., signal collection time) for each pixel is extremely limited.

#The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.

#FIG. 1 is a side view of an embodiment of a hyperspectral imaging sensor according to an embodiment of the present intention;

#FIG. 2 is a perspective, exploded view of the hyperspectral imaging sensor of FIG. 1;

#A description of example embodiments of the invention follows.

#Described embodiments of the invention are not limited in application to details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The described embodiments are capable of other embodiments and of being practiced or implemented in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

#FIG. 1 illustrates that a pixel array 100, of which a sub-array 111 is a part, may be electrically coupled to a CMOS substrate 300 on which both analog and digital electrical modules may be fabricated. Each active pixel in the sub-array 111 of the array 100 (illustrated in FIG. 2) has an individual connection 180 to the CMOS substrate 300. Indium bump bonds, for example, are one common method for providing the connections 180 from the active pixels to the CMOS substrate 300. As will be further described hereinafter, the modules may comprise analog signal collection, amplification, and signal conditioning electronics 320, analog-to-digital (A/D) converters and multiplexor 340, and a number of signal accumulation and shift registers, which together comprise a digital Time-Delay and Integration (TDI) channel 360 for each column of pixels in the array 100. FIG. 1 represents a single spectral channel, which is replicated many times to yield the hyperspectral sensor 10, which is illustrated in more detail in FIG. 2.