Thermal camera lens designwith improved center-field detection range

A head-mounted display (HMD) device wearable by a user and supporting a mixed-reality user experience comprising a display of virtual images for objects in a virtual world and views of objects in a real world, comprising:

• a display engine generating virtual images for the mixed-reality user experience;
• a see-through waveguide combiner configured to receive the virtual images from the display engine and display the virtual images, the see-through waveguide combiner being located on the HMD device in front of an eye of the user, and through which the user views the real world when the HMD device is donned;
• and
• a thermal imaging camera generating thermal images of target objects located in the real world within a field of view (FOV), the thermal imaging camera including a thermal imaging sensor comprising a two-dimensional array of pixels arranged in a focal plane implemented using microbolometers sensitive to infrared (IR) radiation and further including a non-rectilinear lens,
• wherein the non-rectilinear lens focuses IR radiation emitted from the target objects onto the thermal imaging sensor, and
• wherein the non-rectilinear lens imparts distortion to the focused IR radiation that varies non-linearly with a field height in the focal plane.

A method for improving center-field detection range of a thermal imaging camera having a two-dimensional microbolometer array and lens, comprising:

• providing a thermal imaging detector comprising the two-dimensional microbolometer array with a predetermined area, the thermal imaging detector being sensitive to infrared (IR) radiation;
• selecting a field of view (FOV) for the lens;
• fabricating the lens with a distortion profile mathematically described by a polynomial function having terms greater than second degree such that an angular resolution of the lens has a maximum value at a center of the FOV;
• and
• positioning the lens in the thermal imaging camera to focus IR radiation emitted from objects located within the FOV onto the thermal imaging detector over the predetermined area.