BACKGROUND

The present disclosure generally relates to depth sensing, and specifically relates to a shifting diffractive optical element for achieving an adjustable resolution of a structured light pattern for three-dimensional depth sensing.

To achieve a compelling user experience for depth sensing when using head-mounted displays (HMDs), it is important to create a scanning device that provides illumination pattern that is dynamically adjustable in real time. Most depth sensing methods rely on active illumination and detection. The conventional methods for depth sensing involve mechanical scanning or fixed diffractive-optics pattern projection, using structured light or time-of-flight techniques. Depth sensing based on time-of-flight uses a mechanical based mirror device (scanner) to send short pulses into an object space. The depth sensing based on time-of-flight further uses a high-speed detector to time-gate back-scattered light from the object to create high resolution depth maps. However, the mechanical based scanner performs inadequately in scanning speed, real-time reconfiguration and mechanical stability. Depth sensing based on a fixed structured light uses a diffractive optical element to generate a structured light of a static (fixed) pattern projected into an object space. The depth sensing based on the fixed structured light further uses a pre-stored look-up table to compute and extract depth maps. However, the depth sensing based on the fixed structured light is not robust enough for dynamic depth sensing where the adjustment in spatial resolution of an illumination pattern is required.

SUMMARY

A depth camera assembly (DCA) determines depth information associated with one or more objects in a local area. The DCA comprises a structured light generator, an imaging device and a controller. The structured light generator is configured to illuminate a local area with structured light in accordance with emission instructions. The structured light generator includes an illumination source, a mounting element, a diffractive optical element (DOE), and a projection assembly. The illumination source is configured to emit one or more pulses of light based in part on the emission instructions. The mounting element is configured to have a plurality of adjustable positions relative to the illumination source based in part on the emission instructions. The DOE is mounted on the mounting element and generates diffracted scanning beams from the one or more pulses of light, the diffracted scanning beams having a different pattern for each position of the mounting element of the plurality of adjustable positions. The projection assembly is configured to project the diffracted scanning beams as the structured light into the local area. A pattern of the structured light is dynamically adjustable based in part on an adjustable position of the mounting element of the plurality of adjustable positions. The imaging device captures one or more images of at least a portion of the structured light reflected from the one or more objects in the local area. The controller generates the emission instructions and provides the emission instructions to the structured light generator. The controller further determines depth information for the one or more objects based in part on the captured one or more images.

A head-mounted display (HMD) can further integrate the DCA. The HMD further includes an electronic display and an optical assembly. The HMD may be, e.g., a virtual reality (VR) system, an augmented reality (AR) system, a mixed reality (MR) system, or some combination thereof. The electronic display is configured to emit image light. The optical assembly is configured to direct the image light to an eye-box of the HMD corresponding to a location of a user's eye, the image light comprising the depth information of the one or more objects in the local area determined by the DCA.

