METHOD AND SYSTEM FOR REDUCING LINE SEPARATION ARTIFACTS IN INTERLACED IMAGE PROJECTION
An image display system includes an optical subsystem configured to emit a modulated light beam, and a scanning mirror for generating a reflected light beam that is scanned according to randomly selected or pseudo-randomly selected scan patterns to generate multiple image fields of a multiple interlaced scan image. A plurality of different scan patterns can be cycled through, randomly or pseudo-randomly selected, for the different image fields to reduce artifacts that may be observed while viewing a projected image.
1 . A method for displaying a sequence of a plurality of images of virtual content through a viewing assembly of an image projection system, the method comprising:
identifying, from among a set of multiple different scan patterns, a plurality of scan patterns for the plurality of images of virtual content in the sequence, respectively, including at least one scan pattern for each of the plurality of images of virtual content in the sequence; and
synchronously controlling:
an illumination source of the image projection system to emit collimated light corresponding to pixels of the plurality of images of virtual content in the sequence toward a scanning mirror of the image projection system, wherein the scanning mirror is positioned to receive and reflect light from the illumination source toward the viewing assembly of the image projection system; and
an actuator of the scanning mirror to induce a sequence of different movements in the scanning mirror about one or more rotational axes in accordance with the plurality of scan patterns identified for the plurality of images of virtual content in the sequence, respectively, wherein the sequence of different movements comprises a sequence of different oscillations in the scanning mirror about a first rotational axis of the one or more rotational axes, and wherein the different oscillations in the sequence of different oscillations are offset in phase from each other.
2 . The method of claim 1 , wherein the set of multiple different scan patterns comprises a set of k different scan patterns, k representing a value greater than two, wherein the plurality of images in the sequence are displayed using a quantity of m different scan patterns, m representing a value greater than one and less than or equal to k.
3 . The method of claim 2 , further comprising controlling the actuator of the scanning mirror to induce a sequence of m different oscillations in the scanning mirror about the first rotational axis in accordance with each of the plurality of scan patterns identified for the plurality of images of virtual content in the sequence, respectively, and wherein the m different oscillations are offset in phase from each other by a minimum of about 2π/k radians.
4 . The method of claim 3 , wherein the set of k different scan patterns includes a quantity of n different scan patterns identified for each of the plurality of images of virtual content in the sequence, n representing a value greater than one, and further comprising controlling the actuator of the scanning mirror to induce a sequence of n different oscillations in the scanning mirror about the first rotational axis in accordance with the quantity of n scan patterns identified for each of the plurality of images of virtual content in the sequence.
5 . The method of claim 4 , wherein the n different oscillations are offset in phase from each other by a minimum of about 2π/k radians.
6 . The method of claim 4 , wherein the n different oscillations are offset in phase from each other by about 2π/n radians.
7 . The method of claim 4 , wherein each oscillation induced in the scanning mirror about the first rotational axis in accordance with one of the k different scan patterns comprises oscillation about the first rotational axis at a particular frequency, the particular frequency being common across all oscillations induced in the scanning mirror about the first rotational axis in accordance with one of the k different scan patterns.
8 . The method of claim 4 , wherein the n different scan patterns correspond to n different fields of each of the plurality of images of virtual content in the sequence.
9 . The method of claim 4 , wherein n represents a value greater than or equal to four.
10 . The method of claim 2 , wherein k represents a value greater than or equal to twenty.
11 . The method of claim 1 , wherein the sequence of different movements further comprises a second sequence of different oscillations in the scanning mirror about a second rotational axis of the one or more rotational axes, wherein the second rotational axis is orthogonal to the first rotational axis.
12 . The method of claim 11 , wherein each movement in the sequence of different movements comprises oscillation about the first rotational axis at a first frequency, and wherein each movement in the sequence of different movements comprises oscillation about the second rotational axis at a second frequency, wherein the second frequency is different from the first frequency.
13 . The method of claim 12 , wherein the first frequency is substantially equivalent to a natural frequency of the scanning mirror.
14 . The method of claim 1 , wherein the illumination source includes one or more laser sources.
15 . The method of claim 1 , wherein identifying, from among the set of multiple different scan patterns, the plurality of scan patterns for the plurality of images of virtual content in the sequence includes selecting, from among the set of multiple different scan patterns, a plurality of scan patterns for the plurality of images of virtual content in the sequence, respectively, in a pseudo-random or quasi-random manner.
16 . An image projection system comprising:
an illumination source configured to emit collimated light;
a scanning mirror configured to receive and reflect light from the illumination source, wherein the scanning mirror includes an actuator controllable to induce movement in the scanning mirror about one or more rotational axes thereof to adjust an orientation of the scanning mirror in accordance with one or more scan patterns;
a viewing assembly comprising one or more optical components configured to receive and redirect light reflected by the scanning mirror to a user; and
control circuitry operatively coupled to the illumination source and the scanning mirror, the control circuitry configured to display a sequence of a plurality of images of virtual content to the user through the viewing assembly by:
identifying, from among a set of multiple different scan patterns, a plurality of scan patterns for the plurality of images of virtual content in the sequence, respectively, including at least one scan pattern for each of the plurality of images of virtual content in the sequence; and
synchronously controlling the illumination source to emit collimated light corresponding to pixels of the plurality of images of virtual content in the sequence, and the actuator of the scanning mirror to induce a sequence of different movements in the scanning mirror about the one or more rotational axes in accordance with the plurality of scan patterns identified for the plurality of images of virtual content in the sequence, respectively, wherein the sequence of different movements comprises a sequence of different oscillations in the scanning mirror about a first rotational axis of the one or more rotational axes, and wherein the different oscillations in the sequence are offset in phase from each other.
17 . The image projection system of claim 16 , wherein the one or more optical components of the viewing assembly include one or more lenses, mirrors, beam splitters, filters, prisms, polarizers, waveguides, diffractive optical elements, windows, or any combination thereof.
18 . The image projection system of claim 16 , wherein the sequence of different movements further comprises a second sequence of different oscillations in the scanning mirror about a second rotational axis of the one or more rotational axes, wherein the second rotational axis is orthogonal to the first rotational axis.
19 . The image projection system of claim 16 , wherein the control circuitry is configured to identify the plurality of scan patterns in a pseudo-random or quasi-random manner for the plurality of images of virtual content in the sequence, respectively.
20 . A computer program product comprising a non-transitory computer readable storage medium including instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising:
identifying, from among a set of multiple different scan patterns, a plurality of scan patterns for a plurality of images of virtual content in a sequence, respectively, including at least one scan pattern for each of the plurality of images of virtual content in the sequence; and
synchronously controlling:
an illumination source of an image projection system to emit collimated light corresponding to pixels of the plurality of images of virtual content in the sequence toward a scanning mirror of the image projection system, wherein the scanning mirror is positioned to receive and reflect light from the illumination source toward a viewing assembly of the image projection system; and
an actuator of the scanning mirror to induce a sequence of different movements in the scanning mirror about one or more rotational axes in accordance with the plurality of scan patterns identified for the plurality of images of virtual content in the sequence, respectively, wherein the sequence of different movements comprises a sequence of different oscillations in the scanning mirror about a first rotational axis of the one or more rotational axes, and wherein the different oscillations in the sequence are offset in phase from each other.