Scanning projection apparatus with tangential compensation
A scanning projector includes a scanning mirror that sweep a beam in two dimensions. Tangential distortion in a fast-scan dimension is compensated by incorporating a tangent function when determining the light beam location and interpolating pixel data. Tangential distortion in a slow-scan dimension is compensated by driving the scanning mirror nonlinearly in the slow scan dimension such that the light beam sweeps across the display surface at a constant rate.
1. An apparatus comprising:
a laser light source;
a mirror being oscillatable on a first axis, the mirror being positioned to reflect light from the laser light source and sweep a light beam sinusoidally through an angle and across a display surface in a first dimension, resulting in tangential distortion in the light beam location on the display surface as a function of time; and
a beam position determination component that determines a location of the light beam on the display surface, wherein the beam position determination component determines the beam location as a function of the sinusoidal sweep as well as the tangential distortion, and wherein the beam position determination component determines the pixel location as:
x
=
HRES
2
tan
(
A
sin
(
ω
t
)
)
tan
(
A
)
+
HRES
2
.
2. An apparatus comprising:
a laser light source;
a mirror being oscillatable on a first axis, the mirror being positioned to reflect light from the laser light source and sweep a light beam sinusoidally through an angle and across a display surface in a first dimension, resulting in tangential distortion in the light beam location on the display surface as a function of time; and
a beam position determination component that determines a location of the light beam on the display surface, wherein the beam position determination component determines the beam location as a function of the sinusoidal sweep as well as the tangential distortion, and wherein the pixel location determination component determines the pixel location as an approximation of:
x
=
HRES
2
tan
(
A
sin
(
ω
t
)
)
tan
(
A
)
+
HRES
2
.
3. The apparatus of claim 2 wherein the pixel location determination component determines the pixel location as a Taylor series approximation.
4. An apparatus comprising:
a laser light source;
a mirror being movable on two axes, the mirror being positioned to reflect light from the laser light source and onto a display surface, to sweep a light beam sinusoidally in a first dimension responsive to mirror movement on a first axis of the two axes, and to sweep the light beam nonsinusoidally in a second dimension responsive to movement on a second axis of the two axes;
a control loop responsive to a position of the mirror on the second axis, the control loop including a feedback circuit to determine harmonic coefficients to drive mirror movement on the second axis to sweep the light beam linearly with time across the display surface in the second dimension; and
a light beam position determination component that determines a location of the light beam in the first dimension on the display surface, wherein the light beam position determination component determines the beam location as a function of the sinusoidal sweep as well as a tangential error resulting from the sinusoidally swept light beam illuminating a flat surface, and wherein the light beam position determination component determines the location of the light beam in the first dimension as:
x
=
HRES
2
tan
(
A
sin
(
ω
t
)
)
tan
(
A
)
+
HRES
2
.
5. An apparatus comprising:
a laser light source;
a mirror being movable on two axes, the mirror being positioned to reflect light from the laser light source and onto a display surface, to sweep a light beam sinusoidally in a first dimension responsive to mirror movement on a first axis of the two axes, and to sweep the light beam nonsinusoidally in a second dimension responsive to movement on a second axis of the two axes;
a control loop responsive to a position of the mirror on the second axis, the control loop including a feedback circuit to determine harmonic coefficients to drive mirror movement on the second axis to sweep the light beam linearly with time across the display surface in the second dimension; and
a light beam position determination component that determines a location of the light beam in the first dimension on the display surface, wherein the light beam position determination component determines the beam location as a function of the sinusoidal sweep as well as a tangential error resulting from the sinusoidally swept light beam illuminating a flat surface, and wherein the light beam position determination component determines the location of the light beam in the first dimension as:
x
=
HRES
2
tan
(
A
)
[
A
sin
(
ω
t
)
+
A
3
sin
3
(
ω
t
)
3
]
+
HRES
2
.
6. A method comprising:
oscillating a mirror on a first axis to sweep a light beam in a first dimension on a display surface resulting in a sinusoidal sweep of the light beam with tangential distortion in the light beam location on the display surface as a function of time;
determining a display pixel location on the display surface as a function of the sinusoidal sweep and the tangential distortion in the first dimension;
interpolating source pixel data to arrive at display pixel data to display at the display pixel location; and
commanding a laser light source to produce light in accordance with the display pixel data, wherein determining a display pixel location is an approximation of:
x
=
HRES
2
tan
(
A
sin
(
ω
t
)
)
tan
(
A
)
+
HRES
2
.