US Patent No. 9,332,236

IMAGE PROJECTION APPARATUS AND METHOD OF CONTROLLING LIGHT SOURCE


Patent No. 9,332,236
Issue Date May 03, 2016
Title Image Projection Apparatus And Method Of Controlling Light Source
Inventorship Nobuhide Fujioka, Tokyo (JP)
Assignee NEC DISPLAY SOLUTIONS, LTD., Tokyo (JP)

Claim of US Patent No. 9,332,236

1. An image projection apparatus comprising:
light sources provided for each of a plurality of colors to emit a laser beam in each color;
a synthesis element that synthesizes laser beams in each color emitted by said light sources for each color;
an optical modulation element that modulates synthesized light resulting from the synthesis by said syntheses element according
to an image signal;

a projection lens that projects the synthesized light modulated by said optical modulation element; and
a controller that, upon receiving the image signal, determines rate of power of the laser beams in each color emitted by said
light sources for each color, according to the image signal, determines, according to the rate of the power, an upper limit
value of the power of the projected laser beam in each color to the extent that the upper limit value satisfies a safety standard
for the laser beam, and adjusts the laser beam in each color emitted by said corresponding light source so as to prevent the
projected light beam in each color projected by said projection lens from exceeding the upper limit value,

wherein said controller uses the rate of the power of the laser beam in each color and the upper limit value to calculate
a turn-on time for the laser beam within a predetermined period, divided the power of the laser beam by the turn-on time for
the laser beam to calculate a lighting intensity of the laser beam, and controls said corresponding light source in such a
manner that said light source emits a laser beam of the lighting intensity for the turn-on time within the predetermined period.