Patent ID: 11940624
Assignee: BLUE OPTECH CO., LTD.
Field: Optics (Instruments)
Classification: CPC G | IPC F  G

Claim 4:
5. The optical device claimed in claim 1, in which:
the incidence angle of the center image light on the main surface is θ1,, a reflection characteristic boundary angle of half mirror is θ2,, a half angle of the image light angle is θ3, and, the refractive index of the light guide is N,, then, following formulae are satisfied:

{(θ1+(½)θ1)+θ3−θ2}÷(2×θ3)  (1)

[(2×θ3)−{(θ1+θ3)−arcsin(1/N)}]÷(2×θ3)  (2)

(1)=(2), that is:

(3/2)θ1+θ3−θ2=−θ1+θ3+arcsin(1/N)  (3)

so that:

(5/2)θ1−θ2−arcsin(1/N)=0  (4), wherein:
the center image light is the image light that passed through the center line of the angle of view of the image light, and that corresponds to the center of the display image;
the reflection characteristic boundary angle θ2 is a boundary angle at which a rate at which the image light reflected on the back surface of each of the plurality of half mirrors increases;
the formula (1) indicates an angle ratio of the other side image light angle {(θ1+(½)θ1)+θ3−θ2} to the image light angle (2×θ3), and the other side image light angle {(θ1+(½)θ1)+θ3−θ2} is an angle of view that a part of image light of the one side image light side to be reflected on the back surface;
the formula (2) indicates an angle ratio of the one side image light angle [(2×θ3)— {(θ1+θ3)−arcsin(1/N)}] to the image light angle (2×θ3), and the one side image light angle [(2×θ3)−{(θ1+θ3)−arcsin(1/N)}] is an angle of view that a part of the image light on the one side image light not to be totally reflected on the main surface;
the formula (3) is an equation in which the angle ratio of the formula (1) and the angle ratio of the formula (2) are connected by equality; and
the formula (4) is an arrangement of the formula (3).