Optical system device
An optical device is provided which does not need a collimate lens, and which has a high available efficiency of light. The optical device includes a light source unit 1 emitting light with a wavelength λ, and an optical element 2 with a concavo-convex structure including periodical lenses. When n is a natural number equal to or greater than 1, and the size of a k-th (where k is a natural number equal to or greater than 1) pitch from the smallest one among the pitches of the concavo-convex structure is P k , a distance L 1 between the light source unit and the optical element satisfies the following formula 1 for equal to or greater than any one pitch P k . ( n - 0 . 1 ) P k 2 2 λ ≦ L 1 ≦ ( n + 0 . 1 ) P k 2 2 λ ( 1 )
1 . An optical device comprising:
an optical element comprising a plurality of lenses arranged periodically, the lenses allowing light with a wavelength λ to pass therethrough; and
an emitting unit comprising a light source that emits the light with the wavelength λ to the plurality of lenses,
wherein when n is a natural number that is equal to or greater than 1, and a size of a k-th (where k is a natural number that is equal to or greater than 1) pitch from a smallest pitch among pitches of the lenses is P k , a distance L 1 between the emitting unit and the optical element satisfies a following equation 1 for equal to or greater than the any one pitch P k ,
wherein the lenses are aspheric lenses in which boundaries between the lenses are square, rectangular, or hexagonal in a plan view, and
wherein a normal line overlapping rate of a surface of a lens is equal to or smaller than 10%.
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2 . The optical device according to claim 1 , further comprising an aperture mask which is provided with an opening and which blocks some of noise lights that increases an overlapping rate of transmitted lights from the lenses.
3 . The optical device according to claim 2 , wherein the aperture mask has the opening located at a portion including at least an optical axis of the lens.
4 . The optical device according to claim 2 , wherein the aperture mask is placed at an optical path of noise light of the lens.
5 . The optical device according to claim 2 , wherein the aperture mask is placed at a boundary portion between the lenses.
6 . The optical device according to claim 2 , wherein the aperture mask blocks the light emitted to a boundary portion between the lenses.
7 . The optical device according to claim 2 , wherein the aperture mask is formed so as to be integrated with the optical element.
8 . The optical device according to claim 1 , wherein the optical element comprises a light diffusion portion which is formed at a boundary portion between the lenses and which refracts transmitted light to an external side of an emitting angle of the lens.
9 . The optical device according to claim 1 , satisfying the equation 1 for a smallest pitch P 1 and also satisfying the equation 1 for a second smallest pitch P 2 .
10 . The optical device according to claim 1 , further comprising a mirror that reflects the light from the emitting unit.
11 . The optical device according to claim 1 , comprising a plurality of the emitting units.
12 . The optical device according to claim 11 , wherein the emitting units comprise:
a first emitting unit comprising a plurality of light sources each of which emit light with a wavelength λ and which are arranged regularly; and
a second emitting unit comprising a plurality of light sources each of which emit light with a wavelength λ and which are arranged regularly so as to be shifted half period by half period in a vertical direction and in a horizontal direction relative to the plurality of light sources of the first emitting unit.
13 . The optical device according to claim 11 , wherein:
the emitting units comprise a first emitting unit, a second emitting unit and a third emitting unit each comprising a plurality of light sources each of which emit light with a wavelength λ and which are arranged regularly; and
relative to a direction in which the lenses of the optical elements have the pitch P k , the respective light sources of the first emitting unit, the second emitting unit and the third emitting unit are arranged so as to be shifted P k /3 by P k /3.
14 . The optical device according to claim 11 , wherein the respective emitting units are caused to emit the light in sequence at different times.
15 . The optical device according to claim 1 , wherein:
a planar shape of the lens is a square shape or a rectangular shape having any one of sides with a length R; and
regarding the arrangement of the lenses, when i is a natural number that is equal to or greater than 1, respective rows of the lenses continuous in a direction along the side are arranged so as to be shifted R/i by R/i.
16 . The optical device according to claim 9 , wherein when m is a natural number that is equal to or greater than 1, the emitting unit has a plurality of the light sources arranged in a hexatic manner at a pitch of mP 1 or P 1 /m; and
a planar shape of the lens of the optical element is a rectangular shape with a ratio between a short side and a long side that is P 1 :P 2 =1:√3.
17 . The optical device according to claim 16 , wherein: the distance L 1 between the emitting unit and the optical element is 3P 1 2 /2λ or multiples of 3P 1 2 /2λ.
18 . The optical device according to claim 1 , wherein the overlapping rate is determined by a method comprising:
(1) defining a plane perpendicular to an optical axis of the lens as an x-y plane; dividing the lens into n square fine regions on the x-y plane; and assigning non-duplicated numbers from 1 to n to the respective fine regions, wherein a length of one side of each fine region is equal to or less than one-quarter (λ/4) of a wavelength of light emitted from the emitting unit;
(2) defining a center point of an i-th fine region (i=1, 2, . . . , n) among the divided fine regions as Pi, and an inscribed circle thereof as Ci; and defining a group of center points of fine regions other than the i-th fine region as Qi;
(3) defining a normal vector Npi as a normal of the lens surface at an intersection between a line passing through Pi and perpendicular to the x-y plane and the lens surface, and defining a group of normal vectors Nci as normals of the lens surface at intersections between lines passing through Ci and perpendicular to the x-y plane and the lens surface; and defining a minimum value of an angle between Npi and Nci as δθi;
(4) defining a group of normal vectors Nqi at intersections between lines passing through the point group Qi and perpendicular to the x-y plane and the lens surface, wherein each normal vector in the group corresponds to a normal of the lens surface at the respective intersection;
(5) defining a state flag of the i-th fine region as Fi, and setting an initial value of Fi to 0;
(6) calculating, for all i=1, 2, . . . , n, an angle θi between the normal vector Npi and the vector group Nqi, and setting Fi to 1 when θi is equal to or less than δθi; and
(7) determining the normal line overlapping rate as (m/n)×100(%), where m is the number of Fi having a value of 1.
19 . The optical device according to claim 1 , wherein a line in a cross-section of a lens surface is free of any inflection point.