Light scanner and multi-beam generator using the same

{
  "publication_number": "US5574597A",
  "country": "US",
  "kind": "A",
  "title": "Light scanner and multi-beam generator using the same",
  "abstract": "A multi-beam generator has a grating that is provided on a substrate and which is composed of at least three rectangular patterns of unequal width each having only two phase levels. The generator has high efficiency of light utilization, produces multiple beams of uniform intensity from a single laser beam and can be fabricated by a simple process.",
  "claims": [
    "1. A multi-beam generator comprising: a light source; and a grating device which generates at least three beams of light when a beam of light from said light source is irradiated onto said grating device, said grating device comprising: a substrate; and a grating formed on said substrate, said grating comprising a cyclically repeated reference phase pattern comprising a plurality of rectangular regions arranged in a direction along a surface of said substrate, said grating having only two phase levels having optimized phase difference to generate said at least three beams of light; wherein said cyclically repeated reference phase pattern comprises four rectangular regions with two of said rectangular regions, having unequal widths, symmetrically arranged on each side of a center line, each of said four rectangular regions has a width corresponding to one of two parameters h(1) and h(2), h(1) satisfying the following relationship: 126<h(1)/p<0.374, wherein p=a pitch of said reference phase pattern, and wherein an absolute value of a total phase difference, represented as a, introduced by a difference between said two phase levels, satisfies the following relationship: 1.5 radians<|a|<2.5 radians, provided that said difference satisfies the relationship when a value of a is changed by performing one of an addition of multiples of 2π to a, and a subtraction of multiples of 2π from a.",
    "2. A multi-beam generator comprising: a light source; and a grating device which generates at least five beams of light when a beam of light from said light source is irradiated onto said grating device, said grating device comprising: a substrate; and a grating formed on said substrate, said grating comprising a cyclically repeated reference phase pattern, said reference phase pattern comprising a plurality of rectangular regions, said grating having only two phase levels having optimized phase difference to generate said at least five beams of light; wherein said cyclically repeated reference phase pattern comprises six rectangular regions with three of said rectangular regions arranged on each side of a center line, each of said six rectangular regions having a width corresponding to one of three parameters h(1), h(2) and h(3), h(1) and h(2) satisfying the following relationships: 002<h(1)/p<0.047 0.293<h(2)/p<0.361, wherein p=a pitch of said reference phase pattern, and wherein an absolute value of a difference between said two phase levels, represented as a, satisfies the following relationship: 2.235 radians<|a|<4.06 radians, provided that said difference satisfies the relationship when a value of a is changed by performing one of an addition of multiples of 2π to a, and a subtraction of multiples of 2π from a.",
    "3. A multi-beam generator comprising: a light source; and a grating device which generates at least seven beams of light when a beam of light from said light source is irradiated onto said grating device, said grating device comprising: a substrate; and a grating formed on said substrate, said grating comprising a cyclically repeated reference phase pattern comprising a plurality of rectangular regions, said grating having only two phase levels having optimized phase difference to generate said at least seven beams of light; wherein said cyclically repeated reference phase pattern comprises six rectangular regions with three of said rectangular regions arranged on each side of a center line, each of said six rectangular regions having a width corresponding to one of three parameters h(1), h(2) and h(3), h(1) and h(2) satisfying the following relationships: 045<h(1)/p<0.094 0.193<h(2)/p<0.243, wherein p=a pitch of said reference phase pattern, and wherein an absolute value of a, representing the difference between said two phase levels, satisfies the following relationship: 3.55 radians |a|<4.036 radians, provided that said difference satisfies the relationship when a value of a is changed by performing one of an addition of multiples of 2π to a, and a subtraction of multiples of 2π from a.",
    "4. A multi-beam generator comprising: a light source; and a grating device which generates at least seven beams of light when a beam of light from said light source is irradiated onto said grating device, said grating device comprising: a substrate; and a grating formed on said substrate, said grating comprising a cyclically repeated reference phase pattern comprising a plurality of rectangular regions, said grating having only two phase levels having optimized phase difference to generate said at least seven beams of light; wherein said cyclically repeated reference phase pattern comprises eight rectangular regions with four of said rectangular regions arranged on each side of a center line, each of said eight rectangular regions having a width corresponding to one of four parameters h(1), h(2), h(3) and h(4), h(1), h(2) and h(3) satisfying the following relationships: 0.00036<h(1)/p<0.03 0.06<h(2)/p<0.105 0.149<h(3)/p<0.19, wherein p=a pitch of said reference phase pattern, and wherein an absolute value of a, representing the difference between said two phase levels, satisfies the following relationship: 2.45 radians <|a|<3.84 radians, provided that said difference satisfies the relationship when a value of a is changed by performing one of an addition of multiples of 2π to a, and a subtraction of multiples of 2π from a.",
    "5. A multi-beam generator comprising: a light source; and a grating device which generates at least nine beams of light when a beam of light from said light source is irradiated onto said grating device, said grating device comprising: a substrate; and a grating formed on said substrate, said grating comprising a cyclically repeated reference phase pattern, said reference phase pattern comprising a plurality of rectangular regions, said grating having only two phase levels having optimized phase difference to generate said at least nine beams of light; wherein said reference phase pattern comprises eight rectangular regions with four of said rectangular regions arranged on each side of a center line, each of said eight rectangular regions having a width corresponding to one of four parameters h(1), h(2), h(3) and h(4), h(1), h(2) and h(3) satisfying the following relationships: 069<h(1)/p<0.117 0.048<h(2)/p<0.088 0.176<h(3)/p<0.22, wherein p=a pitch of said reference phase pattern, and wherein an absolute value of a, representing the difference between said two phase levels, satisfies the following relationship: 45 radians<|a|<2.9 radians, provided that said difference satisfies the relationship when a value of a is changed by performing one of an addition of multiples of 2π to a, and a subtraction of multiples of 2π from a."
  ],
  "cpc": [
    "G02B 27/106",
    "G02B 27/1086",
    "G02B 5/1871"
  ],
  "assignees": [
    "HITACHI KOKI KK"
  ],
  "filing_date": "1993-05-18",
  "publication_date": "1996-11-12",
  "grant_date": "1996-11-12",
  "priority_date": "1992-05-22",
  "application_number": "US-6255093-A",
  "family_id": "15031340",
  "citations": [
    "DE3117092A1",
    "DE3831743A1",
    "DE4007968A1",
    "US3957354A",
    "US4105289A",
    "US4410237A",
    "US4459690A",
    "US4846552A",
    "US4947413A",
    "US5113286A",
    "US5195103A"
  ]
}