Light intensity converter

• US 6,201,229 B1
• Filed: 08/04/1998
• Issued: 03/13/2001
• Est. Priority Date: 03/09/1998
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Hasegawa, Shinya, Tawa, Fumihiro
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US09/128,656
• Time in Patent Office: 952 Days
• Field of Search: 250/214.1, 250/216, 250/205, 250/201.5, 359/708, 359/718, 359/719, 369/44.12, 369/44.14, 369/112, 369/44.11, 369/44.24, 369/44.23
• US Class Current: 250/201.5
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/06 Shaping the laser beam, e.g. by masks or multi-focusing
• CPC Class Codes: B23K 26/064 by means of optical elements, e.g. lenses, mirrors or prisms
• CPC Class Codes: B23K 26/0648 comprising lenses
• CPC Class Codes: B23K 26/0665 by beam condensation on the workpiece, e.g. for focusing
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 27/09 Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for adapting the beam shape of a laser diode G02B19/0052; adapting the beam shape of an LED G02B19/0061; coupling into light guides using intermediate optical elements G02B6/4204; beam shaping specially adapted for lasers H01S3/005
• CPC Class Codes: G11B 7/1378 Separate aberration correction lenses; Cylindrical lenses to generate astigmatism; Beam expanders
• CPC Class Codes: G11B 7/1381 Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops G11B7/1353 - G11B7/1369 take precedence
• CPC Class Codes: G11B 7/1398 Means for shaping the cross-section of the beam, e.g. into circular or elliptical cross-section

Abstract

The light intensity converter comprises a transparent body including opposite first and second curved surfaces. The body is surrounded by an outer peripheral surface extending between the first and second curved surfaces. The body of the converter is arranged such that the incident light is made incident to the body at the first curved surface and emerges from the second curved surface. The incident light diverges in a certain area and converges in another area, by refraction, so that the light intensity distribution of the incident, first curved surface is converted into a different light intensity distribution while the light travels through the converter, and thus exits from the second curved surface.

Claims

1. A light intensity converter comprising:

a body including a first curved surface extending transversely of a center axis, a second curved surface extending transversely of said center axis, and an outer peripheral surface extending between said first curved surface and said second curved surface; and

wherein said body is constructed such that a light having first light intensity distribution is made incident to said body at said first curved surface, the incident light diverges in a first area in said body and converges in a second area in said body, by refraction, when the light enters said body from said first curved surface, and the light emerges from said body at said second curved surface, the emerging light having a second light intensity distribution different from said first light intensity distribution, wherein said first light intensity distribution is a Gaussian distribution, and said second light intensity distribution is a uniform distribution.

2. A light intensity converter according to claim 1, characterized in that the incident light entering said body at said first curved surface diverges in the central area around said center axis in said body and converges in the peripheral area in said body.

3. A light intensity converter according to claim 1, characterized in that, in said first and second curved surfaces, the amount of inclination in the outermost peripheral portion and the amount of inclination at a point where the inclination changes from ascending to descending or descending to ascending have opposite signs and substantially the same absolute values.

4. A light intensity converter according to claim 1, characterized in that said body has such a thickness that the RMS value of the wavefront aberration of the emerging light with respect to the incident light is not more than 0.07 λ

.

5. A light intensity converter according to claim 1, characterized in that, regarding the light passing through a minute area of said body, the incident angle is substantially the same as the emerging angle.

6. A light intensity converter according to claim 1, characterized in that the shapes of the first and second curved surfaces of said body are determined in the following manner, where a light ray is made incident to the body at an incident point (A) with a first distance (r₁) from the optical axis and emerges from body at an exit point (B), with the second distance (r₂) from the optical axis:

the second distance (r₂) is determined by dividing the amount P₁ of the light existing in the range from the optical axis to said first distance (r₁) by the intensity I which is obtained by dividing the total amount of the incident light by a predetermined area of the emerging light;

the linear distance between the incident point (A) and the exit point (B) is hypothetically given thereby to determine the direction of deflection of the light ray passing through the incident point (A);

the inclinations of the planes passing through the incident point (A) and the exit point (B) are determined according to the law of refraction;

the inclinations of the planes passing through the incident point (A) and the exit point (B) thus determined are integrated by the radial distance from said center axis thereby to determine the curved surfaces on the incident and exit sides;

the curved surface on the exit side is determined from the curved surface on the incident side, the direction of deflection at each arbitrary distance (r₁) and the hypothetically-determined distance (L);

the distance (L) associated with each arbitrary distance (r₁) is changed in such a manner that the curved surface on the exit side determined by integration coincides with the curved surface on the exit side determined from the incident surface; and

the inclinations of the incident and exit surfaces are determined repeatedly so as to converge the distance (L).

9. A light intensity converter according to claim 1, characterized in that an incident aperture (w1) of the incident light is greater than an exit aperture (w2) of the emerging light.

10. A light intensity converter according to claim 1, characterized in that said first curved surface has an annular protrusion (P) about the center axis, and concentric depressions inside and outside the annular protrusion, so that an incident aperture (w1) of the incident light is greater than an exit aperture (w2) of the emerging light.

7. An optical disk drive comprising a light source, a collimating lens, a light intensity converter and an object lens;

said light intensity converter including a body having a center axis, a first curved surface extending transversely of said center axis, a second curved axis extending transversely of said center axis, and an outer peripheral surface extending between said first curved surface and said second curved surface, and wherein said body is constructed such that a light having first light intensity distribution is made incident to said body at said first curved surface, the incident light diverges in a first area in said body and converges in a second area in said body, by refraction when the light enters said body from said first curved surface, and the light emerges from said body at said second curved surface, the emerging light having a second light intensity distribution different from said first light intensity distribution; and

said collimating lens and said light intensity converter are integrated with each other to thereby compensate for focussing of the light irrespective of the deviation of the movable object lens from the optical axis.

8. An optical disk drive comprising a light source, a collimating lens, a light intensity converter, a beam splitter and an object lens, said light intensity converter including a body having a center axis, a first curved surface extending transversely of said center axis, a second curved axis extending transversely of said center axis, and an outer peripheral surface extending between said first curved surface and second curved surface, and wherein said body is constructed such that a light having first light intensity distribution is made incident to said body at said first curved surface, the incident light diverges in a first area in said body and converges in a second area in said body, by refraction when the light enters said body from said first curved surface, and the light emerges from said body at said second curved surface, the emerging light having a second light intensity distribution different from said first light intensity distribution;

and

said light intensity converter being arranged between said beam splitter and said collimating lens.

11. An optical device comprising:

a light source; and

a light intensity converter comprising;

a body including a first curved surface extending tranversely of a center axis, a second curved surface extending transversely of said center axis, and an outer peripheral surface extending between said first curved and surface and said second curved surface; and

wherein said body is constructed such that a light having first light intensity distribution is made incident to said body at said first curved surface, the incident light diverges in a first area in said body and converges in a second area in said body, by refraction, when the light emerges from said body at said second curved surface, the emerging light having a second light intensity distribution, wherein said first light intensity distribution is a Gaussian distribution, and said second light intensity distribution is a uniform distribution.

12. A light intensity converter comprising:

a body including a first curved surface extending transversely of a center axis, a second curved surface extending transversely of said center axis, and an outer peripheral surface extending between said first curved surface and said second curved surface; and

wherein said body is constructed such that a light is made incident to said body at said first curved surface, said first curved surface has an annular protrusion at a peripheral region and concentric depressions inside and outside the annular protrusion so that the incident light diverges in a central area in said body and converges in a peripheral area in said body, by refraction.

13. An optical device comprising:

a light source; and

a light intensity converter comprising;

a body including a first curved surface extending tranversely of a center axis, extending between said first curved surface and said second curved surface; and

wherein said body is constructed such that a light is made incident to said body at said first curved surface, said first curved surface has an annular protrusion at a peripheral region and concentric depressions inside and outside the annular protrusion so that the incident light diverges in a central area in said body and converges in a peripheral area in said body, by refraction.

14. An optical disk drive comprising a light source, a collimating lens, a light intensity converter, and an object lens:

said light intensity converter comprising;

a body including a first curved surface extending transversely of a center axis, a second curved surface extending transversely of said center axis, and an outer peripheral surface extending between said first curved surface and said second curved surface; and

wherein said body is constructed such that a light is made incident to said body at said first curved surface, said first curved surface has an annular protrusion at a peripheral region and concentric depressions inside and outside the annular protrusion so that the incident light diverges in a central area in said body and converges in a peripheral area in said body, by refraction.