Optical lens and optical information recording and reproducing apparatus equipped therewith

• US 6,813,096 B2
• Filed: 11/08/2002
• Issued: 11/02/2004
• Est. Priority Date: 11/15/2001
• Status: Expired due to Fees

• Current Assignee: Konica Corporation (Konica Minolta Inc.)
• Original Assignee: Konica Corporation (Konica Minolta Inc.)
• Inventors: Ohta, Tatsuo
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Harrington, Alicia M
• Application Number:
  US10/290,347
• Publication Number:
  US 20030103271A1
• Time in Patent Office: 725 Days
• Field of Search: 359/637, 359/641, 359/718, 359/719, 359/738, 359/796, 359/722, 359/727, 369/112.01, 369/112.08, 369/112.21, 369/112.23, 369/112.26, 369/44.23, 369/44.32, 369/116
• US Class Current: 359/719
• CPC Class Codes: G02B 1/11 Anti-reflection coatings
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 3/02 with non-spherical faces G02B3/10 takes precedence

Abstract

In an optical lens for use in an optical information recording and reproducing apparatus conducting at least one of recording information on an optical recording medium and reproducing of information recorded on the optical recording medium, by converging light on the optical recording medium, the optical lens includes: lens surfaces provided on both sides of the optical lens; and an antireflection coating provided on the lens surface on at least one side thereof. Thickness of the antireflection coating on a peripheral portion of the lens surface is greater than that of the antireflection coating provided on a center portion of the lens surface.

Claims

1. An optical lens for use in an optical information recording and reproducing apparatus, the optical lens comprising:

(a) at least one lens surface provided on at least one side of the optical lens; and

(b) an antireflection coating provided on the at least one lens surface wherein a thickness of the antireflection coating on a peripheral portion of the lens surface on which an angle θ

is 45°

or more is equal to or greater than a thickness of the antireflection coating provided on a center portion of the lens surface on which the angle θ

is 0°

, wherein an angle formed by a normal line at a certain position on the lens surface where the antireflection coating is provided and by an optical axis is represented by θ

.

2. The optical lens of claim 1, wherein the thickness of the antireflection coating is established so that a wavelength wherein reflectance for light entering at an angle of 0°

for the antireflection coating on the peripheral portion of the lens surface shows the minimum value is equal to or greater than a wavelength wherein reflectance for light entering at the angle of 0°

for the antireflection coating on the center portion of the lens surface shows the minimum value.

3. The optical lens of claim 1, wherein the thickness of the antireflection coating is established so that a wavelength wherein reflectance for light entering the antireflection coating on at least a part of the peripheral portion of the lens surface at an angle of 0°

shows the minimum value is the same as a wavelength wherein reflectance for light entering the antireflection coating on the center portion of the lens surface at the angle of 0°

shows the minimum value.

4. The optical lens of claim 1,

wherein in the case that the optical lens converges light emitted from a laser light source having at least one kind of wavelength in a wavelength range of 630-680 nm on the optical recording medium,

an antireflection coating is provided on the lens surface on the side where the light emitted from the laser light source enters, and thickness of the antireflection coating is established so that reflectance for light entering, at an angle of 0° , the peripheral portion of the lens surface where an angle θ

is 45°

or more shows the minimum value within a range of 630-800 nm, when the angle θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where light emitted from the laser light source enters and by an optical axis.

5. The optical lens of claim 4, wherein the thickness of the antireflection coating provided on the lens surface on the side where the light emitted from the laser light source enters is established so that reflectance for light entering, at the angle of 0°

, the center portion of the lens surface having the angle θ

of 0°

shows the minimum value within a wavelength range of 580-740 nm.

6. The optical lens of claim 4, wherein an antireflection coating is provided on the lens surface on the side from which the light emerges to the optical recording medium, and thickness of the antireflection coating is established so that reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 630-800 nm, when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side from which the light emerges and by an optical axis.

7. The optical lens of claim 4, wherein the laser light source has at least one kind of wavelength in a wavelength range of 630-650 nm,

wherein the optical lens converges light emitted from the laser light source on the optical recording medium, and

wherein an antireflection coating is provided on the lens surface on the side where light emitted from the laser light source enters, and thickness of the antireflection coating is established so that reflectance for light entering, at an angle of 0°

, the peripheral portion of the lens surface where an angle θ

is 45°

or more shows the minimum value within a range of 660-770 nm, and the reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 600-700 nm when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where light emitted from the laser light source enters and by an optical axis, and an antireflection coating is provided on the lens surface on the side from which the light emerges, and thickness of the antireflection coating is established so that the reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 640-740 nm.

8. The optical lens of claim 7, wherein the antireflection coating is provided on the lens surface on the side where the light emitted from the laser light source enters, and the thickness of the antireflection coating is established so that the reflectance for light entering, at the angle of 0°

, the peripheral portion of the lens surface where the angle θ

is 50°

or more shows the minimum value within a range of 670-770 nm when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where the light emitted from the laser light source enters and by an optical axis.

9. The optical lens of claim 4, wherein the laser light source has at least one kind of wavelength in a wavelength range of 650-670 nm,

wherein the optical lens converges light emitted from the laser light source on the optical recording medium, and

wherein an antireflection coating is provided on the lens surface on a side where light emitted from the laser light source enters, and thickness of the antireflection coating is established so that reflectance for light entering, at an angle of ₀°

, the peripheral portion of the lens surface where an angle θ

is 45°

or more shows the minimum value within a range of 660-800 nm, and reflectance for light entering, at the angle of 0 °

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 610-740 nm, when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where light emitted from the laser light source enters and by an optical axis, and an antireflection coating is provided on the lens surface on the side from which the light emerges, and thickness of the antireflection coating is established so that reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 660-740 nm.

10. The optical lens of claim 9, wherein the antireflection coating is provided on the lens surface on the side where the light emitted from the laser light source enters, and the thickness of the antireflection coating is established so that the reflectance for light entering, at the angle of 0°

, the peripheral portion of the lens surface where the angle θ

is 50°

or more shows the minimum value within a range of 700-800 nm, when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where the light emitted from the laser light source enters and by an optical axis.

11. The optical lens of claim 1,

wherein in the case that the optical lens converges light emitted from a laser light source having at least one kind of wavelength in a wavelength range of 400-450 nm on the optical recording medium,

an antireflection coating is provided on the lens surface on the side where the light emitted from the laser light source enters, and thickness of the antireflection coating is established so that reflectance for light entering, at an angle of 0°

, the peripheral portion of the lens surface where an angle θ

is 45°

or more shows the minimum value within a range of 420-520 nm, when the angle θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where light emitted from the laser light source enters and by an optical axis.

12. The optical lens of claim 11, wherein the thickness of the antireflection coating provided on the lens surface on the side where the light emitted from the laser light source enters is established so that reflectance for light entering, at the angle of 0°

, the center portion of the lens surface having the angle θ

of 0°

shows the minimum value within a wavelength range of 380-490 nm.

13. The optical lens of claim 11, wherein an antireflection coating is provided on the lens surface on the side from which the light emerges to the optical recording medium, and thickness of the antireflection coating is established so that reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 400-490 nm, when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side from which the light emerges and by an optical axis.

14. The optical lens of claim 11, wherein the laser light source has at least one kind of wavelength in a wavelength range of 400-420 nm,

wherein the optical lens converges light emitted from the laser light source on the optical recording medium, and

wherein an antireflection coating is provided on the lens surface on the side where light emitted from the laser light source enters, and thickness of the antireflection coating is established so that reflectance for light entering, at an angle of 0°

, the peripheral portion of the lens surface where an angle θ

is 45°

or more shows the minimum value within a range of 420-490 nm, and the reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 380-440 nm, when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where light emitted from the laser light source enters and by an optical axis, and an antireflection coating is provided on the lens surface on the side from which the light emerges, and thickness of the antireflection coating is established so that the reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 400-490 nm.

15. The optical lens of claim 14, wherein an antireflection coating is provided on the lens surface on the side where the light emitted from the laser light source enters, and the thickness of the antireflection coating is established so that the reflectance for light entering, at the angle of 0°

, the peripheral portion of the lens surface where the angle θ

is 50°

or more shows the minimum value within a range of 430-490 nm, when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where the light emitted from the laser light source enters and by an optical axis.

16. The optical lens of claim 1, wherein thickness of the antireflection coating on the peripheral portion of the lens surface is (1-1.5) times that of the antireflection coating on the center portion of the lens surface.

17. An optical information recording and reproducing apparatus comprising:

(a) a laser light source; and

(b) the optical lens of claim 1,

wherein the optical information recording and reproducing apparatus conducts at least one of recording information on the optical recording medium and reproducing information recorded on the optical recording medium, by converging light emitted from the laser light source on the optical recording medium with the optical lens.

18. The optical lens of claim 1, wherein in case that the optical lens converges light emitted from a laser light source having at least one kind of wavelength in a wavelength range of 630-680 nm on the optical recording medium, an antireflection coating is provided on the lens surface on the side where light emitted from the laser light source enters, and thickness of the antireflection coating is established so that reflectance for light entering, at an angle of 0°

, the peripheral portion of the lens surface where an angle θ

is 45°

or more shows the minimum value within a range of 630-800 nm and the reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 580-740 nm when θ

represents an angle formed by a normal line at a certain position on the lens surface on the side where light emitted from the laser light source enters and by an optical axis, and an antireflection coating is provided on the lens surface on the side from which the light emerges, and thickness of the antireflection coating is established so that the reflectance for light entering, at the angle of 0°

, the center portion of the lens surface where the angle θ

is 0°

shows the minimum value within a range of 630-800 nm.