1. An overvoltage protection device comprising:
a doped substrate of a first conductivity type having a first doping level, coated with a doped epitaxial layer of the second conductivity type having a second doping level;
a first doped buried region of the second conductivity type having a third doping level greater than the second level, located at the interface between the substrate and the epitaxial layer in a first portion of the device, wherein the junction between the substrate and the first buried region forms a first diode having its conduction area of the second conductivity type coupled to a first terminal of the device via the epitaxial layer; and
a second doped buried region of the first conductivity type having a fourth doping level greater than the first level, located at the interface between the substrate and the epitaxial layer in a second portion of the device, the junction between the second buried region and the epitaxial layer forms a second diode having its conduction area of the second conductivity type coupled to a second terminal of the device via the epitaxial layer.
2. The device of claim 1, wherein the first and second diodes have their conduction areas of the first conductivity type connected via the substrate.
3. The device of claim 1, wherein the first diode is a diode having a controlled avalanche voltage.
4. The device of claim 1, wherein the second diode is a diode having a controlled avalanche voltage.
5. The device of claim 1, wherein the second diode is a standard diode which is not intended to operate in avalanche.
6. The device of claim 1, wherein the first and second diodes have their conduction areas of the second conductivity type separated by a vertical insulating region crossing the epitaxial layer.
7. The device of claim 1, wherein the second doping level is lower than the first doping level.
8. The device of claim 1, wherein the first doping level is greater than 1018 atomscm3, the second doping level is lower than 1017 atomscm3, the third doping level is greater than 1018 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
9. The device of claim 1, wherein the first doping level is in the range from 1019 to 1021 atomscm3, the second doping level is in the range from 1013 to 1016 atomscm3, the third doping level is in the range from 1019 to 1021 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
10. An overvoltage protection device comprising:
a doped substrate of a first conductivity type having a first doping level, coated with a doped epitaxial layer of the second conductivity type having a second doping level;
a first doped buried region of the second conductivity type having a third doping level greater than the second level, located at the interface between the substrate and the epitaxial layer in a first portion of the device, wherein the junction between the substrate and the first buried region forms a first diode; and
a second doped buried region of the first conductivity type having a fourth doping level greater than the first level, located at the interface between the substrate and the epitaxial layer in a second portion of the device, the junction between the second buried region and the epitaxial layer forms a second diode;
wherein the first diode is a diode having a controlled avalanche voltage.
11. The device of claim 10, wherein the first diode has its conduction area of the second conductivity type coupled to a first terminal of the device via the epitaxial layer, and wherein the second diode has its conduction area of the second conductivity type coupled to a second terminal of the device via the epitaxial layer.
12. The device of claim 10, wherein the second doping level is lower than the first doping level.
13. The device of claim 10, wherein the first doping level is greater than 1018 atomscm3, the second doping level is lower than 1017 atomscm3, the third doping level is greater than 1018 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
14. The device of claim 10, wherein the first doping level is in the range from 1019 to 1021 atomscm3, the second doping level is in the range from 1013 to 1016 atomscm3, the third doping level is in the range from 1019 to 1021 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
15. An overvoltage protection device comprising:
a doped substrate of a first conductivity type having a first doping level, coated with a doped epitaxial layer of the second conductivity type having a second doping level;
a first doped buried region of the second conductivity type having a third doping level greater than the second level, located at the interface between the substrate and the epitaxial layer in a first portion of the device, wherein the junction between the substrate and the first buried region forms a first diode; and
a second doped buried region of the first conductivity type having a fourth doping level greater than the first level, located at the interface between the substrate and the epitaxial layer in a second portion of the device, the junction between the second buried region and the epitaxial layer forms a second diode;
wherein the second diode is a diode having a controlled avalanche voltage.
16. The device of claim 15, wherein the first diode has its conduction area of the second conductivity type coupled to a first terminal of the device via the epitaxial layer, and wherein the second diode has its conduction area of the second conductivity type coupled to a second terminal of the device via the epitaxial layer.
17. The device of claim 15, wherein the second doping level is lower than the first doping level.
18. The device of claim 15, wherein the first doping level is greater than 1018 atomscm3, the second doping level is lower than 1017 atomscm3, the third doping level is greater than 1018 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
19. The device of claim 15, wherein the first doping level is in the range from 1019 to 1021 atomscm3, the second doping level is in the range from 1013 to 1016 atomscm3, the third doping level is in the range from 1019 to 1021 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
20. An overvoltage protection device comprising:
a doped substrate of a first conductivity type having a first doping level, coated with a doped epitaxial layer of the second conductivity type having a second doping level;
a first doped buried region of the second conductivity type having a third doping level greater than the second level, located at the interface between the substrate and the epitaxial layer in a first portion of the device, wherein the junction between the substrate and the first buried region forms a first diode; and
a second doped buried region of the first conductivity type having a fourth doping level greater than the first level, located at the interface between the substrate and the epitaxial layer in a second portion of the device, the junction between the second buried region and the epitaxial layer forms a second diode;
wherein the first and second diodes have their conduction areas of the second conductivity type separated by a vertical insulating region crossing the epitaxial layer.
21. The device of claim 20, wherein the first diode has its conduction area of the second conductivity type coupled to a first terminal of the device via the epitaxial layer, and wherein the second diode has its conduction area of the second conductivity type coupled to a second terminal of the device via the epitaxial layer.
22. The device of claim 20, wherein the second doping level is lower than the first doping level.
23. The device of claim 20, wherein the first doping level is greater than 1018 atomscm3, the second doping level is lower than 1017 atomscm3, the third doping level is greater than 1018 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
24. The device of claim 20, wherein the first doping level is in the range from 1019 to 1021 atomscm3, the second doping level is in the range from 1013 to 1016 atomscm3, the third doping level is in the range from 1019 to 1021 atomscm3, and the fourth doping level is from 2 to 10 times the first doping level.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An image pick-up lens system comprising, from an object side to an image side:
an aperture stop;
a biconvex first lens;
a second lens having a concave surface facing the object side; and
a third lens having a concave surface facing the image side;
wherein the aperture stop and the first, second and third lenses are aligned in that order, the first, second and third lenses are made from essentially the same material, at least one of the first, second and third lenses has a diffraction grating formed thereon, and the following condition is satisfied:
\u22129<f3f<\u22121.7,
wherein f3 is a focal length of the third lens, and f is a focal length of the lens system.
2. The image pick-up lens system in accordance with claim 1, wherein the second lens is a meniscus-shaped lens.
3. The image pick-up lens system in accordance with claim 1, wherein the third lens is a meniscus-shaped lens.
4. The image pick-up lens system in accordance with claim 1, wherein the first lens and the second lens have positive focal power, and the third lens has negative focal power.
5. The image pick-up lens system in accordance with claim 1, wherein the first lens has a diffraction grating formed on a convex surface thereof that faces the image side.
6. The image pick-up lens system in accordance with claim 5, wherein the following condition is also satisfied:
\u2212470<C2\xd7(f1Rn2)<\u2212280,
wherein, C2 is a power phase coefficient of a phase function of the diffraction grating surface of the first lens, and Rn is a normalization radius of the diffraction grating.
7. The image pick-up lens system in accordance with claim 1, wherein the following condition is also satisfied:
1.4<Tf<1.8,
wherein T is a length from the aperture stop to an image pick-up surface.
8. The image pick-up lens system in accordance with claim 1, wherein the following condition is also satisfied:
0.7<f1f<1.2,
wherein, f1 is a focal length of the first lens.
9. The image pick-up lens system in accordance with claim 1, wherein the following condition is also satisfied:
\u22120.6<R4f\xd7(n\u22121)<\u22120.3,
wherein, R4 is a radius of curvature of a surface of the second lens that faces the object side, n is a refractive index of the second lens, and R4f\xd7(n\u22121) is a ratio of a focal length of a surface of the second lens that faces the object side to a total focal length of the lens system.
10. The image pick-up lens system in accordance with claim 1, wherein at least one of the first, second and third lenses has an aspheric surface.
11. The image pick-up lens system in accordance with claim 10, wherein each of the first, second and third lenses has at least one aspheric surface.
12. The image pick-up lens system in accordance with claim 10, wherein opposite surfaces of each of the second and third lenses are aspheric.
13. The image pick-up lens system in accordance with claim 1, wherein the first, second and third lenses are made from essentially the same plastic.
14. The image pick-up lens system in accordance with claim 13, wherein the first and second lenses are made from one of a polyolefin resin and a cyclo-olefin polymer material.
15. An image pick-up system comprising:
an aperture stop for receiving light from an outside of said system;
an image pick-up surface used to accept said light from said aperture stop for image generation of said system; and
at least three lenses disposed between said aperture stop and said image pick-up surface for transmitting said light therebetween, and made of same material, at least one surface of a selective lens of said at least three lenses forming a diffraction grating;
wherein said at least three lenses are made to satisfy at least one of the following conditions:
1.4<Tf<1.8,\u2003\u2003(1)
0.7<f1f<1.2,\u2003\u2003(2)
\u22129<f3f<\u22121.7,\u2003\u2003(3)
\u22120.6<R4f\xd7(n\u22121)<\u22120.3, and\u2003\u2003(4)
\u2212470<C2\xd7(f1Rn2)<\u2212280\u2003\u2003(5)
wherein f is a focal length of said system, T is a length from said aperture stop to said image pick-up surface, f1 is a focal length of a first lens of said at least three lenses closer to said aperture stop, f3 is a focal length of a third lens of said at least three lenses closer to said image pick-up surface, R4 is a radius of curvature of a surface of a second lens of said at least three lenses facing said aperture stop, n is a refractive index of said second lens, R4f\xd7(n\u22121) is a ratio of a focal length of said surface of said second lens facing said aperture stop to said focal length of said system, C2 is a power phase coefficient of a phase function of said diffraction grating, and Rn is a normalization radius of said diffraction grating.
16. The image pick-up system in accordance with claim 15, wherein said at least three lenses are made of same plastic material.
17. An image pick-up system comprising, from an object side to an image side:
an aperture stop;
a biconvex first lens;
a second lens having a concave surface facing the object side; and
a third lens having a concave surface facing the image side;
wherein the aperture stop and the first, second and third lenses are aligned in that order, the first, second and third lenses are made from essentially the same material, the first lens has a diffraction grating formed on a convex surface thereof that faces the image side, and the following condition is satisfied:
\u2212470<C2\xd7(f1Rn2)<\u2212280,
wherein, f1 is a focal length of the first lens, C2 is a power phase coefficient of a phase function of the diffraction grating, and Rn is a normalization radius of the diffraction grating.
18. The image pick-up system in accordance with claim 17, wherein the following condition is also satisfied:
\u22129<f3f<\u22121.7,
wherein f2 is a focal length of the third lens, and f is a focal length of the lens system.