1. An optical disc drive comprising:
a light source including a redinfrared unit and a blue LD, the redinfrared unit being configured to generate both a red beam and an infrared beam, the blue LD being configured to generate a blue beam;
an objective optical system for condensing light from the light source onto a recording surface of an optical disc, the objective optical system including a first and a second object lenses having different focal distances and arranged side by side in a circumferential direction of the disc;
a chassis that is movable radially of the optical disc and supports both the light source and the objective optical system;
an erecting optical system disposed farther away from the optical disc than the objective optical system for causing two beams propagating circumferentially of the disc in opposite directions to be directed toward the first and the second object lenses, respectively;
a first optical path provided between the redinfrared unit and the first object lens, the first optical path including a first section extending circumferentially of the disc to the erecting optical system and a second section extending from the erecting optical system to the first object lens; and
a second optical path provided between the blue LD and the second object lens, the second optical path including a third section extending, in an opposite direction to the first section of the first optical path, to the erecting optical system and a fourth section extending from the erecting optical system to the second object lens.
2. The optical disc drive according to claim 1, wherein the second optical path further includes a fifth section and a sixth section, the fifth section extending in parallel to the third section, the sixth section connecting the third section and the fifth section to each other.
3. The optical disc drive according to claim 1, further comprising a collimating lens that is disposed on the third section of the second optical path and movable circumferentially of the disc.
4. The optical disc drive according to claim 1, further comprising a beam splitter and a light detecting element for the second optical path, wherein the beam splitter causes part of reflected light propagating along the second optical path after reflection by the optical disc to be directed toward the optical disc, the optical detecting element being configured to detect the part of reflected light directed toward the optical disc.
5. The optical disc drive according to claim 4, further comprising an astigmatism generating element disposed between the beam splitter and the light detecting element, wherein the astigmatism generating element is arranged so that an axis of astigmatism makes an angle of substantially 45 degrees with respect to a circumferential direction represented by a reflection pattern resulting from a mid-radius region of the disc, wherein a parting line of the light detecting element substantially coincides with the circumferential direction represented by the reflection pattern.
6. The optical disc drive according to claim 1, wherein the first object lens, in comparison with the second object lens, is closer to a radius of the optical disc drawn from a rotation center of the disc and extending in a direction of chassis movement.
7. The optical disc drive according to claim 1, wherein the first object lens is on a radius of the optical disc drawn from a rotation center of the disc and extending in a direction of chassis movement, the second object lens being offset from the radius.
8. The optical disc drive according to claim 6, wherein the second object lens has a shorter focal distance than a focal distance of the first object lens.
9. The optical disc drive according to claim 1, wherein the erecting optical system is a mirror including a first reflection surface and a second reflection surface, the first reflection surface being configured to cause light traveling along the first optical path to be directed toward the first object lens, the second reflection surface being configured to cause light traveling along the second optical path to be directed toward the second object lens.
10. The optical disc drive according to claim 1, further comprising a vibration-reducing damper spaced away from the chassis in a radially outward direction of the optical disc.
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 electro-chemical fuel cell stack, the stack comprising:
a plurality of fuel cells arranged in a stacked configuration to form a fuel cell assembly, said fuel cell assembly having opposite first and second ends with a length therebetween, said first and second ends corresponding to major planar surfaces of said fuel cell assembly;
first and second end plates, said first and second end plates being disposed respectively on said first and second ends of said fuel cell assembly with a major surface of each of said first and second end plates substantially parallel with said major planar surfaces of said fuel cell assembly, and each of said first and second end plates having a peripheral side wall that is substantially parallel to said length of said fuel cell assembly; and
at least one side plate having opposite first and second ends that are attached respectively to said peripheral side wall of said first and second end plates, said attachment of said at least one side plate to said end plates providing continuous adjustability as to an overlap between said at least one side plate and at least one of said end plates, said at least one side plate holding said first and second end plates in a spaced relation so that at least a planar portion of said major surface of each of said first and second end plates imparts a compressive force on said fuel cell assembly.
2. The stack of claim 1, wherein said first and second ends of said at least one side plate are attached respectively to said first and second end plates so that said compressive force imparted on said fuel cell assembly by said first and second end plates is of a predetermined magnitude.
3. The stack of claim 1, wherein said first and second ends of said at least one side plate are attached respectively to said first and second end plates so that said length of said fuel cell assembly is compressed a predetermined distance.
4. The stack of claim 1, further comprising a pair of side plates attached to opposite side walls of said periphery of each of said end plates.
5. The stack of claim 1, wherein said first and second ends of said at least one side plate each have at least one opening through which a mechanical fastener is inserted to attach said first and second ends of said at least one side plate respectively to said first and second end plates.
6. The stack of claim 5, wherein said at least one opening on at least one of said first or second ends is a slot.
7. The stack of claim 5, wherein a first mechanical fastener that attaches said first end of said at least one side plate to said first end plate has a threaded portion that engages with a threaded opening in said first end plate, and a second mechanical fastener that attaches said second end of said at least one side plate to said second end plate has a threaded portion that engages with a threaded opening in said secondend plate.
8. The stack of claim 5, wherein said at least one opening on at least one of said first and second ends of said at least one side plate is one of a plurality of openings and said plurality of openings are spaced about said at least one of said first and second ends of said at least one side plate.
9. The stack of claim 1, wherein said planar portion of said major surface of each of said first and second end plates is a contact interface distributed over a majority of said major surface.
10. The stack of claim 1, further comprising at least one intermediate member disposed between at least one of said first and second end plates and said fuel cell assembly and wherein said planar portion of said major surface of at least one of said first and second end plates imparts said compressive force on said fuel cell assembly through said at least one intermediate member.
11. The stack of claim 1, wherein said first end assembly includes at least one intermediate member disposed between said first end plate and said first end of said fuel cell assembly.
12. The stack of claim 11, wherein said second end assembly includes a different at least one intermediate member disposed between said second end plate and said second end of said fuel cell assembly.
13. An electro-chemical fuel cell stack, the stack comprising:
a plurality of fuel cells arranged in a stacked configuration to form a fuel cell assembly, said fuel cell assembly having opposite first and second ends with a length therebetween, said first and second ends corresponding to major planar surfaces of said fuel cell assembly;
first and second end plates, said first and second end plates being disposed respectively on said first and second ends of said fuel cell assembly with a major surface of each of said first and second end plates substantially parallel with said major planar surfaces of said fuel cell assembly and at least a planar portion of said major surface of each of said first and second end plates imparting a compressive force on said fuel cell assembly; and
a plurality of side plates having opposite first and second ends that are attached respectively to said first and second end plates, said attachment between said side plates and said end plates providing non-discrete adjustability of an overlap between said side plates and at least one of said end plates over a finite distance, each of said plurality of side plates enclosing a portion of said fuel cell assembly between said first and second end plates and providing a protective enclosure for said fuel cell assembly.
14. The stack of claim 13, wherein said first and second ends of said at least one side plate are attached respectively to said first and second end plates with portions of said first and second ends of said at least one side plate holding said first and second end plates in a spaced relation so that said portions of said first and second ends of said at least one side plate cause said first and second end plates to impart said compressive force on said fuel cell assembly.
15. The stack of claim 13, wherein said at least one side plate has an opening formed therein to allow a terminal formed on a terminal end plate to pass through said at least one side plate.
16. The stack of claim 13, wherein said at least one side plate is made of metal.
17. The stack of claim 13, wherein said at least one side plate provides shielding against electromagnetic interference with said fuel cell assembly.
18. The stack of claim 17, wherein said at least one side plate is electrically grounded.
19. The stack of claim 13, wherein said entire fuel cell assembly between said first and second plates is enclosed by said plurality of side plates.
20. The stack of claim 13, wherein each of said major surfaces of said first and second end plates are substantially rectangular.
21. The stack of claim 13, wherein said planar portion of said major surface of each of said first and second end plates is a contact interface distributed over a majority of said major surface.
22. The stack of claim 13, further comprising at least one intermediate member disposed between at least one of said first and second end plates and said fuel cell assembly and wherein said planar portion of said major surface of at least one of said first and second end plates imparts said compressive force on said fuel cell assembly through said at least one intermediate member.
23. A method of making an electro-chemical fuel cell stack, the method comprising the steps of:
positioning a fuel cell assembly between first and second end plates with a first end of said fuel cell assembly substantially parallel to and adjacent a major surface of said first end plate and a second end of said fuel cell assembly substantially parallel to and adjacent a major surface of said second end plate;
applying an external compressive force to at least one of said end plates so that said fuel cell assembly is compressed by at least a planar portion of said major surface of each of said end plates;
establishing an overlap between at least one side plate and at least one of said end plates, said overlap being continuously adjustable;
attaching at least one side plate to a peripheral side wall of said first and second end plates with first and second ends of said at least one side plate being attached to said first and second end plates respectively so that said first and second end plates remain in a fixed spaced relation with said established overlap and said fuel cell assembly remains compressed when said external compressive force is removed; and
removing said external compressive force from said end plates.
24. The method of claim 23, wherein:
the step of applying an external compressive force includes applying a compressive force of a predetermined magnitude so that said fuel cell assembly experiences a compressive force of said predetermined magnitude; and
the step of attaching at least one side plate to said end plates includes attaching said first and second ends of said at least one side plate to said first and second end plates respectively so that when said compressive force is removed said first and second end plates remain in a fixed spaced relation and maintains said compressive force of said predetermined magnitude on said fuel cell assembly.
25. The method of claim 23, wherein:
the step of applying an external compressive force includes applying a compressive force to said end plates so that said fuel cell assembly is compressed a predetermined distance in the direction of said external compressive force; and
the step of attaching at least one side plate to said end plates includes attaching said first and second ends of said at least one side plate to said first and second end plates respectively so that when said external compressive force is removed said first and second end plates remain in a fixed spaced relation and said fuel cell assembly remains compressed said predetermined distance.
26. The method of claim 23, wherein the step of attaching at least one side plate to said end plates includes attaching a pair of side plates to opposite peripheral side walls of each of said end plates.
27. The method of claim 23, wherein said at least one side plate encloses a length of said fuel cell assembly between said first and second end plates so that said at least one side plate provides a protective enclosure for said fuel cell assembly.
28. The method of claim 23, wherein said planar portion of said major surface of said at least one of said end plates is a contact interface distributed over a majority of said major surface.
29. The method of claim 23, further comprising disposing at least one intermediate member between at least one of said first and second end plates and said fuel cell assembly and compressing said fuel cell assembly with a planar portion of at least one of said first and second end plates through said at least one intermediate member.
30. An electro-chemical fuel cell stack comprising:
a fuel cell assembly having opposite first and second ends with a length therebetween, said first and second ends corresponding to major planar surfaces of said fuel cell assembly;
a first end assembly disposed on said first end of said fuel cell assembly, said first end assembly having a first end plate with a major surface substantially parallel with said planar surface of said first end of said fuel cell assembly;
a second end assembly disposed on said second end of said fuel cell assembly, said second end assembly having a second end plate with a major surface substantially parallel with said major planar surface of said second end of said fuel cell assembly; and
at least one side plate having opposite first and second ends that are respectively attached to a side wall of said first and second end plates, said attachment allowing a continuous range of overlap between said at least one side plate and at least one of said end plates in a direction corresponding to said length of said fuel cell assembly, said at least one side plate holding said first and second end plates in a spaced relation so that at least a planar portion of each of said major surfaces of said first and second end plates imparts a compressive force on said fuel cell assembly through said first and second end assemblies.