What is claimed is:
1. A rare earth element-containing hydrogen storage alloy, wherein at least Mg, Cl or Pb element is present as one of impurities in said alloy matrix in a content of no higher than 80 ppm, no higher than 10 ppm or no higher than 100 ppm, respectively, by weight.
2. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein alkali metal elements are present as impurities in said alloy matrix in a total content of no higher than 10 ppm by weight.
3. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein alkaline earth metal elements, including Mg, are present as impurities in said alloy matrix in a total content of no higher than 100 ppm by weight.
4. A rare earth element-containing hydrogen storage alloy, wherein at least nonmetal elements or alkaline earth metal elements are present as impurities in said alloy matrix in a total content of no higher than 1,200 ppm or no higher than 100 ppm, respectively, by weight.
5. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein a sulfur element is present as one of impurities in said alloy matrix in a content of no higher than 10 ppm by weight.
6. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein an oxygen element is present as one of impurities in said alloy matrix in a content of no higher than 400 ppm by weight.
7. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein a carbon element is present as one of impurities in said alloy matrix in a content of no higher than 500 ppm by weight.
8. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein a nitrogen element is present as one of impurities in said alloy matrix in a content of no higher than 50 ppm by weight.
9. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein a boron element is present as one of impurities in said alloy matrix in a content of no higher than 10 ppm by weight.
10. A rare earth element-containing hydrogen storage alloy according to claim 1, wherein a fluorine element is present as one of impurities in said alloy matrix in a content of no higher than 10 ppm by weight.
11. A rare earth element-containing hydrogen storage alloy, said alloy having an oxygen concentration which shows a sharp decrease from the alloy surface towards the inner part in a surface layer covering from the surface to a depth of 20 nm and has a value of no higher than 10 weight % on average in said surface layer.
12. A rare earth element-containing hydrogen storage alloy, said alloy having a surface hardness of at least 600 kgmm2 in terms of Vickers hardness.
13. A rare earth element-containing hydrogen storage alloy, said alloy comprising a Ni element and showing a rapid decrease in oxygen-combined Ni atom concentration in a surface layer covering from the alloy surface to a depth of 20 nm, wherein the proportion of the oxygen-combined Ni atoms to the total Ni atoms is not greater than 5 weight % on the average in said surface layer.
14. A rare earth element-containing hydrogen storage alloy according to claim 1, which has a composition represented by formula Mm(NiCoM)x wherein Mm is at least one rare earth element selected from the group consisting of Ce, La, Pr and Nd, M is at least one element selected from the group consisting of Mn, Al, Cu Fe and Ti and x is within the range of 4.0 to 6.0.
15. A process of producing a rare earth element-containing hydrogen storage alloy having a composition represented by formula Mm(NiCoM)x wherein Mm is at least one rare earth element selected from the group consisting of Ce, La, Pr and Nd, M is at least one element selected from the group consisting of Mn, Al, Cu, Fe and Ti and x is within the range of 4.0 to 6.0; which comprises a step of melting at least a part of starting materials by the use of a plasma melting method and reduces a content of at least Mg, Cl or Pb element present as one of impurities in said alloy matrix to no higher than 80 ppm, no higher than 10 ppm or no higher than 100 ppm, respectively, by weight.
16. A process of producing a rare earth element-containing hydrogen storage alloy according to claim 15, wherein at least one of the starting materials molten by the use of a plasma melting method is a Misch metal.
17. A process of producing a rare earth element-containing hydrogen storage alloy according to claim 15, wherein all the starting materials are molten by the use of a plasma melting method.
18. A process of producing a rare earth element-containing hydrogen storage alloy according to claim 15, which comprises a step of melting all the starting materials by the use of a high-frequency induced melting method prior to said melting step using a plasma melting method.
19. A process of producing a rare earth element-containing hydrogen storage alloy according to claim 15, which comprises a melting step using a high-frequency induced melting method after said melting step using a plasma melting method.
20. A method of producing a rare earth element-containing hydrogen storage alloy according to claim 15, wherein the plasma melting method is carried out in an atmosphere of inert gas.
21. A method of producing a rare earth element-containing hydrogen storage alloy according to claim 20, wherein the inert gas is argon or helium.
22. A method of producing a rare earth element-containing hydrogen storage alloy according to claim 15, wherein the plasma melting method is performed using a water-cooled metallic hearth for accommodating a melt.
23. A method of producing a rare earth element-containing hydrogen storage alloy according to claim 22, wherein the melt accommodated in the water-cooled metallic hearth is agitated by the high-frequency magnetic field induced by arranging high-frequency coils around said hearth and sending high-frequency electricity thereto.
24. A method of producing a rare earth element-containing hydrogen storage alloy according to claim 23, wherein the water-cooled metallic hearth has a cylindrical crucible-form space provided with segments arranged symmetrically with respect to the vertical axis and holds the melt in a floating condition with a high-frequency magnetic field induced inside thereof by flowing a high-frequency electric current so as to surround the hearth.
25. A method of producing a rare earth element-containing hydrogen storage alloy according to claim 15, wherein the plasma melting method is carried out by setting a positive electrode on the torch side and a negative electrode on the melt side to generate plasma.
26. A negative electrode for an alkaline rechargeable battery, which has on a conductive support a hydrogen storage alloy according to claim 1.
27. A negative electrode according to claim 26, which provides the alkaline rechargeable battery having a discharge capacity of at least 250 mAhg in at least the third charge-discharge cycle carried out at 20 C.
28. A negative electrode according to claim 26, which provides the alkaline rechargeable battery wherein the discharge capacity in the discharge operation carried out at 20 C. under the high efficienty discharge condition of 3C is not lower than 70% of the discharge capacity in the discharge operation carried out at 20 C. under the discharge condition of 0.2C.
29. A negative electrode according to claim 26, which provides the alkaline rechargeable battery wherein the discharge capacity at 10 C. is not lower than 50% of the discharge capacity at 20 C.
30. An alkaline rechargeable battery having a negative electrode according to claim 26.
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. A display system, comprising:
a light source;
a spatial light modulator;
an optical path for directing light from the light source to the spatial light modulator, the optical path comprising a mirror for modulating the light; and
a controller for controlling the mirror;
wherein the mirror is selectively insertable into and removable out of the optical path to regulate transmission of the light to the spatial light modulator.
2. The display system of claim 1, wherein the mirror is also selectively partially insertable into the optical path to allow transmission of a portion of the light.
3. The display system of claim 1, wherein the spatial light modulator is a DMD.
4. The display system of claim 1, wherein the mirror is a fold mirror.
5. The display system of claim 4, wherein the fold mirror, when inserted into the optical path, folds the light at an angle of approximately 90 degrees.
6. The display system of claim 4 wherein the fold mirror is placed at a stop of the optical path.
7. The display system of claim 1, wherein the selectively-insertable mirror reflects light along the optical path when inserted.
8. The display system of claim 1, further comprising a light dump for absorbing light from the light source that is not transmitted along the optical path by operation of the mirror.
9. The display system of claim 1, wherein the mirror is mounted such that it translates laterally when inserted or removed from the optical path.
10. The display system of claim 1, wherein the mirror is rotatably mounted such that it rotates about an axis of rotation when inserted or removed from the optical path.
11. The display system of claim 10, wherein the axis of rotation is located at an end of the mirror.
12. The display system of claim 1, wherein the display system is a projection display system.
13. An optical path for use in a display system, the optical path comprising:
a light source for emitting light along a light path;
a mirror selectably insertable into and removable out of the light path for controlling the propagation of the light along the light path;
a spatial light modulator disposed in the light path after the mirror, the spatial light modulator for receiving the light transmitted along the light path; and
a light dump for absorbing light emitted by the light source but not transmitted along the light path after the mirror.
14. The optical path of claim 13, further comprising an integrator tube disposed to collimate light emitted by the light source and at least one relay lens disposed to receive light collimated by the integrator tube;
wherein the at least one relay lens is disposed between the integrator tube and the mirror.
15. The optical path of claim 14 wherein the mirror is disposed between at least one of the at least one relay lens and the light dump.
16. The optical path of claim 13, wherein the mirror is a fold mirror disposed at a stop of the optical path.
17. The optical path of claim 16, wherein the mirror folds a portion of the propagating light at an angle of approximately 90 degrees when partially inserted into the optical path.
18. The optical path of claim 17, wherein light not folded by the mirror is substantially absorbed by the light dump.
19. A method of providing modulated light in a visual display system, said method comprising:
receiving light in a first portion of an optical path;
selectively directing the received light to a second portion of the optical path, wherein the selective directing step is performed by inserting and retracting a fold mirror into and out of the optical path of the received light; and
modulating the directed light in the second portion of the optical path with a spatial light modulator.
20. The method of claim 19, wherein the inserting the fold mirror directs at least a portion of the light to the second portion of the optical path.
21. The method of claim 19, wherein a light dump is positioned to receive light not directed to the second portion of the optical path.
22. The method of claim 19, further comprising emitting light from a light source toward the first portion of the optical path.
23. The method of claim 19, the modulating the directed light further comprising creating a visual image.
24. The method of claim 23, further comprising projecting the visual image toward a display screen.