1. A method of adjusting a condition of an electron beam when an image is formed by scanning said electron beam on a sample, and detecting secondary electrons emitted by the sample, and accumulating a plurality of frames obtained by said scanning, comprising the steps of:
forming a luminance histogram of the image obtained by scanning said electron beam; and
adjusting a current of said electron beam so that a brightness of said image obtained by the formed luminance histogram corresponds to a predetermined gray-scale.
2. A method of adjusting condition of the electron beam according to claim 1, wherein said number of frames to be accumulated is determined so that a result of multiplication of said number of frames to be accumulated and a current of said adjusted electron beam equals to a predetermined constant number.
3. A method of adjusting condition of the electron beam according to claim 2, wherein said constant number is different according to a kind of a sample.
4. A scanning electron microscope comprising:
an electron beam source;
a lens for converging an electron beam emitted from said electron beam source onto a sample;
a scanning deflector for scanning an electron beam converged on said sample on the basis of a number of accumulation frames set;
a detector for detecting electrons emitted from said sample; and
a controller for forming a luminance histogram of an image obtained by scanning said electron beam, and adjusting a current of said electron beam so tat a brightness of said image obtained by the formed luminance histogram corresponds to a predetermined gray-scale.
5. A scanning electron microscope according to claim 4, wherein said controller has a function for determining said number of accumulation frames so that a result of multiplication of a number of accumulation frames and said current of said electron beam equals to a predetermined constant number.
6. A scanning electron microscope according to claim 5, wherein said controller comprises different constant numbers for each kind of said sample.
7. A scanning electron microscope comprising:
an electron beam source;
a lens for converging an electron beam emitted from said electron beam source onto a sample;
a scanning deflector for scanning an electron beam converged on said sample on the basis of a number of accumulation frames set;
a detector for detecting electrons emitted from said sample; and
a controller for forming an image on the basis of said electrons detected by said detector, said controller having functions for determining said number of said accumulation frames on the basis of a current of said electron beam and a constant number representing a relation between said current of said electron beam and a number of accumulation frames, said constant number being different according for each kind of said sample.
8. A scanning electron microscope according to claim 7, said constant number is a product of multiplication of said current of said electron beam and said number of accumulation frames.
9. A method of adjusting condition of the electron beam according to claim 1, wherein a number of the frames is determined based on a relational expression between the adjusted electron beam current and the number of frames.
10. A scanning electron microscope according to claim 4, wherein a number of the frames is determined based on a relational expression between the adjusted electron beam current and the number of frames.
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 LED lighting device comprising:
a cap having an inner space;
an insulative base mounted in the inner space;
a circuit board assembly mounted on the insulative base and having
multiple circuit boards intersecting each other to form a light frame with a crisscross section; and
multiple LEDs mounted on two opposite surfaces near a longitudinal edge of each circuit board and emitting light toward different directions;
a bulb envelope securely mounted on the cap and enclosing the circuit board assembly and the base.
2. The LED lighting device as claimed in claim 1, wherein the circuit board assembly further comprises
a top circuit board mounted on one end of the light frame opposite to the insulative base and electrically connecting to the circuit boards; and
multiple LEDs mounted on the top circuit board.
3. The LED lighting device as claimed in claim 2, wherein the top circuit board is crisscross.
4. The LED lighting device as claimed in claim 2, wherein the top circuit board is circular.
5. The LED lighting device as claimed in claim 2, wherein the top circuit board is rectangular.
6. The LED lighting device as claimed in claim 2, wherein the circuit board assembly further has a protrusion formed on the end of the light frame, and the top circuit board has a through hole mounted around the protrusion.
7. The LED lighting device as claimed in claim 3, wherein the circuit board assembly further has a protrusion formed on the end of the light frame, and the top circuit board has a through hole mounted around the protrusion.
8. The LED lighting device as claimed in claim 4, wherein the circuit board assembly further has a protrusion formed on the end of the light frame, and the top circuit board has a through hole mounted around the protrusion.
9. The LED lighting device as claimed in claim 5, wherein the circuit board assembly further has a protrusion formed on the end of the light frame, and the top circuit board has a through hole mounted around the protrusion.
10. The LED lighting device as claimed in claim 1, wherein the circuit board assembly further has multiple top LEDs mounted near a top edge of each of the circuit boards and emitting light toward a direction opposite to the base.
11. The LED lighting device as claimed in claim 10, wherein the top LEDs are perpendicularly mounted on the circuit boards.
12. The LED lighting device as claimed in claim 10, wherein the lights emitted by the top LEDs and by the LEDs mounted near the longitudinal edge of each circuit board are in different directions orthogonal to each other.
13. The LED lighting device as claimed in claim 1, the insulative base is a glass base.
14. The LED lighting device as claimed in claim 1, the bulb envelope has a shape of a candle fire.
15. The LED lighting device as claimed in claim 1, the bulb envelope has a shape of a ball.
16. The LED lighting device as claimed in claim 6, wherein the protrusion of the light frame is formed on a top edge of one of the circuit boards.
17. The LED lighting device as claimed in claim 7, wherein the protrusion of the light frame is formed on a top edge of one of the circuit boards.
18. The LED lighting device as claimed in claim 8, wherein the protrusion of the light frame is formed on a top edge of one of the circuit boards.
19. The LED lighting device as claimed in claim 9, wherein the protrusion of the light frame is formed on a top edge of one of the circuit boards.
20. The LED lighting device as claimed in claim 1, wherein each of the circuit boards has a slot.