Method and apparatus for measuring the height of an object

• US 6,069,701 A
• Filed: 12/02/1997
• Issued: 05/30/2000
• Est. Priority Date: 12/04/1996
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sasaki, Hideaki, Hashimoto, Yutaka, Kazui, Shinichi
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US08/982,509
• Time in Patent Office: 910 Days
• Field of Search: 356/376, 356/375, 356/377, 356/359, 356/381, 250/561
• US Class Current: 356/613
• CPC Class Codes: G01B 11/0608 Height gauges
• CPC Class Codes: G01N 21/88 Investigating the presence of flaws or contamination

Abstract

A method and an apparatus for measuring the height of an apex of an object with high accuracy without influence of the surface state of the object are disclosed. Correlation coefficients of respective positions of a waveform formed from digital data indicative of the height of the object detected by a head portion of a detector and a previously prepared standard waveform are calculated while moving the waveforms in the vertical and horizontal directions and the height of an apex position of the standard waveform at a position having a largest correlation coefficient from the calculated result is decided as the height of the apex of the object. Accordingly, the height of the apex can be decided from the whole detected waveforms without influence of local abnormality of the reflected light quantity waveform due to minute ruggedness or discoloration of the surface of the object.

Claims

1. A method of measuring the height of an object, comprising the steps of:

extracting data indicative of the height of the surface of the object by utilization of light;

changing relative positions of a previously provided standard waveform with respect to a waveform obtained from said height data arbitrarily;

calculating correlation coefficients of said waveform and said standard waveform at each of said changed positions; and

deciding the height of an apex of the object from said calculated result.

2. A method according to claim 1, wherein said step of extracting the data of the height, comprises:

irradiating light to the object;

detecting positions of the light reflected by the surface of the object; and

detecting the height of the surface of the object from said detected positions.

3. A method according to claim 1, wherein said step of changing the positions, comprises:

superposing a center position of said waveform onto a center position of said standard waveform;

moving said waveform or said standard waveform by any distance in any direction from said superposed position; and

repeating the operation of moving said waveform or said standard waveform by any distance in any direction from said moved position by any number of times.

4. A method according to claim 1, comprising:

superposing a center position of said waveform onto a center position of said standard waveform; and

moving said standard waveform from said superposed position in a vertical or horizontal direction by a predetermined distance and repeating the operation of moving said standard waveform by the predetermined distance in the vertical or horizontal direction from said moved position by any number of times.

5. A method according to claim 1, wherein said step of deciding the height, comprises:

deciding the height of an apex position of said standard waveform at a position having a largest value of said correlation coefficients at the positions as the height of the apex of the object.

6. A method according to claim 3, wherein said step of deciding the height, comprises:

deciding the height of an apex position of said waveform or said standard waveform at a position having a largest value of said correlation coefficients at the positions as the height of the apex of the object.

7. A method according to claim 4, wherein said step of deciding the height, comprises:

deciding an added result of a movement amount in a vertical direction to a position having a largest value of the correlation coefficients of said positions and the height of the apex position of said standard waveform as the height of the apex of said object.

8. A method of measuring the height of a plurality of objects mounted on an upper surface of a base in a row, comprising the steps of:

irradiating light to the objects disposed in each row;

scanning each row by light;

detecting positions of light reflected by surfaces of the objects in each row to thereby extract data indicative of the height of the surfaces of the objects;

changing a relative position of a previously prepared standard waveform with respect to waveforms corresponding to the objects obtained from said height data for each of said waveforms arbitrarily;

calculating correlation coefficients of said waveform and said standard waveform in said changed positions; and

deciding the height of apexes of the objects for each row from said calculated result.

9. A method according to claim 8, wherein said step of changing said position, comprises:

superposing a center position of said waveform onto a center position of said standard waveform;

moving said waveform or said standard waveform from said superposed position in any direction by any distance; and

repeating the operation of moving said waveform or said standard waveform from the moved position in any direction by any distance by any number of times.

10. A method according to claim 8, comprising:

superposing a center position of said waveform onto a center position of said standard waveform; and

moving said standard waveform from said superposed position in a vertical or horizontal direction by a predetermined distance and repeating the operation of moving said standard waveform by the predetermined distance in the vertical or horizontal direction from said moved position by any number of times.

11. A method according to claim 8, wherein said step of deciding the height, comprises:

deciding the height of an apex position of said standard waveform at a position having a largest value of said correlation coefficients at the positions as the height of the apex of the object.

12. A method according to claim 9, wherein said step of deciding the height, comprises:

deciding the height of an apex position of said waveform or said standard waveform at a position having a largest value of said correlation coefficients at the positions as the height of the apex of the object.

13. A method according to claim 10, wherein said step of deciding the height, comprises:

deciding an added result of a movement amount in a vertical direction to a position having a largest value of the correlation coefficients of said positions and the height of the apex position of said standard waveform as the height of the apex of said object.

14. A method according to claim 8, wherein said standard waveform is prepared for each row by:

scanning the objects disposed in each row by light;

detecting positions of light reflected by surfaces of the objects in each row and reflected light quantities to thereby extract data indicative of the height of the surfaces of the objects and light quantity data;

extracting data corresponding to the light quantity data exceeding a predetermined level, of the height data of the surfaces of the objects as effective data; and

adding and averaging the effective data for each row.

15. An apparatus for measuring the height of an object, comprising:

a stage capable of being moved in front and rear directions and in right and left directions;

detection means for irradiating light to the object mounted on said stage and detecting positions of light reflected by a surface of the object;

measurement means for extracting data indicative of the height of the surface of the object from the positions of the reflected light detected by said detection means;

memory means for storing said extracted height data and a previously provided standard waveform; and

decision means for changing a relative position of said standard waveform to a waveform obtained from said height data arbitrarily and calculating correlation coefficients of said waveform and said standard waveform in said changed positions to decide the height of an apex of the object from said calculated result.

16. An apparatus according to claim 15, wherein said decision means includes:

means for deciding the height of an apex position of said standard waveform at a position having a largest value of said correlation coefficients of said positions as the height of the apex of the object.