Three-dimensional measuring system and method of measuring the shape of an object

• US 6,151,118 A
• Filed: 11/18/1997
• Issued: 11/21/2000
• Est. Priority Date: 11/19/1996
• Status: Expired due to Term

• Current Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Original Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Inventors: Norita, Toshio, Tanabe, Hideki, Uchino, Hiroshi
• Primary Examiner(s): Pham, Hoa Q
• Application Number:
  US08/972,432
• Time in Patent Office: 1,099 Days
• Field of Search: 356/237, 356/376, 356/375, 356/387, 356/386, 356/384, 356/385, 356/398, 356/237.1-237.6, 364/488, 364/490, 364/578, 382/149, 382/141, 382/153
• US Class Current: 356/602
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object

Abstract

A three-dimensional measuring system comprises an optical system for emitting a light and optically scanning an object, a measuring sensor having an image pickup surface consisting of a plurality of picture elements and adapted to receive the light reflected on the surface of the object, a galvanometer mirror for changing a direction in which the light irradiates the object, a system controller for driving the measuring sensor so as to allow the same to output information on the quantity of light incident on each of the picture elements, and a barycentric calculation circuit for finding an instant when the light traverses each of the picture elements. This instant is found by implementing a barycentric calculation on the basis of outputs of the measuring sensor taken for a prescribed period of time and an instant at which each of the outputs is taken. The measuring system further comprises a host computer for finding a position on the surface of the object corresponding to each of the picture elements. This position is found on the basis of a relationship between a direction in which the light irradiates the object at an instant when the light traverses each of the picture elements and a direction in which the light reflected on the surface of the object is incident on each of the picture elements.

Claims

1. A three-dimensional measuring system for measuring a shape of an object, said three dimensional measuring system comprising:

an optical mechanism for emitting a light that illuminates the object, and optically scanning the object;

an image pickup sensor for receiving light reflected from the object, said image pickup sensor having a plurality of light-receiving regions across which the reflected light traverses;

a scanning device for changing a direction in which said light illuminates said object;

an image pickup control device for driving said image pickup sensor to output information indicating an amount of the reflected light incident on each of said light-receiving regions over time;

a first arithmetic unit for determining a time when said reflected light traverses each of said light-receiving regions, each time being determined by implementing a barycentric calculation based on samples (x) of the information output by said image pickup sensor taken periodically over a prescribed period of time and an instant (i) at which each of said samples (x) is taken; and

a second arithmetic unit for determining a position on a surface of said object that corresponds to each of said light-receiving regions, each position being determined based on a relationship between the direction in which said light illuminates said object at the time when said reflected light traverses the light-receiving region and a direction in which said reflected light is incident on the light-receiving region.

2. A three-dimensional measuring system as defined in claim 1, wherein said first arithmetic unit comprises:

a first adder for calculating a first sum Σ

(x·

i), said first sum being a summation of products for all samples (x), with each product being of a sample (x) and a corresponding instant (i) at which the sample (x) was taken;

a second adder for calculating a second sum Σ

(x) for all of said samples (x); and

a divider for calculating a quotient Σ

(x·

i)/Σ

(x) of the first sum divided by the second sum, said quotient being a temporal center N_peak of gravity.

3. A three-dimensional measuring system as defined in claim 1 or 2, wherein each said prescribed period of time is a period of time for allowing said reflected light to traverse an effective domain of a corresponding light-receiving region, said effective domain corresponding to a measurable range within which said object falls.

4. A three-dimensional measuring system for measuring a shape of an object, said three dimensional measuring system comprising:

an optical mechanism for emitting a light that illuminates the object, and optically scanning the object;

an image pickup sensor for receiving light reflected from the object, said image pickup sensor having an image pickup surface including a plurality of light-receiving regions across which the reflected light traverses;

a scanning device for changing a direction in which said light illuminates said object;

an image pickup control device for driving said image pickup sensor to output information indicating an amount of the reflected light incident on each of said light-receiving regions over time;

a first arithmetic unit for determining a position on said image pickup surface on which a largest amount of reflected light from light illuminating said object in a specific direction is incident, said position being found by implementing a barycentric calculation based on samples (x) of the information output by said image pickup sensor and position coordinates (i) of reflected light incident on said light-receiving regions that falls within a predetermined vertical light-receiving range on the image pickup surface and with which said samples (x) correspond; and

a second arithmetic unit for determining a position on a surface of said object that corresponds to each of said light-receiving regions, each position on the surface of said object being determined based on a relationship between said specific direction and a direction in which said reflected light is incident on said position determined by said first arithmetic unit.

5. A three-dimensional measuring system as defined in claim 4, wherein said first arithmetic unit comprises:

a first adder for calculating a first sum Σ

(x·

i), said first sum being a summation of products for all samples (x), with each product being of a sample (x) and the corresponding position coordinate (i);

a second adder for calculating a second sum Σ

(x) for all of said samples (x); and

a divider for calculating a quotient Σ

(x·

i)/Σ

(x) of the first sum divided by the second sum, said quotient being a spatial center M_peak of gravity.

6. A three-dimensional measuring system as defined in claim 4 or 5, wherein said predetermined vertical light-receiving range corresponds with an effective domain of said light-receiving regions that correspond to a measurable range within which said object falls.

7. A method of measuring a shape of an object, said method comprising:

a projecting step of projecting a light onto the object and scanning the object with the light;

a receiving step of receiving light reflected from the object with an image pickup sensor having a plurality of light-receiving regions across which the reflected light traverses according to the scanning of the object;

a sampling step of periodically sampling information indicating an amount of the reflected light incident of on each of said light-receiving regions over time period;

a storing step of storing into a memory the information which is periodically sampled over a predetermined time period for each of said light-receiving regions;

a first determining step of determining a time when said reflected light traverses each of said light-receiving regions, each time being determined by implementing a barycentric calculation based on samples (x) of the information stored in the memory and an instant (i) at which each of said samples (x) is taken; and

a second determining step of determining a position on a surface of said object that corresponds to each of said light-receiving regions, each position being determined based on a relationship between a direction in which said light illuminates said object at the time when said reflected light traverses the light-receiving region and a direction in which said reflected light is incident on the light-receiving region.

8. A method according to claim 7, wherein said first determining step comprises:

calculating a first sum Σ

(x·

i), said first sum being a summation of products for all samples (x), with each product being of a sample (x) and a corresponding instant (i) at which the sample (x) was taken;

calculating a second sum Σ

(x) for all of said samples (x); and

calculating a quotient Σ

(x·

i)/Σ

(x) of the first sum divided by the second sum, said quotient being a temporal center N_peak of gravity.

9. A method of measuring a shape of an object, said method comprising:

a projecting step of projecting a light onto the object and scanning the object with the light;

a receiving step of receiving light reflected from the object with an image pickup sensor having an image pickup surface including a plurality of light-receiving regions across which the reflected light traverses according to the scanning of the object;

a sampling step of periodically sampling information indicating an amount of the reflected light incident on each of said light-receiving regions over time period;

a storing step of storing into a memory the information which is periodically sampled for each of said light-receiving regions;

a first determining step of determining a position on said image pickup surface on which a largest amount of reflected light from light illuminating said object in a specific direction is incident, said position being found by implementing a barycentric calculation based on samples (x) of the information stored in the memory and position coordinates (i) of reflected light incident on said light-receiving regions that falls within a predetermined vertical light-receiving range on the image pickup surface and with which said samples (x) correspond; and

a second determining step of determining a position on a surface of said object that corresponds to each of said light-receiving regions, each position on the surface of said object being determined based on a relationship between said specific direction and a direction in which said reflected light is incident on said position determined in said first determining step.

10. A method according to claim 9, wherein said first determining step comprises:

calculating a first sum Σ

(x·

i), said first sum being a summation of products for all samples (x), with each product being of a sample (x) and the corresponding position coordinate (i);

calculating a second sum Σ

(x) for all of said samples (x); and

calculating a quotient Σ

(x·

i)/Σ

(x) of the first sum divided by the second sum, said quotient being a spatial center M_peak of gravity.

11. A three-dimensional measuring apparatus for measuring a shape of an object, said three-dimensional measuring apparatus comprising:

a scanner for emitting a light that illuminates the object, and scanning the object with the light;

an image pickup sensor for receiving light reflected from the object, said image pick sensor having a plurality of light-receiving regions across which the reflected light traverses according to the scanning of the object;

an image pickup controller for driving said image pickup sensor to sample information indicating an amount of the reflected light incident on each of said light-receiving regions at each of sampling instants over a scanning period;

a first arithmetic unit for determining a time when said reflected light traverses each of said light-receiving regions, each time being determined by implementing a barycentric calculation based on samples (x) of the information output by said image pickup sensor taken at each of the sampling instants belonging to a prescribed period of time and an sampling instant (i) at which each of said samples (x) is taken; and

an output unit for outputting information relating to said determined time for calculating a position on a surface of said object that corresponds to each light-receiving regions.

12. A three-dimensional measuring apparatus as defined in claim 11, wherein said first arithmetic unit comprises:

a first adder for calculating a first sum Σ

(×

·

1), said first sum being determined a summation of products for all samples (x), with each product being of a sample (x) and

a corresponding instant (i) at which the sample (x) was taken;

a second adder for calculating a second sum Σ

(x) for all of said samples (x); and

a divider for calculating a quotient Σ

(×

·

1)/Σ

(x) of the first sum divided by the second sum, said quotient being a temporal center N_peak of gravity.

13. A three-dimensional measuring apparatus as defined in claim 11, wherein said prescribed period of time is a period of time for allowing said reflected light to traverse the light-receiving regions belonging to an effective range, said effective range corresponding to a measurable range within which said object falls.

14. A three-dimensional measuring apparatus as defined in claim 11, further comprising:

a second arithmetic unit for determining based on the information output by said output unit, the position on the surface of said object that corresponding to each of said light-receiving regions.

15. A three-dimensional measuring apparatus for measuring a shape of an object, said three-dimensional measuring apparatus comprising:

a scanner for emitting a light that illuminates the object, and scanning the object with light;

an image pickup sensor for receiving light reflected from the object, said image sensor having an image pickup surface including a plurality of light-receiving regions across which the reflected light traverses according to the scanning of the object;

an image pickup controller for driving said image pickup sensor to sample information indicating an amount of the reflected light incident on each of said light-receiving regions at each of sampling instants over a scanning period;

a first arithmetic unit for determining a position on said image pickup surface on which a largest amount of reflected light from light illuminating said object is incident for each of the sampling instants, each position being found by implementing a barycentric calculation based on samples (x) of the information output by said light-receiving regions belonging to said predetermined light-receiving range and position coordinates (i) of said light-receiving regions which takes said samples (x);

and an output unit for outputting information relating to said determined position for calculating a position on the object surface.