Vision system illumination calibration apparatus

• US 4,979,135 A
• Filed: 09/25/1989
• Issued: 12/18/1990
• Est. Priority Date: 01/27/1988
• Status: Expired due to Term

• Current Assignee: Storage Technologies Corporation (Oracle Corporation)
• Original Assignee: Storage Technologies Corporation (Oracle Corporation)
• Inventors: Moy, Michael E.
• Primary Examiner(s): Dixon, Joseph L.
• Application Number:
  US07/412,170
• Time in Patent Office: 449 Days
• Field of Search: 364/559, 364/571.01, 364/513, 364/571.02, 364/571.05, 73/1 R, 356/394, 358/93, 358/101, 358/107, 901/47, 382/8, 382/48, 382/50, 250/205
• US Class Current: 700/259
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G05B 2219/37009 Calibration of vision system, camera, adapt light level
• CPC Class Codes: G05B 2219/37572 Camera, tv, vision
• CPC Class Codes: G05B 2219/45057 Storage handling for disks or material
• CPC Class Codes: G05B 2219/50275 Safety, verify correct code of chosen tool, probe
• CPC Class Codes: G11B 15/6835 the cassettes being transferred to a fixed recorder or player using a moving carriage
• CPC Class Codes: G11B 23/38 Visual features other than those contained in record tracks or represented by sprocket holes the visual signals being auxiliary signals
• CPC Class Codes: G11B 27/36 Monitoring, i.e. supervising the progress of recording or reproducing for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06

Abstract

The vision system illumination calibration apparatus uses a pair of lamps, located one on either side of a vision element to illuminate a set of machine-readable characters imprinted in bar code format on a label affixed to a calibration target plate. The required level of illumination is set by the use of a predetermined calibration target label. The vision system is positioned opposite this calibration target label and the illumination level is varied in sequential steps. Control software identifies a range of illumination levels in which the calibration target label is accurately read by the vision element and sets the level of illumination of the lamps in this range of values.

Claims

1. In a self-calibrating object handling system which contains a vision element for reading machine-readable data imprinted on said objects and a source of illumination that produces a light beam and is operable at any one of a plurality of predefined levels which levels are sequentially ordered from a first to a last, a method of automatically adjusting the level of illumination provided by said source of illumination as a function of the distinguishability of said machine-readable data read by said vision element comprising the steps of:

positioning said vision element opposite a predetermined calibration target having a series of machine-readable data imprinted thereon to illuminate said calibration target with said light beam;

adjusting the level of illumination provided by said source of illumination sequentially level by level from said first predefined level of illumination to said last predefined level of illumination;

producing with said vision element a matrix of data points, each data point corresponding to the level of illumination of a corresponding point on said calibration target, said matrix being inclusive of said series of machine-readable data imprinted on said predetermined calibration target, at each level of said plurality of levels of illumination;

comparing each said matrix of data points produced by said vision element at each of said plurality of levels of illumination with a set of data stored in a memory, which set is representative of said series of machine-readable data; and

setting said source of illumination at a level of illumination greater than or equal to the one level of illumination in said sequential levels of illumination wherein said series of machine-readable data first matched said stored set of data.

2. The method of claim 1 further including the step of:

terminating the step of setting if said step of comparing fails to match said produced matrix of data points with said stored set of data for greater than a predetermined number of sequential levels of illumination.

3. The method of claim 1 further including the step of:

terminating the step of setting if said step of comparing fails to match said produced matrix of data points with said stored set of data for greater than a predetermined number of sequential levels of illumination.

4. The method of claim 1 further including the step of:

altering said set one level of illumination to a level greater than or equal to the level at which said comparison first consistently matches said produced matrix of data points with said stored set of data when said comparison, at a level of illumination subsequent to said first level of illumination, fails to match said produced matrix of data points with said stored set of data.

5. The method of claim 1 further including the step of:

setting the level of illumination intensity to a level that is the average of a maximum level of illumination intensity and said level of illumination intensity that said comparison first consistently matches said produced matrix of data points with said stored set of data.

6. The method of claim 1 wherein said step of increasing includes the steps of:

storing data indicative of a fixed number of equal sized steps of illumination between a minimum level of illumination and a maximum level of illumination;

sequentially reading out said stored data in order of increasing illumination intensity;

activating said source of illumination to produce a level of illumination representative of said read data.

7. In a self-calibrating object handling system which contains a vision element for reading machine-readable data imprinted on said objects, a first and a second source of illumination to produce a pair of light beams to illuminate said objects, wherein said first and said second sources of illumination are positioned one on either side of said vision element, aimed at a predefined area in the field of vision of said vision element and are operable at any one of a plurality of predefined levels which levels are sequentially ordered from a first to a last, a method of adjusting the level of illumination provided by said first and second sources of illumination as a function of the distinguishability of said machine-readable data read by said vision element, comprising the steps of:

positioning said vision element opposite a predetermined target having a series of machine-readable data imprinted thereon;

fixing the level of illumination of said first source of illumination;

increasing the level of illumination provided by said second source of illumination sequentially level by level from said first level of illumination to said last level of illumination;

producing with said vision element a matrix of data points, each data point corresponding to the level of illumination of a corresponding point on said predetermined target, said matrix being inclusive of said series of machine-readable data imprinted on said predetermined target at each level of illumination;

comparing said matrix of data points produced by said vision element at each of said plurality of predefined levels of illumination with a set of data stored in a memory, which set is representative of said series of machine-readable data;

setting said source of illumination at a level of illumination greater than or equal to the one level of illumination in said sequential levels of illumination wherein said produced matrix of data points representative of said series of machine-readable data first matched said stored set of data.

8. The method of claim 7 further including the step of:

terminating the step of selection if said step of comparing fails to match said produced matrix of data points with said stored set of data for greater than a predetermined number of said levels of illumination.

9. The method of claim 7 further including the step of:

terminating the step of selection if said step of comparing fails to match said produced matrix of data points with said stored set of data for greater than a predetermined number of sequential levels of illumination.

10. The method of claim 7 wherein said step of increasing includes the steps of:

storing data indicative of a fixed number of equal sized steps of illumination between a minimum level of illumination and a maximum level of illumination;

sequentially reading out said stored data in order of increasing illumination intensity; and

activating said first source of illumination to produce a level of illumination representative of said read data.

11. The method of claim 7 further including the step of:

altering said set one level of illumination to a level greater than or equal to the level at which said comparison first consistently matches said produced matrix of data points with said stored set of data when said comparison, at a level of illumination subsequent to said first level of illumination, fails to match said produced matrix of data points with said stored set of data.

12. The method of claim 11 wherein said step of altering includes the step of:

setting the level of illumination intensity to a level that is the average of a maximum level of illumination intensity and said level of illumination intensity that said comparison first consistently matches said produced matrix of data points with said stored set of data.

13. In a self-calibrating object handling system which contains a vision element for reading machine-readable data imprinted on said objects and a source of illumination that produces a light beam to illuminate said objects and is operable at any one of a plurality of predefined levels which levels are sequentially ordered from a first to a last, apparatus for automatically adjusting the level of illumination provided by said source of illumination as a function of the distinguishability of said machine-readable data, comprising:

calibration target means having a set of machine-readable data imprinted thereon;

means for positioning said vision element opposite said calibration target means set of machine-readable data;

means for stepwise sequentially increasing the level of illumination produced by said source of illumination from a first of a plurality of predefined levels to a last of said plurality of predefined levels;

wherein said vision element produces a matrix of data points, each data point corresponding to the level of illumination of a corresponding point on said calibration target, said matrix being inclusive of said set of machine-readable data imprinted on said calibration target means;

means for storing a set of data representative of said set of machine-readable data imprinted on said calibration target means;

means responsive to said increasing means for comparing said matrix of data points produced by said vision element at each of said plurality of levels of illumination with said stored set of data; and

means responsive to said comparing means for setting said source of illumination to operate at a level of illumination greater than or equal to the one of said plurality of levels of illumination at which said comparing means first consistently determines that said produced matrix of data points match said stored set of data.

14. The apparatus of claim 13 wherein said increasing means includes:

means for storing data indicative of a fixed number of levels of illumination between a minimum level of illumination and a maximum level of illumination;

means for sequentially reading out said stored data in order of increasing level of illumination; and

means responsive to said read data for activating said source of illumination to produce a level of illumination representative of said read data.

15. The apparatus of claim 13 wherein said selecting means includes:

means responsive to said comparing means for identifying said level of illumination that said comparing means first consistently determines that said produced matrix of data points match said stored set of data;

means responsive to said identifying means for computing the average of said identified level of illumination and a maximum level of illumination; and

means responsive to said computing means for selecting the level of illumination closest to said average as said selected level of illumination.

16. The apparatus of claim 13 further including:

means responsive to said comparing means for disabling said selecting means if said comparing means fails to match said produced matrix of data points with said stored set of data for greater than a predetermined number of sequential levels of illumination.

17. The apparatus of claim 13 wherein said machine-readable data comprise a bar code.

18. The apparatus of claim 13 further including:

white calibration target means having a white surface imprinted thereon;

means for positioning said vision element opposite said white target means;

means responsive to said vision element positioned opposite said white calibration target means for activating said source of illumination to a maximum level of illumination; and

means for storing data indicative of data read out of said vision element for said maximum level of illumination at said white calibration target means.

19. The apparatus of claim 13 further including:

black calibration target means having a black surface imprinted thereon;

means for positioning said vision element opposite said black calibration target means;

means responsive to said vision element positioned opposite said black calibration target means for activating said source of illumination to a minimum level of illumination; and

means for storing data indicative of data read out of said vision element for said minimum level of illumination at said black calibration target means.

20. The apparatus of claim 19 further including:

means responsive to said stored data illustrative of said minimum level of illumination and a maximum level of illumination for determining the operability of said vision element.

21. In an object handling system which contains a vision element for reading machine-readable data imprinted on said objects, a first and a second source of illumination each located on opposite sides of said vision element and aimed at a point in the field of vision of said vision element to produce first and second beams of light to illuminate said objects, where said first source of illumination is operable at any one of a plurality of predefined levels which levels are sequentially ordered from a first to a last, apparatus for automatically adjusting the level of illumination provided by said first and second sources of illumination as a function of the distinguishability of said machine-readable data read by said vision element comprising:

calibration target means having a set of machine-readable data imprinted thereon;

means for positioning said vision element opposite said calibration target means set of machine-readable data;

means for maintaining said second source of illumination at a fixed level of illumination;

means for stepwise sequentially increasing the level of illumination produced by said first source of illumination from a first of a plurality of levels of illumination to a last of said plurality of levels of illumination;

wherein said vision element produces a matrix of data points, each data point corresponding to the level of illumination of a corresponding point on said calibration target, said matrix being inclusive of said set of machine-readable data imprinted on said calibration target means;

means for storing a set of data representative of said set of machine-readable data imprinted on said calibration target means;

means responsive to said increasing means for comparing said matrix of data points produced by said vision element at each of said plurality of levels of illumination with said stored set of data; and

means responsive to said comparing means for setting said first source of illumination to operate at a level of illumination greater than or equal to the level of illumination that said comparing means first consistently determines that said produced matrix of data points match said stored set of data.

22. The apparatus of claim 21 wherein said increasing means includes:

means for storing data indicative of a fixed number of levels of illumination between a minimum level of illumination and a maximum level of illumination;

means for sequentially reading out said stored data in order of increasing level of illumination; and

means responsive to said read data for activating said first source of illumination to produce a level of illumination representative of said read data.

23. The apparatus of claim 21 wherein said selecting means includes:

means responsive to said comparing means for identifying said level of illumination that said comparing means first consistently determines that said produced matrix of data points match said stored set of data;

means responsive to said identifying means for computing the average of said identified level of illumination and a maximum level of illumination; and

means responsive to said computing means for setting the level of illumination to a level closest to said average as said selected level of illumination.

24. The apparatus of claim 21 further including:

means responsive to said comparing means for disabling said setting means if said comparing means fails to match said produced matrix of data points with said stored set of characters for greater than a predetermined number of sequential levels of illumination.

25. The apparatus of claim 21 wherein said machine-readable data comprise a bar code.

26. The apparatus of claim 21 further including:

white calibration target means having a white surface imprinted thereon;

means for positioning said vision element opposite said white calibration target means;

means responsive to said vision element positioned opposite said white calibration target means for activating said first source of illumination to a maximum level of illumination; and

means for storing data indicative of data read out of said vision element for said maximum level of illumination at said white calibration target means.

27. The apparatus of claim 26 further including:

black calibration target means having a black surface imprinted thereon;

means for positioning said vision element opposite said black calibration target means;

means responsive to said vision element positioned opposite said black calibration target means for activating said first source of illumination to a minimum level of illumination; and

means for storing data indicative of data read out of said vision element for said minimum level of illumination at said black calibration target means.

28. The apparatus of claim 27 further including:

means responsive to said stored data illustrative of said minimum and said maximum levels of illumination for determining the operability of said vision element.

29. In a self-calibrating object handling system which includes a vision element for reading machine-readable data imprinted on said objects and a source of illumination that is operable at any one of a plurality of predefined levels which levels are sequentially ordered from a first to a last a method of automatically adjusting the level of illumination provided by said source of illumination as a function of the distinguishability of said machine-readable data read by said vision element comprising:

calibration target means having a set of machine-readable data imprinted thereon;

means for positioning said vision element opposite said calibration target means set of machine-readable data;

means for storing a set of data representative of a fixed number of levels of illumination between a minimum level of illumination and a maximum level of illumination;

means for sequentially reading out said stored set of data in order of increasing level of illumination;

means responsive to said reading out means for activating said source of illumination to produce a level of illumination representative of said data read out of said storing means;

means for producing a matrix of data points, each data point corresponding to the level of illumination of a corresponding point on said calibration target, said matrix being inclusive of said set of machine-readable data imprinted on said calibration target means;

means for storing a set of data representative of said set of machine-readable data imprinted on said calibration target means;

means responsive to said activating means for comparing said matrix of data points produced by said vision element at each level of illumination with said stored set of data;

means responsive to said comparing means for identifying said level of illumination that said comparing means first consistently determines that said produced matrix of data points match said stored set of data;

means responsive to said identifying means for computing the average of said identified level of illumination and said maximum level of illumination;

means responsive to said computing means for setting said source of illumination to operate at the level of illumination closest to said average as said set level of illumination; and

means responsive to said comparing means for disabling said setting means if said comparing means fails to match said produced matrix of data points with said stored set of data for greater than a predetermined number of sequential levels of illumination.