EP0257749A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Methods and apparatus for monitoring the diffuse reflectivity of a surface
Assignee: De la Rue Systems Ltd
•
Filing: 1987-07-06
•
Granted: —
•
Expires: 2007-07-06
Abstract
Abstract A method and apparatus for monitoring the diffuse reflectivity of a portion of a surface is described. The method is particularly applicable to soil detection of banknotes. The method comprises exposing the surface portion (3) to a beam of radiation from a source (2). At least one part of the diffuse radiation reflected by the surface portion (3) is sensed by a sensor (6) located closely behind an aperture (7) such that the aperture (7) defines, in effect, a sensing position situated such that the intensity of the diffusely reflected radiation sensed is substantially invariant within a working range of distances (D) between the aperture (7) and the surface portion (3). A value representative of the diffuse reflectivity of the surface portion (3) is then determined from the sensed intensities.
Inventors
- 👤 Derek Anthony Melleney
- 👤 David C. Reeves
- 👤 Michael Potter
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 18:13
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/47; G01N21/4738; G01N21/474; G07; G07D; G07D7/00; G07D7/06; G07D7/12; G07D7/121; G07D7/181; G07D7/187; G01N21/84; G01N21/88; G01N21/94
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
96 words
A method of monitoring the diffuse reflectivity of a portion of a surface (3), the method comprising exposing the surface portion to a beam of radiation (9); sensing the intensity of a part of the diffuse radiation, reflected by the surface portion, at a sensing position situated such that the intensity of the diffusely reflected radiation sensed at the sensing position is substantially invariant within a working range of distances (D) between the sensing position and the surface portion; and determining from the sensed intensity a value representative of the diffuse reflectivity of the surface portion.
Claim 2
Independent Claim
96 words
A method of monitoring the diffuse reflectivity of a portion of a surface (3), the method comprising exposing the surface portion to a beam of radiation (9); sensing the intensity of a part of the diffuse radiation, reflected by the surface portion, at a sensing position situated such that the intensity of the diffusely reflected radiation sensed at the sensing position is substantially invariant within a working range of distances (D) between the sensing position and the surface portion; and determining from the sensed intensity a value representative of the diffuse reflectivity of the surface portion.
Claim 3
Dependent Claim
35 words
A method according to claim 1, comprising placing an apertured mask between a radiation sensor (6) and the surface portion such that an aperture (7) in the apertured mask is situated at the sensing position.
Claim 4
Dependent Claim
60 words
A method according to claim 1 or claim 2, comprising sensing the intensity of the diffuse radiation at two sensing positions, each of the sensing positions being situated such that the intensity of the diffusely reflected radiation sensed at the sensing position is substantially invariant within a working range of distances (D) between the sensing position and the surface portion.
Claim 5
Dependent Claim
41 words
A method according to claim 3, wherein the two sensing positions are asymmetrically arranged relatively to the surface portion to reduce sensitivity to variations within an extended working range of distances (D) between the two sensing positions and the surface portion.
Claim 6
Independent Claim
35 words
A method according to any preceding claim, comprising filtering the light which reaches the or each of the sensing positions to match the response of the system substantially to the response of the human eye.
Claim 7
Independent Claim
21 words
A method according to any preceding claim, comprising carrying out the steps of the method on successive portions of the surface.
Claim 8
Dependent Claim
80 words
A method according to claim 6, comprising storing the values obtained from successive portions of the surface; summing n successive values, starting with the first value; repeating the summing step for sets of n values starting with the second, third, fourth, etc value, until the last value obtained from the surface is included in a sum; and comparing the maximum of the sums with a threshold value to ascertain whether the soil state of the surface is acceptable or unacceptable.
Claim 9
Independent Claim
16 words
A method according to any preceding claim, wherein the beam of radiation (9) comprises white light.
Claim 10
Independent Claim
64 words
A method according to any preceding claim, comprising causing a reference surface (8) to be exposed to the beam of radiation (9), sensing diffuse radiation reflected by the reference surface at the or each of the sensing positions to generate respective reference values, and subsequently normalising the intensities sensed at the or each of the sensing positions by comparison with the respective reference values.
Claim 11
Dependent Claim
45 words
10 . A method according to any preceding claim, wherein the surface (3) is defined by a sheet, the method further comprising causing the sheet to move in one of two directions (13, 14) according to the diffuse reflectivity of a portion of the surface.
Claim 12
Dependent Claim
115 words
Apparatus for monitoring the diffuse reflectivity of a surface, the apparatus comprising a radiation beam source (2); a surface support member (10) mounted such that the radiation impinges, in use, on a surface (3) supported by the support member; and a radiation sensor (6) for generating a signal for feeding to processing means (11); the signal corresponding to the intensity of a part of the diffuse radiation reflected by the surface and passing through a sensing position, and the sensing position being situated such that the intensity of the diffusely reflected radiation sensed at the sensing position is substantially invariant within a working range of distances (D) between the sensing position and the surface (3).
Claim 13
Dependent Claim
115 words
Apparatus for monitoring the diffuse reflectivity of a surface, the apparatus comprising a radiation beam source (2); a surface support member (10) mounted such that the radiation impinges, in use, on a surface (3) supported by the support member; and a radiation sensor (6) for generating a signal for feeding to processing means (11); the signal corresponding to the intensity of a part of the diffuse radiation reflected by the surface and passing through a sensing position, and the sensing position being situated such that the intensity of the diffusely reflected radiation sensed at the sensing position is substantially invariant within a working range of distances (D) between the sensing position and the surface (3).
Claim 14
Dependent Claim
35 words
Apparatus according to claim 11, wherein an apertured mask is placed between the radiation sensor (6) and the surface (3) such that an aperture (7) in the apertured mask is situated at the sensing position.
Claim 15
Dependent Claim
69 words
Apparatus according to claim 11 or claim 12, wherein there are two of the radiation sensors (6) for generating respective signals corresponding to the sensed intensity at two sensing positions, each of the sensing positions being situated such that the intensity of the diffusely reflected radiation sensed at the sensing position is substantially invariant within a working range of distances (D) between the sensing position and the surface (3).
Claim 16
Dependent Claim
20 words
Apparatus according to claim 13, wherein the two sensing positions are not substantially symmetrically arranged relatively to the surface (3).
Claim 17
Dependent Claim
38 words
Apparatus according to any one of claims 11 to 14, wherein there is a filter for the or each of the sensing positions to match the response of the system substantially to the response of the human eye.
Claim 18
Dependent Claim
34 words
Apparatus according to any of claims 11 to 15, wherein the source includes focussing means (4) to focus the beam of radiation (9) on a surface supported by the support member (10) in use.
Claim 19
Dependent Claim
46 words
Apparatus according to any one of claims 11 to 16, wherein at least part of the support member (10) is movable relatively to the beam of radiation (9) and the or each of the sensing positions whereby a series of positions on the surface is scanned.
Claim 20
Dependent Claim
59 words
Apparatus according to any one of claims 11 to 17, wherein at least that part (8) of the support member (10) which is illuminated when no surface is supported has a substantially uniform reflectance whereby radiation received at the or each of the sensing positions after reflection by said uniform reflectance part (8) is used to set a reference.
Claim 21
Dependent Claim
21 words
Apparatus according to claim 18, wherein the part (8) of the support member (10) having a uniform reflectance reflects white light.
Claim 22
Dependent Claim
77 words
Apparatus according to any one of claims 11 to 19, wherein the or each of the sensing positions is situated at an angle of between +20° and -20° relatively to the surface (3), and/or at a separation of between 10 mm and 17 mm perpendicularly to the beam of radiation (9) before diffuse reflection by the surface (3), for a working range of distances (D) of between 8 mm and 15 mm perpendicularly to the surface (3).
Claim 23
Dependent Claim
112 words
Sheet feeding apparatus comprising monitoring apparatus according to any one of claims 11 to 20; transport means (10), part of which comprises the support member of the monitoring apparatus, for conveying single sheets (3) past the region which is irradiated; processing means (11) connected to the or each of the sensors (6) of the monitoring apparatus for determining the diffuse reflectivity of the surface and for determining the acceptability of a sheet (3); and a diverter (12) positioned in the sheet path downstream of the monitoring apparatus and controlled by the processing means to divert each sheet in different directions according to whether the sheet is determined to be acceptable or unacceptable.
Claim 24
Dependent Claim
7 words
Banknote feeding apparatus according to claim 21.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.