Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
  • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
  • G01J2003/466—Coded colour; Recognition of predetermined colour; Determining proximity to predetermined colour

Definitions

• the present invention concerns a method of detecting a predetermined colour in a signal from a colour-sensitive CCD array using an analogue video technique, which signal constitutes a measure of the intensity in three separate spectral bands which can be combined to produce all visible colours.
• the invention also concerns an arrangement for performing the method according to the invention.
• the object of the present invention is to provide a method which can easily detect from a signal from a colour-sensitive CCD array using an analogue video technique whether an illuminated article has a given predetermined colour.
• This object is achieved in that: upper and lower interval limits corresponding to the predetermined colour are defined for respective spectral bands; the signal corresponding to the intensity of the respective band is compared with said interval limits; an indication is provided for each spectral band when the signal therefor lies within the permitted interval; and an output signal indicates whether the pasetemiined colour is detected.
• a particular characteristic of the method according to the invention is that the interval limits are defined by adjustment with respect to the predetermined colour in the conditions in which the detection process is to be performed.
• a visual indication that the signal for a spectral band lies within the permitted interval is provided by a light signal.
• a further object of the present invention is to provide an arrangement for detecting a predetermined colour in a signal from a colour-sensitive CCD array using an analogue video technique, which signal constitutes a measure of the intensity in at least three separate spectral bands, which can be combined to produce all visible colours.
• the arrangement is characterized in that setting means are provided for defining upper and lower interval limits corresponding to the predetermined limits for the respective spectral bands; in that a comparator device operatively connected to the CCD array is arranged so as to compare the signal corresponding to the intensity in the respective spectral band with said interval limits; in that means operatively connected to said device are arranged to indicate when the signal for a spectral band lies within the permitted interval; and in that the arrangement is disposed such that it emits an output signal to indicate if the correct colour is detected.
• the arrangement according to the invention is preferably to be used for detecting articles which pass at relatively high speed on a conveyor track.
• the article can, for example, be a refuse sack, but any other type of article is also possible.
• the article for which it is to be established whether said article has a particular colour is illuminated with light of a predetermined colour, preferably white light.
• a CCD array 1 using an analogue video technique and whose output signal constitutes a representation of the light detected in three separate spectral bands is directed towards the article.
• the type of camera to be used in no way restricts the invention.
• the camera 1 divides the colour into three different spectral bands, for example, red, green and blue, which each represent per se separate wavelength ranges and which can be combined so that substantially all the different colours of the spectrum can be formed.
• the output signal from the camera 1 comprises three electrical signals corresponding to the intensity in the respective spectral band. These signals are analogue, which means that the level of the signal for each spectral band is variable from zero to the highest level.
• An arrangement 2 according to the invention receives output signals from the camera.
• the arrangement 2 according to the invention is to be set up in the environment in which the arrangement is to be used. This means, for example, that when the arrangement is used for detecting an article moving on a conveyer belt, the camera 1 is to be mounted at the location at the side of the conveyor belt where this camera is to be operated by the conveyor belt, before the interval limits are set. It will be appreciated that the arrangement 2 according to the invention can be moved but the camera 1 must be subject to the same conditions when the interval limits are set as when the conveyor belt is operated. If the conditions in the environment of the camera change, the interval limit settings must also be changed.
• the level of the above-mentioned electrical signal is used to define interval limits for an interval disposed about the signal level. This level is defined in the same way for each spectral band
• the arrangement 2 comprises means 5 for indicating the relation of the respective colour signal to an upper and lower limiting value.
• the embodiment in question uses light emitting diodes which, by means of a light signal, indicate whether a signal lies within a given range in order thereby to facilitate the setting process.
• the light emitting diodes When the potentiometers have been set in their end settings, the light emitting diodes indicate that the signal is in the interval defined by the potentiometers, since each visible colour can be set in this way.
• the arrangement can be disposed to emit an output signal only for the pi-edetermined colour.
• the interval has to be quite narrow, i.e. the low level is adjusted upwards and the high level is adjusted downwards. If, for example, the detection of white light is desired, the signals corresponding to the different spectral bands essentially have to be the same. In the case of red-green-blue signals the interval limits for each of the signals representing the red, blue or green wavelength ranges have to form an interval about the value which represents one- third of the total light reflected. The permitted highest and lowest interval limits have to lie quite close to one another. If, in contrast, the colour to be detected may be an entire colour scale, the permitted interval can be increased.
• the certainty that a given colour has correctly been detected can be increased by calculating a mean value of a number of input images.
• the accuracy of the system can be increased when colour variations occur on the article to be detected, for example owing to undesired shadowing on the article.
• the demand for uniform colour quality on the article inspected is thus not as great.
• the signal which is received from the camera 1 is compared with the interval limits stored in the setting means 3 in a comparator device 4. If the camera signal falls within this interval, an appropriate output signal is received from this comparator device 4. This output signal is supplied to the device 5 which emits a light signal if the signal corresponds to the desired colour or colour interval.
• the speed at which the detection process occurs depends on the input speed of the camera. This means that as input speeds increase, the detection speed can be increased.
• the output signal from the arrangement according to the invention is preferably binary and can be produced in a number of different ways, for example by an opening/closing relay.
• the output signal is an indication of whether an article of the correct colour has been located in front of the camera; further processing of the coloured article can be based on this output signal.
• the arrangement according to the invention can be provided with an adapter at its input.
• This adapter can divide the incoming signal into at least three separate spectral bands by analyzing and filtering incoming spectra.
• the arrangement according to the invention can then, as explained above, be used to establish whether the input signal represents a given predetermined colour.
• An arrangement for performing the method according to the invention for detecting a plurality of predetermined colours comprises setting means 3 for each colour, i.e. an assembly of potentiometers for each colour. These potentiometers are used in the above-mentioned way in order to indicate upper and lower interval limits adapted to the predetermined colour for each part of the spectral band.
• the comparator device 4 is arranged to carry out comparisons with the interval limits defined for respective colours.
• the manner in which this arrangement for detecting a plurality of colours is to be brought about is self-evident for a person skilled in the art in the light of the above description for detecting a p-- ⁇ ete ⁇ nined colour or colour scale.
• a microprocessor is preferably employed which is used in the manner well- known to a person skilled in the art.

Landscapes

• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Spectrometry And Color Measurement (AREA)
• Color Television Image Signal Generators (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=20396870

Family Applications (1)

Country Status (4)

Families Citing this family (4)

Family Cites Families (4)

• 1995
  • 1995-01-19 SE SE9500165A patent/SE507257C2/sv not_active IP Right Cessation
• 1996
  • 1996-01-19 JP JP8521902A patent/JPH11502611A/ja active Pending
  • 1996-01-19 WO PCT/SE1996/000046 patent/WO1996022512A1/en not_active Application Discontinuation
  • 1996-01-19 EP EP96901177A patent/EP0804720A1/de not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events