# US 10,768,098 B2 · Spectrum recovery in a sample

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- Number: US 10,768,098 B2
- Document ID: US10768098B2
- Status: Granted
- Kind: B2
- Application number: 16/428,490
- Filed: 2019-05-31
- Published: 2019-12-26
- Granted: 2020-09-08
- Earliest claimed: 2018-06-26
- Assignees: Datacolor Inc.
- Applicants: Datacolor Inc.
- Inventors: Zhiling Xu
- Web page: https://patentgrep.com/patent/US10768098B2

## CPC

- G01N 21/274: {Calibration, base line adjustment, drift correction}
- G01N 21/25: Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N 21/255: {Details, e.g. use of specially adapted sources, lighting or optical systems}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A method and a system are provided for obtaining improved spectra recovery results of a measurement of a sample through the use of a calibration matrix obtained from calibration measurement values using at least one illumination source. By calculating the reflectance spectrum of a collection of calibration samples across several rounds of measurements and cascading the results, an improved calibration matrix can be used to convert the sample measurement values to more accurate results.

## Claims

### Claim 1

A color measurement system comprising:
at least one illuminant configured to produce a light beam having one or more spectral power distributions (SPD) at a sample;
a color measurement device configured to generate data in response to light from the at least one illuminant and reflected off the sample being incident on a light sensing portion of the color measurement device; and
a processor having a memory and configured to receive the output signal from the color measurement device, and calculate a recovered reflectance spectrum of the sample using at least the output signal generated when the sample is illuminated by the at least one illuminant, wherein the recovered reflectance spectrum is calculated by generating a sample matrix using the data output from the color measurement device upon illumination of the sample, and obtaining the product of the sample matrix and a calibration value,
wherein the calibration value is a matrix calculated using at least a matrix of concatenated calibration matrices and at least a matrix of concatenated master calibration matrices, wherein the concatenated calibration matrices includes a first calibration matrix of measurement values for a plurality of reference objects obtained under at least one measurement criterion and at least one additional calibration matrix of measurement values for the plurality of reference objects obtained under the same at least one measurement criterion.

### Claim 2 (depends on 1)

The system of claim 1, wherein the at least one measurement criterion used to capture the first calibration matrix of measurement value includes at least one of: sample orientation, sample placement, number of illuminants, type of illuminants, and sample capture geometry.

### Claim 3 (depends on 2)

The system of claim 2, wherein the first calibration matrix includes a plurality of measurements made under one or more illuminants.

### Claim 4 (depends on 3)

The system of claim 3, wherein the sample matrix includes a plurality of measurements made under the same illuminants as the first calibration matrix.

### Claim 5 (depends on 2)

The apparatus of claim 2, wherein the concatenated matrices are represented by S
where
S
⁢
=
(
s
1
,
1
…
s
1
,
n
⋮
⋱
⋮
s
m
,
1
…
s
m
,
n
x
1
,
1
…
x
1
,
n
⋮
⋱
⋮
x
m
,
1
…
x
m
,
n
)
where sm,n are measurement values of the first calibration matrix and xm,n are the measurement values obtained in the at least one additional calibration matrix, and wherein m corresponds to a given reference object and n refers to the channel.

### Claim 6 (depends on 5)

The apparatus of claim 5, wherein the measurement values for sm,n are obtained under at least one illuminant.

### Claim 7 (depends on 1)

The apparatus of claim 1, wherein the reflectance spectrum r of the sample is calculated according to:
r
=
s
*
(
pinv
⁡
(
SBCRA
⁢
⁢
1
…
SBCRAn
)
*
(
R
…
R
)
)
where, SBCRA1-SBCRAn each corresponds to a calibration matrix of measurements made of a plurality of calibration standards under the same at least one measurement criterion and each R is the same master calibration matrix of the plurality calibration standards obtained using a master measurement device.

### Claim 8 (depends on 1)

The apparatus of claim 1, wherein the reflectance spectrum r of the sample is calculated according to:
r
=
s
*
(
pinv
⁡
(
SBCRA
⁢
⁢
1
…
SBCRAn
)
*
(
R
1
…
R
n
)
)
where, SBCRA1-SBCRAn each corresponds to a calibration matrix of measurements made of a plurality of calibration standards under the same at least one measurement criterion and R1-Rn each corresponds to a measurement matrix of measurements made of the plurality of calibration standards obtained using the master measurement device under the same measurement conditions.

### Claim 9 (depends on 7)

The apparatus of claim 7, wherein the master measurement device has more wavelength channels than the light sensing portion of the color measurement device.

### Claim 10 (depends on 9)

The apparatus of claim 9, wherein the master calibration matrix was obtained from a measurement device having a number of wavelength channels that is less than or equal to about 31 spectral channels.

### Claim 11 (depends on 1)

The apparatus of claim 1, further comprising a display device to display the calculated reflectance spectrum of the sample.

### Claim 12 (depends on 1)

The apparatus of claim 1, wherein the generating step further includes the step of accessing from a memory, the master calibration matric.

### Claim 13 (depends on 1)

The apparatus of claim 1, wherein the generating step further includes the step of accessing from a memory, the calibration value.

### Claim 14

A method for identifying the color properties of a sample, the method comprising:
capturing, using a sample color sensing device, a sample measurement value of a sample illuminated by at least one illuminant;
generating, using at least one processor having memory and configured to execute code, a recovered color value for the sample using at least the sample measurement value and a calibration value, wherein the calibration value is a matrix derived using at least a matrix of concatenated calibration matrices and a matrix of concatenated master calibration matrices, wherein each of the matrix of concatenated calibration matrices includes a first measurement matrix of measurements of a plurality of reference tiles under at least one illuminant and at least one additional measurement matrix of measurements of the plurality of reference tiles under the at least one illuminant used to obtain the first measurement matrix; and
outputting at least the calculated color properties.

### Claim 15 (depends on 14)

The method of claim 14, wherein the recovered color value for the sample is calculated according to:
Rcalculated=T*M
where T is a sample measurement matrix of the sample measurements obtained and M is the calibration matrix.

### Claim 16 (depends on 14)

The method of claim 14, wherein the concatenated matrix S is generated according to:
S
⁢
=
(
s
1
,
1
…
s
1
,
n
⋮
⋱
⋮
s
m
,
1
…
s
m
,
n
x
1
,
1
…
x
1
,
n
⋮
⋱
⋮
x
m
,
1
…
x
m
,
n
)
where sm,n and xm,n are both the measurement values from the same sample m at the same channel n.

### Claim 17 (depends on 16)

The method of claim 16, wherein the concatenated matrices are obtained by capturing, using a calibration color sensing device having the same number of wavelength channels as the sample color sensing device, the measurement values for the first measurement matrix under at least one illuminant, and capturing at least the measurement values of the at least one additional measurement matrix under the same at least one illuminant used to capture the measurement values for the first measurement matrix.

### Claim 18 (depends on 14)

The method of claim 14, wherein the calibration value M is derived according to:
M
=
pinv
⁡
(
SBCRA
⁢
⁢
1
SBCRA
⁢
⁢
2
…
SBCRAn
)
*
(
R
R
…
R
)
.
where, SBCRA1-SBCRAn are measurement matrices of a plurality of calibration standards obtained under the same measurement conditions and each R is the same measurement matrix of the plurality calibration standards obtained using a master measurement device.

### Claim 19 (depends on 14)

The method of claim 14, wherein generating the recovered color value further comprises accessing the master calibration value from a memory remote to the processor.