Instrument calibration process for photoelectric integral colorimeter - Database & Sql Blog Articles

1

. Instrument Calibration Principle of Photoelectric Integral Colorimeter

As mentioned earlier, due to

CIE

Spectral tristimulus value function

x(

λ

)

Has two peak wavelengths, so

x(

Enter

)

Can be divided into long wave regions

x ₁ (

λ

)

And short-wave regions

x _b (

λ

)

And its

x _b (

λ

)

versus

z(A)

Similar in shape, there is a certain proportional relationship between them.

X _b /Z=

owe. In this case, the spectral matching of the photoelectric integral detector can be performed in two different ways: one is to self-connect: the spectral response of one detector is matched into

x(

λ

)

,Ding

(A)

Enter

)

Curve, the other is to match the spectral responses of the three detectors to true, χ

(

λ

)

,

y(

λ

)

,

z(

λ

)

Curve, reuse scale factor

K

Obtain

X

Total stimulus value

X=X ₁ +X _b =X ₁ +KZ

.

Different photodetector spectral matching methods lead to different calibration methods for the corresponding colorimetric instruments. The following two different chroma correction processes are specifically discussed below:

(1)

The spectral response of the three photodetectors of the colorimetric instrument are respectively matched into

x(

λ

)

,

y(

λ

)

,

z(

λ

)

curve

As shown

6-30

As shown, the detector of the color measurement instrument to be calibrated is aligned on the photometric guide.

X

,

Y

,

Z

Color source of tristimulus values

(

Standard swatch

)

, adjusting three current-voltage converters as photoelectric signal processing circuits

(

Operational Amplifier

)

The size of the feedback resistor or the amplification factor of its successor, ie

6-31

middle

R ₁

,

R _v

,

R ₁₂

. Etc., so that the displayed reading value is compared with the tristimulus value of the standard color source.

X

,

Y

,

Z

In the meantime, the instrument has reached the instrument calibration state;

Some photoelectric integral colorimeter probes are made into a planar receiving surface, then

Y

The channel can be calibrated by illumination

Instrument calibration

As shown

6-32

Shown. At this time, you can

Y

The channel acts as an illuminometer detector, and the instrument is calibrated and adjusted on the photometric guide by using the luminous intensity standard lamp.

Y

Channel correction potentiometer

(

Change the amplifier's magnification

).

2

. Application examples

The color correction of the color luminance meter is used as an example to illustrate the calibration process of the photoelectric integral color measuring instrument.

(1)

Calibration of color luminance meter

Color luminance meter uses brightness as the calibration unit,

6-33

Is its adoption

CIE

Standard light source

A (

Luminous intensity is

I)

Schematic diagram of the calibration device for calibration. Instrument and magnesium oxide

(

Barium sulfate

)

The distance from the whiteboard is

r

, the illuminance of the surface of the magnesium oxide whiteboard is

E=I/r2In

. In addition, magnesium oxide whiteboard is known as a standard light source.

A

The reflectance when illuminating is

p

From which you can calculate the standard light source

A

Tristimulus values ​​of magnesium oxide whiteboard under illumination

X1

,

r

,

Z

. Here, by the way, the reflectance of the magnesium oxide whiteboard is explained.

p

The juice calculation method firstly measures the ratio of the spectral reflectance of the magnesium oxide whiteboard to the standard whiteboard provided by the national metrology department on the spectrophotometer, thereby obtaining the spectral reflectance of the magnesium oxide whiteboard.

p(

λ

)

And then using the theory of colorimetry to calculate the magnesium oxide whiteboard

CIE

Standard light source

A

Reflectance under illumination

p

.

(1)

Calibration of color luminance meter

Color luminance meter uses brightness as the calibration unit,

6-33

Is its adoption

CIE

Standard light source

A (

Luminous intensity is

I)

Schematic diagram of the calibration device for instrument calibration. Instrument and magnesium oxide

(

Barium sulfate

)

The distance from the whiteboard is

r

, the illuminance of the surface of the magnesium oxide whiteboard is

E=I/r ²

. In addition, magnesium oxide whiteboard is known as a standard light source.

A

The reflectance when illuminating is

p

From which you can calculate the standard light source

A

Tristimulus values ​​of magnesium oxide whiteboard under illumination

X ₁

,

r

,

Z

. Here, by the way, the reflectance of the magnesium oxide whiteboard is explained.

p

The juice calculation method firstly measures the ratio of the spectral reflectance of the magnesium oxide whiteboard to the standard whiteboard provided by the national metrology department on the spectrophotometer, thereby obtaining the spectral reflectance of the magnesium oxide whiteboard.

p(

λ

)

And then using the theory of colorimetry to calculate the magnesium oxide whiteboard

CIE

Standard light source

A

Reflectance under illumination

p

.

When the illuminance of the surface of the magnesium oxide whiteboard is

Z

When the brightness of the surface is:

L=PE/

Ï€

When the instrument is calibrated, first adjust the color luminance meter

Y

Channel, so that the displayed reading value is equal to

L ₀

Generally, the distance between the standard lamp and the standard whiteboard can be adjusted so that

L=100cd

/

m ²

To facilitate calibration work. Then adjust the corresponding

X ₁

with

Z

Channel, making tristimulus values

X ₁

,

Y

,

Z

Meet the standard light source calculated above

A

Tristimulus values ​​of magnesium oxide whiteboard under illumination

X ₁

,

Y

,

Z

The ratio is corrected.