OPB780-KIT データシートの表示（PDF） - TT Electronics.

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OPB780-KIT

Color Sensor Evaluation Kit

TT Electronics. 

OPB780-Kit

Color Sensor Evaluation Kit

One of the critical parts of the OPB780Z is the LED. It

is very important to understand its characteristics

relative to forward current and temperature. The

below chart shows how the forward current of the LED

changes the Chromatic coordinates.

As can be seen, increasing the forward current of the

LED lowers the “Y” value while minimally changing the

“X” value. The projected most optimum light

(equivalent to sun light at 12 noon with no

contaminates in the air) has both “X” and “Y” chromatic

values of 1/3. Chromatic numbers below 1/3 consist of

more Blue or Green wavelengths and numbers above

1/3 consist of more Red or Yellow wavelengths. As

can be seen a forward current of approximately 4 mA

would provide the most optimum “Y” value.

Forward Current vs Chromaticity

Coordinate

0.35

TA = 25° C

0.34

1 mA

0.33

5 mA

0.32

20 mA

0.31

50 mA

0.30

100 mA

0.29 0.30 0.31 0.32 0.33 0.34

X

Ambient Temperature vs Chromaticity

Coordinate

0.35

IFP = 20 mA

0.34

0.33

-30° C

0° C

0.32

25° C

50° C

0.31

85° C

0.30

0.29 0.30 0.31 0.32 0.33 0.34

X

The graphs show the change in chromaticity vs

temperature. As the temperature reduces the “X”

value moves closer toward the optimum (1/3) value.

In conclusion, the lower the forward current and the

cooler the temperature, the closer the LED transmits to

the optimum chromatic values of “X”=1/3 and “Y”=1/3.

In order to provide sufficient light levels and the best

color resolution, the white LED should be driven with

at least 20 mA of forward current and operated at

room temperatures (approx. 25°C). These conditions

result in chromatic ranges of about “X”=0.31 and

“Y”=0.32.

The responsivity of the each diode group is dependent

on the angular position of the device to the object.

The graphs showing the typical variance of the Output

frequency of the device vs both Azmuth (twist) and

Zenith (bend) are shown in the two graphs.

OPTEK reserves the right to make changes at any time in order to improve design and to supply the best product possible.

Issue A.2 11/09

Page 4 of 9

OPTEK Technology Inc. — 1645 Wallace Drive, Carrollton, Texas 75006

Phone: (972) 323-2200 or (800) 341-4747

FAX: (972) 323-2396 sensors@optekinc.com www.optekinc.com

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