v1 ch 3 measuring devices
DESCRIPTION
Testing visible LEDTesting radiometric IR LEDscorrection for the Law of cosinesTesting optic communicationsTRANSCRIPT
![Page 1: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/1.jpg)
Chapter 3
Measuring / Testing Optoelectric Devices
![Page 2: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/2.jpg)
![Page 3: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/3.jpg)
• Luminous Intensity• 1 candela (cd) = 4 π lumens (lm)• Equivalent to one lumen per steradian (1 lm/sr)
• Data Sheet for LED• Red LED has Iv = 70 mcd (millicandelas)
• How many lumens is this?• 70 mcd = 0.88 lm
• Angle of Half Intensity• Half power
cdlm
mcdcd
_1_4
_1000_1
![Page 4: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/4.jpg)
LEDs
![Page 5: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/5.jpg)
![Page 6: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/6.jpg)
![Page 7: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/7.jpg)
![Page 8: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/8.jpg)
![Page 9: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/9.jpg)
![Page 10: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/10.jpg)
![Page 11: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/11.jpg)
![Page 12: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/12.jpg)
Light Intensity Meter
Light intensity meter receives unfiltered light that does not correspond to response of human eye.
![Page 13: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/13.jpg)
![Page 14: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/14.jpg)
Color Temperature Meter
Color
![Page 15: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/15.jpg)
Exposure Value
![Page 16: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/16.jpg)
Exposure Value
Aperture Value
Time Value
Speed Value
Brightness ValueBfl is the illuminated object's
brightness in foot-Lamberts
![Page 17: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/17.jpg)
Exposure ValueCan make Exposure Value equal to Brightness
Value if the Speed Value is zero.
If the Speed Value (Sv) is zero.
If S equals 3.3, then Sv is zero.
If S equals 3.1, then Sv is close to zero,which corresponds to ASA(ISO) of 3.1
Can then use the Exposure Value from the meter directly to find Brightness Value
![Page 18: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/18.jpg)
Lambert's Law or Law of Cosines
detector.
![Page 19: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/19.jpg)
![Page 20: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/20.jpg)
Spectroradiometer
A spectroradiometer is also called a scanning colorimeter.
It does a lot of number crunching to determine the amount of light at each wavelength.
![Page 21: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/21.jpg)
Red LED
Problem with measuring LEDs is the light energy usually peaks in the red region of the light spectrum.Standard sensor does not match the CIE curve.Need to use filter for the specific LEDs wavelength.
![Page 22: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/22.jpg)
Reflectance
Dark paper has low reflectance. Light paper has high reflectance.
Divide luminous reading in foot-Lamberts by illuminance in footcandles to derive reflectance factor.
Luminance = Illuminance X Reflectance Factor
![Page 23: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/23.jpg)
Transmissivity
Transmissivity - the ratio of light which passes through a material to the light incident upon its surface.
![Page 24: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/24.jpg)
Index of Refraction
Describes relative transmittance of optical filter with respect to its wavelength.
Determines amount of incident light reflected at the filter/air interface.
Plastic filter with a refraction index of 1.5 reflects 4% of the light at the interface when the light is normal or perpendicular to the filter.
![Page 25: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/25.jpg)
Photometer should have color response as close to the CIE curve as possible. Silicon photodiode with glass filters provide a better CIE curve match than selenium and cadmium cells.
![Page 26: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/26.jpg)
Numerical aperture (NA) refers to the sine of the half angle of the acceptance cone of the light.
Characterizes the range of angles over which the system can accept or emit light.
![Page 27: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/27.jpg)
Exposure Time
f value of a lens – the ratio of its clear or opened aperture to the focal length
where k = 3.33 (constant)
N is the f-stop B is the scene illumination (foot-Lamberts)
S is ASA (ISO) rating of film
t is exposure time
t is the interval the shutter remains open in seconds
BSkNt
2
![Page 28: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/28.jpg)
Greyscale
A grayscale is a chart of progressively darker shades of gray placed next to one another.
You use the greyscale to determine how much contrast the camera delivers.
![Page 29: V1 Ch 3 Measuring Devices](https://reader034.vdocuments.net/reader034/viewer/2022042610/5695d04c1a28ab9b0291e049/html5/thumbnails/29.jpg)