9- Photometry Flashcards Preview

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Flashcards in 9- Photometry Deck (43):
1

Radiometry deals with

Power produced by a source of EM radiation

Does not take into account visibility of the source

2

Photometry deals with

Effect that radiation has on the visual system

3

Photopic luminosity curve describes

The sensitivity of the eye to different wavelengths

It is the difference between photometry and radiometry

4

Certain wavelengths are more efficient at stimulating the visual system then other wavelengths of light

Fact

5

Luminous power is

Total amount of light that emerges in ALL directions from the source

Lumen (lm)

6

Luminous intensity is

Light power produced in a GIVEN direction by poit source

Candela (cd)=1lm/str

7

Luminance is

The amount of light coming OFF a surface

Cd/m2, nit, apostilb

8

Illuminance is

The luminance power that falls ON a surface

Lm/m2, lux
Lm/ft2

9

Inverse square law states that

As a surface is moved away from from a point source, the number of lumens falling on it decreases with the square of the distance, decreasing the illumination

10

Inverse square law equation

E= I/d2

11

The amount of light relfected(brightness) is dependent on these 4 things

1. How much light illuminates the source

2. Distance from light source

3. Reflectance of surface

4. Tilt of the surface

12

Speculation reflector-

Reflects all the light in ONE direction

Surface looks shiny

13

Diffuse reflector

Scatters light in ALL directions

Surface looks matte or dull

14

Look at slides 18-20

Units

15

Retinal illumination is the

Amount of light falling on the retina

Trolands (Td)

16

Retinal illumination is directly proportional to these 2 things

Object luminance and pupil AREA

17

Retinal illuminance formula

Td= nits x mm2
=luminance of object area in nits x pupil area

18

As temperatures increases the peak wave ____
And the area under the curve(power) ____

Peak decreases
Power increases

19

2,000 K sources appear yellow-white because

It has more energy in long wavelength region

20

10,000 K source appears blue-white because

There is more energy in the short wavelength region

21

The higher the color temperature (bluer color) the more_______

Light scatters and larger area of discomfort glare

22

Higher color temperatures affects these 2 patients a lot

Presbyopia and cataract patients

23

The peak luminance efficacy of photopic vision is

680 lu/W at 555

24

The peak luminous efficacy of Scott pic vision is

1700 lu/W at 507 nm

25

RGB cones peak response is at

555 nm

26

Rods peak sensitivity is at

507 nm

27

Colored filters do what

Absorb/reflect some wavelengths that are incident upon it

28

Bandpass filters

Pass only a certain spectral band of light

29

Narrowband filters

Pass only a narrow spectral band of light

30

Broadband filters

Pass only a broader spectral band of light

31

Long pass filters

Transmit long wavelengths of light, but not shorter wavelenghts

32

Interference filters

Produce a very narrow band of light based on interference principle of light

33

Subtractive color mixtures filter

Color filters subtract light

2 filter combination in sequence transmits less light than either one by itself

34

Additive color mixtures filter

Light from different filters is added

Light is projected through 2 different color filters and combined on a screen

More light than either one by itself

35

Neutral density filter

Transmits all wavelengths equally, and minimizing color distortion

36

ND filters are specified by their

Optical density (OD)

37

Optical density equation

OD= log(1/T)

T fraction transmittance of the filter

OD in log units

38

What are ND filters used for

Sunglasses (block UV)

Minimize color distortion in patients with anomalous color vision

39

Using a ND with high OD will do what to transmission and absorption

Lower transmission
Greater absorption of light

40

An ND wth a low OD will do what to transmission and absorption

Higher transmission
Less absorption

41

T/F ocular tissues are vulnerable to UV radiation

True

42

Acute exposure to UVC can cause this in the eye

Solar keratitis

43

Chronic UV exposure can play a role in development of these

Pinguecula
Pterygium
Cataracts
AMD