A.2.5 Front frame reflection characteristics
A.2.5.1 Front frame reflectance
Background
The reflectance of the FPD front frame that surrounds the active screen area is of
great importance for visual ergonomics.
A low front frame reflectance can cause a disturbingly high contrast between the
frame and the active screen area. On the other hand, a frame of high reflectance
can cause a high contrast when seen against a low luminance screen.
It is commonly recommended that there should be no more than a 3:1 difference
in luminance between the task area and its immediate surrounds (e. g. FPD front
frame, documents, room, walls etc) and no more than a 10:1 difference between
the task area and more distant surroundings.
Definition
Reflectance is the ratio of the reflected luminous flux to the incident flux on a
FPD front frame surface and under specified lighting and measurement
conditions.
Applicability
All FPDs.
Test procedure requirements
See B.2.5.1.
References
Please see reference 12, 17 and 20 in chapter R.2 References.
Mandate:
The front frame shall have a reflectance value that is between 20% and 80%.
The following information shall be submitted:
A test report from a test laboratory accepted by TCO Development.
A.2.5.2 Front frame gloss
Background
Front frame gloss influences visual comfort and legibility by drawing attention
away from the task at hand. The higher the gloss value the more likely it is that
the surface will create irritating specular reflexes (mirror-like reflexes) from
ambient lighting. If the gloss value is high enough, the problem of reflection
images can occur. Also, the distinctness of the reflection influences its perceived
impact.
The front frame shape can in some situations make a smooth frame act as a mirror
and consequently increase the contrast between reflections and their background
to a level that is far beyond the values that can be accepted by a user.
Definition
Gloss is a measure of how a light beam, physically described as luminous flux, is
scattered at the surface when incident against that surface. Gloss is a function of
the directional reflectance properties of a surface.
Applicability
All FPDs.
Test procedure
See B.2.5.2.
References
Please see reference 5, 6 and 7 in chapter R.2 References.
Mandate:
The gloss value G(60°) shall be 30 gloss units or less.
The following information shall be submitted:
A test report from a test laboratory approved by TCO Development.
B.2.5 Front frame reflection characteristics
B.2.5.1 Front frame reflectance
B.2.5.1.1 Preparation of the FPD for testing
• No special preparation of the FPD is needed.
• The FPD frame surfaces to be tested for reflectance shall be clean.
• Measurement areas shall be as flat as possible in order to avoid measuring
errors.
• If the front frame of the FPD is curved, a measurement could be made
elsewhere on the housing, provided that the measured surface microstructure,
texture and colour are the same as the surface of the front frame.
• If no absolutely flat test surface can be found on the screen frame, the
manufacturer can also supply a flat piece of material with optical properties
fully equivalent to the front frame material.
B.2.5.1.2 Equipment
Integrating sphere, luminance meter and a calibrated diffuse white reflectance
standard.
B.2.5.1.3 Test method
The measured surface shall be selected on the darkest area of the frame surface.
If the front frame has more than one colour, or a greyscale, all colours and the
greyscale shall be measured. Logos, brand names, type marks, control buttons,
and other small markings are excluded from the measurements and the
requirements.
The selected FPD front frame surface for measurement shall be illuminated with
uniform diffuse white stable light either from an integrating sphere, which is
placed very close to the front frame, or by stable diffuse lighting.
The luminance LFPD of the selected test area shall be measured orthogonally to the
surface either through the sphere or orthogonally to the test surface under diffuse
lighting.
Keeping the measurement geometry and the diffuse lighting conditions constant,
the measured FPD frame surface shall be replaced by a diffuse white, calibrated,
reference sample with known reflectance ÁREF, and its luminance LREF shall be
measured.
B.2.5.1.4 Test evaluation
The front frame reflectance Á is as follows:
REF
REF
FPD
L
Á = L × Á
where
LFPD is the measured luminance on the frame
LREF is the measured luminance on the reflectance reference
ÁREF is the reflectance of the reference
Any correction factors shall be included in the calculation.
The reflectance value shall be presented in % with no decimal places.
(The mandate, according to clause A.2.5.1 is the following:
The front frame shall have a reflectance value that is between 20% and 80%).
B.2.5.1.5 Overall uncertainty
d ± 2% units.
See B.2.0.7.
B.2.5.2 Front frame gloss
B.2.5.2.1 Preparation of the FPD for testing
• No special preparation of the FPD is needed.
• FPD frame surfaces to be tested shall be clean.
• A gloss measurement instrument needs an absolutely flat surface to function
properly.
• If the front frame of the FPD is curved, a measurement could be made
elsewhere on the housing, provided that the measured surface microstructure,
texture and colour are the same as the surface of the front frame.
• If no absolutely flat test surface can be found on the screen frame, the
manufacturer can also supply a flat piece of material with optical properties
fully equivalent to the front frame material.
B.2.5.1.2 Equipment
A gloss meter in accordance with ISO2813, ASTM D 523 or DIN 67 530, and a
calibrated reference standard.
The measurement of gloss shall be made using an instrument with an incident
light beam angle of 60° to the normal of the measured surface.
B.2.5.1.3 Test method
Measurement of gloss shall be made at several locations on the front frame of the
FPD. Logos, brand names, type marks, control buttons and other small markings
are excluded from the measurements and the requirements.
Gloss in different directions shall also be measured at the selected locations.
B.2.5.1.4 Test evaluation
The gloss results shall be presented in gloss units with no decimal places.
The highest recorded gloss value shall be reported.
(The mandate, according to clause A.2.5.2, is the following:
The gloss value G(60o) shall be 30 gloss units or less).
B.2.5.1.5 Overall uncertainty
d ± 2 gloss units.
See B.2.0.7.
