[0001] This invention concerns a luminaire with mirror reflectors, which can either be recessed
in the ceiling, fitted flush to it or hung beneath it. It consists of a housing containing
at least one lamp fitted inside a concave reflector, which is built into the housing
and which longitudinally extends above a row of small, transverse mirrors. Each of
these is fitted on its upper side with a light-reflecting cover and their outermost
parts fit into specially-provided recesses in the main reflector.
[0002] Similar luminaires are common when they are equipped with transverse mirrors having
an almost v - shaped cross-section and a flat strip of reflective material attached
to their upper sides, and aim at providing low-level luminance in the usual angle
of observation.
[0003] By "usual angle of observation" we mean here the angle in which one predominantly
looks in the normal practice of using his sight. For example, in carrying out a desk
task consisting of reading and writing on a horizontal surface, we can consider as
usual an angle of observation ranging from ⁺ 10° to the perpendicular of the desk
top to angles lying on a horizontal plane (visual communications). For such task lighting
it is common or desirable to construct the optical system in such a way as to prevent
radiating large quantities of light allowing bright light spots to be visible within
a beam shielding angle of 30-45°. to the horizontal angle of observation. Similar
inconvenient light spots often occur when use is made of reflectors incorporating
transverse mirrors, which are already on the market. These disturbances are the result
of reflection from the flat, reflective strip of material one finds on these transverse
mirrors.
[0004] The most common methods used today to prevent these spots are the following:
- the covers placed above the v-shaped mirrors are either made out of a substance
which reflects very little light, such as black synthetic material or are painted
black, thus leading to a more than 20 % reduction in light-output ratio;
- no covers are used at all, thus creating less bright spots, due to the fact that
only the raised edges of the v-shaped mirrors reflect the light - this still causes
a more than 10 % reduction in light-output ratio;
- the lateral sides of the v-shaped mirrors are pulled through to such a high point
(nearly or completely equalling the shielding angle α) in such a way that the spots
which occur are in principle not visible from the angle in which the lamp itself is
visible, thus causing the spots to disappear, as it were, behind the lamp.
[0005] In some designs the uppermost side of the row of mirrors is left open as well, in
order to avoid that any potential reflection that falls on it via the multiple reflections
in the concave, longitudinal reflector which are bein reflected onto unexpected and
undesired surfaces could become once again visible as bright spots. In this case a
reduction in light-output ratio of more than 20% can be reached. Such a solution to
the problem was put forward in French patent no. 2.554.549. The shortcomings in the
solution we have been dealing with here were thus described at that time and place.
[0006] The invention here described aims, through the use of an optical system based on
the original transverse mirrors, at directing the light in such a way that:
1) the task to be lit is illuminated in the most efficient way possible, thus creating
optimum illuminance levels of light intensity and optimum luminance and/or colour
contrast. The task lighting can regard for example reading, writing, drawing or VDU
work, or it can involve assembling/checking various elements in industrial spaces;
2) large quantities of incident light rays emanating from the luminaire are prevented
from being beamed directly into the eyes of the observer from angles which hardly
differ from the usual angle of observation, thus reducing the viewer's capacity to
perceive small contrasts and/or details and, in so doing, creating an disability glare;
3) surfaces, (even relatively small ones) which are highly luminant in relation to
their normal backgrounds are prevented from being visible from angles which hardly
differ from the usual angle of observation (psychological or discomfort glare). Besides
the disturbance provoked by looking directly at the spots in the luminaire, reflections
from these highly-luminous spots onto a VDU can hinder the VDU operator's task.
[0007] In order to direct the light in the way just described, the invention defines the
shape of the above-mentioned, light-reflecting covers in such a way that an observer,
while looking obliquely or askance towards the luminaire will fail to see the troublesome
light spots which are occuring due to reflection on the reflector from the above-mentioned
transverse mirrors, outside sof the lamp fitted to the luminaire and its mirrored
image on the reflector. This will not happen if the angle of observation, in relation
to the ceiling, is less than 30-45°, that is, the desired angle of observation, in
which an observer just fails to perceive the lamp or its mirrored image. This is done
in such a way that the observer who fails to perceive the lamp is also unable to see
any light spots at all.
[0008] In a preferably applied embodiment, the above-mentioned transverse mirrors, when
seen in longitudinal section, consist of a right-angled part on the bottom, above
which is fitted a covering strip of material, which v-shaped strip may be described
as having the lines of the v-shape forming an angle that is approximately 90-120°,
the two lines of which being joined by a curved piece which is tangentially attached
to them both.
[0009] Other details and advantages of the invention will become clear from the following
description of a luminaire, built in accordance with said invention. This description
is to be seen solely as an example, and does not limit the invention.
Figure 1 is a cross-section of the luminaire, according to the invention.
Figure 2 is a longitudinal cross-section of a part of the same luminaire.
Figure 3 is, on a different scale, a side view of a transverse mirror.
Figure 4 is, on a different scale, a side-view of the commonly used type of transverse
mirror.
Figure 5, also on a different scale, is a cross-section of a transverse mirror, as
a variant.
[0010] The luminaire, in accordance with the invention specifications and as shown in the
above-mentioned figures, consists essentially of a housing indicated as (1) in Figure
1.
[0011] The elements and parts necessary for fitting at least one lamp (2) do not pertain
to the essence of the invention itself, and will therefore not be described herein
any further.
[0012] Built into the housing (1), this reflector (3) is mounted partially along each side
and partially above the lamp (2). Seen in section, it is mainly concave. This reflector
can consist of either a single piece or, as seen in Figure 1, three different parts.
[0013] Along the whole length of the reflector (3) small transverse mirrors are mounted.
The outer edges of these mirrors are fastened to the reflector (3) in specially-provided
recesses. When seen in cross-section, both the transverse mirrors according to the
invention, as well as those which have been in regular use until now, display, at
least in part, a v-shaped section. In order to allow the scope of the invention to
better emerge, reference is first made to the design shown on Figure 4. The commonly-used
transverse mirrors (5) are mostly v-shaped in section, and their straight upper parts
are fitted with a cover (6) that is clipped either above or onto the v-shaped part
of the transverse mirror. In order to avoid beaming the amount of light by means of
these covers in the "wrong" direction, and thus causing the above-mentioned discomforting
light effects, these covers have until now either been painted with a highly light-absorbent
material, such as matt black enamel, or made out of matt black synthetic material.
The result is a reduction in the total amount of light emanating from the luminaire.
[0014] According to the invention, the total amount of light beamed is kept at maximum levels,
and an observer, who looks obliquely or askance towards the luminaire from an angle
of less than 30-45° to the ceiling, no longer sees the discomforting light spots described
above; in other words, if the observer is unable to see the lamp itself, he is equally
unable to see any light spots.
[0015] Two different designs for this are possible, and for the sake of clarity, they are
represented in section, on Figures 3 and 5.
[0016] The transverse mirrors (4) (Figures 1, 2 and 3) consist of two, right-angled parts
(7), shown in longitudinal section, which both, when seen in cross-section, combine
to form a v-shape. If the case may be, they can be made out of a single piece. The
right-angled concave parts (7) of the transverse mirrors (4) are joined at the top
with strips (8) consisting of two nearly-flat, parallel parts. Seen in front view
or in longutudinal section, these strips have a v-shaped appearance. The lines of
this v-shape cross one another, forming an angle β of between ± 90-120°. An essential
element for the invention is the fact that the angle α (formed between the tangent
(a) and the lamp (2), and the tangent (b) with the reflector underside) coincides
with the angle βʹ (formed by the tangent (c) with the upperside of a transverse mirror
(4), and the tangent (b) with the reflector underside). The strips (8) run between
the two lines of the v-shape along a curve which forms a tangential circular connection
with the above-mentioned v-shaped strips.
[0017] The strips (8) rise upwards at their outermost parts, and above them is a cover (9)
made out of light-reflecting material. The shape of the cover (9) (the angles βʹ and
the rounded part beneath the lamp(s)) has been chosen in such a way that, combined
with the uppermost longitudinal mirror and the lateral longitudinal mirrors (3)),
if one glances sideways from any angle which in relation to the horizontal plane is
less than the angle α, hardly any highly-luminant spots or none at all would be noticeable.
The light striking the cover (9) is then reflected at an angle greater than the angle
α.
[0018] The amount of light recuperated from the cover (9) in certain cases results in a
more than 20% increase in the total light-output as comapred to certain other designs
which make no use of this specially-designed, light-reflecting cover (9). The special
curve of this cover (9), combined with the curving of the longitudinal mirrors (3),
means that it is not necessary that the sides (8) of the transverse mirrors and the
attached light-reflecting cover (9) are placed so high that angle βʹ coincides, as
it were, with angle α.
[0019] The most common designs are those where angle βʹ is approximately 28° and where angle
α is approximately 40°, thus giving rise to the fact that the vertical strips (8)
here fail to act as a "cover" for the light spots, which would then be visible on
the longitudinal reflector (3) from an angle less than angle α.
[0020] The flat strips (8) and the concavely-bent parts (7) can either be constructed out
of a single piece or consist of two separate parts.
[0021] As can be seen from Figure 1, it can be deduced that the shape of the light-reflecting
covers (9), as in the design described sabove, has been worked out in such a way as
to bring about the complete or practically-complete disappearance of the discomforting
light spots which occur in most other designs and are visible from angles which are
less than the strived after shielding angle 2 in relation to the usual angle of observation.
An added important advantage is that this comes about without having to make use
of strongly light-absorbent materials to cover the upperside of the transverse mirrors.
This means that the quantity of light falling on the covers (9) of the v-shaped transverse
mirrors (4) is either not absorbed by them or is not beamed in "discomforting directions",
but instead is beamed by the proposed mirrored, light-recuperation system in such
a direction that this quantity of light can be profitably made use of for increasing
illuminance levels and luminance and colour contrasts during everyday sight tasks.
[0022] This is also the case of the design shown in section, on Figure 5. The transverse
mirrors (10) on Figure 5 consist of an upper and a lower part. The lower part (11),
as seen in cross-section, shows the same rounded profile as in the transverse mirrors
(4), and the outer edges of the latter can optionally be similarly anchored in the
same way in the recesses of the reflectors (3). The upper part (12) of a transverse
mirror (10) is made in a reverse v-shape, the base of which fits into the base of
the v-shaped lower part (11). The uppermost angle of the reverse v-shaped upper part
(12) is not greater than 50°. These structures, namely the transverse mirrors (10),
can consist of two components but could, if necessary, be made out of a single piece
of material.
[0023] The transverse mirrors (10), which in cross-section approach more or less the shape
of a parallelogram, also offer advantages similar to those described above in as
regards the transverse mirrors (4).
[0024] The invention naturally is not limited to the above-mentioned designs, and several
changes could be made to them without going outside the framework of the patent application.
1. A luminaire incorporating mirror reflectors, which can either be recessed in, fitted
flush to, or hung beneath a ceiling, (usually a suspended one), consisting of a housing
containing at least one lamp fitted inside a concave reflector, which is incorporated
in the housing and which longitudinally extends above a row of small, tranverse mirrors,
each of the latter being fitted on its upper side with a light-reflecting cover, and
its outer edges anchored in specially-provided recesses in the main reflector, characterized
in that the shape of the above-mentioned, light-reflecting covers is so designed that
an observer, who looks obliquely or askance in the direciton of the luminaire, fails
to notice, outside of the therein fitted lamp (2) and its mirror image reflected on
said reflector (3), the discomforting light spots caused by reflection from the abovementioned
transverse mirrors bouncing off the reflector (3),when this is viewed at an angle
which in relation to the ceiling is less than 30-45°, that is, the strived after angle
from which a viewer just fails to perceive the lamp or its mirror image.
2. A luminaire according to claim 1, characterized in that the above-mentioned transverse
mirrors (4), when seen in longitudinal section, consist of a right-angled lower part
(7), above which is fitted a covering strip of material (8) which is v-shaped, the
lines of the v-shape forming an angle of approximately 90-120°, and the two above-mentioned
lines being joined by a curved piece tangentially attached to them both.
3. A luminaire according to claim 2, characterized in that the above-mentioned, uppermost,
right-angled parts, when seen in cross-section, are of a reverse v-shape.
4. A luminaire according to one of claims 2-3, characterized in that distinguishing
feature being that the above-mentioned strips (8), which when seen in longitudinal
section are shaped like a right-angle, run either parallel, or nearly parallel one
on top of another.
5. A luminaire according to one of claims 2-4, characterized in that a light-reflecting
cover is fitted between the above-mentioned strips (8).
6. A luminaire according to claim 1, characterized in that the above-mentioned transverse
mirrors (10), when seen longitudinally, consist of two parts of a right-angled appearance,
lying one on top of another, to wit, an upper part (11) and a lower part -(12), which,
when seen in cross-section, take on the shape of two triangles sharing a common base.
7. A luminaire according to claim 6, characterized in that the above-mentioned triangle,
which belong to upper part (12), have a vertical angle that is not greater than 50°.