CA2281517A1

CA2281517A1 - Illumination device for a projector

Info

Publication number: CA2281517A1
Application number: CA002281517A
Authority: CA
Inventors: Franc Godler
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-02-19
Filing date: 1997-08-28
Publication date: 1998-08-27
Also published as: DE29703797U1; WO1998037455A1; CN1251663A; EP0961950A1; JP2001511913A

Abstract

The invention relates to a lighting device for illuminating an extensive, image-creating field (62) in a projector, comprising light-source elements and a reflector (10) arranged behind said light-source elements. The light-source elements take the form of a plurality of lamps (48, 50, 52, 54), preferably xenon-containing gas discharge reflector lamps. The reflector (10) consists of a plurality of adjoining reflector segments (12, 14, 16, 18), whereby each of the reflector segments (12, 14, 16, 18) is optically aligned with one of the lamps (48, 50, 52, 54) in such a way that the result is a generally evenly illuminated surface.

Description

1 [amended sheet) Illumination Device for a Proieetor Technical Field The invention relates to an illumination device fir illtunination of an extended image-gcnerating; field in a projector, in which the image-generating field is illu~ninatcd by ~r plurality of lamps, which illuminate different areas of the image-generating;
field.
lU The invention particularly relates to video projectors, in which the image-generating; field is fornied by a liquid crystal field (liquid crystal display or panel), the liquid crystals being energized according to video signals. However, the image-generating field can also he a diapositivc field.
Background Art Halogen metal vapour larnps are usually used in projectors of high power. Such halt>Ken metal vapour lamps have a dtuability of about 250 to 1000 hours, which is tutdcsirably short. They arc very expensive, such that projectors equipped with such tamps practically 2U can he used only for commercial purposev.
Lamps ccmtaining xenon are known, which are used as lamps for vehicle headlamps.
Such lamps arc produced in large scale manufacture and, thus, they are relatively inexpensive. Purthennore, they have long durability of over 3000 hours. The disadvantage of these lamps containing xenon is that their luminosity is limited. The luminous flux of such lamps is maximum 5000 Int at an electrical rower crl' S0 W.
However, projection cyf :r liquid crystal field on a screen by means of a video projector requires a luminous flux of the lamp of at least 150001m if a corresponding luminosity of, for example, 2UU to 300 ANSI-lumen shall be achiCVed at the screen.

2 ~amendcd sheet) 17F 42 14 2ti2 A 1 discloses an illuraination device for illumination of an extended image-gcnerating licld in a projector, in which the image-gencratin6 field is illuminated by a plurality of lamps, which illuminate different areas of the image-generating field. A
diapositive is directly illuminated by an arrangement c~f many tightly racked light sources. This is done to avoid the disadvantage of relatively large structural vhape of usual capacitor systems. Miniature filament lamps, optical fibres ur luIIltIlollS diodes are prr~poscd as light ar~urccs.
US 4,OR6,010 A relates tc, an illumination device, particularly for a photocopying apparatus. In this device two longitudinal lamps or pairs of lamps having cylindrical reflectors are arranged on both sides of a surface to be illuminated.
US 3,777,135 A relates to an illumination device, particularly likewise for a photocopying apparatus. In this device four lamps having cylindrical rellecte~rs are arranged around the surface to be illumitu~ted and outside this surface. 'fhe lamps are tuhuisrr lamps.
Diaclosurc of Invention It is the object r~l' the invention to provide an inexpencivr illuminaticm device I'c>r :.v projector having high power and long durability for projection of an extended image-generating field, particularly a liquid crystal field, for video projection.
Accordinb to the invention this object is achieved by (a) a reflectr~r, which consists of a plurality of udjuc;ent rellrctor sections and the shape of which substantially corresponds to the shape of the image-generating field, (b) each of these reflector sections, in which one of the lamps each is located, being, optically aligned with this lamp, suc:.h that each lamp substantially illuminates an associated part of the image-generating field, 3 (s~mended sheet( (c) the lamps are gas discharge lamps, particularly gas discharge lamps containing xenon, each including - a base, - n longitudinal glass hc~dy having a first end facing the base and a second end remote from the base, - a first electrode arranged in the glass body close to the first end, - a second electrode arranged in the glass body close to the second end, - a firU power lead comiected to the first electrode, and - ~, second power lead connected to the second electrode anc3 extending along the glass body between the base and the second end of the glass body.
Far achieving the object a reflector having a plurality of adjacent reflector sections is provided. The shape (rectangular) and size of this reflector whstantially corresponds tn the aha~ of the image-generatinb fiald. The image-generating field is relatively large in order to achieve a good resolution.
Onc lamp is 1c>cated in each of these reflector sections, such that each lamp substantially illutttinates an associated part of the image-generating field. 'fhc required high total power for illumination ~f the image-generating field and for achieving a sufficient brightness of tltc image thrown cm a screen is divided onto several, for example four, lamps, ~f which each individually already has a high brightness, which, however, alone is not sufficient for illuminating the total image-generating field.
A particular type of lamps is used, namely gas discharge larttps containing xenon and having a particular construction. Such lamps are used as headlamps for vehicles. 'Thus, 4 (amended sheet they are produced in large scale manufacture and, thus, they arc inexpansivc.
Furthermore, they have long durability.
Modifications of the invention are subject matter ofthe sub-cl:~ims.
An embodiment of the invention will now be described in greater detail with reference to the accomranying drawings.
Brief Description of the Urawinga big. 1 is a schematic illustration and shows a front view of an embodiment of an illumination device having a lamp unit having four rellcctor sections.
Fig. 2 is a schematic sectional illustration and shows a side view of a prr~jector having an illumination device according to big. 1.
Fig. 3 is a schematic-perspective illustr~rtir~n and shows a tilted front view of the projector of Fig. 2.
Pig.4 is a ~cc;hematic illustration and shows a side view of a spotlight lamp containing xenon.
Preferred Embodiment of the Invention In Fig. 1 numeral 10 designates a lamp unit of an illumination device. 'fhc lamp unit l0 has a rectangular reflector 1 1. The rellector I I can be made of reflecting metal, however, preferably of glass having a metal-coating transparent for infrared radiation.
'I'hc reflector 11 is divided into four adjaccat rectangular reflector sections 12, 14, 16 and 18. In Fig. I
the rcflrctor sections 12, 14, 16 and 18 form paraboloids convex to the back, the axes 20, 22, 24 and 26 extending though the vertex of the paraboloids being offset relative to the centres c~f the respective reflector section 12, 14, 16 and 18, respectively, towards the centre c~f the total ret7ector 11. This is indicated by corresponding contour linex (far example 3U) as an example in the reflector section 18, the elevation z as a function n('thc distance r to the axis 26 of the reflector section 18 bein6 z = rl/4f (f =
focal length).
holes 32, 34, 36, and 38, respectively, for srotlight lamps containing xenon are provided S in the vertex of the respective paraboloidal retlcetor sections 12, l4, 1 G
and 18, respectively. These holes 32, 34, 36 and 38 arr circular having lateral cut-outs 4(1, 42, 44 and 46, respectively, for the power lead of the spotlight lamps containing xenon. in the illustrated embodiment the reflector 1 1 has the following dimensions (rig.
1):
- The overall size of the reflector 1 1 is ax - 176 mm and ay = 132 mm.
- The overall sicc of the respective rctlcetor sections 12, 14, 16 and 2U is bx = 88 mm and by - fifi mm.
- The vertex of the paraholoids are located at distances ex ~ 35 mtn surd cy =
2G.2 mm from the inner edges of the reflector sections 12, 14, 15 and 20.
- The focal length f of the paraboloids is t= 20 mm.
- 'The holes 32, 34, 36 and 38 have a diameter of 12 mm.
- The lateral cut-outs 40, 42, 44 and 4G are G x 4 mm.
Figs. 2 and 3 show a projector, in which the lamp unit 10 shown in >;ig.l is used.
2U Corresponding elements are designated in Figs. 2 and 3 by the same reference numerals as in Fig. 1.
One spotlight lamp 48, 50, 52 and 54, resrectively, containing xenon is located in each of the holes 32, 34, 3G and 38 (Fig. I ). The lamps 48, 50, 52 and 54, respectively, arc located in the local point of the respective reflector section 12, 14, 16 and 18, respectively, and yupporicd on the rear side of the reflector 1 1 and adjustablC rclativr t«
the reflector sections 12, 14, 16 and 18, respectively, by means of adjusting ,crews, of which only two adjusting screws 56 and 58 can be seen in his. 2.
An infrared filter 6U (His. 2), an image-generating field in the form of a liquid crystal field 62, a hresnel lens 64 and an objective lens 66 arc located in the path of rays from the lamp unit 1 U.

An image is generated on the liquid crystal field 62 in known manner arid therefore not tirrthcr described herein, which image is imaged by the Frcsnel lens G4 and the objective lens onto a screen (nol illustrated).
1n the illustrated en~bcodiment, a liquid crystal field 62 having the size 13U
x 98 mm shall be regularly illuminated by the lamp unit 10. The lamp unii 10 is slightly larger than the surface of the liquid crystal field 62 and is spaced by approximately 20 cm from the liquid crystal field 62.
lU
The rctlectlng surfaces of the rctycctor sections 12, 14, 7 G and 18 are prewided with t:~cets (not illustrated). Only the surfaces in an area close to the lamps 48, 50, 52 and 54 are faceted, such that approximately 2/3 cU' the respective surfaces arc smooth.
Some of the facets arc deadened depending on the radiation characteristics of the I~tmps 48, S0, S2 and 54. The surfaces to be deadened can be determined by calculation and/or experimentally.
Due t~ the particular design of the reflector sections 12, 14, 16 and 18 and the eccentric arrangement c~f the lamps 48, SU, 52 and 54 in these reflector sections l2, 14, 16 anti 1 R, a regular illumination of the liquid crystal field 62 is achieved. Furihermc~rc, the 2U adjustahility of the hunps 48, 50, 52 and 54 allows a tine adjustment.
In a further embodiment (not illustrated) each of the lamps containing xenon is provided with an iron core and coil, which arc supported on the rear side of the reflector in the proximity of the lamps. Tl~e iron care hav an air gap, in which the discharge space of the lamp is located. 'fhe air gap starts from the rear side of the reflector and ends there.
Further fine adjustment of the illumination can be achieved by applying a magnetic field.
In I~ig. 4 a commercial headlamp containing xenon is illustrated, which headlamp can be used in the present invention. The lscmp ccmsistv of a base 6fi, a glass body 70 having ate upper and a lower electrode, a lower power lead 72 and an upper power lead 74.
The upper power lead extends axially along the glass body 70 from the base to the rod c~f the glasrs body 70 ndmote liom the base 68.

The nonunifi~rm radial radiation characteristics of the illustrated lamp is caused by the shadow caused by the upper power lead 74 and by a salt tilling in the discharge space. 1n the cmbc~diment illustrated in Figs. 1-3, the orientation of the lamps 48, SU, 52 and 54 is S chosen such that the upper power Iced 74 points towards the centre e~f the.
total reflector.
In these directions and towards earth's surface thrre arc disturbances in the radiation characteristics. This is compensated for by the offset of the lamps 48, SU, 52 and S4 towards the centre of the total reflector and by applying a magnetic field. It shall be noted that the present invention is not limited to such an orientation of the lamps 48, 50, 52 and lU 54. 1f the disturbances of the radiation characteristics of the lamps 48, 50, 52 and 54 would p«int in another direction, then the offset ol' the (amps 48, 50, 52 and 54 will be done in this direction.

Claims

1. Illumination device for illumination of an extended transparent image-generating field in a projector, in which the image-generating, field is illuminated by a plurality of lamps (48,50,52,54), which illuminate different areas of the image-generating field, characterized by (a) a reflector (11), which consists of a plurality of adjacent reflector sections (12,14,16,18) and the shape of which substantially corresponds to the shape of the image-generating field (62), (b) each of these reflector sections (12,14,16,18), in which one of the lamps (48,50,52,54) each is located, being optically aligned with this lamp (48,50,52,54), such that each lamp substantially illuminates an associated part of the image-generating field, (c) the lamps (48,50,52,54) are gas discharge lamps, particularly gas discharge lamps containing xenon, each including - a base (68), - a longitudinal glass body (70) having a first end facing the base (68) and a second end remote from the base (68), - a first electrode arranged in the glass body (70) close to the first end, - a first power lead (72) connected to the first electrode, and - a second power lead (72) connected to the second electrode and extending along the glass body (70) between the base (68) and the second end of the glass body (70).

2. Illumination device as set forth in claim 1, characterized in that the image-generating field (62) is formed by a liquid crystal field.

3. Illumination device as sot forth in claim 1 or 2, characterized in that the reflector (11) consists of glass having an infrared-transparent metal coating.

4. Illumination device as set forth in anyone of the claims 1 to 5, characterized in that the reflector (11) has a rectangular basic shape and consists of four rectangular reflector sections (12,14,16,18), one of the lamps (48,50,52,54) being arranged in front of each of the reflector sections (12,14,16,18).

5. Illumination device as set forth in anyone of the claims 1 to 4, characterized in that the lamps (48,50,52,54) are supported on the rear side of the reflector (11) and extend through holes (32,34,36,313) in the reflector (11).

6. Illumination device as set forth in claim 5, characterized in that the holes (32,34,36,38) for the lamps (48,50,52,54) have a circular shape and lateral cutouts (40,42,44,46) for the power lead (74).

7. Illumination device as set forth in claim 5 or 6, characterized in that the lamps (48,50,52,54) are adjustable relative to the reflector (11).

8. Illumination device as set forth in anyone of the claims 1 to 7, characterized in that the reflector sections (12,14,16,18) are paraboloids, the lamps (48,50,52,54) teeing located in the focal points thereof.

9. Illumination device as set forth in anyone of the claims 1 to 8, characterized in that the lamps (48,50,52,54) are offset relative to the centres of the reflector sections (12,14,16,18).

10. Illumination device as set forth in claim 9, characterized in that the axes (20,22,24,26) of the paraboloids likewise are offset relative to the centres of the reflector sections (12,14,16,18), such that they extend through the offset lamps (48,50,52,54).

11. Illumination device as set forth in anyone of the claims 1 to 10, characterized in that the reflectivity of the reflecting surfaces of the reflector (11) or of the reflector sections, respectively, is differing locally.

12. Illumination device as set forth in anyone of the claims 1 to 11, characterized in that the reflecting surfaces of the reflector (11) or of the reflector sections, respectively, are faceted.

13. Illumination device as set forth in claim 12, characterized in that the reflecting surfaces of the reflector (11) or of the reflector sections, respectively, are faceted in predetermined areas and smooth in other areas.

14. Illumination device as set forth in anyone of the claims 1 to 13, characterized by means generating a magnetic field, the magnetic field of which penetrating the discharge space of the lamps and influencing the radiation of the lamps (48,50,52,54), such that the gas mixture of ions and electrons of the lamps (48,50,52,54) become free from gravitational influences.