JP2001125049A - Optical synthesizer and light source for illumination using the same as well as liquid crystal projector using both - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical synthesizer which is capable of supplying a light quantity allowing the sufficient observation of a projected image in a bright room as well, allows the projection as it is without interruption in spite of the burn-out of a lamp and is capable of regulating the color tones of the projected image to a desirable color tone and eliminating the light loss with simple constitution, a light source for illumination using the same as well as a liquid crystal projector using both. SOLUTION: Two PS polarized light splitting and synthesizing devices 31 and 32 which separate a linearly polarized light component to a P wave and an S wave, then modulates and synthesizes the one linearly polarized light component in the same polarization direction as the polarization direction of the other linearly polarized light component are arranged on two optical paths intersecting orthogonally with each other and a polarization beam splitter 33 is arranged in the position where the two optical paths intersect. Further, a λ/2 plate 6 which modulates the light to the linearly polarized light component of the polarization direction different from the linearly polarized light component synthesized with the PS polarized light splitting and synthesizing device 32 is arranged between the PS polarized light splitting and synthesizing device 32 and the polarization beam splitter 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light combiner, an illumination light source using the same, and a liquid crystal projector using the same.

[0002]

2. Description of the Related Art In recent years, presentations by enlarging and projecting electronic images via a computer or the like with a liquid crystal projector have been increasing. Generally, a liquid crystal projector includes a light source for illumination, an optical system for splitting illumination light,
The liquid crystal panel includes a liquid crystal panel that transmits the divided light, a combining unit that combines light transmitted through the liquid crystal panel, and a projection optical system that enlarges and projects the combined light.

FIG. 9 is a schematic configuration diagram showing a conventional example of a liquid crystal projector. In this conventional example, the liquid crystal projector includes dichroic mirrors 12a, 12c and reflection mirrors 12b, 12c that reflect light emitted from the illumination light source 11 to reflect light of a predetermined wavelength and pass light of other wavelengths.
The light is divided into light of three primary colors, R, G, and B, through d and 12e, and guided to condenser lenses 13a, 13b, and 13c.
b, 13c, and are condensed to enter the liquid crystal panels 14a, 14b, 14c adapted to the three primary color lights, and the light emitted by each liquid crystal panel is reflected by only the corresponding color light. Incident on a cross prism 15 configured by combining four triangular prisms each having a reflecting surface that transmits light other than the three primary colors, emit light in one direction, and enter the projection lens 16 in one direction. The light emitted from the projection lens is projected on a screen (not shown) so that an image can be observed.

In general, an illumination light source 11 used in a liquid crystal projector has a lamp 1 as shown in FIG.
a and a parabolic reflector 1b (or, as shown in FIG. 11, in addition to this, a concave lens 1c), and a light emitted from the lamp 1a is parabolically reflected. The light is reflected by the mirror 1b (in the case of FIG. 11, the parabolic reflection mirror 1b
, The direction of the light reflected in the convergence direction is refracted by the concave lens 1c), so that the light is emitted as parallel rays. As the lamp 1a, a discharge lamp such as an ultra-high pressure mercury lamp or a metal halide lamp is used. Among them, the ultra-high pressure mercury lamp is widely used because of its high luminous efficiency and utilization efficiency.

[0005]

Since the presentation is performed in a bright room, there is a demand for a bright liquid crystal projector which can be observed even in a bright room. However, in the conventional liquid crystal projector, the illumination light source is configured on the assumption that the projector is used in a dark room. Therefore, when used in a bright room, the projected image becomes relatively dark, and a clear projected image cannot be obtained. . Further, even if the power of the lamp itself used for the illumination light source is increased to make the illumination light even brighter, a high power discharge lamp cannot be manufactured.

There is also a need for a liquid crystal projector that does not interrupt video even if the lamp goes out during a presentation. However, with conventional LCD projectors,
If the lamp burns out, the image cannot be projected without replacing it with a new lamp, and because the lamp is hot and hot, it cannot be used until the lamp cools down, and the presentation is interrupted. Was gone.

Further, the ultra-high pressure mercury lamp has a problem that a red color is hardly produced due to the emission spectrum of mercury.

Also, since polarized light is used for the liquid crystal panel,
Liquid crystal panels 14a, 14b, and 14c are provided on the respective optical paths of the liquid crystal projector shown in FIG.
Before reaching 14c, the light is modulated into one linearly polarized light component using a polarizing means (omitted in FIG. 9). In this case, if only one of the two different linearly polarized light components is transmitted through the polarizing plate and made incident on the liquid crystal panel, the amount of light is reduced by half.

If one of the two different linearly polarized light components is modulated into the other linearly polarized light component, a bright projected image can be supplied without losing the light amount. Providing the means increases the number of components and complicates the configuration of the entire liquid crystal projector. Further, the characteristics of the dichroic mirror are greatly different between the S wave and the P wave, and cause a light amount loss.

Therefore, according to the present invention, it is possible to supply a sufficient amount of light for observing the projected image even in a bright room, to continue projection without interruption even when the lamp is cut off, and to further improve the color tone of the projected image. You can adjust the color tone,
Furthermore, it is possible to eliminate light loss with a simple configuration,
It is an object of the present invention to provide a photosynthesizer, an illumination light source using the same, and a liquid crystal projector using the same.

[0011]

The light combiner according to the present invention is arranged on two optical paths orthogonal to each other, separates a linearly polarized light component into a P wave and an S wave, and then splits one of the linearly polarized light components. Are modulated in the same polarization direction as the other linearly polarized light component and combined to produce mutually different polarized light components, and a polarization beam splitter disposed at a position where the two optical paths intersect. It is characterized by having.

The optical combiner according to the present invention is arranged on two optical paths orthogonal to each other, and separates a linearly polarized light component into a P wave and an S wave, and then converts one linearly polarized light component into the other linearly polarized light component. Two PS polarization splitting / combining means for modulating and combining in the same polarization direction as the polarization component to make the same polarization component, a polarization beam splitter disposed at a position where the two optical paths intersect, and one of the PS A first polarization modulator disposed between the polarization beam splitter / combiner and the polarization beam splitter for modulating a linearly polarized light component into a linearly polarized light component having a polarization direction different from that of the linearly polarized light component synthesized by the PS polarization beam splitter / combiner; And a polarization component modulating means.

[0013] The light combiner according to the present invention is preferably arranged such that, at the exit side of the polarizing beam splitter, P
A second polarization component modulating means for modulating in the same polarization direction as the other linearly polarized light component is provided in accordance with a position where one of the linearly polarized light component of the wave and the S-wave passes.

According to a third aspect of the present invention, there is provided an illumination light source according to any one of the first to third aspects, wherein parallel light beams are directed toward the light combiner on the respective light paths on the respective incident sides orthogonal to each other. It is characterized by comprising a light source for irradiation and a lens array in which a plurality of microlenses are combined to converge parallel light beams from the respective light sources into a plurality of light beams.

Further, the liquid crystal projector according to the present invention comprises an illumination light source, an optical system for splitting the illumination light, a liquid crystal panel transmitting the split light, and synthesizing means for synthesizing the light transmitted through the liquid crystal panel. In a liquid crystal projector including a projection optical system for enlarging and projecting the combined light, the illumination light source according to claim 4 is used as an illumination light source.

The liquid crystal projector according to the present invention is preferably characterized in that lamps having different emission spectra are used for each of the illumination light sources.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of a light combiner according to the present invention. FIG. 2 is a diagram illustrating the principle of a PS polarization splitter / synthesizer used in the present embodiment.
And λ / 2 on the optical path of the polarized light component reflected by the second polarizing film.
(B) shows a state in which a λ / 2 plate is arranged on the optical path of a polarized light component transmitted through the first polarizing film. FIG. 3 is a schematic configuration diagram showing an embodiment of an illumination light source according to the present invention using the light combiner of the present embodiment. FIG. 4 shows a lens array used in the illumination light source of the present embodiment. FIG. 5B is a front view, FIG. 5B is a plan view of FIG. 5A, FIG. 5C is a right side view of FIG. 5A, and FIG. 5 is a schematic diagram showing an embodiment of a liquid crystal projector according to the present invention using the illumination light source of the present embodiment. It is a block diagram.

As shown in FIG. 1, the light combiner 3 of the present embodiment comprises first and second PS polarization division combiners 31, 32.
, A polarizing beam splitter 33, and a λ / 2 plate 34. The first and second PS polarization division combiners 31 and 32 are respectively arranged on two optical paths orthogonal to each other. The polarization beam splitter 33
It is arranged at a position where two optical paths intersect. The λ / 2 plate 34 is disposed between the one PS polarization splitting / combining device 32 and the polarization beam splitter 33, and makes the linearly polarized light component different from the linearly polarized light component synthesized by the PS polarization splitting / combining device 32. It plays the role of first polarization direction modulating means for modulating the polarization direction into a linearly polarized light component.

The PS polarization splitter / combiner 31 (32)
As shown in (a), two sets of minute polarizing films 31a, 31b (32a, 32b) are provided in a transparent thin plate member in accordance with the number of incident light beams. The linearly polarized light component is rotated by 90 degrees to the exit position of the polarized light component reflected by the polarizing films 31a, 31b (32a, 32b) to match the polarized light component transmitted through the polarizing film 31a (32a).
It is provided with polarization component modulating means such as a / 2 plate 31c (32c).

The two polarizing films 31a, 31b (32a, 3
2b) shows that the polarization characteristics are the same and the P
One of the linearly polarized light components of the wave and the S wave is transmitted, and the other is reflected. Here, for convenience of explanation, it is assumed that a P wave is transmitted and an S wave is reflected. Also, the PS polarization splitting / combining device 31
(32) indicates that the incident light flux is converted to the PS polarization splitter / combiner 31.
From the incident side of (32), the two polarizing films 31a and 31b (3
2a, 32b) and passes through the first polarizing film 31a (32
The arrangement is adjusted so as to be incident on a).

According to the PS polarization splitter / synthesizer configured as described above, the P wave transmitted through the first polarizing film 31a (32a) is directly used as the PS polarization splitter / synthesizer 31 (3).
2). Further, the first polarizing film 31a (32
The S wave reflected in a) is converted to the second polarizing film 31b (32b).
Reflected by the second polarizing film 31b (32b) toward
After exiting from the polarization splitter / combiner 31 (32),
The polarization direction is rotated by 90 degrees by the λ / 2 plate 31c (32c) and modulated into a P wave. The light modulated by the P wave and emitted from the PS polarization combiner 32 is modulated into the S wave by transmitting through the λ / 2 plate 34.

The polarizing beam splitter 33 has a polarizing film for transmitting one linearly polarized light component and reflecting the other. Here, it is assumed that the P wave is transmitted and the S wave is reflected.

Therefore, according to the present embodiment, the P wave from the PS polarization splitter 31 passes through the polarization plane of the polarization beam splitter 33, and the P wave from the PS polarization splitter 32 is λ /
Modulated into S-waves by the two plates 34, and polarized beam splitter 3
The light reflected by the third polarization plane is combined as light passing through the optical path in the same direction with different linearly polarized light components. Therefore, if the illumination light sources are provided on the optical paths orthogonal to each other in the light combiner of the present embodiment, light from the respective light sources can be efficiently combined, and bright illumination light can be obtained.

Incidentally, the λ / 2 plate 31c (32c) corresponds to FIG.
As shown in (b), it may be arranged on the optical path of the polarized light component transmitted through the first polarizing film 31a. In that case, the P wave transmitted through the first polarizing film 31a (32a) is
The polarization direction is rotated by 90 degrees by c (32c) and modulated into an S-wave. Further, the S-wave reflected by the first polarizing film 31a (32a) is reflected by the second polarizing film 31b (32b) toward the second polarizing film 31b (32b) and is reflected by the PS polarization splitting / combining device 31 (32). ). Therefore, the light emitted from the PS polarization splitter / combiner 31 (32) becomes an S wave. Therefore, the light combiner of the present embodiment is replaced with the PS polarization splitter / combiner 31.
Λ / 2 plate 31c and PS / 2 polarization splitter / combiner 32
2 (a) and FIG. 2 (b), respectively, so that different polarization components are emitted from the PS polarization splitter / combiner 31 and the PS polarization splitter / combiner 32. In this way, the configuration may be such that the λ / 2 plate 34 is not provided.

As shown in FIG. 3, the illumination light source 11 according to the present embodiment irradiates a parallel light beam onto each light path on the respective incident sides of the light combiner 3 which are orthogonal to each other. And second light sources 1 and 4, and lens arrays 2 and 5 each including a combination of a plurality of microlenses for converging parallel light rays from each of the light sources 1 and 4 into a plurality of light fluxes.

The first light source 1, like the light source 1 shown in FIG. 10, is composed of a lamp 1a and a parabolic reflector 1b. As the lamp 1a, a high-pressure discharge lamp such as a mercury lamp or a metal halide lamp is used. Parabolic reflector 1b
Is formed in a parabolic shape such that the reflection surface reflects the light emitted from the lamp 1a and the directions of the light beams become parallel. As shown in FIG. 4, the first lens array 2 is configured by arranging a plurality of small-diameter condensing lenses 2a vertically and horizontally on the same plane. The parallel light beams emitted from the light source 1 are converged into a plurality of light beams.

The second light source 4 is, like the first light source 1,
It is composed of a lamp 1a and a parabolic reflector 1b. Similarly to the first lens array 2, the second lens array 5 is configured by arranging a plurality of small-diameter condensing lenses 5a on the same plane.
Are converged into a plurality of light beams.

The first light source 1 and the second light source 4 are
Any structure may be used as long as the light emitted from the lamp 1a can be converted into parallel light and emitted in one direction.
As shown in FIG. 11, a combination of concave lenses 1c is also applicable.

The first and second light sources 1, 4 and the first and second lens arrays 2, 5 are arranged on the same optical path.
Each light beam converged by the first lens array 2 is P
Each polarizing film 31 of the s-polarized light splitting / combining device 31 (32)
The position is adjusted so that the light passes through the space between a (32a) and 31b (32b) and enters the polarizing film 31a (32a).

FIG. 5 shows a liquid crystal projector in which the illumination light source 11 of the present embodiment having the above-described configuration is replaced with the conventional illumination light source 11 shown in FIG. . In FIG. 5, unlike the one in FIG. 9, lenses 17a, 17b, and 17c are inserted at predetermined positions between the illumination light source 11 and the condenser lenses 13a, 13b, and 13c.
The light beams converged by the lens array 1 and the second lens array 5 are dichroic mirrors 12a and 12c,
After an image of the light source is formed in the middle of the optical path passing through the reflecting mirrors 12b, 12d, and 12e, the light source is adjusted so that it does not diffuse more than the diameter of the condenser lens.

Since the illumination light source and the liquid crystal projector of the present embodiment are configured as described above, the parallel light from the first light source 1 is converged by the first lens array 2 into a plurality of light beams. The light is modulated into a P-wave by the PS polarization splitter / combiner 31 and passes through the polarization film of the polarization beam splitter 33. On the other hand, the parallel light from the second light source 4 is converged by the second lens array 5 to be converted into a plurality of light beams, and is then modulated into a P wave by the PS polarization splitting / combining unit 32, after which the λ / 2 plate 34 Are modulated into S waves, and reflected by the polarizing film of the polarizing beam splitter 33. In this way, the light from the two light sources is combined in a state where the P-wave and the S-wave have the same optical axis.

After that, the combined light passes through the lens 17a,
Dichroic mirrors 12a, 12c, reflection mirror 12
b, lens 17b, reflection mirror 12d, lens 17c,
After being divided into light of three primary colors of R, G and B via a reflection mirror 12e and guided to condenser lenses 13a, 13b and 13c, a liquid crystal panel 14 adapted to each color light of the three primary colors.
Lights of the three primary colors are combined via a, 14b, 14c and a cross prism 15, emitted in one direction, incident on a projection lens 16, and projected as an image on a screen (not shown) via the projection lens 16.

Therefore, according to the light combiner of the present embodiment, the illumination light source using the same, and the liquid crystal projector using the same, the illumination light from the two light sources is synthesized without loss of light amount. The amount of light can be almost doubled, and the same lamp as before can be supplied to the liquid crystal projector with the amount of light capable of observing the projected image in a bright room.

Further, even if the lamp of one of the two light sources is cut off during use of the liquid crystal projector, the illumination light from the other light source is emitted, so that the lamp does not need to be replaced. The image can be continuously projected.

Further, since light from two separate light sources is combined, a lamp having high luminous efficiency and utilization efficiency such as an ultra-high pressure mercury lamp is used as a lamp of one light source, and a lamp of the other light source is used as a lamp of the other light source. In the mercury emission spectrum, if the two light source lamps complement each other with different emission spectra, such as using a lamp with a weak red emission spectrum characteristic in the emission spectrum of mercury, the color tone of the projected image can be adjusted, Can be improved.

The light combiner of the present embodiment and the light source for illumination using the same can be applied to other optical devices that require illumination light, such as a slide projector, in addition to a liquid crystal projector.

FIG. 6 is a schematic configuration diagram showing another embodiment of a light combiner according to the present invention, and FIG. 7 is a schematic configuration diagram showing another embodiment of an illumination light source according to the present invention using the light combiner of this embodiment. FIG. 8 is a schematic configuration diagram showing another embodiment of a liquid crystal projector according to the present invention using the illumination light source of the present embodiment. As shown in FIG. 6, in addition to the configuration of the optical combiner of the embodiment of FIG. 1, the optical combiner of this embodiment has a second optical path on the optical path combined via the polarizing beam splitter 33.
A λ / 2 plate 6 is provided as polarization component modulation means.

The λ / 2 plate 6 is a polarizing beam splitter 3
On the exit side of No. 3, a plurality of S-waves are arranged in accordance with the position where the linearly polarized light component of the S-wave passes, and the S-wave is modulated to the P-wave by rotating the linearly polarized light component by 90 degrees.

As the second polarization component modulating means,
Instead of the λ / 2 plate 6, a PS polarization splitting / combining means as shown in FIG. 2 can be used. In that case, since all the incident light becomes S-wave, it is reflected by the polarizing film and λ /
After passing through the two plates, the polarization direction is rotated by 90 ° to become a P-wave.

The liquid crystal projector shown in FIG. 8 is configured by replacing the illumination light source 11 of the present embodiment thus configured in place of the illumination light source 11 of the embodiment shown in FIG. is there. FIG.
In the same manner as in the embodiment of FIG.
The lenses 17a, 17b, and 17c are inserted at predetermined positions between the condenser lenses 13a, 13b, and 13c from the first lens array 1 and the second lens array 5, respectively.
Is converged by the dichroic mirror 12
After the light source image is formed in the middle of the optical path passing through the reflection mirrors 12a, 12c, 12c, and 12e, the light source is adjusted so as not to diffuse more than the diameter of the condenser lens.

According to the light combiner of the present embodiment thus configured, the illumination light source using the same, and the liquid crystal projector using them, in addition to the effects of the embodiments shown in FIGS. And the first light source 1 and the second light source 4
Since all the different linearly polarized light components that make up the light from the lens are emitted as the same linearly polarized light component, a bright projected image can be obtained without wasting light on projectors that include optical members that use polarized light, such as liquid crystal panels. Can supply. In addition, since the light of the same linear polarization component is used inside the illumination light source, there is no need to provide a polarizing means on the optical path of each color light from the dichroic mirror to the liquid crystal plate, and the configuration can be simplified accordingly. it can.

The light combiner of the present embodiment and the illumination light source using the same can be applied to other optical devices that require polarized illumination light besides the liquid crystal projector.

The arrangement of the small diameter condenser lenses 2a and 5a of the first lens array 2 and the second lens array 5 is not limited to the arrangement of the above embodiment. Also,
Correspondingly, the transmitting portion 3a, the reflecting portion 3b of the mirror 3, and the λ / 2 plate 6 may have any shape and arrangement as long as the respective light beams can be transmitted or reflected as in the above embodiment. It may be configured.

Further, the liquid crystal projector using the light source for illumination of the present invention is not limited to the liquid crystal projector of the cross prism type as in each of the above-described embodiments, but may be applied to other types of liquid crystal projectors. It can be configured by combining illumination light sources.

Further, the light combiner of the present invention and a light source for illumination using the same can be widely applied to devices requiring illumination means in addition to the above-described devices.

[0046]

As described above, according to the present invention, an efficient and bright light amount can be supplied. In particular, when used in a liquid crystal projector, it can supply a sufficient amount of light for observing the projected image even in a bright room, and can continue to project without interruption even when the lamp is turned off, and furthermore, the color tone of the projected image Can be adjusted to a preferable color tone.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a photosynthesizer according to the present invention.

FIG. 2 is a diagram illustrating the principle of a PS polarization splitter / synthesizer used in the present embodiment. FIG. 2 (a) shows a state in which a λ / 2 plate is arranged on the optical path of a polarization component reflecting first and second polarizing films. (B) shows a state in which a λ / 2 plate is arranged on the optical path of the polarized light component transmitted through the first polarizing film.

FIG. 3 is a schematic configuration diagram showing an embodiment of an illumination light source according to the present invention using the light combiner of the present embodiment.

FIGS. 4A and 4B show a lens array used for the illumination light source of the present embodiment, wherein FIG. 4A is a front view, FIG. 4B is a plan view of FIG.
It is a right view of (a).

FIG. 5 is a schematic configuration diagram showing one embodiment of a liquid crystal projector according to the present invention using the illumination light source of the present embodiment.

FIG. 6 is a schematic configuration diagram showing another embodiment of a photosynthesizer according to the present invention.

FIG. 7 is a schematic configuration diagram showing another embodiment of the illumination light source according to the present invention using the light combiner of the present embodiment.

FIG. 8 is a schematic configuration diagram showing another embodiment of the liquid crystal projector according to the present invention using the illumination light source of the present embodiment.

FIG. 9 is a schematic configuration diagram showing a conventional example of a liquid crystal projector.

FIG. 10 is a schematic configuration diagram showing a conventional example of an illumination light source.

FIG. 11 is a schematic configuration diagram showing another conventional example of an illumination light source.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 First light source 1a Lamp 1b Parabolic reflector 1c Concave lens 2,5 Lens array 2a, 5a Condenser lens with small diameter 3 Light combiner 31,32 PS polarization combiner / divider 31a, 31b, 32a, 32b Polarizer 31c , 32c, 34, 6 λ / 2 plate 33 polarizing beam splitter 4 second light source 11 illumination light source 12a, 12b dichroic mirror 13a, 13b, 13c condenser lens 14a, 14b, 14c liquid crystal panel 15 cross prism 16 projection lens

Claims (6)

[Claims] 1. A linear polarization component, which is arranged on two optical paths orthogonal to each other, separates a linearly polarized light component into a P wave and an S wave, and then converts one linearly polarized light component into the same polarization direction as the other linearly polarized light component. An optical combiner comprising: two PS polarization division / synthesizing means for modulating and combining to generate different polarization components; and a polarizing beam splitter arranged at a position where the two optical paths intersect. 2. After being arranged on two optical paths orthogonal to each other and separating a linearly polarized light component into a P wave and an S wave, one linearly polarized light component is turned into the same polarization direction as the other linearly polarized light component. Two PS polarization splitting / combining means for modulating and combining to make the same polarization component, a polarization beam splitter disposed at a position where the two optical paths intersect, one PS polarization splitting / combining means and the polarization The linearly polarized light component is disposed between the
A first polarization component modulating means for modulating a linearly polarized light component having a polarization direction different from that of the linearly polarized light component synthesized by the s-polarized light splitting / combining means. 3. The light source according to claim 1, wherein the polarization side of the polarization beam splitter is modulated in the same polarization direction as the other linearly polarized light component in accordance with a position where one of the linearly polarized light components of the P wave and the S wave passes. 3. The light combiner according to claim 1, further comprising two polarization component modulation means. 4. A light source for irradiating a parallel light beam to the light combiner on each of the light paths of the light combiner according to any one of claims 1 to 3 orthogonal to each other on the incident side, and each of the light sources. A lens array in which a plurality of microlenses are combined to converge parallel light beams from the light into a plurality of light beams. 5. An illumination light source, an optical system for splitting illumination light, a liquid crystal panel transmitting the split light, synthesizing means for synthesizing light transmitted through the liquid crystal panel, and enlarging and projecting the synthesized light. A liquid crystal projector comprising: a projection optical system that performs the illumination according to claim 4, wherein the illumination light source according to claim 4 is used as an illumination light source. 6. A liquid crystal projector according to claim 5, wherein lamps having different emission spectra are used for each of said illumination light sources.