DE10044650A1 - Color separation-synthesizing optical system for LC projector, has dichroic mirror whose wavelength cut-off characteristics depends on projection angle of light, so that mean wavelength of light is equal - Google Patents

Abstract

Optical system has dichroic mirrors (30,31A) which split R, G, B light and irradiate on liquid crystal light valves (34R,34G). Dichroic prisms synthesize R, G, B color light. The wavelength cut off characteristics of the mirror (31A) depends on the projection angle ( tau 1, tau 2) of light projected from lens (23), so that the mean wavelength of the light irradiated on the LC light valve is equal. Independent claims are also included for the following: (a) Optical integrator; (b) Lighting system; (c) Liquid crystal projector

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an optical Integrator, which is a pair of lens arrays facing each other opposite, and a condenser to achieve one contains uniform distribution of illuminance, and an optical color separation / synthesis system, a lamp and a liquid crystal projection device in which the optical integrator is used in each case.

2. Description of the related art

From a liquid crystal projection device have been required to have high light utilization effectiveness and have a projected image without color uniformity and brightness.

Fig. 24 shows a liquid crystal projection device according to the prior art.

The center of a lamp 11 is arranged in a light source 10 at a focal point of a parabolic mirror 12 . Almost parallel white light emitted from the light source 10 is directed onto an optical integrator 20 . The radiation intensity of the light source 10 is not uniform on a light emission surface thereof, and the optical integrator 20 is used to make the intensity distribution uniform.

The optical integrator 20 includes a lens array 21 (facet-like lens), a lens array 22, and a superimposed condenser 23 in which tens to hundreds of the rectangular convex lenses of the lens array 22 take the images of respective rectangular convex lenses of the lens array 21 through the condenser 23 on liquid crystal valves 34 R, 34 G and 34 B form and overlay. A distance between the lens arrays 21 and 22 is set to be equal to the focal length of the lenses of the lens array 21 so that the total luminous flux that each lens of the lens array 21 traverses is input to the corresponding rectangular lens of the lens array 22 . Through the optical integrator 20 , the distribution of the illuminance on the liquid crystal light valves 34 R, 34 G and 34 B is essentially uniform.

Of the white light from the optical integrator 20 , the blue light component B passes through a dichroic mirror 30 , while the green light component G and the red light component R are reflected by the dichroic mirror 30 . The reflected light is directed to a dichroic mirror 31 , where the light is further separated into the red light component R, which passes through the dichroic mirror 31 , and the green light component, which is reflected by the dichroic mirror 31 . The blue light that passes through the dichroic mirror 30 is reflected by a total reflection mirror 32 , propagates through a field lens 33 B, and then enters the liquid crystal light valve 34 B. The green light, which is reflected by the dichroic mirror 31 , passes through a field lens 33 G and then enters the liquid crystal light valve 34 G. The red light, which passes through the dichroic mirror 31 , passes through a field lens 33 R and enters the liquid crystal valve 34 R.

Each of the liquid crystal light valves 34 B, 34 G and 34 R is provided with a liquid crystal panel and with polarizing plates on both sides, and the transmittance of each pixel on each light valve changes in response to an image signal provided for the corresponding liquid crystal panel.

Exiting light from the liquid crystal light valve 34 B passes through dichroic prisms 35 and 36 to enter a projection lens 37 . Leaking light from the liquid crystal light valve 34 G is reflected by the dichroic prism 35 and passes through the dichroic prism 36 to enter the projection lens 37 . Outgoing light from the liquid crystal light valve 34 R is reflected by a total reflection prism 38 and further reflected by the dichroic prism 36 to enter the projection lens. As a result, an enlarged projected image is displayed on a screen, not shown.

The field lenses 33 B, 33 G and 33 R are used to improve the brightness of the projected image by curving light in respective peripheral portions of the lenses toward the optical axis.

(1) color unevenness

In an optical system without an optical integrator are differences of angles of incidence depending on Positions on a dichroic mirror small but in an optical system with an optical integrator are the Differences are large, and furthermore an angle of incidence ver division around every point on the dichroic mirror available. Because a cut-off wavelength of the dichroic Depends on an angle of incidence, there is one Color unevenness on a light valve.

Particularly when a metal halide lamp or a mercury lamp such as an ultra-high pressure mercury lamp (UHP) is used as the lamp 11 , a cutoff wavelength shift of only a few nm of the dichroic mirror 31 causes a serious color unevenness because of a light emission peak in the Near 575 to 585 nm is present, which represents an edge wavelength on the long wavelength side of the green light. This tendency applies in a similar way to the display of the red color from the three primary colors.

Because for this reason according to the state of the art a bright one Line spectrum of 585 nm of a mercury lamp is not  once could be used partially, this led to a Decrease in illuminance.

According to the prior art, the above wavelength was reduced obviously not included to ensure color purity afford by doing without the yellow light band. If the color unevenness is a viewer himself was still annoying by taking such a measure part of the light in a red optical path by bandwidth correction with vertical incidence no filter. Hence the effectiveness of light use low.

(2) Aperture of a projection lens

In order to increase the light utilization effectiveness, it is effective to reduce reflection-free light by enlarging a diameter of the parabolic mirror 12 . In a general liquid crystal projection device, a parabolic mirror 12 with a diameter between about 60 nm and about 100 nm has been used. On the other hand, liquid crystal panels of liquid crystal light valves 34 B, 34 G and 34 R have been used, each having a size of 1.3 to 1.8 inches (33 mm to 46 mm) in the diagonal. Therefore, the light directed from the optical integrator 20 onto the liquid crystal panel is converging light. The light from all of the lenses of the lens array 22 enters every point on a liquid crystal panel. Light emerges from the liquid crystal panel at an angle of divergence equal to the angle of convergence of the incident light and is directed onto the projection lens 37 . Therefore, when using the projection lens 37 with a larger diameter, a higher effectiveness of the use of light is required.

However, a larger diameter of the projection lens 37 has not only affected a size of a device towards a larger one, but also an increase in costs, which in turn has prevented the implementation of a compact device and an increase in the effectiveness of light use.

(3) Illuminance unevenness

A liquid crystal is in a liquid crystal panel of the TN type used by an active matrix control ver drive in terms of a reaction speed and Contrast is controlled.

In a light valve in which such a liquid crystal panel is used, the transmittance depends on an angle of incidence ϕ (see FIG. 26), as shown in FIG. 25. The dependence on an angle of incidence differs according to a voltage applied to a pixel of the liquid crystal panel, that is, according to a black display (lowest transmittance), a white display (highest transmittance) or a halftone display.

In a TN (twisted nematic) liquid crystal panel the dependence of the transmittance on an idea angles can be controlled by orienting the front egg supply of the liquid crystal by a process and by a Rubbing step on the board is changed. In general there is a dependence on an angle of incidence longitudinally a direction of a shorter side of the liquid crystal blackboard, and on the black display, for example, has a Light beam with ϕ <0 a lower transmittance, but a light beam with ϕ <0 has a higher transmissi onsgrad, resulting in an ad with poorer quality is presented.

The contrast is defined as (highest transmission degree) / (lowest transmittance). It is necessary, increase the contrast to improve the display quality ser.

Since light from all of the lenses of the lens array 22 of FIG. 24 reaches every point on a light valve, an average value differs from angles of incidence according to a position on the light valve.

Therefore there is an unevenness in the lighting strength on a projected image.

On the other hand, as shown in FIG. 26, since an arc between opposite electrodes in the lamp 11 goes up according to a temperature distribution, the amount of light from the lenses in the upper half of the lamp 11 is larger than that in its lower half. From the point of view of each point on the liquid crystal panel 34 B, therefore, an amount of light from lenses in the upper half of the lens array 22 is larger than that in its lower half. Since an average angle of incidence, which differs according to a position on the liquid crystal light valve 34 B, is shifted, this results in an unevenness in the illuminance on a projected image.

Fig. 27 shows changes in illuminance on a screen along a direction, from top to bottom, in cases where the entire area of the screen is displayed only in white, only in black or only in a halftone color. Since an image on a screen is reversely formed by the projection lens, a distribution of the illuminance along a direction from top to bottom on the liquid crystal light valve 34 B is opposite to that on the screen.

If an optical gradient filter is used, to reduce the unevenness of the illuminance ren, the light use effectiveness is reduced.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an optical integrator that the display quality by reducing the color unevenness or the illuminance can improve or the light groove efficiency, and an optical color separation / synthesis system,  a lamp and a liquid crystal to provide stall projection device, each of which the optical integrator is used.

A "dichroic mirror", which will be used in the following Det is a term that, for example, is a dichroiti prism that has the same function as that has dichroic mirrors.

According to one aspect of the present invention, a Optical color separation / synthesis system provided which comprises: an optical integrator with first and second lenses arrays to images of convex lenses of the first lens array on each area by respective convex lenses of the second Overlay lens arrays; an optical color separation system with at least one dichroic mirror to get white light from the optical integrator in a variety of colors to separate ten; a variety of light valves used in the respective areas are arranged to the respective Receive colored lights from the optical color separation system, and an optical color synthesis system which the above Color lights synthesized by the light valves, in which the dichroic mirrors such a spectral gradient that has average transmission waves length of a luminous flux that is on every point on the light valve that corresponds to the dichroic mirror is essentially the same.

According to this aspect of the present invention, since dichroic mirrors such a spectral gradient has transmittance, are cut-off wavelengths of luminous flux men who fall on the dichroic mirror, being converge at every point on the light valve, essentially the same, reducing the color unevenness can be decorated.

By such a reduction in color non-uniformity is also a usable bandwidth larger, which the Light use effectiveness can be improved.  

Other aspects, goals and advantages of the present Invention will emerge from the following detailed description in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of the present invention shows an optical system of a liquid crystal projection apparatus ULTRASONIC the first embodiment;

Fig. 2 is a schematic diagram showing an optical system for explaining a method of determining the spectral characteristic of the dichroic mirror 31 A of Fig. 1;

Fig. 3 is a schematic diagram showing an optical system for explaining a method of determining the spectral characteristic of the dichroic mirror 31 A of Fig. 1;

Fig. 4 is a graph showing a relationship between a position on the dichroic mirror 31 A and an incident angle θ A 31 A men on the dichroic mirror for Bestim shows its spectral characteristic;

Fig. 5 is a schematic diagram showing an optical ULTRASONIC system according to the present invention shows a liquid crystal projection apparatus of the second embodiment;

Fig. 6 is a schematic diagram showing an optical system for explaining a method of determining the spectral characteristic of the dichroic mirror 30 A of Fig. 5;

Fig. 7 is a schematic diagram showing an optical system for explaining a method of determining the spectral characteristic of the dichroic mirror 30 A of Fig. 5;

Fig. 8 is a graph showing a relationship between a position on the dichroic mirror 30 A and an angle of incidence q on the dichroic mirror 30 A for determining its spectral characteristic;

Fig. 9 is a schematic diagram showing an optical ULTRASONIC system according to the present invention shows a liquid crystal projection apparatus of the third embodiment;

Fig. 10 is a graph showing a relationship between a position on the dichroic mirror 31A and an angle of incidence θ on the dichroic mirror 31A for determining a spectral characteristic;

Fig. 11 is a graph showing the spectral transmittance of a dichroic mirror for s-polarized light, p-polarized light and non-polarized light;

Fig. 12 is a schematic diagram showing an optical system ULTRASONIC a portion of a liquid crystal projection apparatus of the fourth embodiment according to the present the invention;

Fig. 13 is a schematic diagram showing an optical system ULTRASONIC a portion of a liquid crystal projection apparatus of the fifth embodiment according to the present the invention;

Fig. 14 is a schematic diagram showing an optical system ULTRASONIC a portion of a liquid crystal projection apparatus of the sixth embodiment according to the vorlie constricting invention;

Fig. 15 is a schematic diagram showing an optical system ULTRASONIC a portion of a liquid crystal projection apparatus of the seventh embodiment according to the present invention shows;

Fig. 16 is a schematic diagram showing an optical system ULTRASONIC a portion of a liquid crystal projection apparatus of the eighth embodiment according to the present invention shows;

Fig. 17 is an enlarged view of the lens array and PBS array of Fig. 16;

Fig. 18 is a graph showing measurement results of the degree of transmission depending on the angle of incidence in the PBS array of Fig. 15;

Fig. 19 is a schematic diagram of the present invention shows an optical system of a liquid crystal projection apparatus ULTRASONIC the ninth embodiment;

Fig. 20 is a schematic diagram stall projection apparatus ver a simplified form of an extracted portion of the Flüssigkri of Figure 19; Fig.

Fig. 21 (A) to 21 (C) are schematic diagrams, the elements are shown which are usable in place of the wedge-shaped prism 40 B of FIG. 20;

Fig. 22 is a schematic diagram showing an optical system ULTRASONIC a portion of a liquid crystal projection apparatus of the tenth embodiment according to the present the invention;

Fig. 23 is a schematic diagram showing an optical system ULTRASONIC a portion of a liquid crystal projection apparatus of the eleventh embodiment according to the present the invention;

Fig. 24 is a schematic diagram showing an optical system of a prior art liquid crystal projection device;

Fig. 25 is a graph showing the dependency of the transmittance and the contrast on an incident angle of a liquid crystal light valve;

Fig. 26 is a schematic diagram showing a simplified form of an extracted part from the liquid crystal projection device of Fig. 24; and

Fig. 27 is a graph showing changes in illuminance on a screen along a top-to-bottom direction in cases when its entire area is displayed only in white, only in black, or only in a halftone color.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, in which the same Reference signs same or corresponding parts over several Denoting views across are now preferred below Embodiments of the present invention are described.

First embodiment

Fig. 1 shows an optical system of a liquid crystal projection device of the first embodiment according to the present invention. This device differs from that of FIG. 24 only in terms of a dichroic mirror 31 A.

A lamp 11 is, for example, an ultra-high pressure mercury lamp or a metal halide lamp.

A dichroic mirror 30 is an optical high pass filter which transmits the blue light B with a wavelength of 500 nm and less and reflects light with a wavelength longer than 500 nm. A dichroic mirror 31 A is an optical low-pass filter which transmits the red light with a wavelength of 580 nm or more and reflects light with a shorter wavelength than 580 nm.

Fig. 2 and 3 show a simplified optical system for explaining a determination method of the spectral characteristic of the dichroic mirror 31. A of FIG. 1,.

An optical integrator 20 superimposes the images of the respective convex lenses of a lens array 21 on the light entry surface of a liquid crystal light valve 34 R between the ends X1 and X2 of the light entry surface through the respective convex lenses of a lens array 22 and a condenser 23 .

An angle of incidence of a light beam that propagates along the optical axis Z on the dichroic mirror 31 A is 45 degrees.

An unevenness in the green color is mostly recognizable by the presence of an emission peak which has a wavelength of approximately 575 nm, and a cutoff wavelength on the long wavelength side of the green light is determined by the dichroic mirror 31A . Since the dichroic mirror 31 A is arranged closer to the liquid crystal light valve 34 R than to the optical integrator 20 , a converging luminous flux that passes through every point on the dichroic mirror 31 A occurs in a part on the liquid crystal 34 R. Viewed differently, and as shown in Fig. 3, there is a difference between average angles of incidence of light incident on first and second areas on dichroic mirror 31 A when attention is focused on the luminous flux from that Light that emerges from the entire surface of the optical integrator 20 converges on an end point X1 or its opposite end point X2 on the liquid crystal light valve 34 R. This is the reason that there is a color unevenness on the liquid crystal light valve 34 R.

To reduce color non-uniformity, a dichroic mirror is used that has such a spectral transmittance that depends on a position on it (a spectral gradient transmittance) that the average cut-off wavelength at each point on the dichroic mirror 31 A is essentially the same when the liquid crystal light valve 34 R is in use. That is, the spectral transmittance characteristic of the dichroic mirror 31 A depends on a position on it, so that an average wavelength of a luminous flux incident at every point on the liquid crystal light valve 34 R has substantially the same value. This condition also applies in the following second and third embodiments.

Thus, in the first embodiment, the dichroic mirror 31A has this spectral Gradiententransmissionsgrad, in Fig. 2 is a cut-off wavelength for a one incidence angle (θ1 + θ2) / 2 at a midpoint M between the points E and F at each point substantially the same Value (580 nm in this embodiment), with optical paths from opposite ends L1 and L2 on the exit surface of the optical integrator 20 to a point X on the liquid crystal light valve 34 R and the points E and F on the dichroic mirror 31 A through angles of incidence θ1 or θ2.

The dichroic mirror 31 A has a multilayer dielectric film that has been evaporated on an obliquely arranged glass substrate, and a film thickness is controlled in an evaporator to gradually change from one end to the other end of the glass substrate in the following manner to implement the spectral gradient transmittance described above. That is, a glass substrate is placed in the evaporation apparatus so that a straight line passing through the centers of an evaporation source and the glass substrate forms an angle ψ with the normal to the glass substrate, and the respective dielectric layers are formed by vapor deposition.

The angle ψ is determined in the following manner ( 1 ) or ( 2 ).

• 1. The angle ψ is determined so that Grenzwellenlän conditions of average luminous flux, which are incident at opposite ends of the dichroic mirror 31 A, are substantially the same to each other.
• 2. The angle ψ is determined so that the relationship λ1 = λ2 applies. λ1 is a cutoff wavelength for a light beam with an angle of incidence (θA + θB) / 2 at a midpoint M1 between points A and B, with optical paths from the opposite ends L1 and L2 on the exit surface of the optical integrator 20 to that Extend end point X1 on liquid crystal light valve 34 R and pass through points A and B on dichroic mirror 31 A with angles of incidence θA and θB, respectively. Similarly, λ2 is a cut-off wavelength for a light beam having an incident angle (θC + θD) / 2 at a midpoint M2 between points C and D, with optical paths from the opposite ends L1 and L2 on the exit surface of the optical integrator 20 extend the end point X2 on the liquid crystal light valve 34 R and pass through the points C and D on the dichroic mirror 31 A with angles of incidence θC and θD, respectively.

This section ( 2 ) is described in another aspect with reference to FIG. 4. Fig. 4 shows a relationship between a position on the dichroic mirror 31 A and an angle of incidence θ on the dichroic mirror 31 A.

Points P1 to P4 concerning intersections of 4 op tables ways which are shown in Fig. 3, with the dichroi tables mirror 31 A, and combinations of the points and their incident angles are the point P1 (A, θA), the point P2 (B, θB), point P3 (C, θC) and point P4 (D, θD). A point Q1 corresponds to a light beam with an incident angle (θA + θB) / 2 at the midpoint M1 between the points A and B. A point Q2 corresponds to a light beam with an incident angle (θC + θD) / 2 at the midpoint M2 between the Points C and D. The dichroic mirror 31A is designed to have such a spectral transmittance that cutoff wavelengths on a straight line passing through points Q1 and Q2 are substantially the same. A cutoff wavelength is in fact for a light beam with an incident angle θ 31 A substantially constant at any point on the dichroic mirror, the point above a point on the straight line of Fig. 4 corresponds.

In the prior art, the straight line was one with θ = 45 °, which was parallel to the abscissa.

The angles of incidence of the 4 optical paths from FIG. 3 on the dichroic mirror 31 A are as follows:

θA = 34.8 ° = 45 ° - 10.2 °

θB = 66.4 ° = 45 ° + 21.4 °

θC = 23.6 ° = 45 ° - 21.4 °

θD = 55.2 ° = 45 ° + 10.2 °

That is, a converging luminous flux with angles of incidence in the range of 45 ° -10.2 ° to 45 ° + 21.4 ° on the dichroic mirror 31 A impinges on the liquid crystal light valve 34 R at one end X1, and through Average angle of incidence is 45 ° + 5.6 °. A converging luminous flux with angles of incidence in the range of 45 ° - 21.4 ° to 45 ° + 10.2 ° on the dichroic mirror 31 A impinges on the liquid crystal light valve 34 R at the other end X2, and the average angle of incidence is 45 ° - 5.6 °. Therefore, the average angle of incidence on the dichroic mirror 31 A continuously changes over a segment between X1 and X2 on the liquid crystal light valve 34 R from 45 ° + 5.6 ° to 45 ° - 5.6 °.

Although a cut-off wavelength of the dichroic mirror 31 A depends on an angle of incidence, the state of the art has arisen since the dichroic mirror was designed such that a cut-off wavelength is independent of a position on the dichroic mirror 31A for light with an angle of incidence of 45 ° was a color non-uniformity on the liquid crystal light valve 34 R.

When the dichroic mirror 31A with the above-described spectral gradient transmittance is used, the above-described angle of incidence corresponds to 45 ° θ (design angle of incidence) on the straight line of Fig. 4, and a converging luminous flux with a deviation from this θ corresponds to that between -17.7 ° and + 17.7 °, enters one end X1 on the liquid crystal light valve 34 R, while a converging luminous flux with a deviation from this θ that is between -20.2 ° and +20.2 ° lies, in the other end X2 on the liquid crystal light valve 34 R enters. Therefore, each average of the deviations across a segment from one end X1 to the other end X2 on the liquid crystal light valve 34 R is substantially zero, thereby making it possible to largely reduce color unevenness.

Since, according to the prior art, a color unevenness occurs on a screen image if the spectral emission peak of the lamp 11 is in a range of limit wavelengths which depend on an angle of incidence on the dichroic mirror 31 A, filtered light with a narrow bandwidth was also used. to avoid color unevenness. In contrast, when the dichroic mirror 31 A with the spectral gradient transmittance is used, the range of cutoff wavelengths is decreased by a large amount, and thereby a usable bandwidth can be increased to improve the light utilization efficiency.

Second embodiment

Fig. 5, an optical system schematically shows a liquid crystal projection apparatus of the second embodiment according to the present invention. This device differs from FIG. 24 with respect to the dichroic mirror 30 A and 31 C and the dichroic prisms 35 A and 36 A.

The dichroic mirror 30 A is an optical low-pass filter which transmits the red light R with a wavelength of 580 nm or more and reflects light with a shorter wavelength than 580 nm.

The dichroic mirror 31 C is a high-pass filter which transmits light with a wavelength of 500 nm and less and reflects light with a longer wavelength than 500 nm.

Escaping light from the liquid crystal light valve 34 R passes through the dichroic prisms 35 A and 36 A to enter the projection lens 37 . Leaking light from the liquid crystal light valve 34 G is reflected by the dichroic prism 35 A and passes through the dichroic prism 36 A to enter the projection lens 37 . Leaking light from the liquid crystal light valve 34 B is reflected by the total reflection prism 38 and further reflected by the dichroic prism 36 A to enter the projection lens 37 . With such a configuration, an enlarged projected image is obtained on a screen, not shown.

FIGS. 6 and 7 show simplified optical systems for explaining a determination method of the spectral Charak teristik of the dichroic mirror 30 A of Fig. 5.

The optical integrator 20 superimposes the images of the respective convex lenses of the lens array 21 on the light entry surface of the liquid crystal light valve 34 B between opposite ends X1 and X2 through the respective convex lenses of the lens array 22 and the condenser 23 .

An angle of incidence of a light beam that propagates along the optical axis Z on the dichroic mirror 30 A is 45 degrees.

A limit wavelength on the long wavelength side of the green light, the chromatic unevenness of which is most likely to be visually recognized, is determined by the dichroic mirror 30 A. Since the dichroic specific mirror is 30 A located closer to the optical integrator 20 as the liquid crystal light valve 34 R, occurs is converging luminous flux that each point on the dichroic mirror 30. A passes through in the entire top of the liquid crystal light valve 34 R area a. Since the entrance surface of the liquid crystal light valve 34 R is narrower than the exit surface of the optical integrator 20 , there is a large difference in the angle of incidence on the dichroic mirror 30 A between two optical paths from opposite ends L1 and L2 of the exit surface of the optical integrator 20 , which the Run through dichroic mirror 30 A and hit each point on the liquid crystal light valve 34 R. For this reason there is a color unevenness on the liquid crystal valve 34 R.

In order to reduce this color non-uniformity, the dichroic mirror 30 A with the spectral gradient transmittance is used for an angle of incidence (θ1 + θ2) / 2 at a midpoint M between the points E and F for each point L on the exit surface of the optical integrator 20 is essentially the same, with optical paths extending from each point L on the exit surface of the optical integrator 20 to the opposite ends X1 and X2 on the liquid crystal light valve 34 R and the points E and F on the dichroic mirror 30 A with angles of incidence θ1 and run through θ2.

The dichroic mirror 30 A is formed in a similar manner to the dichroic mirror 31 A of the first embodiment. However, the section ( 2 ) described above is replaced by the following section ( 2 ').

• 1. ( 2 ') The angle ψ is determined such that the relationship λ1 = λ2 applies. λ1 is a cut-off wavelength for a light beam with an angle of incidence (θA + θB) / 2 at a center M1 in FIG. 2 between points A and B, with optical paths from one end L1 to the exit surface of the optical integrator 20 extend opposite ends X1 and X2 on the liquid crystal light valve 34 R and pass through the points A and B on the dichroic mirror 30 A with angles of incidence θA and θB, respectively. Similarly, λ2 is a cut-off wavelength for a light beam with an angle of incidence (θC + θD) / 2 at a center M2 between points C and D, with optical paths from the other end L2 on the exit surface of the optical integrator 20 to the opposite ones Extend ends X1 and X2 on the liquid crystal light valve 34 R and pass through the points C and D on the dichroic mirror 30 A with angles of incidence θC and θD, respectively.

This section ( 2 ') is described in another aspect with reference to FIG. 8. Fig. 8 shows a relationship between a position on the dichroic mirror 30 A and an angle of incidence θ on the dichroic mirror 30 A.

The points P1 to P4 relate to intersections of 4 optical paths shown in FIG. 7 with the dichroic mirror 30 A, and combinations of the points and their angles of incidence are the point P1 (A, θA), the point P2 (B, θB), point P3 (C, θc) and point P4 (D, θD). A point Q1 corresponds to a light beam with an incident angle (θA + θB) / 2 at the center point M1 between points A and B. A point Q2 corresponds to a light beam with an incident angle (θC + θD) / 2 at a center point M2 between the points C and D. the dichroic mirror 30 a is designed to have such a spectral transmission degree that cutoff wavelengths on a straight line passing through the points Q1 and Q2 in wesentli surfaces are the same. A cut-off wavelength for a light beam with an angle of incidence θ is namely essentially constant at every point on the dichroic mirror 30 A, the point corresponding to a point on the above straight line from FIG. 4.

The angles of incidence of the 4 optical paths from FIG. 8 on the dichroic mirror 30 A are as follows:

θA = 34.8 ° = 45 ° - 10.2 °

θB = 23.6 ° = 45 ° - 21.4 °

θC = 66.4 ° = 45 ° + 21.4 °

θD = 55.2 ° = 45 ° + 10.2 °

That is, a converging luminous flux with angles of incidence in the range of 45 ° -10.2 ° to 45 ° + 21.4 ° on the dichroic mirror 30 A impinges on the liquid crystal light valve 34 R at the end X1, and the average angle of incidence is 45 ° + 5.6 °. A converging luminous flux with angles of incidence in the range of 45 ° -21.4 ° to 45 ° + 10.2 ° on the dichroic mirror 30 A impinges on the liquid crystal light valve 34 R at the other end X2, and the average angle of incidence is 45 ° - 5.6 °. Therefore, average angles of incidence on the dichroic mirror 30 A continuously change from 45 ° + 5.6 ° to 45 ° - 5.6 ° across the segment between X1 to X2 on the liquid crystal light valve 34 R.

Although a cut-off wavelength of the dichroic mirror 30 A depends on an angle of incidence, the state of the art has arisen because the dichroic mirror was designed such that a cut-off wavelength regardless of a position on the dichroic mirror 30A is 580 nm for light with an angle of incidence of 45 ° was a color non-uniformity on the liquid crystal light valve 34 R.

When the dichroic mirror 30 A with the above-described spectral gradient transmittance is used, the above-described angle of incidence corresponds to 45 ° θ (design angle of incidence) on the straight line of Fig. 8, and a converging luminous flux with a deviation from this θ corresponds to that between + 9.73 ° and + 6.27 °, enters one end X1 on the liquid crystal light valve 34 R, while a converging luminous flux with a deviation from this θ is between -7.53 ° and - 6.23 ° lies, in the other end X2 on the liquid crystal light valve 34 R enters. Therefore, each average of the deviations across the segment from one end X1 to the other end X2 on the liquid crystal light valve 34 R is substantially zero, thereby making it possible to largely reduce color unevenness.

Since, according to the prior art, a color non-uniformity arises on a screen image if the spectral emission peak of the lamp 11 is in a range of limit wavelengths which depend on an angle of incidence on the dichroic mirror 30 A, filtered light which has a narrow bandwidth was also used , used to avoid color unevenness. In contrast, when the dichroic mirror 30 A with the spectral gradient transmittance is used, the range of cut-off wavelengths is reduced by a large amount, and thereby a usable bandwidth can be increased to improve the light utilization efficiency.

Third embodiment

Fig. 9 schematically shows an optical system of a liquid crystal projection apparatus of the third exporting approximate shape according to the present invention.

The device is designed with such a modification as compared to the device of Fig. 5 to realize a compact device so that a total reflection mirror 39 is inserted between the optical integrator 20 A and the dichroic mirror 30 A to an optical path around To bend 90 degrees. By such a configuration, the dichroic mirror 30 A, which is arranged closer to the optical integrator 20 in FIG. 5, is substantially in the middle (somewhat closer to the optical integrator 20 ) between the exit surface of the optical integrator 20 and the Liquid crystal light valve 34 R positioned.

In order to reduce color unevenness in this case, the dichroic mirror 30 A must have a spectral characteristic which is substantially midway between that of the first and second embodiments. A preferable spectral characteristic of the dichroic mirror 30 A, which was obtained experimentally by the inventors of the present invention, is shown in FIG. 10. Points A to D and O in the graph correspond to those of FIG. 7.

With the dichroic mirror 30 A, which has such a smooth spectral gradient transmittance, the color unevenness could be effectively reduced.

Furthermore, the optical integrator 20 A, as shown in FIG. 9, has a PBS array 24 which converts non-polarized light into s-polarized light and is arranged between the lens array 22 and the condenser 23 .

Fig. 11 shows the spectral transmittance of the dichroic mirror 30 A for s-polarized light, p-polarized light and non-polarized light.

A spectral transmittance for non-polarized light is substantially the same as the average characteristic of those of p-polarized light and s-polarized light, and its spectral characteristic near a cut-off wavelength is gently tilted as improved in the 30 A dichroic mirror graph, and further a spectral characteristic near the cutoff wavelength is made steeper, whereby a chromatic characteristic is further improved. If a light valve uses only p-polarized light, a polarization conversion means such as a half-wave plate can be inserted on the entrance side of the light valve to convert s-polarized light to p-polarized light.

Fourth embodiment

Fig. 12 shows an optical system schematically a portion of a liquid crystal projection apparatus of the four th embodiment of the present invention.

In the light source 10 , a luminous part is arranged between opposite electrodes of the lamp 11 at a focal point of the parabolic mirror 12 . The lamp 11 is a metal halide lamp with an electrode gap of 1.5 mm and a power of 150 W. The parabolic mirror 12 is a cold mirror of the UV and IR separation type with a focal length of 14 mm and a diameter of 80 mm. The light source 10 emits light mainly parallel to the optical axis, but since the luminous part is not a point, the light is diverging light with the maximum angle of +/- 3.1 ° oblique to the optical axis.

In the optical integrator 20 B of the condenser 23 on the flat surface of the lens array 21 is liable, and a UV filter, which is made of a dielectric multilayer film is formed on the incident surface of the condensate sors 23rd With such a configuration, the number of refractive interfaces is reduced by 4 compared to the case when the lens array 21 , the condenser 23 and the UV filter are arranged separately, with the result that an amount of transmitted light is increased by a percentage in the loading increases from 4 to 20%.

UV filters are arranged separately by 4, with the result that a lot of transmitted light by a percentage in the loading increases from 4 to 20%.

The lens arrays 21 and 22 A are arranged at a distance of 60 mm between them, which is equal to the focal length of the lens array 21 . The lens array 21 has a matrix of 9 columns × 12 rows, which is constructed from rectangular convex lenses each having a size of 9 mm × 6.7 mm. On the other hand, the lens array 22 A according to the light convergence by the condenser 23 at a focal length of 220 mm has a reduced shape of the lens array 21 and a matrix of 9 columns × 12 rows, which consist of rectangular convex lenses with a size of 6.7 mm × each 5.0 mm is constructed, and a focal length of 45 mm.

Emitted from the lamp 11 light beams are reflected by the parabolic mirror 12, to be parallel to the optical axis is substantially, and the light converged by the condenser 23, whose focal point is disposed on the liquid crystal light valve 34 R. Converge from light passing currents from the lens array 21 to enter 22 A into respective lenses of the lens array. Since diverging light from the light source 10 exists, each light spot on the lens array 22 A has a diameter of about 6.5 mm, and all emerging light fluxes from the lens array 21 enter respective lenses of the lens array 22 A.

Each lens of the lens array 22 A forms an image of egg ner corresponding lens of the lens array 21 on the flues sigkristallichtventil 34 R. Therefore, arrives at each point on the liquid crystal light valve 34 R light from all lenses of the lens array 22 A. Since the condenser 23 near the lens array 21 is arranged, the lens array 22 A can be made smaller, with the result that an angle of convergence of the luminous flux entering each point on the liquid crystal light valve 34 R is smaller than that of the prior art.

More specifically, since opposing prior art lens arrays were the same in size, a convergence angle of light entering the center of the liquid crystal valve 34 R is as follows:

tan ^-1 ((40.5 ² + 40.2 ² ) ^1/2 / 180) = +/- 17.6 °

On the other hand, an angle of convergence of this embodiment is as follows:

tan ^-1 ((30.2 ² + 30.0 ² ) ^1/2 / 180) = +/- 13.3 °

Thus, a convergence constraint can be achieved in this embodiment by a percentage of 30% compared to that of the State of the art can be reduced.

Since a convergence angle of incident light on the liquid crystal light valve 34 R is equal to a divergence angle of light exiting the liquid crystal light valve 34 R, the light propagates toward the projection lens with a divergence angle of 13.3 °. The distance between the projection lens and the liquid crystal light valve 34 R is 145 mm, and therefore all the light from the light valve can be projected onto a screen through a projection lens having an effective diameter of 69 mm.

Since, according to the prior art, a divergence angle of light emerging from the liquid crystal light valve was 34 R +/- 17.6 °, an effective diameter of the projection lens had to be 92 mm. Since the cost of the projection lens generally increases in proportion to the square of this diameter, the diameter of 69 mm can reduce the cost of the projection lens by half compared to the aperture of 92 mm.

In other words, if the diameter of the projection lenses according to the prior art and in the fourth embodiment form are equal to each other to be 69 mm  the use of light in the fourth embodiment in Ver improved immediately to the state of the art.

Although the condenser 23 is arranged on the entry side of the lens array 21 in this embodiment, it should be mentioned that a similar effect can also be obtained if the condenser 23 is arranged on the exit side of the lens array 21 .

Fifth embodiment

Fig. 13 shows an optical system schematically a portion of a liquid crystal projection apparatus of the five th embodiment of the present invention.

This embodiment has the same configuration as that of FIG. 12, except that an elliptical mirror 12 A is used instead of a combination of the parabolic mirror 12 and the condenser 23 of FIG. 12, and further the total reflection mirror 39 is between the lines senarrays 21 and 22 A arranged.

In the light source 10 A, a luminous part is arranged between opposite electrodes of the lamp 11 at a first focal point of the elliptical mirror 12 . The elliptical mirror 12 A is a cold mirror which is coated with a UV / IR separating filter, has a focal length of 14 mm, a distance of 250 mm between focal points and a diameter of 80 mm.

Since the total reflection mirror 39 is arranged in the optical integrator 20 C between the lens arrays 21 and 22 A, the liquid crystal projection device can be more compact.

A luminous flux, which is emitted by the lamp 11 , forms a light spot at the second focal point of the elliptical mirror 12 A. At this second focal point, the center of the liquid crystal light valve 34 R is arranged.

The luminous flux emitted from the light source 10 A is converging light, and emerging light from the lens array 21 is converged to enter respective lenses of the lens array 22 A that are smaller in size than the lens array 21 . As a result, an effect similar to that of the fourth embodiment can also be achieved in this fifth embodiment.

In addition, in the fifth embodiment, since the condenser 23 of FIG. 12 is unnecessary, lower cost and lighter weight can be obtained.

Sixth embodiment

Fig. 14 shows an optical system schematically a portion of a liquid crystal projection apparatus of the sixteenth th embodiment of the present invention.

An optical integrator 20 D is provided with a lens array 21 A, which has the same function as that of the combination of the lens array 21 and the condenser 23 of FIG. 12. The lens array 21 A is configured from rectangular convex lenses each having the same size and focal length as the lenses of the lens array 21 , and lenses that do not form the central portion of the lens array 21 A are decentered lenses whose eccentric centers are centered on the center of the Lens arrays 21 A coincide.

Exiting converging light fluxes from the lens array 21 A come into respective lenses of the lens arrays 22 a A, which is smaller in size than the lens array 21 A. Under such an optical condition, an effect similar to that of the fourth embodiment can also be achieved in this sixth embodiment, whereby it is possible to further reduce the number of optical components.

Seventh embodiment

Fig. 15 shows an optical system schematically a portion of a liquid crystal projection apparatus of the sieve th embodiment of the present invention.

An optical integrator 20 E differs from the optical integrator 20 C of FIG. 13 in that a PBS array 24 is arranged on the exit side of the lens array 22 A.

The PBS array 24 serves to convert incident non-polarized light into s-polarized light. In the PBS array 24 are prisms each having a cross section of a parallelogram, disposed in a row with a lung Tei, which those of the lenses of the lens array half is 22 A. A polarized light beam splitter (PBS) 241 is made of a dielectric multilayer film that transmits p-polarized light and reflects s-polarized light. Reflection films for s-polarized light 242 are made of a dielectric multilayer film. PBSs and reflection films for s-polarized light are formed alternately at the respective transitions between the prisms. A half-wave plate 243 is attached to the light exit surface of every other prism. Each center of the PBSs positioned on the optical axes of the respective lenses of the lens array 22 A.

Light incident on the PBS 241 is separated into reflected s-polarized light and transmitted p-polarized light. The reflected s-polarized light is reflected again by the reflection film for s-polarized light 242 and emerges from the PBS array 24 . The transmitted p-polarized light is converted into s-polarized light by the half-wave plate 24 . Since the liquid crystal light valve 34 R uses only s-polarized light, the light use efficiency is further improved compared to the case of non-polarized incident light.

In order to maximize the light incidence effectiveness on the PBS array 24 , the distance between the lens array 21 and the PBS array 24 is set so that light fluxes from the lenses of the lens array 21 on the PBS array 24 are converged.

Eighth embodiment

Fig. 16 shows an optical system schematically a portion of a liquid crystal projection apparatus of the eighth embodiment according to the present invention.

The PBS array 24 A of the optical integrator 20 F is, as shown in Fig. 17, constructed so that components of the array 24 A are symmetrically arranged on both sides of a prism 240 with a cross section of a right-angled isosceles triangle. The reason why such a 24 A PBS array is used is described below.

Fig. 18 shows the transmittance of a PBS array in dependence on the angle of incidence was measured by an OF INVENTION of the present invention. Measurements were made changing an angle of incidence of a non-polarized light beam on the PBS array 24 of FIG. 15, which has the maximum polarization effectiveness at an angle of incidence of 45 °. The measured light rays were as follows:
◊: non-polarized light → p-polarized light that was transmitted through the PBS 241 , → s-polarized light that was converted by the half-wave plate 243
▱: non-polarized light → s-polarized light reflected by the PBS 241 , → s-polarized light reflected by the reflection film for s-polarized light 242 , → emerging

The results show that the sum of Transmittance of ◊ and ▱ decreases when an incident angle is changed to be less than or greater than 45 degrees be the case when an angle of incidence is less than 45 degrees  is a smaller rate of decrease than the case if an angle of incidence is greater than 45 degrees.

Ideally, the angle of incidence dependence of each PBS of the PBS array can be changed individually in order to to increase the transmittance, but this is due an enormous cost increase is not practical.

Therefore, a symmetrical configuration as shown in Fig. 17 is constructed for the PBS array 24 A to reduce an amount of light whose angle of incidence on the PBSs of the PBS array 24 A is larger than 45 degrees, with the result that suppresses a reduction in the polarization effectiveness and the light utilization effectiveness is further improved.

Furthermore, there is the other feature that a division of the PBSs of the PBS array 24 A by δ is less than half that of the lens array 22 A. This is because, through the condenser 23, light fluxes passing through the lens array 21 are inclined to the optical axis side, and a distance between adjacent light fluxes on the PBS array 24 A becomes compared to that on the lens array 22 A reduced by δ. Such a reduction can also improve light utilization.

Ninth embodiment

Fig. 19 shows an optical system schematically a liquid crystal projection apparatus of the ninth exporting approximate shape according to the present invention.

In this device, wedge-shaped prisms 40 R, 40 G and 40 B are inserted on the incidence side of the liquid crystal light valves 34 R, 34 G and 34 B, respectively.

FIG. 20 is a simplified form of an extracted part from the optical system of a liquid crystal projection device of FIG. 19 for explaining an operation of the wedge-shaped prism 40 B. In FIG. 20, optical paths of the strongest luminous flux are shown.

This luminous flux from the optical integrator 20 enters the entire surface of the liquid crystal light valve 34 B. The wedge-shaped prism 40 B breaks the luminous flux and essentially sets an angle of incidence at each point on the liquid crystal light valve 34 B to -ϕm, at which the contrast in the graph of FIG. 25 is maximized.

This reduces the transmittance of light incident on the liquid crystal light valve 34 B, which receives a black indication signal for the full area, on the entire surface of the liquid crystal light valve 34 B, with the result that a projected image not only with improved contrast but also is obtained with reduced unevenness in illuminance.

In other words, there is no light attenuation filter with a spectral gradient characteristic is required is to increase the non-uniformity of illuminance reduce, it is possible to increase the light utilization effectiveness improve.

The same applies to the liquid crystal light valves 34 G and 34 R in FIG. 19.

It should be mentioned that the wedge-shaped prism 40 B can either be arranged between the field lens 33 B and the condenser 23 or between the condenser 23 and the lens array 22 .

Fig. 21 (A) to 21 (C) is a multiple wedge-shaped prism sheet 40 BX, a multiple inclination prism sheet 40 BY and a multiple wedge-shaped prism sheet show 40 BZ, each of which may be used instead of the wedge-shaped prism 40 B of Fig. 20.

The multi-wedge prism blade 40 BX has a saw tooth shape to make the prism 40 B thinner, and it has the same function as the wedge-shaped prism 40 B.

The multi-tilt prism 40 BY has such a shape that tilt angles of a plurality of slopes are gradually changed so that each angle of incidence of the strongest luminous flux on the liquid crystal light valve can be 34 B -ϕm, and thus the effect described above is further enhanced.

The multi-wedge shaped prism sheet 40 BZ has such a sawtooth shape that the surface portions of the multi-tilt prism 40 BY are extracted to make the prism thinner.

Tenth embodiment

Fig. 22 shows an optical system schematically a portion of a liquid crystal projection apparatus of the ten th embodiment of the present invention.

In this device, instead of using the wedge-shaped prism 40 B of Fig. 20, the optical axes of the light source 10 and the optical integrator 20 are integrally inclined to the optical axis of the liquid crystal light valve 34 B, so that the strongest luminous flux from the light source 10 into the liquid crystal light valve 34 B occurs at an angle of essentially -ϕm.

According to the tenth embodiment, without the addition add a new optical element not only the Un uniformity of illuminance on a projector th picture, but the quality of a black one Display can also be improved, and this can help Contrast can be increased.

Eleventh embodiment

Fig. 23 shows an optical system schematically a portion of a liquid crystal projection apparatus of the eleventh embodiment according to the present invention.

This device is configured so that in the device shown in Fig. 20, the wedge-shaped prism 40 B is not used and the condenser 23 is replaced by a decentered condenser 23 A, and thereby the strongest luminous flux occurs from the light source 10 in the liquid crystal light valve 34 B at an angle of substantially -ϕm Chen. The decentered condenser 23 A of the optical integrator 20 G is analogous to such a configuration as if in FIG. 20 an enlarged wedge-shaped prism 40 B is connected to the condenser 23 .

According to the eleventh embodiment, since it is not necessary to use an additional wedge-shaped prism 40 B, the number of components of the liquid crystal projection device can be reduced.

Claims (8)

1. Optical color separation / synthesis system with:
an optical integrator having first and second lens arrays to overlay images of convex lenses of the first lens array on each area by respective convex lenses of the second lens array;
an optical color separation system having at least one dichroic mirror to separate white light from the optical integrator into a plurality of colored lights;
a plurality of light valves arranged in the respective areas to receive the respective color lights from the optical color separation system, and
an optical color synthesis system, which synthesizes the named color lights from the light valves,
in which the dichroic mirror has such a specular gradient transmittance that an average wavelength of a luminous flux incident on every point on the light valve corresponding to the dichroic mirror is substantially the same. 2. Optical color separation / synthesis system according to claim 1, in which the dichroic mirror is formed such that a cutoff wavelength for an angle of incidence (θ1 + θ2) / 2 at a midpoint M between first and second points on the dichroic mirror with respect to each point X the light valve, which corresponds to the dichroic mirror, is essentially the same as the first and second Points lie on optical paths that are opposite each other lying ends L1 and L2 on the exit surface of the optical integrator to point X, being the dichroic mirror with angles of incidence of θ1 or run through θ2.   3. Optical color separation / synthesis system according to claim 1, in which the dichroic mirror is formed such that a cutoff wavelength for an angle of incidence (θ1 + θ2) / 2 at a midpoint M between first and second points on the dichroic mirror with respect to each point L. the exit surface of the optical integrator essentially lichen is the same as which first and second points optical paths that are from point L to counter First overlap ends X1 and X2 on the light valve ken, which corresponds to the dichroic mirror, being the dichroic mirror with angles of incidence of θ1 or run through θ2. 4. Optical color separation / synthesis system according to claim 1, in which the spectral gradient transmittance of the dichroic mirror is determined so that average limit wavelengths of luminous fluxes at the first and second opposite ends on the dichroic Incident mirrors are essentially the same. 5. Optical integrator with:
a first lens array having a plurality of convex lenses; and
a second lens array which has a plurality of convex lenses, the convex lenses of which overlap images of the respective convex lenses of the first lens array in one area,
in which a lens pitch of the convex lenses of the second lens array is shorter than that of the first lens array. 6.Light with:
a first lens array having a plurality of convex lenses;
a second lens array having a plurality of convex lenses, the convex lenses of which overlap images of the respective convex lenses of the first lens array on an area and a lens pitch of the convex lenses of the second lens array is shorter than that of the first lens array;
an open-ended elliptical mirror facing the first lens array; and
a lamp which has a luminous part which is arranged at a first focal point of the elliptical mirror,
at which the second focal point of the elliptical mirror lies on the area mentioned. 7. Liquid crystal projection device with:
a light source;
an optical integrator that contains:
a first lens array having a plurality of convex lenses; and
a second lens array which has a multiplicity of convex lenses, the convex lenses of which overlap images of the respective convex lenses of the first lens array in one area,
a light valve arranged in said area to receive light from the optical integrator;
a field lens, which is arranged on the inlet side of the light valve;
a projection lens that receives light coming from the light valve; and
a refractive agent disposed on the entrance side of the light valve and refracting light incident on one side so that the contrast of a projected image increases. 8. Liquid crystal projection device with:
a light source;
an optical integrator that contains:
a first lens array having a plurality of convex lenses; and
a second lens array which has a multiplicity of convex lenses, the convex lenses of which overlap images of the respective convex lenses of the first lens array in one area,
a light valve arranged in said area to receive light from the optical integrator;
a field lens, which is arranged on the inlet side of the light valve; and
a projection lens that receives light coming from the light valve,
in which the light source and the optical integrator have a common optical axis that is inclined to an optical axis of the light valve so that the contrast of a projected image increases.