JPH0862599A - Liquid crystal projector - Google Patents

Abstract

PURPOSE: To provide a liquid crystal projector capable of obtaining a projection video whose luminance is high without using a particular projecting lens. CONSTITUTION: A light beam emitted from a light source 1 is made parallel beam by a parabolic mirror 2. The parallel beam irradiate the entire surface of a liquid crystal panel 9 by an integrating lens 4 constituted of a first convex lens group 4A and a second convex lens group 4B having plural convex lenses, and a condenser lens 5, and the light beam transmitted through the panel 9 irradiates a screen by the projecting lens 10. At this time, on the assumption that the arc length of the light source 1 is LA, the focal distance of the mirror 2 is FR, the length of the convex lenses in horizontal direction constituting the lens groups 4A and 4B are DI, and the focal distance of the convex lens is FI; the ratio for the lengthes in the horizontal direction to the focal distance in the convex lens (FI/DI) satisfies 2FR/LA<FI/DI<2.5FR/LA.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector using a liquid crystal panel as a display means.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal projector using three liquid crystal panels has been generally used as a projection device, and this type of liquid crystal projector will be described with reference to FIG.

In FIG. 3, white light from a light source 1 is collimated by a parabolic mirror 2 and then radiated toward a UV / IR cut filter 3. The UV / IR cut filter 3 removes unnecessary ultraviolet rays and infrared rays from the white light, and the removed light passes through the first convex lens group 4A,
And enters the integrator lens 4 including the second convex lens group 4B. Here, the first convex lens group 4A and the second convex lens group 4B have a configuration in which convex lenses are formed on the upper, lower, left and right sides of one glass plate as shown in FIG.

The integrator lens 4 acts so that the incident light has a uniform brightness on a liquid crystal panel, which will be described later, and the light passing through the integrator lens 4 passes through a condenser lens 5 to obtain a first color separation dichroic. It is emitted to the mirror 6A.

The first color separation dichroic mirror 6A separates the incident light into red light, and the separated red light is passed through the first reflection mirror 7A and the red condenser lens 8R to the red liquid crystal panel. It is emitted to 9R.

The first color separation dichroic mirror 6A transmits light other than red light and emits it to the second color separation dichroic mirror 6B.

The second color separation dichroic mirror 6B separates the green light from the incident light, and the separated green light is emitted to the green liquid crystal panel 9G through the green condenser lens 8G.

The blue light transmitted through the second color separation dichroic mirror 6B is converted into the blue condenser lens 8B.
The light is incident on the blue liquid crystal panel 9B via.

Each of the liquid crystal panels 9R, 9G and 9B is optically modulated based on a video signal.

The light modulated by the liquid crystal panel 9R for red and the light modulated by the liquid crystal panel 9G for green are the first
The combined light is combined by the color combining dichroic mirror 6C, and the combined light is emitted to the second color combining dichroic mirror 6D.

The light modulated by the blue liquid crystal panel is emitted to the second color combining dichroic mirror 6D via the second reflecting mirror 7B.

In the second-color combining dichroic mirror 6D, the light modulated by the blue liquid crystal panel 9B and the above-mentioned combined light are combined, and the combined light of the three primary colors is projected onto the projection lens 1.
It is enlarged and displayed on the screen through 0.

Next, the operating principle of the integrator lens will be described with reference to FIG.

FIG. 5 shows a single-plate type projector using one liquid crystal panel, and of the convex lenses constituting the first convex lens group 4A, the optical path of light incident on one convex lens at the center is indicated by a solid line. It is also located away from the center 1
The optical path of the light incident on the two convex lenses is shown by the dotted line.

The light incident parallel to one convex lens at the center is focused by the other convex lens facing the other, enters the condenser lens 5 and the condenser lens 8, and is then irradiated on the entire surface of the liquid crystal panel 9. Enters the projection lens 10.

On the other hand, the light incident parallel to one convex lens located at a position away from the center is focused by the opposite convex lens, and then the center line of the light passes through the center of the liquid crystal panel 9 by the condenser lens 5. Then, the light enters the projection lens 10 through the condenser lens 8 and the liquid crystal panel 9.

At this time, if the integrator lens 4 and the condenser lens 5 are not provided, the light reflected by the parabolic mirror 2 becomes bright at the center, so that the projected image on the screen is also bright at the center and the peripheral part is dark. Will be. On the other hand, when the integrator lens 4 and the condenser lens 5 are used, the light incident on one convex lens irradiates the entire surface of the liquid crystal panel 9, so that it is possible to obtain a projected image without unevenness in brightness.

Further, even if the light is obliquely incident on the convex lens, the same result can be obtained within a certain range.

FIG. 6 shows an optical path when light is obliquely incident on one of the convex lenses constituting the first convex lens group 4A.

The light obliquely incident on one convex lens is focused by the opposite convex lens and is refracted so that its center line becomes horizontal. Then, the refracted light passes through the condenser lens 5 and the condenser lens 8 and irradiates the entire surface of the liquid crystal panel 9, as in the case of parallel light. The reason why two convex lenses are used is to irradiate the entire surface of the liquid crystal panel 9 with light that is not parallel light.

As described above, by adding the integrator lens 4 and the condenser lens 5, the light emitted from the light source 1 can be uniformly applied to the entire surface of the liquid crystal panel 9.

[0022]

However, the conventional liquid crystal projector has the following drawbacks.

The light transmitted through the liquid crystal panel 9 does not reach the screen unless it enters the entrance pupil of the projection lens 10.
Does not contribute to brightness. That is, as shown in FIG. 7, the light incident on the convex lens near the center does not enter the entrance pupil of the projection lens, and the projected image on the screen becomes dark. Therefore, the projection lens 10 having a large entrance pupil may be used, but the projection lens 10 becomes large and the cost becomes very high.

The present invention has been made in view of the above drawbacks, and an object of the present invention is to provide a liquid crystal projector capable of obtaining a high-luminance projection image without using a special projection lens.

[0025]

According to the present invention, light from a light source is converted into parallel light by a parabolic mirror, and the parallel light is composed of a first convex lens group having a plurality of convex lenses and a second convex lens group. , And a condenser lens for irradiating the entire surface of the liquid crystal panel and projecting the light transmitted through the liquid crystal panel onto a screen by a projection lens. In the liquid crystal projector, the arc length of the light source is LA, and the focal length of the parabolic mirror is Let FR be DI, the horizontal length of the convex lenses that form the first convex lens group and the second convex lens group be DI, and the focal length of the convex lenses be FI, then the ratio of the horizontal length of the convex lenses to the focal length ( FI / DI) is

[0026]

[Equation 2]

A liquid crystal projector characterized in that it is configured so as to satisfy the above condition.

[0028]

According to the present invention, the ratio of the horizontal length of the convex lens to the focal length (FI / DI) is configured as described above.
A bright projected image can be obtained on the screen.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a liquid crystal projector using an integrator lens, in which the arrangement of the integrator lens is optimized so as to obtain high brightness.

An embodiment of the liquid crystal projector of the present invention will be described below with reference to the drawings.

In FIG. 8, assuming that the distance from the liquid crystal panel to the entrance pupil is L1, the distance from the liquid crystal panel 9 to the condenser lens 5 is L2, and the entrance pupil radius is R1, the light that can be incident on the entrance pupil is condensed. The distance R2 at the position of the lens 5 is given by the following equation.

[0032]

(Equation 3)

As is clear from the equation (3), it is necessary to increase the value of R2 in order to make much light enter the entrance pupil. However, increasing R1 requires a large projection lens with a large entrance pupil, so it is difficult to increase R1, and it is difficult to reduce L1 further in the design of the optical system. For this reason, in order to increase the value of R2, the liquid crystal panel 9 is moved to the condenser lens 5
It is necessary to increase the distance L2 to. Assuming that the distance L1 from the liquid crystal panel 9 to the entrance pupil is 250 mm, the radius R1 of the entrance pupil is 30 mm, and the distance R2 of the light that can enter the entrance pupil at the position of the condenser lens 5 is 55 mm, the light is collected from the liquid crystal panel 9. The distance L2 to the optical lens 5 is about 480
mm.

FIG. 9 shows the relationship between L2 and the amount of light entering the entrance pupil.

As is clear from FIG. 9, the amount of light entering the entrance pupil increases as L2 increases, but the light reflected by the parabolic mirror 2 becomes brighter as it approaches the center, and therefore its inclination increases with L2. Becomes loose with.

Next, the relationship between L2 and the amount of light entering the liquid crystal panel 9 will be considered.

In FIG. 10, DL is the size of the image display portion of the liquid crystal panel 9, DI is the first and second convex lens groups 4
The size of one convex lens A, 4B, FI is the focal length of one convex lens, L3 is the condenser lens 5 and the first and second
Assuming the distance from the convex lens groups 4A and 4B, the following relationship is established.

[0038]

[Equation 4]

Further, by transforming the equation 4,

[0040]

(Equation 5)

It becomes

Here, in order to allow light to enter the image display portion of the liquid crystal panel 9, as shown in FIG. 1, the first convex lens group 4A is used.
It is necessary that the light emitted from the one convex lens constituting the above-mentioned lens is incident on the one convex lens constituting the opposite second convex lens group 4B.

However, the light reflected by the parabolic mirror 2 is all parallel when the light source 1 is a point light source as shown in FIG. 11, but in reality the light emitting portion has a certain length. Therefore, the light incident on the convex lens that constitutes the first convex lens group 4A is not parallel.

Therefore, in addition to the parallel light, oblique light is also incident on the convex lenses constituting the first convex lens group 4A, and if the oblique light has an inclination angle of a certain value or more, the second convex lens group facing the second convex lens group is opposed. It does not enter the convex lens that constitutes 4B.

Therefore, in order to increase the amount of light incident on the convex lens forming the second convex lens group 4B facing through the convex lens forming the first convex lens group 4A, DI is increased.
It is necessary to increase the value of / FI.

That is, the light incident on one convex lens which constitutes the first convex lens group 4A is TAN-1 (DI / 2FI).
It is possible to effectively use the light up to the angle of
The traveling direction is corrected by the second convex lens groups 4A and 4B, and the liquid crystal panel 9 is illuminated.

As described above, the amount of light applied to the liquid crystal panel 9 increases as the DI / FI increases, that is, the L2 decreases, and the diagram shown in FIG. 12 is obtained.

In FIG. 12, the amount of light incident on the first convex lens group 4A gradually decreases as the angle increases. Therefore, as L2 decreases, the increasing tendency of the light incident on the liquid crystal panel 9 moderates. Become.

From the above, in order to increase the amount of light incident on the image display portion of the liquid crystal panel 9, it is desirable to reduce L2, and the light is incident on the entrance pupil of the projection lens 10 described above. Conflict with the conditions.

Therefore, it is necessary to set L2 to an optimum value.

Next, FIG. 13 shows the relationship between the brightness on the screen and L2.

FIG. 13 is a diagram in which FIG. 9 and FIG. 12 are combined, and has a characteristic of having a peak between A and B.

In FIG. 12, at the points from point A to point B, the amount of light incident on the liquid crystal panel 9 is approximately 80% to 90% of the light reflected by the parabolic mirror 2.
That is, it is sufficient to design a convex lens group that irradiates the liquid crystal panel 9 with 80% to 90% of the light reflected by the parabolic mirror 2.

Next, consider the angular distribution of the light reflected by the parabolic mirror 2.

In FIG. 2, LA is the length of the light emitting portion of the light source (arc length), and FR is the focal length of the parabolic mirror 2.

The angle of the light reflected at the point C where the vertical direction of the center of the light emitting portion and the curved surface of the parabolic mirror 2 intersect is:

[0057]

(Equation 6)

Can be obtained by: LA = 7 mm, FR
= 15 mm, θ = 6.7 degrees.

Then, at each reflection point of the parabolic mirror 2,
When the angle of light is obtained, 98% of the light exists within the range of 1.2θ, 90% of the light exists within the range of θ, and 0.8
It was found that 80% of the light existed within the range of θ.

Therefore, in order to utilize the amount of light which is 80% to 90% of the amount of light reflected by the parabolic mirror 2,
The distance between the first and second convex lens groups 4A and 4B, and the diameter of the convex lens forming the first and second convex lens groups 4A and 4B may be designed so that light in the range of 8θ to 1.0θ can be used. Good.

Therefore, from FIG. 1, the angle range of light that can be effectively used in the convex lenses constituting the first and second convex lens groups 4A and 4B is

[0062]

(Equation 7)

Therefore, the specification of the convex lens may be such that the following expression is satisfied.

[0064]

[Equation 8]

Substituting the equations 6 and 7 into the equation 8,

[0066]

[Equation 9]

It becomes

Here, when the angle is small, TAN (a ·
X) = a · TAN (X) holds, so if we transform Equation 9,

[0069]

[Equation 10]

It becomes

Therefore, it suffices to set the specification of one convex lens within the range that satisfies the expression (10). The shape of one convex lens on the light incident surface is matched with the shape of the liquid crystal panel 9 because the light of this shape is applied to the liquid crystal panel 9. For example, in the case of the NTSC system, the ratio of the horizontal direction to the vertical direction is 4 : It is 3. DI in Equation 10 is a horizontal value as an average value in the horizontal, vertical, and diagonal directions.

[0072]

The present invention enters the above-mentioned configuration and can display a bright projected image on the screen.

[Brief description of drawings]

FIG. 1 is a diagram showing an effective angle range of light incident on a convex lens.

FIG. 2 is a diagram showing an angular distribution of light reflected by a parabolic mirror.

FIG. 3 is an optical block diagram of a conventional liquid crystal projector using a convex lens.

FIG. 4 is a perspective view showing an incident side convex lens group and an outgoing side convex lens group.

FIG. 5 is an operation diagram of the convex lens group when parallel light is incident.

FIG. 6 is an operation diagram of the convex lens group when light having an angle is incident.

FIG. 7 is a diagram showing a problem of a conventional liquid crystal projector.

FIG. 8 is a diagram showing positions that can enter an entrance pupil.

FIG. 9 is a diagram showing the relationship between the amount of light entering the entrance pupil and the distance between the liquid crystal panel and the condenser lens.

FIG. 10 is a diagram showing the relationship between the shape of the liquid crystal panel and the specifications of the convex lens group.

FIG. 11 is a diagram showing reflected light on a parabolic surface in the case of a point light source.

FIG. 12 is a diagram showing a relationship between light entering a liquid crystal panel and a distance between the liquid crystal panel and a condenser lens.

FIG. 13 is a diagram showing the relationship between the brightness on the screen and the distance between the liquid crystal panel and the condenser lens.

[Explanation of symbols]

 1 light source 2 parabolic mirror 4 integrator lens 4A first convex lens group 4B second convex lens group 5 condenser lens 9 liquid crystal panel 10 projection lens

Claims (1)

[Claims] 1. A liquid crystal panel comprising a converging lens for converting light from a light source into parallel light by a parabolic mirror, and an integrator lens including a first convex lens group having a plurality of convex lenses and a second convex lens group, and a condensing lens. In the liquid crystal projector which irradiates the entire surface of the liquid crystal and projects the light transmitted through the liquid crystal panel onto the screen by the projection lens, the arc length of the light source is LA, the focal length of the parabolic mirror is FR, and the first convex lens group. , And the horizontal length of the convex lens forming the second convex lens group is DI, and the focal length of the convex lens is FI.
Then, the ratio of the horizontal length of the convex lens to the focal length (FI / DI) is as follows. A liquid crystal projector, characterized in that it is configured so as to satisfy.