JPH0772448A - Projection display for compensating chromatic aberration - Google Patents

Abstract

PURPOSE:To reduce the dividing angle for color direction of a transmitting light beam caused by the prism action of a transmissive screen to smaller than a half. CONSTITUTION:The projecting distance for a red color projection lens 4 is made larger than the projecting distance for a blue color projection lens 6, the relative value DELTAD/D of the difference of distances DELTAD is set to be 0.5 to 1.5 times of the reciprocal of the Abbe number of the refractive index of the structural member of the transmissive screen 7. By this constitution, the incident viewing angle of blue light on the screen 7 is made larger than the incident viewing angle of red light. The difference of the angle of transmitted light in the main direction from the transmissive screen 7 is reduced to smaller than a half.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromatic-aberration-correction projection display capable of correcting a difference in vertical directional characteristics between red and blue due to chromatic aberration of a transmissive screen.

[0002]

2. Description of the Related Art FIG. 2 shows a plan view of a conventional projection display of the optical three-primary-color image superposition type. 1, 2,
Reference numerals 3 are projection tubes for red, green and blue, respectively. Reference numerals 4, 5 and 6 are projection lenses. Reference numeral 7 is a transmissive screen. Reference numerals 8 and 9 are horizontal directional characteristics of the screen. USP4432010 discloses a structure of a double-sided lenticular lens that diverges light in the horizontal direction as an effective means for correcting the red / blue difference in the horizontal directional characteristic of a transmissive screen. However, the USP does not describe vertical red / blue deviations.

FIG. 3 is a side view of the projection display of FIG. 1 to 7 are the same as in FIG. The screen 7 is composed of a Fresnel lens and a horizontal diverging double-sided lenticular lens. Conventionally, the deviation between different colors of the vertical directional characteristic in the transmissive screen of this type has not been considered a problem.

However, the inventor has made a prototype of a so-called multi-screen display in which a large number of unit-projection displays are arranged in a matrix to form a large screen, and as a result of detailed evaluation thereof, a problem has been found.

The problem found will be described with reference to FIG. FIG. 3A is a side view of the unit displays stacked in three stages (three rows), and 7,7 ′ and 7 ″ are screens. A solid arrow R indicates a main emission direction of red light, A dotted arrow B indicates the main emission direction of blue light, 17 indicates the position of the viewer's eyes, and a graph 18 in the figure (b) shows R / B when the screen is looked up from the direction of the viewing position 17. As can be seen from the figure, the lower end of the upper screen looks reddish and the upper end of the lower screen looks bluish, so the color suddenly changes at that boundary and when viewed as a whole multi-screen display. Fig. 5 shows the results of the elucidation of the cause of the inhibition of uniformity.
Shown in. FIG. 19 shows a convex lens for easily expressing the action of the Fresnel lens. In the figure, α is the vertical angle of view, and Δα is the R / B angle deviation of the emitted light. According to the optical principle, the Δα / α ratio is the reciprocal of the Abbe number. That is,
Refractive index: The value of n is generally relatively large for blue,
Since it is smaller than red, the above angle deviation: Δα is generated. That is, it was clarified that the cause of the uniformity inhibition was the color direction separation phenomenon due to the prism action of the transmissive screen. Therefore, the color unevenness shown in FIG. 4B is generated.

Based on the above-mentioned elucidation result, the result of observing one stand-alone projection type display in detail is shown in FIG.
10 to 16 of the above. In the figure, 10 and 10 'are red vertical directional characteristics, 11 and 11' are blue vertical directional characteristics, and 12 is red and blue vertical directional characteristics at the center of the screen. Direction 13
Looking down the top edge of the screen, it looks reddish. Looking up from the top of the screen from direction 14, it looks bluish. Looking down the bottom edge of the screen from direction 15, it looks bluish. In general terms, the upper and lower edges of the screen look bluish when viewed from the inside and reddish when viewed from the outside. That is, it was confirmed that a phenomenon corresponding to the cause shown in FIG. 5 was observed.

By the way, as a means for overcoming the above problems, it is not possible to use a screen consisting of a total of three Fresnel lenses, a double-sided lenticular lens for vertically diverging light, and a double-sided lenticular lens for horizontally diverging light. It is a sufficient condition. However, the three-panel screen is expensive.

Therefore, there has been an ongoing search for means for reducing the chromatic aberration of the vertical direction directional characteristic by using an inexpensive screen having a two-layer structure as in the prior art.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the angle in the color direction of emitted light due to the prism action of a transmission screen to less than half.

[0010]

In one embodiment of the present invention, the red projection lens is arranged farther from the screen than the blue projection lens.

In another embodiment, the height of the red projection lens is higher than that of the blue projection lens when the screen has an average downward refractive power.

[0012]

With the above-mentioned means, the screen has a function of preliminarily correcting in the opposite direction on the incident side of the screen that the refractive power of the screen against red is weaker than that of blue.
Therefore, on the screen emission side, the directions of the R / B emitted lights can be corrected so as to match each other. Therefore, the phenomenon of color direction separation can be reduced.

[0013]

FIG. 1 shows the first embodiment of the present invention. Same figure
(a) is a plan view, 1 to 7 are projection tubes as in FIG.
A projection lens and a screen. D is the distance between the green projection lens and the screen, that is, the projection distance of the green projection lens. ΔD is the difference between the projection distance of the red projection lens and the projection distance of the blue projection lens.

FIG. 1B is a side view. Reference numeral 4 is a red projection lens, 6 is a blue projection lens, and 7 is a screen. α is the vertical angle of view, and Δα is the blue / red angle of view difference. According to the trigonometric method, the ΔD / D ratio is equal to Δlog cot α, and the latter is Δcot α / cot α, that is, Δα / (cos α · sin
equal to α). Further, the value of α is usually within about 0.4 rad in an optical system which is normally used, and in this case, the ΔD / D ratio is almost equal to Δα / α. That is, the number 1 is established.

[0015]

[Equation 1]

On the other hand, there is a relationship of approximately 2 between Δα and the refractive index: n. Here, Δn is the refractive index difference between red and blue, and A is the Abbe number.

[0017]

[Equation 2]

From Equations 1 and 2, Equation 3 is obtained as a condition for eliminating the phenomenon of outgoing light in the color direction.

[0019]

[Equation 3]

An object of the present invention is to reduce the color direction separation phenomenon to less than half as described above. The condition corresponding to this is as shown in Formula 4.

[0021]

[Equation 4]

That is, the constitutional requirement of this embodiment is that the projection distance of the red projection lens is the relative value of the projection distance difference of the blue projection lens: ΔD: ΔD / D is the reciprocal of the Abbe number of the refractive index of the screen constituent member. It should be in the range of 0.5 to 1.5 times.

The effect is that the angle difference between the main directions of the red and blue emitted lights can be reduced to less than half that of the prior art, as shown by the screen emitted lights: 20 and 20 'in FIG. 1 (b). The Abbe number is about 80 for acrylic materials and about 40 for styrene materials.

This is the end of the description of the first embodiment of the present invention.

Next, applying the above-mentioned first embodiment of the present invention,
When a multi-screen display is constructed, the remaining problems are shown in FIG. 6, and the solution is shown in FIG. 7 as a second embodiment of the present invention. Both figures are side views.

In FIG. 6, reference numerals 7, 7 ', 7 "denote upper, middle and lower screens, respectively, and 21 denotes a conjugate point where the main directions of green emitted light of the respective screens merge. Lower screen: 7" Does not have an upshifting refractive power on average. The middle screen is slightly bent downward. The upper screen is strongly refracted downward. As shown in the same figure, such a difference in the lower refractive power can be achieved by making the positions of the centers of the Fresnel lens elements: 22, 23, 24 in the screen of each step different for each step as shown in the figure. It will be understood from the description of USP4919518.

In FIG. 6, the angle Δβ is the angular difference between the red / blue main emission directions. The existence of the angle Δβ is a remaining problem.

A means for reducing the angle Δβ to less than half is shown in FIG. 7 as a second embodiment. FIG. 7 is a side view similar to FIG. 7, 7 ', 7 "and 21 are the same as those in FIG.
Reference numerals 4'and 4 "are projection lens positions for red, and reference numerals 6,6 'and 6" are projection lens positions for blue. ΔD in the figure has already been described in the first embodiment. ΔH in the figure is the difference in the arrangement height of the red / blue projection lenses. In order to reduce the angle Δβ by half, it is necessary to satisfy the following equation.

[0029]

[Equation 5]

In the above equation, the angle β is the downward refraction angle of the light emitted from the screen: 7, as shown in FIG.

The effect of this embodiment is that the chromatic aberration due to the emission direction of the main emission light of the screen: β can be reduced by half.

This concludes the description of each embodiment of the present invention. In each of the embodiments, a method using three projection tubes and three projection lenses has been illustrated, but it can be applied to a method using three liquid crystal panels corresponding to three primary colors and three projection lenses. Is obvious.

[0033]

According to the present invention, the chromatic aberration of the vertical directional characteristic of the transmission screen can be reduced by half by properly setting the arrangement position of the red / blue projection lens.

Therefore, it is possible to provide a projection display having an excellent color balance. Therefore, the application of the projection display can be expanded to fields such as preliminary evaluation of various designs.

[Brief description of drawings]

FIG. 1 (a) is a plan view and FIG. 1 (b) is a first embodiment of the present invention.
It is a side view.

FIG. 2 is a plan view of a conventional technique.

FIG. 3 is a side view of the prior art.

FIG. 4 is a side view of the prior art.

FIG. 5 is a side view for explaining a cause of a problem in the conventional technique.

FIG. 6 is a side view for explaining a remaining problem of the first embodiment.

FIG. 7 is a side view showing a second embodiment of the present invention.

[Explanation of symbols]

1, 2, 3 ... Red, green, blue projection tubes, 4, 5, 6 ... Red, green, blue projection lenses, 7 ... Screen, 17 ... Viewer eye position, 19 ... Convex lens.

Claims (2)

[Claims] 1. In a projection display having a transmissive screen, a red projection lens, a green projection lens and a blue projection lens, the projection distance of the red projection lens is larger than that of the blue projection lens. And none, and
Difference between both projection distances: Relative value of ΔD: Value of ΔD / D is set within a range of 0.5 to 1.5 times the reciprocal of the Abbe number of the refractive index of the screen constituent member. A chromatic aberration correction type projection display characterized by the following. 2. A multi-screen display in which unit projection displays having a few co-transmissive screens, a red projection lens, a green projection lens and a blue projection lens are stacked in multiple stages, and the upper red projection lens is The placement height is set higher by ΔH than the placement height of the upper blue projection lens, and the ratio of ΔH and projection distance: D: ΔH / D is set to the value of the upper screen. Ratio of average downward refraction angle: β and Abbe number: A: β / A value of 0.
A chromatic-aberration-correction projection display characterized by being configured and set within a range of 5 times to 1.5 times.