CN1769953A - Projection image display apparatus and projection optical unit to be used therein - Google Patents

Abstract

In a projection type image display apparatus, for enlarging an image on a image display apparatus 1 by means of a projection lens 2 , thereby projecting the enlarged image onto a screen 6 , obliquely, being inclined thereto, between the projection lens 2 and a rear-surface mirror 5 , there are disposed free shaped surface mirrors 3 and 4 , each having a free shaped surface for compensating a trapezoidal distortion due to oblique projection of the enlarged image. The surface configuration of the free shaped surface mirror is so shaped as to satisfy a following equation.

Description

The projecting optical unit of projection image display and use thereof

Technical field

The present invention relates to for example colored enlarged image is projected in and carry out the projection image display that image shows on the screen, relate in particular to relative screen inclination projection enlarged image and can on screen, obtain the projection image display of enlarged image and the projecting optical unit of use thereof.

Background technology

By projecting optical unit with the coloured image enlarging projection on the image-displaying member of projection type Braun tube and liquid crystal indicator (liquid crystal panel) etc. on screen, in the so-called projection type color image display device, requirement obtains fully big enlarged image on screen, simultaneously, shorten the depth size of device.In order to realize this requirement, in the prior art, known for example as the special flat 5-134213 communique, spy opened open 2000-162544 communique, spy and open the 2002-357768 communique is put down in writing, the screen technology of coming the enlarging projection image relatively from vergence direction (the screen normal is with predetermined angle relatively).

But the image as if from relative screen inclination direction projection image-displaying member has then produced so-called keystone distortion on the image of projection on the screen.In order to eliminate this distortion, in the projecting optical unit that above-mentioned patent documentation 1 is put down in writing, be to make in burnt converter (afocal conversion) deflection of the nothing of screen side configuration to suppress the structure of this keystone distortion.But, because this patent documentation 1 disclosed no its multiplying power of burnt converter is low, so therefore the wide-angle difficulty of projected image, has the problem of slimming that can not implement device.

In addition, by the projecting optical unit that above-mentioned patent documentation 2 is put down in writing, from its structure, the wide-angleization of projected image is still very difficult.Therefore, thus the unit application that is difficult to patent documentation 2 is put down in writing is arranged in the problem of the abundant slimming of rear projection type color image display device implement device.Further, in the projecting optical unit that this patent documentation 2 is put down in writing,, also has the problem of the difficulty made owing to need the employed lens of deflection respectively.

Further, the projecting optical unit of above-mentioned patent documentation 3 records has: the first refractor system of positive focal power, the second refractor system that negative focal power is arranged and the light path mirror of turning back is arranged.In this structure, in the lens that constitute the above-mentioned second refractor system with negative focal power, at least two deflection systems that lens differ from one another for its rotation axes of symmetry.Therefore, during fabrication, be difficult to fully guarantee the positional precision of each lens, therefore, have the still very difficult problem of making.

As mentioned above, in the projecting optical unit of composing images display device,, can need from the so-called oblique-angle projection of relative screen inclination direction enlarging projection in order more to shorten its depth.And, further shorten in order to make depth, need make the angle of this oblique-angle projection bigger.

But under the bigger situation of the angle that makes this oblique-angle projection, it is big that above-mentioned keystone distortion also further becomes.Therefore, need further to become the big amount of deflection that this keystone distortion is used of proofreading and correct.Thus, make the optical unit that satisfies this requirement and further become difficult.In addition, relevant therewith, need make required lens diameter also become big.That is, in the optical system of above-mentioned prior art, the depth that makes projecting optical unit and then image display device is difficult more for a short time.

Summary of the invention

The invention provides a kind ofly in the device of relative screen inclination projected image, can reduce the technology of the display characteristic that the distortion of the image on the screen brings into play.

In addition, the present invention especially provides a kind of can reduce the image fault on the screen in rear projection type display apparatus, reduce the technology of the depth size of device simultaneously.

The present invention has first optical system, comprise that being amplified in the image that shows on the image-displaying member carries out a plurality of lens that projection is used, and the central shaft of optical axis and above-mentioned image-displaying member about equally; Second optical system, to project on this screen with predetermined angle from the normal of the above-mentioned relatively screen of enlarged image of first optical system, described second optical system comprises optical element, and this optical element has the curved surface that is used for the enlarged image from described first optical system is reflected and is directed at described screen.And, the invention is characterized in, when the optical path length that reflects the light that incides described screen by described optical element is optical range, crooked this optical element, come catoptrical part with first optical range, make concave surface towards its reflection direction, crooked with the next catoptrical part of second optical range shorter than described first optical range, make convex surface towards its reflection direction.

Among the present invention, at described optical element is that its reflecting surface is the curved reflector of free form surface (free shapedsurface) shape, described second optical system is carried out under the situation of projection with predetermined angle from the normal of the described relatively screen in below of described screen, be preferably described curved reflector, the part that the center of the described image-displaying member of crooked contrast more leans on the light of the image of top to reflect, make concave surface towards its reflection direction, has positive focal power, and the part that the center of the described image-displaying member of crooked contrast more leans on the light of the image of below to reflect makes convex surface towards its reflection direction.In addition, above-mentioned optical element is preferred for the minute surface of free form surface shape.In addition, preferably further comprise flat back side mirror, be used to reflect enlarged image, and project to the rear side of described screen from described optical element.Further, among the present invention, preferably described optical element is configured in the below of described back side mirror, further, described optical element preferably is made of two free form surface mirrors at least.

The present invention has: first optical system, be to comprise a plurality of be used to amplify image that shows on the described image-displaying member and the lens that carry out projection, and optical axis is by the approximate centre of described image-displaying member, the centered optical system that is made of the face for the shape of this symmetrical; Second optical system will be from the described relatively screen inclination projection of the enlarged image of described first optical system.And further feature of the present invention is that described second optical system comprises optical element, and this optical element has and is used to proofread and correct the keystone distortion that the oblique-angle projection by described enlarged image produces and/or the free form surface of aberration.

Above-mentioned optical element is included as the curved reflector of free form surface shape.And, the part that center crooked this curved reflector, the described image-displaying member of contrast more leans on the light of the image of top to reflect, make concave surface towards its reflection direction and have positive focal power (power), and the part that the center of the described image-displaying member of crooked contrast is more reflected by the light of the image of below makes convex surface towards its reflection direction and have negative focal power.

The present invention also can with the face of the vertical direction of this screen of the normal parallel of described screen in, it is L2 by described reflecting surface for the light of the lower end of L1, described enlarged image reflects the distance that arrives on the described screen by described reflecting surface that light in the upper end of establishing this enlarged image reflects the distance that reaches on the described screen, the upper end of the picture on the described screen is Dv to the distance of lower end, when the normal angulation that incides the light of central authorities of described screen-picture and this screen is θ, constitute the formula below satisfying:

|L1-L2|＜1.2·sinθ·Dv。

In addition, the absolute value of the difference of preferred above-mentioned L1 and L2 | L1-L2| forms littler than the situation that is shaped as the plane of this free form surface.In addition, with the face of the vertical direction of this screen of the normal parallel of described screen in, reflecting the distance that reaches on the described screen is L2 at the light of the upper end of establishing this enlarged image reflecting surface by free form surface for the light of the lower end of L1, the enlarged image reflecting surface by free form surface reflects the distance that arrives on the screen, the upper end of the picture on the described screen is when the distance of lower end is Dv, form these, make it satisfy following formula:

|L1-L2|＞0.4·Dv。

According to the present invention, can reduce keystone distortion by the oblique-angle projection generation of image, simultaneously, can reduce the optics depth of device.

Description of drawings

Fig. 1 is illustrated in the projection type video display device of embodiments of the present invention, especially the sectional view of the basic structure of its projecting optical unit;

Fig. 2 is for the oblique-angle projection to the screen of above-mentioned projecting optical unit is described, and amplifies the partial enlarged drawing of a part that shows above-mentioned Fig. 1;

Fig. 3 is the figure of variation of the optics depth of the relative tilt incident angle of expression in the above-mentioned projecting optical unit;

Fig. 4 is the figure of variation of size of the free form surface mirror of the relative tilt incident angle of expression in the above-mentioned projecting optical unit;

Fig. 5 is the structure of projecting optical unit of expression embodiments of the invention 1 and the figure of light path;

Fig. 6 is the figure of distortion performance of the projecting optical unit of expression the foregoing description 1;

Fig. 7 is the figure of bright spot performance of the projecting optical unit of expression the foregoing description 1;

Fig. 8 is the structure of projecting optical unit of expression embodiments of the invention 2 and the figure of light path;

Fig. 9 is the figure of distortion performance of the projecting optical unit of expression the foregoing description 2;

Figure 10 is the figure of bright spot performance of the projecting optical unit of expression the foregoing description 2;

Figure 11 schematically illustrates the relative screen inclination of the projecting lens that makes centered optical system and figure under the situation of oblique incidence;

Figure 12 is a concrete example of the projecting lens of present embodiment.

Embodiment

Below, the embodiment that present invention will be described in detail with reference to the accompanying.At first, accompanying drawing 1 is the sectional view of the basic structure of the projecting optical unit that uses in projection image display, the especially rear projection image display device of expression one embodiment of the present invention.

In the basic structure of this projecting optical unit shown in Figure 1, the light that the image-displaying member 1 that disposes from the downside at figure penetrates is by comprising a plurality of first optical systems 2 (being specially projecting lens) with refractor of rotationally symmetrical surf shape.Afterwards, the surface reflection of first catoptron 3 of the reflecting surface by having the free form surface shape (below, be called " free form surface mirror "), and further, reflect by the second free form surface mirror 4.After this reflected light reflects by the back side mirror 5 with plane reflection face as the 3rd optical system, incide the back side of screen 6.In addition, in the present embodiment, will be called second optical system by the optical system that the above-mentioned first free form surface mirror 3 and the second free form surface mirror 4 constitute.

Here, above-mentioned image-displaying member 1 for example can be the element of the emissive type of projection type Braun tube etc., maybe can be the infiltration type element of liquid crystal panel etc.In addition, in the figure, the element of the infiltration type that is formed by liquid crystal panel for above-mentioned image-displaying member 1 constitutes the illumination unit of for example lamp required under the situation etc., omits its diagram.In addition, for example adopt liquid crystal panel to be used as under the situation of this image-displaying member 1, also can be to use three liquid crystal panels to synthesize the mode of the image of a plurality of colors, but, in the figure, for required synthetic with prism etc. under this situation, omit its diagram.In addition, as can be seen from the figure, above-mentioned image-displaying member 1 with the central configuration of its display frame on the optical axis of above-mentioned first optical system (projecting lens) 2.Like this, by with the central configuration of the display frame of image-displaying member 1 on the optical axis of above-mentioned first optical system, can realize the little optical system of depth brought by oblique-angle projection, and can not become the size of big lens.

And, as shown in Figure 1, penetrate from the central authorities of the picture of above-mentioned image-displaying member 1, the central authorities of the entrance pupil by above-mentioned first optical system (projecting lens) 2, afterwards, light 11 oblique incidences of central authorities of picture of inciding screen 6 are to screen.Here, incide among the some P0 of screen at this light 11, normal and these light 11 angulations of establishing screen cover are θ, and the back is called it " oblique incidence angle ".In addition, this cross section shown in Figure 1 has shown the cross section of the above-mentioned projecting optical unit in the plane that the normal by the light 11 of the picture central authorities of inciding above-mentioned screen 6 and this screen forms.That is, this cross section is the cross section with the vertical direction of the normal parallel of screen 6.

On the other hand, in above-mentioned cross section, the light 12 that penetrates from the picture lower end of above-mentioned image-displaying member 1 is along the straight line of the central authorities of the entrance pupil of lower end that connects this picture and above-mentioned first optical system (projecting lens) 2, incide the position that is positioned at corresponding on this screen, that is, on the some P1 of the upper end of the picture on the screen 6.This light 12 is called L1 from the some P3 by (reflection) second free form surface mirror 4 through the optical path length that the some P2 on the above-mentioned back side mirror 5 arrives the some P1 on the screen.In addition, penetrate from the picture upper end of above-mentioned image-displaying member 1, straight line along the central authorities of the entrance pupil of upper end that connects this picture and above-mentioned first optical system (projecting lens) 2 enters, and, incide be positioned at as corresponding to the position on this screen, be the some P4 of lower end of the picture of screen 6.This light 13 is called L2 from the some P6 by (reflection) second free form surface mirror 4 through the optical path length that the some P5 on the back side mirror 5 arrives the some P6 on the screen.

And in the projecting optical unit of present embodiment, above-mentioned optical path length L1, L2 (optical path length poor) constitute the formula 1 below satisfying.

|L1-L2|＜1.2·sinθ1·Dv

Wherein, Dv is the size of the picture on the screen in the cross section of Fig. 1.In other words, be distance from the some P1 of the picture on the screen 6 upper end to the some P4 of this picture lower end.In addition, θ is above-mentioned oblique incidence angle.Further, in the projecting optical unit of present embodiment, the absolute value of the difference of above-mentioned optical path length L1 and L2 | L1-L2| constitutes littler than the situation that is shaped as the plane that makes the second free form surface mirror 4.

Below describing in detail and make the poor of above-mentioned optical path length | L1-L2| satisfies the reason of above-mentioned formula.

In addition, owing to make relative screen 6 oblique incidences of light from the projecting lens 2 that constitutes above-mentioned first optical system, can be so turn back (reflection) and then can reduce this point of depth size of the image display device of rear projection type thus by fine understanding by above-mentioned back side mirror 5.

Here, the projecting lens 21 (corresponding to the symbol 2 of Fig. 1) that Fig. 2 represents centered optical system relatively screen 27 (corresponding to the symbol 6 of Fig. 1) tilts, and makes the synoptic diagram under the situation of light 22,23,24 oblique incidences.In this Fig. 2, when the light 22 that penetrates along optical axis in the picture central authorities from the image-displaying member 20 (corresponding to the symbol 1 of Fig. 1) placed at the optical axis of projection optical system 21 arrives above-mentioned screen 27, represent size as follows with picture near the vertical direction of the light this screen 22.That is, the size of this picture be the line vertical with this light 22 with the intersection point of the intersection point P11 of the light 23 of its top and the light 24 of the line vertical and its downside with above-mentioned light 22 between distance.And its size is the Dv of picture size (length of longitudinal direction) of the image-displaying member 20 of original (that is, the situation of screen vertical direction incident under) relatively projection on screen 27.

But, because oblique incidence is from the light of the picture of image-displaying member 20, so in fact arrived some P12 on the above-mentioned screen 27 from the light 23 of the top that this picture penetrates.Therefore, the picture on the screen becomes bigger than Dv, and this becomes the reason of aliasing.Simultaneously, the light 23 above penetrating from this picture and below light 24 between produced deviation at projecting lens 21 to the optical path length of screen 27 too.In addition, the extent of this optical path length be equivalent to approx with from the vertical line of the light 22 of picture central authorities and from the intersection point P11 of the light 23 of picture top, and the intersection point of this light 23 and screen 27 between distance.

Therefore, in above-mentioned Fig. 1, illustrated in the projecting optical unit of present embodiment of its structure, in the outside slightly of projecting lens 21 (corresponding to the symbol 2 of Fig. 1), as mentioned above, disposed free form surface mirror (among Fig. 1, the first free form surface mirror 3 and the second free form surface mirror 4).Therefore, proofreaied and correct under the situation of above-mentioned aliasing by this free form surface mirror thinking, on screen 27, for example will move on the point of representing by P14 Fig. 2 from above-mentioned some P12 from the position that the light above the picture 23 arrives.In addition, mobile like that shown in symbol 26 in the drawings from the light 24 of picture below.That is, thus, the size (length of longitudinal direction) that projects to the picture of the above-mentioned image-displaying member 20 on the screen 27 is the Dv as original size.

Here, Figure 11 schematically illustrates by the free form surface mirror and reflects from the light as the projecting lens of rotational symmetric optical system, and the state under the situation of screen inclination incident relatively.In Figure 11, on the optical axis of projection optical system 21, place image-displaying member 20, the light 22 that optical axis from the picture central authorities of this image-displaying member 20 along projection optical system 20 penetrates (below, it is called central ray) reflect by mirror 28 after, come oblique incidence to screen 27 with angle θ.At mirror 28 is under the situation on plane, by the picture original oblique-angle projection of projection optical system 21 projections on screen 27.At this moment, be asymmetric at the point that incides on the screen towards the light 23 (being illustrated by the broken lines) of the upside of Figure 11 on the screen-picture with the some P23 that light 24 (being illustrated by the broken lines) towards the lower side incides relative above-mentioned central ray 22 incidents of point on the screen.Therefore, on the image on the screen, produced keystone distortion.At this moment, along the optical path length towards the mirror 28 of the light 23 of the upper end of above-mentioned screen-picture to screen 27 and along towards the mirror 28 of the light 24 of the lower end of above-mentioned screen-picture to having produced very big deviation between the optical path length of screen 27.

Here, if make the free form surface that is shaped as of mirror 28 come correcting distortion, then in the screen-picture towards the light of the upside of Figure 11 light 25 downward side shiftings as Figure 11, further, be that the light 26 of Figure 11 is such towards the light of lower side.Thus, above-mentioned light 25 point that incides screen is symmetry with the some P23 that light 26 incides relative above-mentioned central ray 22 incidents of point of screen.Therefore, can confirm that distance that light 25 incides the point of screen and the point that light 26 incides screen and correct picture size Dv about equally, have proofreaied and correct distortion.At this moment, from the optical path length along the mirror 28 of above-mentioned light 25 to screen 27, with diminish from comparing with the situation of light 24 with above-mentioned light 23 to the difference of the optical path length of screen 27 along the mirror 28 of above-mentioned light 26.

Promptly, in the present embodiment, be shaped as the free form surface shape by what make mirror 28, reduced from along poor with from along optical path length of the optical path length towards the mirror 28 of the light of the upside of above-mentioned screen-picture to screen 27 towards the mirror 28 of the light of the lower side of above-mentioned screen-picture to screen 27.As a result, suitably proofreaied and correct the distortion that causes by oblique-angle projection.

One example of the free form surface shape of the mirror 28 that well-corrected distortion is as mentioned above used is described with reference to Figure 11.In the mirror 28, the optical path length of picture central authorities from mirror 28 to screen of the relative screen of crooked reflection than the long light of central ray 22 (promptly, among Figure 11, towards than the some P23 on the screen more by the light (for example light 25) of the part of upside) part, make concave surface towards its reflection direction.That is,, make it have positive light coke also in the part of upside, being the reflecting surface of concave surface than some P22 mirror 28, reflection central ray 22.On the other hand, the optical path length of picture central authorities from mirror 28 to screen of the relative screen of crooked reflection than the short light of central ray 22 (promptly, among Figure 11, towards light (for example light 26) than the part of the some P23 downside on the screen) part, make convex surface towards its reflection direction.That is,, make it have negative power also in the part of downside, being the reflecting surface of convex surface than some P22 mirror 28, reflection central ray 22.

Mainly, the reflection of the free form surface mirror 28 of crooked present embodiment has the part of the light 25 of first optical range, make concave surface towards its reflection direction, crooked reflection has the part of the light 26 of second optical range shorter than first optical range, makes convex surface towards its reflection direction.Because in the present embodiment, come the oblique-angle projection image from the below of screen, so the center of the reflectance image-displaying member of the free form surface mirror 28 of crooked present embodiment is the top of mirror 28 by the part of the light of the image of top more, make concave surface towards its reflection direction, and have positive focal power.On the other hand, the center of crooked reflectance image-displaying member is the bottom of mirror 28 by the part of the light of the image of below more, makes convex surface towards its reflection direction, and has negative focal power.

If get back to Fig. 2, when correcting distortion, be approximately the size that is equivalent to above-mentioned some P13 and puts the distance between the P14 from the light 25 of the top of picture and difference from the optical path length between the light 26 of the below of picture.That is, on screen 27, compare before the picture size of the above-mentioned image-displaying member 20 of projection (length of longitudinal direction) and the graphic distortion correction and reduced.In more detail, adjust the surface of free form surface mirror, make poor (the optical path length poor) of above-mentioned optical path length be the degree of the distance that is equivalent to a P13 and some P14 from the projecting lens 21 that produces between the light 24 of the light 23 of the top that the picture of image-displaying member 20 penetrates and below to screen 27.Thus, by this free form surface mirror, can proofread and correct above-mentioned aliasing.

In addition, can be similar to by following formula 2 and obtain distance between the P14 of above-mentioned some P13 and point (below, it is made as Lx).

Lx＝Dv·(sinθ)/(cosθ’)

Here, θ ' is in the cross section of above-mentioned Fig. 2, the above-mentioned image-displaying member 20 after going out from the free form surface mirror partly draw the angle.For example, if the structure of the projecting optical unit of the color image display device that consideration generally can extensively obtain in market etc. are made as for example about 30 degree with above-mentioned value of partly drawing the angle, then following formula 2 becomes following formula 3.

Lx＝1.2·(sinθ)·Dv

In addition, above-mentioned approximate in, also comprised the free form surface mirror and be configured in apart from the abundant locational condition far away of screen.But, approaching under the situation of screen at this free form surface mirror, the difference of above-mentioned optical path length is littler value.Therefore, as can be seen the difference of above-mentioned optical path length than the littler condition that just becomes of value of following formula.Thus, in comprising first optical system of a plurality of refractors, can realize the correction of the keystone distortion that the oblique incidence by projected light brings, and can deflection lens and increase lens diameter.That is,, can realize having reduced the depth of this optical system according to present embodiment, and its projecting optical unit easy to manufacture.

Here, further, in order to realize making easier projecting optical unit, below, describe the size that is used to make above-mentioned free form surface mirror in detail and be abundant little condition.

Accompanying drawing 3 expression as above-mentioned shown in Figure 1 using free form surface mirror (the first free form surface mirror 3 and the second free form surface mirror 4) to proofread and correct in the optical system of keystone distortion, under the situation that its oblique incidence angle θ has changed, follows the value of the depth of its variation.The value of this depth is the minimum value of attainable device.That is, the transverse axis of the curve among this figure is oblique incidence angle θ.On the other hand, its longitudinal axis is represented the length of depth, and here, the length of this depth is standardized by the big or small Dv of the picture on the screen in the above-mentioned cross section shown in Figure 1, represents with relative value.In addition, the depth shown in here is meant by paraxial calculating, by under the hands-off each other condition of light of back side mirror 5 bendings, and the value of calculating from the result's of the position of having adjusted back side mirror 5 opticpath.Certainly wherein do not comprise lens barrel and mirror thickness etc.Below, it is called " optics depth ".

That is, as shown in Figure 3, " oblique incidence angle " θ is big more as can be seen, and the depth (optics depth) that constitutes the optical system of projecting optical unit can be more little.Further, the depth of this optical system is according among above-mentioned Fig. 1, the light 12 of the picture top on the screen 6 with towards the extended corner of the light 13 of below and different.And, this extended corner as previously mentioned, in the optical system of the present invention of the reflecting surface that has used the free form surface shape, and towards the light of picture upper end and poor towards the optical path length of the light of picture lower end | L1-L2| equates.Therefore, the parameter that this Fig. 3 has represented to establish with the difference of optical path length is DL, above-mentioned optical path length poor | the variation of the above-mentioned depth under the different situation of L1-L2|.That is, represented that poor (that is, the value of DL) of optical path length is big more, the depth of this optical system is more little.In addition, this DL is that big or small Dv by picture removes the poor of above-mentioned optical path length strictly speaking | the value of L1-L2| (DL=|L1-L2|/Dv).

Here, the optical system that diminishes significantly as the depth that makes device, for example in order to make the optics depth be varied down to below 0.5 times of size of screen-picture, from above-mentioned Fig. 3 as can be seen, can make " angle of oblique incidence " θ is 35 degree above (wherein, the difference of optical path length is under the situation of (DL=0.4)).

On the other hand, above-mentioned its size of free form surface mirror is big more, and its manufacturing is difficult more.Thus, making this free form surface mirror is to be important below the size of Guangdong regulation.For example, in above-mentioned structure shown in Figure 1, the size that also makes back side mirror 5 is the about more than 70% of screen-picture.Under the situation of the rear-projection that is applied to the big picture more than 50 inches, the size of this back side mirror 5 is the size that has surpassed 500mm.Therefore, be that the free form surface shape that satisfies above-mentioned condition is difficult with the surface working of this back side mirror 5.That is, the manufacturing with free form surface mirror of this size is actually difficulty.In other words, in the rear-projection of above-mentioned structure shown in Figure 1, making back side mirror 5 is inappropriate for free form surface.

Therefore, in the present embodiment, also as above-mentioned shown in Figure 1, the above-mentioned free form surface mirror of configuration on the light path before coming crooked its light path by this back side mirror.Near the configuration free form surface mirror bottom of above-mentioned screen 6 has more specifically been proposed.And then proposed to constitute this free form surface mirror by the first free form surface mirror 3 and the second free form surface mirror 4, be configured near the situation in bottom of above-mentioned screen 6.But even also there is the difference according to condition in the configuration structure of this free form surface mirror, the size of this free form surface mirror is from the excessive situation of the viewpoint of its manufacturing.

For example, Fig. 4 is illustrated in the above-mentioned configuration structure shown in Figure 1, along with the size as the second free form surface mirror 4 of big free form surface mirror, obtains the result of the variation of " oblique incidence angle " θ relatively.In addition, in this Fig. 4, its transverse axis is " oblique incidence angle " θ, and its longitudinal axis is represented required size for this free form surface mirror.Here, the size of so-called above-mentioned free form surface mirror is meant as the size in the above-mentioned cross section shown in Figure 1 (some P3 is to the distance of P6), and the big or small Dv by the picture on the screen in this cross section standardizes and shows.

As shown in Figure 4, " angle of oblique incidence " θ is big more as can be seen, and free form surface mirror size is big more.In addition, poor at above-mentioned optical path length | under the different situation of L1-L2|, the difference of this optical path length is big more as can be seen, and the size of free form surface mirror can be more little.

But, under for example 50 inches etc. the situation of rear-projection of big picture that is above-mentioned structure shown in Figure 1, becoming from the manufacturing that makes the free form surface mirror, easily this puts, the size (that is, as the size in the cross section of above-mentioned Fig. 1 of its minor face) of wishing above-mentioned free form surface mirror 4 is picture size about below 0.3 times on the screen.

Therefore, if consider the above-mentioned Fig. 4 of this condition, under the difference of this optical path length was 0.4 situation, the angle θ that need make oblique incidence was below 35 degree as can be seen.On the other hand, be under 0.5 the situation in the difference of this optical path length, the angle θ of this oblique incidence is big near 50 degree.

Here, if except the curve of above-mentioned Fig. 3, the curve of further combined diagram 4, then aforesaid in order to reduce " optics depth " can become the angle θ of this oblique incidence greatly.On the other hand, in order to reduce the size of free form surface mirror, need reduce the angle θ of this oblique incidence.That is, both are opposite tendency for the angle θ of oblique incidence as can be seen.Therefore, exist as can be seen and can not make the size of depth and free form surface mirror be varied down to the following situation of size of hope simultaneously according to condition.

Therefore, if be conceived to poor as the optical path length of above-mentioned parameter | (in the strictness, DL=|L1-L2|/Dv), the difference of optical path length is big more as can be seen, and the size of optics depth, free form surface mirror also changes to more little direction simultaneously for L1-L2|.Therefore, in order to satisfy both conditions, preferably become the poor of big optical path length.

That is, be appreciated that from above-mentioned Fig. 3 and curve shown in Figure 4 it is below the desired value that existence is satisfied (1) optics depth simultaneously; (2) size of free form surface mirror also is the scope of angle θ of the oblique incidence of following these two conditions of size easy to manufacture.And for the angle θ of this oblique incidence is set, poor (being DL=|L1-L2|/Dv in the strictness) that should understand above-mentioned optical path length is more than 0.4.

In addition, above shown in above-mentioned embodiment shown in Figure 1, be that the basis describes with the structure of bending direction in the plane that comprises the short side direction of picture (longitudinal direction) of the light path that forms by the free form surface mirror.But, can understand on the contrary with above-mentioned Fig. 1, under the situation of the structure in the bending direction of light path is the plane of the long side direction (horizontal direction) that comprises picture, also can constitute same as described abovely.That is, in this structure, can reduce depth, reduce the size of above-mentioned free form surface mirror simultaneously.Therefore, in this structure, certainly obtain optical system easy to manufacture.That is, as mentioned above, when can be implemented in the depth that reduces rear projection image display device, reduce the size of free form surface mirror, thus, make its optical unit easy to manufacture.

Further, the numerical value of lifting this each several part below describes the specific embodiment of the optical unit of rear projection image display device of the present invention described above in detail.

[embodiment 1]

Use accompanying drawing 5～Fig. 7 and Figure 12, and then the numerical value shown in the following table 1, embodiments of the invention 1 are described.Fig. 5 has represented the ray plot of present embodiment 1.That is first optical system 32 of light that penetrates from image-displaying member 31, by constituting by a plurality of refractors in the configuration of the downside of figure.Afterwards, reflect by the first free form surface mirror 33 and then the second free form surface mirror 34 that constitutes second optical system.And, reflect by surface, and incide on the screen 36 as the back side mirror 35 of level crossing.

Here, above-mentioned first optical system is the centered optical system that the plane of refraction by axisymmetric shape constitutes fully, and in these planes of refraction 4 are made of axisymmetric aspheric surface, and other are made of sphere.In addition, used here axisymmetric aspheric surface is used part (local) the cylinder coordinate system of each face, and formula 1 formula below the cause is represented.

[formula 1]

$Z=\frac{{\mathrm{<figure-callout\; id="2"\; label="cr"\; filenames="A20051008777900331.png,A20051008777900361.png"\; state="\{\{state\}\}">cr</figure-callout>}}^2}{1+\sqrt{1-(1+k)c^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20051008777900331.png,A20051008777900361.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+{A\&CenterDot;\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="A20051008777900281.png,A20051008777900311.png"\; state="\{\{state\}\}">r</figure-callout>}}^4+{B\&CenterDot;\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="A20051008777900281.png,A20051008777900331.png"\; state="\{\{state\}\}">r</figure-callout>}}^6+{C\&CenterDot;\mathrm{<figure-callout\; id="8"\; label="r"\; filenames="A20051008777900331.png,A20051008777900361.png"\; state="\{\{state\}\}">r</figure-callout>}}^8+{D\&CenterDot;r}^{10}+{E\&CenterDot;\mathrm{<figure-callout\; id="12"\; label="r"\; filenames="A20051008777900281.png"\; state="\{\{state\}\}">r</figure-callout>}}^{12}+{F\&CenterDot;r}^{14}+{G\&CenterDot;r}^{16}+{H\&CenterDot;r}^{18}+{J\&CenterDot;\mathrm{<figure-callout\; id="20"\; label="r"\; filenames="A20051008777900291.png,A20051008777900301.png"\; state="\{\{state\}\}">r</figure-callout>}}^{20}$

Here, r is the distance apart from optical axis, Z represent to sink (sag) amount.In addition, c is the curvature on summit, and k is the constant of the cone, and A～J is the coefficient that the power of r is taken advantage of item.

Then, the free form surface that constitutes above-mentioned second optical system uses with the vertex of surface of each face and represents as the formula 2 that local orthogonal coordinate system (x, y, the z) cause of initial point comprises below X, Y polynomial.

[formula 2]

$Z=\frac{{\mathrm{<figure-callout\; id="2"\; label="cr"\; filenames="A20051008777900331.png,A20051008777900361.png"\; state="\{\{state\}\}">cr</figure-callout>}}^2}{1+\sqrt{1-(1+k)c^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20051008777900331.png,A20051008777900361.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+\underset{m}{\mathrm{\&Sigma;}}\&CenterDot;\underset{n}{\mathrm{\&Sigma;}}\left(C(m,n){\&CenterDot;x}^m{\&CenterDot;y}^n\right)$

Here, Z represent with the X-axis direction vertical with Y-axis on the sinkage of shape of free form surface, c is the curvature on the summit, r is the distance of the initial point on the plane of X, Y-axis, k is the constant of the cone, C (m, n) is polynomial coefficient.

Further, Figure 12 represents a configuration example of the projecting lens of present embodiment 1, has represented to comprise the numerical value of the lens data of the optical unit that constitutes present embodiment 1 in the following table 1.Here, if with object plane, be that the display surface of image-displaying member is made as " S0 ", then face numbering (Surface) is represented by symbol S0～S28 successively.The face of each optical parameter of representing corresponding to S0～S24 of Figure 12 of S0～S24 wherein.S1 and S2 be respectively comprise the dichronic mirror that synthesis example uses as the display image of three image-displaying members light compositing portion inject outgoing plane.S25～S28 is corresponding to the face (reflecting surface, screen cover) of each optical parameter shown in S0～S24 of Fig. 5.That is, S25 represents the reflecting surface of the first free form surface mirror 33, and S26 represents the reflecting surface of the first free form surface mirror 34, and S27 represents the reflecting surface of plane mirror 35, and S28 represents image planes, i.e. screen cover.In addition, in this table 1, Rd represents the radius-of-curvature of each face, and among above-mentioned Fig. 5, this face has in the left side under the situation of the center of curvature, by on the occasion of expression, represents with negative value under the situation opposite with it.In addition, in following table 1, TH represent with the interplanar distance of following one side from, concrete, expression from the summit of this lens face to the distance on the summit of next lens face.In addition, in table 1, nd represents the refractive index of each lens element shown in Figure 12, the Abbe number that ν d represents this lens element.

[table 1]

The surface	Rd	TH	nd	νd
					S0	Infinitely great	26.648
S1	Infinitely great	31.342	1.51680	64.2
					S2	Infinitely great	5.000
S3	69.501	10.611	1.84666	23.8
					S4	-346.318	0.878
S5	46.651	0.176	1.52020	52.0
					S6	44.766	9.698	1.49700	81.6
S7	127.627	0.896
					S8	39.691	12.175	1.49700	81.6
S9	-43.950	3.514	1.75520	27.5
					S10	19.725	0.878
S11	20.067	8.503	1.49700	81.6
					S12	689.692	0.176	1.52020	52.0
S13	886.801	13.352
					S14	Infinitely great	41.092
S15	172.780	13.158	1.65412	39.6
					S16	-54.522	0.914
S17	65.972	8.766	1.84666	23.8
					S18	141.037	7.835
S19	-75.773	3.514	1.74400	44.7
					S20	63.046	22.101
S21	-29.490	3.514	1.62041	60.3
					S22	-38.329	21.310
S23	-28.154	8.784	1.49091	58.0
					S24	-104.400	71.000
S25	Infinitely great	-184.324	REFL
					S26	Infinitely great	295.000	REFL
S27	Infinitely great	-305.000	REFL
					S28	Infinitely great	-0.028

In addition, in above-mentioned Fig. 5 and Figure 12, this interplanar distance and is represented with negative value when the right side from representing with positive value when relatively next lens face of this lens face is present in the left side.

In addition, in above-mentioned table 1, S7, S15, S23 and four of S24 look like the above and are made of rotational symmetric aspheric surface.The aspheric coefficient of these 4 faces is by following table 2 expression.

[table 2]

The surface	Asphericity coefficient
									S5	K	1.500680822	C	-8.24339E-13	F	1.61598E-20	J	-1.93321E-27
A	-8.3275E-07	D	-3.56542E-15	G	1.35042E-22
								B		2.23608E-10	E	-5.78524E-18	H	2.8807E-25
S13	K	-10391.2727	C	-4.99381E-11	F	1.69886E-18	J										-3.05003E-23
								A	8.03455E-06	D	-1.73066E-13	G	8.0916E-20
	B	1.00416E-08	E	-1.61553E-15	H	3.57997E-21
								S23	K	-0.80933684	C	-8.243E-13	F	4.63854E-22	J		5.64589E-29
A	-7.4205E-07	D	-6.15312E-16	G	4.18233E-24
									B	-5.2292E-10	E	-5.01633E-19	H	1.68124E-26
S24	K	2.01004872	C	-4.54763E-14	F	1.00003E-22	J										1.82161E-31
								A	2.57707E-07	D	-4.02986E-17	G	1.94643E-25
	B	-1.888E-10	E	1.89957E-20	H	2.44674E-28

In addition, in above-mentioned table 1, as mentioned above, S25 and S26 are illustrated among above-mentioned Fig. 5, as the reflecting surface of the free form surface shape of the first free form surface mirror 33 of second optical system and the second free form surface mirror 34.Shape for the free form surface of these reflectings surface illustrates its details below.

At first, the initial point of establishing this local coordinate is configured in the free form surface of S25 (the first free form surface mirror 33) and leaves the interplanar distance shown in the S24 table on the position of (TH) on the optical axis of above-mentioned first optical system.Therefore, incide on the initial point of local coordinate of above-mentioned S25 from the light of the picture of image-displaying member 31 central authorities by the optical axis of first optical system 32 (below, be called " central ray ").

On the other hand, the Y-axis of the local coordinate of S26 and Z axle are positioned at the cross section of above-mentioned Fig. 5, the configuration of the above-mentioned relatively central ray of this Z axle with roughly tilting 40 degree.And, the free form surface of above-mentioned S26 is configured in its local coordinate ground initial point is positioned on the path by the above-mentioned central ray of above-mentioned S25 face reflection, and leave the shown interplanar distance of above-mentioned S25 face on the position of (TH).That is, the Y-axis of the local coordinate of this S26 and Z axle are positioned at the cross section of above-mentioned Fig. 5, and this Z axle incides the 26th above-mentioned central ray configuration relatively with roughly tilting 40 degree.

The value of coefficient of having represented the shape of these two free form surfaces in the table 3 below.

[table 3]

The surface	The free form surface coefficient
									S25			C17	3.97589E-10	C34	-5.28699E-13	C51	7.9672E-17
K	0	C19	1.38201E-09	C36	-2.88117E-12	C53	1.26856E-16
								C4		-0.00069127	C21	4.54608E-09	C37	1.79988E-15	C55	7.52318E-16
C6	-0.0001909	C22	-6.4426E-12	C39	2.49E-15	C56	-3.27811E-19
								C8		-9.2333E-06	C24	1.51157E-11	C41	-8.82702E-15	C58	-1.40336E-18
C10	-8.2751E-08	C26	1.70954E-11	C43	-1.81468E-15	C60	2.6418E-19
								C11		5.35449E-08	C28	1.51335E-12	C45	-1.44137E-14	C62	2.53399E-18
C13	-3.1103E-08	C30	4.52321E-13	C47	-1.04839E-16	C64	1.6311E-19
								C15		-1.6043E-08	C32	-6.12012E-14	C49	-5.79322E-17	C66	7.9022E-18
S26			C17	4.6176E-10	C34	7.67414E-15	C51										4.78267E-19
								K	0	C19	-2.516E-10	C36	-4.95185E-16	C53	1.7748E-19
	C4	-0.00152375	C21	-1.26156E-11	C37	1.17737E-17	C55									-1.35846E-18
								C6	-0.00023622	C22	-5.60687E-13	C39	-1.8562E-16	C56	-2.07357E-22
	C8	-1.3215E-05	C24	5.9598E-12	C41	1.10968E-16	C58									3.30436E-22
								C10	-4.8572E-06	C28	7.73069E-13	C43	3.95986E-17	C60	-5.48769E-21
	C11	2.5034E-08	C28	1.30848E-12	C45	-1.71225E-16	C62									3.14467E-21
								C13	-8.124E-08	C30	-9.81285E-15	C47	1.59137E-20	C64	-3.02674E-22
	C15	-3.1293E-08	C32	3.92768E-14	C49	-1.61716E-18	C66									-3.14013E-21

As mentioned above, in this first embodiment, distance between two free form surface mirrors (the first free form surface mirror 33 and the second free form surface mirror 34) is about 180mm, but in order to proofread and correct keystone distortion preferably, preferably these two free form surface mirrors is spaced apart more than the 150mm.This is because if two free form surface mirrors are near excessively, then the coefficient function of parameter as both has produced repetition, has restricted the ability of this distortion correction, and can not the well-corrected keystone distortion.

As the picture angle of above-mentioned first optical system 32, preferably will be made as below 15 degree from the output of the upper end of the picture on the image-displaying member 31, the light and the optical axis angulation of central authorities that passed through the entrance pupil of this first optical system.Thus, can keep the interval of above-mentioned two free form surface mirrors, the size that guarantees the free form surface mirror simultaneously is for littler.

Further, as can be seen, in present embodiment 1, curvature c and circular cone coefficient k are 0 from above-mentioned table 1, table 3.It greatly produces in the direction of the keystone distortion that is caused by oblique incidence in oblique incidence, and its amount distortion reduces in the vertical direction different with it.Therefore, in the direction of oblique incidence and vertical therewith direction, need greatly different function, act on above-mentioned curvature c and circular cone coefficient k (that is, its value being made as 0) on all directions by not utilizing the rotation symmetry, and can the well-corrected aliasing.

In addition, further, in the optical system of the foregoing description 1, in the mirror of the mirror of above-mentioned S25 and S26 face, the configuration of the coordinate axis almost parallel ground of its local coordinate system, thus, can well-corrected aliasing and bright spot shape.

The situation of the aliasing that expression is obtained by the optical unit of the present embodiment 1 of specifically having represented its numerical value in above-mentioned in accompanying drawing 6.In addition, the longitudinal direction of this Fig. 6 (y axle) is consistent with the above-below direction of above-mentioned Fig. 5, on the other hand, and the vertical direction of above-mentioned y axle on its transverse direction (x axle) expression and the screen, the i.e. depth direction of above-mentioned Fig. 5.The central authorities of the rectangular central authorities expression projected picture shown in this figure.And, in the figure,, represent the correction situation of the aliasing that causes by above-mentioned free form surface mirror (mirror 33 of S25 and the mirror 34 of S26) by the case of bending that shows that longitudinal direction four is cut apart, transverse direction 8 is cut apart the straight line of projected picture.

Further, the bright spot chart of the above-mentioned present embodiment 1 of expression in accompanying drawing 7.In this Fig. 7, begin expression by (1) shape to the bright spot chart of the numeral of (8) from upside.That is, represent the bright spot figure chart of the relative value of this XY coordinate for the light beam of (1,1), (0,1), (0.6,0.6), (1,0), (0,0), (0.6 ,-0.6), (1 ,-1), (0 ,-1) 8 ejaculations from scheming to go up order.In addition, the transverse direction of each bright spot figure chart is represented the x direction on the screen, and longitudinal direction is represented the y direction on the screen.

Shown good performance from the optical unit of last above-mentioned as can be seen present embodiment 1.

[embodiment 2]

Then, use accompanying drawing 8～10 and 12, further below shown in table 4～table 6, describe second embodiment of optical unit below in detail.

At first, Fig. 8 represents the ray plot of present embodiment 2.That is, the light that penetrates from the image-displaying member 41 in the configuration of the downside of figure is by comprising first optical system 42 of a plurality of refractors.Afterwards, the first free form surface mirror 43 by second optical system further reflects by the second free form surface mirror 44.And, reflect by back side mirror 45, and incide on the screen 46 as level crossing.

Here, above-mentioned first optical system is the centered optical system that the plane of refraction by axisymmetric shape constitutes fully, and in these planes of refraction 4 are made of axisymmetric aspheric surface, and other are made of sphere.In addition, axisymmetric aspheric surface used herein uses the local cylinder coordinate system of each face, is represented by the formula of representing in the above several 1.

Then, the free form surface that constitutes above-mentioned second optical system uses with the vertex of surface of each face local rectangular coordinate system (x, y, z) as initial point, by comprise X, Y polynomial in the above the formula 2 of expression represent.

Further, represented to comprise the numerical value of the lens data of the optical unit that constitutes present embodiment 2 in the table 4 below.Here the face of each optical unit of representing corresponding to S0～S24 of Figure 12 of the S0～S24 of table 4.If establish object plane, be the display surface of image-displaying member for " 0 ", then from S1 to S27, come presentation surface numbering (Surface) successively, S28 is image planes, i.e. screen cover.In addition, identical with the foregoing description 1, S25 represents the reflecting surface of the first free form surface mirror 43, and S26 represents the reflecting surface of the first free form surface mirror 44, and S27 represents the reflecting surface of plane mirror 45.In addition, in this table 4, Rd represents the radius-of-curvature of each face, in above-mentioned Fig. 8, has in the left side under the situation of the center of curvature at this face, represents with positive value, under the situation opposite with it, represents with negative value.In addition, in table 4, distance between the TH presentation surface, expression from the summit of this lens face to the distance on the summit of next lens face.In addition, in this Fig. 8, at relative this lens face, next lens face is positioned under the situation in left side, and this interplanar distance on the other hand, being positioned under the situation on right side, is represented with negative value from using on the occasion of representing.Identical with table 1, nd represents the refractive index of each lens shown in Figure 12, and ν d represents the Abbe number of this lens element.

[table 4]

The surface	Rd	TH	nd	νd
					S0	Infinitely great	26.648
S1	Infinitely great	31.342	1.51680	64.2
					S2	Infinitely great	4.945
S3	69.501	10.611	1.84666	23.8
					S4	-346.318	0.878
S5	46.651	0.176	1.52020	52.0
					S6	44.766	9.698	1.49700	81.6
S7	127.627	0.896
					S8	39.691	12.175	1.49700	81.6
S9	-43.950	3.514	1.75520	27.5
					S10	19.725	0.878
S11	20.067	8.503	1.49700	81.6
					S12	689.692	0.176	1.52020	52.0
S13	886.801	13.352
					S14	Infinitely great	41.092
S15	172.780	13.158	1.65412	39.6
					S16	-54.522	0.914
S17	65.972	8.766	1.84666	23.8
					S18	141.037	7.835
S19	-75.773	3.514	1.74400	44.7
					S20	63.046	22.101
S21	-29.490	3.514	1.62041	60.3
					S22	-38.329	21.310
S23	-28.154	8.784	1.49091	58.0
					S24	-104.400	71.055
S25	Infinitely great	-188.359	REFL
					S26	Infinitely great	399.251	REFL
S27	Infinitely great	-456.800	REFL
					S28	Infinitely great

In addition, in this table 4, S7, S15, S23 and S24 are rotational symmetric aspheric surfaces, and the aspheric coefficient table of these 4 faces is shown in the following table 5.

[table 5]

The surface	Asphericity coefficient
									S5	K	1.500680822	C	-8.24339E-13	F	1.61598E-20	J	-1.9332E-27
A	-8.32748E-07	D	-3.56542E-15	G	1.35042E-22
								B		2.23608E-10	E	-5.78524E-18	H	2.8807E-25
S13	K	-10391.27271	C	-4.99381E-11	F	1.69886E-18	J										-3.05E-23
								A	8.03455E-06	D	-1.73066E-13	G	8.0916E-20
	B	1.00416E-08	E	-1.61553E-15	H	3.57997E-21
								S23	K	-0.809336837	C	-8.243E-13	F	4.63854E-22	J		5.64589E-29
A	-7.42052E-07	D	-6.15312E-16	G	4.18233E-24
									B	-5.2292E-10	E	-5.01633E-19	H	1.68124E-26
S24	K	2.01004872	C	-4.54763E-14	F	1.00003E-22	J										1.82161E-31
								A	2.57707E-07	D	-4.02986E-17	G	1.94643E-25
	B	-1.88796E-10	E	1.89957E-20	H	2.44674E-28

In addition, in above-mentioned table 5, constitute above-mentioned second optical system, be respectively the reflecting surface of free form surface shape by S25 and S26.

At first, the initial point of establishing this local coordinate is configured in the free form surface of S25 (the first free form surface mirror 43) and leaves the interplanar distance shown in the S24 table on the position of (TH) on the optical axis of above-mentioned first optical system.Therefore, from the output of the picture of image-displaying member 41 central authorities and incide by the light on the optical axis of first optical system 42 on the initial point of local coordinate of S25.In addition, the Y-axis of the local coordinate of S25 and Z axle are positioned at the cross section of above-mentioned Fig. 8, the configuration of the above-mentioned relatively central ray of Z axle with having tilted 40 degree.

Then, the free form surface of S26 face (the second free form surface mirror 44) is leaving the initial point of the interplanar distance shown in the table from this local coordinate of the position of (TH) configuration from S25 on the path of the above-mentioned central ray that is reflected by above-mentioned S25.The Y-axis of the local coordinate of this S26 and Z axle also are positioned at the cross section of above-mentioned Fig. 8, and in addition, its Z axle incides the above-mentioned central ray configuration of S28 relatively with roughly tilting 40 degree.

Represented to be used to represent the value of the coefficient that the shape of these two free form surfaces is used in the table 6 below.

[table 6]

Surface	Zi is by Qu Mian Department number
									S25			C17	3.97589E-10	C34	-5.28699E-13	C51	7.9672E-17
K	0	C19	1.38201E-09	C36	-2.88117E-12	C53	1.26856E-16
								C4		-0.000691267	C21	4.54608E-09	C37	1.79988E-15	C55	7.52318E-16
C6	-0.000190895	C22	-6.4426E-12	C39	2.49E-15	C56	-3.2781E-19
								C8		-9.23329E-06	C24	1.51157E-11	C41	-8.82702E-15	C58	-1.4034E-18
C10	-8.27507E-06	C26	1.70954E-11	C43	-1.81468E-15	C60	2.6418E-19
								C11		5.35449E-08	C28	1.51335E-12	C45	-1.44137E-14	C62	2.53399E-18
C13	-3.11028E-08	C30	4.52321E-13	C47	-1.04839E-16	C64	1.8311E-19
								C15		-1.60433E-08	C32	-6.12012E-14	C49	-5.79322E-17	C66	7.9022E-18
S26			C17	7.68193E-10	C34	1.45696E-14	C51										1.74584E-18
								K	0	C19	-3.65862E-10	C38	1.73155E-16	C53	4.62669E-19
	C4	-0.001950537	C21	-6.13372E-12	C37	1.59114E-17	C55									-4.7246E-18
								C6	-0.000339517	C22	-6.72953E-13	C39	-4.3057E-16	C56	-1.293E-21
	C8	-1.84573E-05	C24	1.11136E-11	C41	2.57812E-16	C58									-1.1144E-21
								C10	-6.96717E-06	C26	1.33572E-12	C43	1.1365E-16	C60	-1.4953E-20
	C11	3.71786E-08	C28	3.6145E-12	C45	-5.4775E-16	C62									1.12898E-20
								C13	-1.20188E-07	C30	-1.16523E-14	C47	-5.90407E-19	C64	-1.7461E-21
	C15	-5.26802E-08	C32	7.60132E-14	C49	-4.12886E-18	C66									-1.1862E-20

As mentioned above, in this second embodiment, distance between two free form surface mirrors (the first free form surface mirror 43 and the second free form surface mirror 44) is about 180mm, but in order to proofread and correct keystone distortion preferably, preferably these two free form surface mirrors is spaced apart more than the 150mm.This is because if two free form surface mirrors are near excessively, then the coefficient function of parameter as both has produced repetition, has restricted the ability of this distortion correction, and can not the well-corrected keystone distortion.

As the picture angle of above-mentioned first optical system 42, preferably will be made as below 15 degree from the upper end output of the picture of image-displaying member 41, the light and the optical axis angulation of central authorities that passed through the entrance pupil of this first optical system.Thus, can keep the interval of above-mentioned two free form surface mirrors, the size that guarantees the free form surface mirror simultaneously is for littler.

Further, as can be seen, in present embodiment 2, curvature c and circular cone coefficient k are 0 from above-mentioned table 4, table 6.It greatly produces in the direction of the keystone distortion that is caused by oblique incidence in oblique incidence, and its amount distortion reduces in the vertical direction different with it.Therefore, in the direction of oblique incidence and vertical therewith direction, need greatly different function, be used in the above-mentioned curvature c that acts on all directions in the rotation symmetry and circular cone coefficient k (promptly by unfavorable, its value is made as 0), and can the well-corrected aliasing.

In addition, further, in the optical unit of the foregoing description 2, in the free form surface mirror of above-mentioned S25 face and the free form surface mirror of S26 face, the configuration of the coordinate axis almost parallel ground of its local coordinate system, thus, can well-corrected aliasing and bright spot shape.

The situation of the aliasing that expression is obtained by the optical unit of present embodiment 2 in accompanying drawing 9.In addition, the longitudinal direction of this Fig. 9 (y axle) is consistent with the above-below direction of above-mentioned Fig. 8, the vertical direction of above-mentioned y axle on its transverse direction (x axle) expression and the screen, the i.e. depth direction of above-mentioned Fig. 8.In addition, rectangular central authorities shown in this Fig are central authorities of projected picture.And, in the figure,, represent the correction situation of the aliasing that causes by above-mentioned free form surface mirror (the 25th mirror 43 and the 26th mirror 44) by the case of bending that shows that longitudinal direction four is cut apart, transverse direction 8 is cut apart the straight line of projected picture.

Further, the bright spot chart that expression is obtained by the optical unit of the foregoing description 2 among Figure 10.In this Figure 10, begin expression by (1) shape to the bright spot chart of the numeral of (8) from upside.That is, represent the bright spot figure chart of the relative value of this X, Y coordinate for the light beam of (1,1), (0,1), (0.6,0.6), (1,0), (0,0), (0.6 ,-0.6), (1 ,-1), (0 ,-1) 8 ejaculations from top order.In addition, the transverse direction of each bright spot figure chart is represented the directions X on the screen, and longitudinal direction is represented the Y direction on the screen.

Shown good performance from the optical unit of last above-mentioned as can be seen present embodiment 2.

As mentioned above,, can realize making the depth size of device very little, and it make also easy rear projection type polychrome graphics display device according to present embodiment.In addition, in the superincumbent explanation, the image display device of rear projection type only has been described.But present embodiment is not limited only to the display device of this rear projection type.For example, in above-mentioned optical system (unit),, then can obtain the image display device of front projection type if remove back side mirror and image-displaying member is contained in a structure in the device to the free form surface mirror.Thus, can implement device to the image display device of the little front projection type of the very short compact of the distance of screen and the keystone distortion that causes by oblique incidence.

Here, sum up the projecting optical unit of the projection type video display device that is used for above-mentioned various explanations.At first, in the present embodiment, on the structure of the projecting optical unit that is amplified in the next relative screen inclination projection of image that shows on the image display device, there is feature.This projecting optical unit has: include a plurality of refractors of rotationally symmetrical surf shape first optical system, comprise second optical system and the plane reflection face of the reflecting surface with the one or more free form surface shape that in the path of the light beam projecting that will penetrate to the screen, disposes from this first optical system.In this image-displaying member, with the central configuration of its display frame on the optical axis of this first optical system.And, present embodiment be characterised in that with the vertical cross-section of screen method line parallel in, optical path length at the light 12 that will incide above-mentioned screen shown in Figure 1 upper end is made as L1, when the optical path length that incides the light 13 of screen lower end is made as L2, if this catoptron is the free form surface shape, making the absolute value of difference of L1 and L2 | L1-L2| is that the situation on plane is littler than the reflecting surface of this second optical system.

In addition, the shape of the reflecting surface of above-mentioned free form surface is for example following like that.That is, the part of light (for example, the light 12 of Fig. 1) catoptron, that reflection has first optical range is bent into concave surface and has positive focal power towards its reflection direction.In addition, part catoptron, that reflection has the light (for example, the light 13 of Fig. 1) of second optical range shorter than first optical range is bent into convex surface and has negative focal power towards its reflection direction.

The projecting optical unit of the formula below the normal angulation θ that further, according to present embodiment, provide above-mentioned L1 and L2, the distance D v from the upper end of the picture on the screen to the lower end, incides the light of central authorities of this screen-picture and this screen satisfies.

|L1-L2|＜1.2·sinθ·Dv

In addition, in above-mentioned projecting optical unit, provide the upper end of satisfying the picture on above-mentioned optical path length L1, above-mentioned optical path length L2, the above-mentioned screen to satisfy the projecting optical unit of following conditions formula to the distance D v of lower end.

|L1-L2|＞0.4·Dv

Thus, can make effective size of reflecting surface fully little, can realize the projection arrangement of easier manufacturing with above-mentioned free form surface shape.

Further, in the projecting optical unit of present embodiment, above-mentioned second optical system is made of two free form surface mirrors.And, between the reflecting surface of these free form surface mirrors, along being more than the 150mm from the picture central authorities of the image-displaying member distance by the light of the central authorities of the entrance pupil of first optical system.Thus, keystone distortion that can the well-corrected oblique-angle projection.

Further, in the projecting optical unit of present embodiment, in above-mentioned vertical cross-section, the light and the optical axis angulation of the central authorities of output of the upper end of the picture from the image-displaying member and the entrance pupil by first optical system are below 15 degree.Thus, the size of above-mentioned free face reflecting surface can be reduced, projection arrangement easy to manufacture can be realized.Further, the shape of reflecting surface that has this free form surface shape in the projecting optical unit of present embodiment need not produce the coefficient of rotation symmetric shape only by the polynomial expression of X, Y coordinate is represented.In addition, in the projecting optical unit of present embodiment, above-mentioned second optical system is made of two free form surface mirrors.And, each coordinate axis of the local coordinate system of these two faces almost parallel ground configuration each other.

By structure recited above, present embodiment can obtain having reduced the good image quality of the distortion of the image on the screen in oblique-angle projection, can shorten the depth of device simultaneously.

Claims (17)

1. a projection type video display device is characterized in that, comprising:

Image-displaying member;

Screen;

First optical system comprises a plurality of lens that are used to amplify the display image on the described image-displaying member and carry out projection; And

Second optical system will be carried out projection with predetermined angle from the normal of the described relatively screen of enlarged image of described first optical system,

Wherein, described second optical system comprises optical element, and this optical element has the curved surface that is used for the enlarged image from described first optical system is reflected and is directed at described screen,

When the optical path length that reflects the light that incides described screen by described optical element is optical range, crooked this optical element, come catoptrical part with first optical range, make concave surface towards its reflection direction, crooked with the next catoptrical part of second optical range shorter than described first optical range, make convex surface towards its reflection direction.

2. projection image display according to claim 1, it is characterized in that: described optical element is that its reflecting surface is the curved reflector of free form surface shape, described second optical system is carried out projection from the normal of the described relatively screen in below of described screen with predetermined angle

Described curved reflector, the part that the center of the described image-displaying member of crooked contrast more leans on the light of the image of top to reflect, make concave surface towards its reflection direction, and the part that the center of the described image-displaying member of crooked contrast more leans on the light of the image of below to reflect makes convex surface towards its reflection direction.

3. projection image display according to claim 1 is characterized in that: further comprise flat back side mirror, be used to reflect the enlarged image from described optical element, and project to the rear side of described screen.

4. projection image display according to claim 3 is characterized in that: the below that described optical element is configured in described back side mirror.

5. projection image display according to claim 4 is characterized in that: described optical element comprises that its reflecting surface is at least two mirrors of free form surface shape.

6. a projection type video display device is characterized in that, comprising:

Image-displaying member;

Screen;

First optical system is to comprise a plurality ofly to be used to amplify image that shows on the described image-displaying member and the lens that carry out projection, and optical axis is by the approximate centre of described image-displaying member, the centered optical system that is made of the face for the shape of this symmetrical;

Second optical system will be from the described relatively screen inclination projection of the enlarged image of described first optical system;

Wherein said second optical system comprises optical element, and this optical element has and is used to proofread and correct the keystone distortion that the oblique-angle projection by described enlarged image produces and/or the free form surface of aberration.

7. projection image display according to claim 6 is characterized in that: the free form surface of described optical element comprises at least one minute surface.

8. projection image display according to claim 6, it is characterized in that: described optical element is included as the curved reflector of free form surface shape, the part that center crooked this curved reflector, the described image-displaying member of contrast more leans on the light of the image of top to reflect, make concave surface towards its reflection direction and have positive focal power (power), and the part that the center of the described image-displaying member of crooked contrast is more reflected by the light of the image of below makes convex surface towards its reflection direction and have negative focal power.

9. a projecting optical unit that is used for projection image display is characterized in that, comprising:

First optical system comprise a plurality ofly being used to be amplified in image that shows on the described image-displaying member and the lens that carry out projection, and the central shaft of optical axis and described image-displaying member about equally; With

Second optical system will project on this screen with predetermined angle from the normal of the described relatively screen of enlarged image of described first optical system,

Wherein said second optical system comprises optical element, this optical element have be used for to the enlarged image from described first optical system reflect and be directed at described screen, be the reflecting surface of free form surface shape;

The part that center crooked described optical element, the described image-displaying member of contrast more leans on the image of top to reflect, make concave surface towards its reflection direction, and the part that the center of the described image-displaying member of crooked contrast more leans on the image of below to reflect makes its convex surface towards its reflection direction.

10. projection image display according to claim 9 is characterized in that: described optical element is the curved reflector of free form surface shape.

11. projection image display according to claim 10 is characterized in that: described optical element comprises two described curved reflectors.

12. projection image display according to claim 9, it is characterized in that: with the face of the vertical direction of this screen of the normal parallel of described screen in, it is L1 that light in the upper end of establishing this enlarged image reflects the distance that reaches on the described screen by described reflecting surface, it is L2 that the light of the lower end of described enlarged image reflects the distance that arrives on the described screen by described reflecting surface, the upper end of the picture on the described screen is Dv to the distance of lower end, when the normal angulation that incides the light of central authorities of described screen-picture and this screen is θ, constitute the formula below satisfying:

|L1-L2|＜1.2·sin θ·Dv

13. projection image display according to claim 9, it is characterized in that: with the face of the vertical direction of this screen of the normal parallel of described screen in, it is L2 by described reflecting surface for the light of the lower end of L1, described enlarged image reflects the distance that arrives on the described screen by described reflecting surface that light in the upper end of establishing this enlarged image reflects the distance that reaches on the described screen, the upper end of the picture on the described screen is when the distance of lower end is Dv, form these, make it satisfy following formula:

|L1-L2|＞0.4·Dv

14. projection image display according to claim 9, it is characterized in that: the center that contrasts described image-displaying member more leans on the part that the image of top reflects to have positive focal power, and the center that contrasts described image-displaying member more leans on the part that the image of below reflects to have negative focal power.

15. a projecting optical unit that is used for projection type video display device is characterized in that, comprising:

First optical system, be to comprise a plurality of be used to be amplified in image that shows on the described image-displaying member and the lens that carry out projection, and optical axis is by the approximate centre of described image-displaying member, the centered optical system that is made of the face for the shape of this symmetrical; With

Second optical system is used for from the described relatively screen inclination projection of the enlarged image of described first optical system,

Wherein said second optical system comprises optical element, and this optical element has and is used to proofread and correct the keystone distortion that the oblique-angle projection by described enlarged image produces and/or the free form surface of aberration.

16. projection image display according to claim 15 is characterized in that: described optical element comprises at least one minute surface.

17. projection image display according to claim 15, it is characterized in that: described optical element is included as the curved reflector of free form surface shape, the part that center crooked this curved reflector, the described image-displaying member of contrast more leans on the image of top to reflect, make concave surface towards its reflection direction, and has a positive focal power, and the center of the described image-displaying member of crooked contrast is more by the part that reflects of the image of below, makes convex surface towards its reflection direction and have negative focal power.

Images