JP2603340B2 - Projection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a projection apparatus that combines a plurality of images to form a projection image, and particularly relates to a technique relating to an optical system thereof.

2. Description of the Related Art Projection devices that combine a plurality of images having a certain color component to obtain a color image, for example, are well known, but their methods can be classified into several types.

FIG. 8 shows a system called a three tube three lens system. Images emitted from blue, green, and red light-emitting cathode ray tubes 39, 40, and 41 are enlarged and projected on a screen 13 via projection optical systems 12 corresponding to the respective tubes to obtain color images.

FIG. 9 shows a system called a three tube one lens system. Images of three colors emitted from CRTs 39, 40, and 41 emitting blue light, green light, and red light are synthesized by a color synthesizing optical system 11 including a half mirror, and are projected onto a screen 13 via one projection optical system 12. To obtain a color image.

FIG. 10 shows a system called a three-panel one-lens system. White light emitted from an illumination optical system including a reflection mirror 1, a light source 2, and a condenser lens 3 is separated into three colors of blue light, green light, and red light by color separation optical systems 4, 5, and 6, and After irradiating the bulb (liquid crystal element) 8 and modulating the image,
Each decomposed light is constituted by a color combining optical system 11, and projects an image on a screen 13 via a projection optical system 12.

[Problems to be Solved by the Invention] However, it is ideal for a projection lens to project and render an original image as it is, but in reality, it is affected by aberrations generated by the projection lens. Therefore, in particular, when a color image is obtained by combining the different color components described above, it is necessary to sufficiently correct the chromatic aberration remaining in the projection optical system, particularly, the chromatic aberration of magnification. If the chromatic aberration of magnification remains, a so-called registration error occurs in which the three colors of light are separated on the screen 13, resulting in a reduction in resolution and a reduction in image quality.

On the other hand, in particular, in a projection apparatus for obtaining a color image using a CRT as shown in FIGS. 9 and 10, the sizes of the images projected on the CRTs 39, 40, and 41 are compatible. It is relatively easy to make electrical changes, and it is also possible to correct the chromatic aberration of magnification remaining in the projection optical system to some extent.

However, in a method of obtaining a color image using a liquid crystal panel, it is difficult to change the screen size.

On the other hand, it is possible to correct aberrations to some extent from the viewpoint of lens design, such as using an achromatic lens in the projection optical system or increasing the number of lens components, but there is a limit to this. At the same time, there is a practical problem that leads to an increase in cost, weight and size.

An object of the present invention is to solve such a problem.

[Means for Solving the Problems] In the present invention, the size of each projected image and the focus are substantially the same, and the characteristic feature is that a plurality of images of different color components are provided. And a synthesizing unit for synthesizing the images of the respective image forming units, wherein the projection device projects the synthesized image via one projection optical system. At least one of the image forming units A lens group having a positive power and a lens group having a negative power are disposed between the lens group and the synthesizing means, and magnification correction is performed by moving one of the lens groups or changing the power, and moving both lens groups. The focus position is corrected in the step (2), and the adjustment is performed so that the projected images substantially match.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

2 is a light source such as a halogen lamp, a xenon lamp or a metal halide lamp, 1 is a reflection mirror, 3 is a condenser lens, and 4 is a first which reflects only a blue light component near 480 mm.
Dichroic mirror, 5 is a second dichroic mirror that reflects only the green light component near 540 mm, 6 is 600 m
A third dichroic mirror that reflects only the red light component near m, 7 is a reflecting mirror having a mirror surface, 8a, 8b, and 8c are light valves (liquid crystal panels) that form an original image, 9a and 9b.
Is a correction means for optically correcting a color shift, having a configuration described later. Reference numeral 10 denotes an optical element which is optically equivalent to the correction means 9a and 9b in a reference state (before correction). Numeral 11 denotes a color synthesizing optical system which is composed of a cross dichroic prism in which two dichroic mirrors are made orthogonal. Reference numeral 12 denotes a projection optical system including a zoom lens, and reference numeral 13 denotes a screen.

In the above configuration, each image formed on each of the liquid crystal panels 8a, 8b, 8c is illuminated by the illumination light of each color separated by each dichroic mirror (4, 5, 6), while the color combining optical system After being synthesized by 11, it enters the projection lens 12 and
Then, the color image is projected on the screen 13 in an enlarged manner.

FIG. 2 is a diagram specifically showing the correction means 9a and 9b described above. The correcting means 9a and 9b are provided in the first lens group 1 having different refractive powers.
4 and at least two lens groups of the second lens group 15. When a difference in relative image size caused by chromatic aberration of the projection lens itself, particularly a chromatic aberration of magnification, occurs in a projected image, that is, when a registration error occurs, there are two cases. The distance between the lens groups is changed (indicated by an arrow 16), and adjustment is performed so that the size of each image matches that of the reference green light, that is, registration adjustment.

In the present embodiment, the correction means is moved integrally in the optical axis direction (indicated by arrow 17) to perform focus adjustment, and further moved in the direction intersecting the optical axis (indicated by arrow 18). The position of the projected image on the screen for blue / red light is matched with that for green light (adjustment of misalignment).
Note that the same effect can be obtained by performing an operation of moving the light valve 8 in a direction parallel to or perpendicular to the optical axis by supporting the light valve on a moving mechanism instead of the operations indicated by arrows 17 and 18. be able to.

Next, an embodiment in which the correction means is configured in another form is shown in FIG. In the present embodiment, an example is shown in which a part of the lens of the correction means is made of a transparent elastic or fluid substance made of silicon rubber or the like. Numeral 19 denotes a fluid material which is sealed in the transparent elastic film 21. Then, by adjusting the pressure through the cylinder 22, the curvature of the transparent elastic film changes, so that the refractive power changes and the magnification can be changed. The imaginary edge indicated by 20 indicates the position of the transparent elastic film in the equilibrium state. FIG. 3 (A) shows a state where pressure is applied, and FIG. 3 (B) shows a state where pressure is reduced.

 Next, another embodiment will be described with reference to FIG.

In this embodiment, the transparent thin-film electrode 24 for supplying power to the transparent dielectric 23 as a part of the lens of the correction means is connected to the power supply 26.
An example is shown in which a known element having a property that the focal length changes when a voltage is applied from the device is used.

This element is already known, for example, from JP-A-57-19216 or JP-A-59-78317. Briefly, by applying a voltage to the transparent thin-film electrode 24 from the power supply 26, the refractive index of the transparent dielectric 23 changes in the direction perpendicular to the optical axis, and the characteristic diagram shown in FIG. The axis R is a device having a characteristic having a refractive index distribution as shown by a curve 29 indicated by a distance from the center of the transparent dielectric 23 in a direction perpendicular to the optical axis).

Therefore, the same magnification effect as that obtained by the operation 16 shown in FIG. 2 can be obtained, and a color image with good image quality can be obtained.

By the way, when the projection optical system is a zoom lens in particular, the chromatic aberration of magnification characteristics fluctuates according to the focal length. An example will be described.

FIG. 6 is a graph in which the horizontal axis represents the zooming focal length f of the projection optical system 12 and the vertical axis represents the magnification β. The blue light magnification variation curve 31 and the red light magnification are based on the green light projection magnification (straight line 35). FIG. 6 is a characteristic diagram showing a variation curve 32.

The basic operation and configuration of this embodiment using a projection optical system having a chromatic aberration variation characteristic due to zooming as shown in FIG. 8 will be described with reference to FIG. FIG. 7 is a diagram in which a portion from the light valve 8 to the projection optical system 12 for one of the three colors of light, for example, blue light in FIG. The apparatus shown in FIG. 2 used in the first embodiment is used as the correcting means 9, and a zoom lens including a focus group 33, a zoom group 34 and a relay group 35 is specifically used as the projection optical system 12. 36 is a position detecting means (encoder or potentiometer) 37 for detecting the position of the zoom unit 34, and 38 is a part of the lens 14 of the correcting means,
The driving means (motor) of the correcting means 9. The zoom position signal of the position detecting means 36 is sent to a magnification correction signal generator 39. In FIG. 39, there are magnification chromatic aberration fluctuations as shown in FIG. 6 at each zoom position of the zoom group 34, and the lens 14 is mainly moved to cancel the fluctuations. 9 has a ROM in which the overall positional relationship is stored in advance, and a position control command is sent to the driving means 37 and 38 in accordance with the contents of the ROM. By providing the same mechanism for the red light example, a clear image without registration errors can be obtained in the entire zooming range of the projection optical system 12.

In addition, when focusing is performed, the chromatic aberration variation characteristic of magnification as shown in FIG. 6 generally changes in a conventional zoom lens. This characteristic
If the focus group 33 is provided with the same position detection means as that described above in the focus group 33 and stored in the ROM, a clear image without registration errors can be obtained even in the entire projection distance range by the same operation as described above. .

Although the above-mentioned example aims at the high compensation of the registration error, in the case of a general-purpose device, the compensation for the compensation is provided in one optical path for projecting the color component image having the most different size with respect to the other color component images. The registration error may be reduced by changing the image size by attaching one lens.

Although the liquid crystal panel is used as the image forming apparatus 8 in the embodiment of the present invention described above, the present invention is not limited to this, and a cathode ray tube may be used.

As described above, the projection apparatus according to the present invention can match the projected images of blue, green, and red light with the correction of the chromatic aberration of magnification of the projection optical system in a weak state. High quality projected images can be obtained.

2. Description of the Related Art In recent years, in the field of color display devices, there has been an increasing tendency to demand higher resolution and higher quality images. A projection type display device using a conventional light valve has the advantages of small size, light weight, and low cost, but is inferior in resolution and image quality as compared with other types using a CRT or the like. The present invention significantly improves this drawback, and provides a high-quality color image with a low-cost projection display device with less restrictions on installation conditions, and has an effect of expanding the application range in the field of the projection display device. Bring.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. FIG. 2 is a configuration diagram of the correction means 9 used in the first embodiment of the present invention. FIG. 3 is a configuration diagram of the correction means 9 used in the second embodiment of the present invention. FIG. 4 is a configuration diagram of the correction means 9 used in the third embodiment of the present invention. FIG. 5 is a refractive index characteristic diagram of the element shown in FIG. FIG. 6 is a graph showing a change characteristic of lateral chromatic aberration caused by zooming of the projection optical system 12 used in FIG. FIG. 7 is a detailed view of portions 8, 9, 11, and 12 in FIG. 1 used in the fourth embodiment of the present invention. FIGS. 8, 9 and 10 are diagrams showing a conventional projection display apparatus. 8 light valve 9 correction means 11 color synthesizer 12 projection optical system

Claims (2)

(57) [Claims] An image forming means for forming a plurality of images of different color components; and a synthesizing means for synthesizing the images of the respective image forming means, and projecting the synthesized image via one projection optical system. A lens group having a positive power and a lens group having a negative power are arranged between at least one of the image forming means and the synthesizing means, and the movement or power of one of the lens groups is arranged. A projection apparatus, wherein magnification is corrected by a change, focus position is corrected by movement of both lens groups, and adjustment is performed so that projected images substantially match. 2. The projection optical system is a zoom lens,
2. The projection apparatus according to claim 1, further comprising control means for controlling movement or power change of the lens group in conjunction with zooming of the zoom lens.