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Projection lens

A projection lens and image magnification technology, which is applied in the field of projection lenses, can solve the problems of impracticality and cost increase, and achieve the effect of suppressing optical focus changes

Inactive Publication Date: 2003-05-21
PANASONIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although a patent has been applied for this relationship, it is necessary to have no inclination to the shell lens in the direction of the optical axis, and the mechanism of the shell lens must be moved appropriately, which increases the cost and is not practical.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment approach 1

[0038] Next, a projection lens according to Embodiment 1 of the present invention will be described with reference to the drawings.

[0039] figure 1 , Figure 5 and Figure 7 The projection lens configuration diagrams of Example 1, Example 2, and Example 3 of Embodiment 1 are in order. According to the projection lens described in the first aspect of the present invention, the lenses from the first group to the fourth group are lenses of positive magnification, the second group has the largest positive magnification in the whole system, and the fourth group has the second largest positive magnification. big lens. The fifth lens group is a negative magnification lens with a concave surface facing the screen side, which mainly corrects image curvature. The first group of lenses and the third group of lenses have the main function of correcting spherical aberration and coma aberration, the second group of lenses undertakes a considerable part of the positive magnification of...

Embodiment 1

[0048] figure 1 It is a configuration diagram of a projection lens of Example 1 of Embodiment 1. This embodiment 1 is in F NO =1.1, focal length f0=77.6, magnification=9.2, half screen angle of view=39 ° in the projection lens, satisfying the condition of claim 1 will make the optical performance (MTF) good, even if the temperature of the optical coupling liquid of the 5th group From 20°C to 66°C, the change in back focus distance is also within 0.05mm, and this is an example of designing with the aim of setting the distortion aberration within 6%.

[0049] exist figure 1 Among them, the first group lens G1, the third group lens G3, the fourth group lens G4 and the shell lens G5 of the fifth group lens are all acrylic resin plastic lenses, and the second group lens G2 is a SK5 glass lens. The filling material L between the CRT fluorescent screen F and the fifth group of shell lenses G5 uses the optical coupling fluid already mentioned, in order to prevent the contrast betwe...

Embodiment 2

[0097] Figure 5 It is a configuration diagram of a projection lens of Example 2 of Embodiment 1 of the present invention. Embodiment 2 As for Embodiment 1, only the surface spacing between the fourth group and the fifth group, especially the effective aperture and the surface interval outside the effective aperture are enlarged. In this way, although the focus adjustment of the projection lens of the present invention is carried out by moving the first group to the fourth group relative to the fifth group, when the finished product is that the surface interval between the fourth group and the fifth group is narrow, it is due to the When the lens barrel on the 4th group side interferes with the structure on the 5th group side. Especially in the case of high magnification use, compared to the case of low magnification use, the plane interval between the 4th group and the 5th group is narrowed, and phase interference is likely to occur, so it is enlarged compared to Example 1. ...

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Abstract

A projection lens comprises 5 lenses in 5 groups including: a first-group lens that is a positive lens; a second-group lens that is a positive lens having the largest positive power (the inverse number of focal length) in the whole lens system; a third-group lens that is a positive lens; a fourth-group lens that is a positive lens; and a fifth-group lens that is a negative lens with its concave surface facing a screen side, in order from the screen side, wherein each lens of the first, third, fourth and fifth groups has at least one aspheric surface. The distance between the first-group lens and the second-group lens is relatively short, and the positive power in the fourth-group lens is relatively high. In the projection lens, an optical focal shift due to the temperature change in the fifth-group lens is hardly caused, and therefore a projection lens with minimal distortion aberration can be provided at a low cost.

Description

technical field [0001] The present invention relates to a projection lens, in particular, to a projection lens suitable for use in a projection television for enlarging and projecting images of a cathode ray tube onto a screen. Background technique [0002] Projection TV is to use the projection lens to enlarge and project the images of B (blue), G (green), R (red) three-color monochrome CRT (cathode ray tube) onto the screen and synthesize them. , showing a large-screen color image. Recently, the demand for large-screen TVs in general households has increased, and the demand for projection TVs has also increased, and small projection TV devices with the same image quality as TVs are required. [0003] Therefore, as a projection lens, it is required to have a large aperture ratio, wide angle, and good imaging performance. In the past, there have been projection lenses made entirely of glass lenses, or projection lenses made entirely of plastic lenses in order to reduce cos...

Claims

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Application Information

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IPC IPC(8): G02B11/30G02B13/16G02B13/18
CPCG02B13/16
Inventor 高桥昌之木村俊介
Owner PANASONIC CORP
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