WO2006136490A1

WO2006136490A1 - Fine adjustment for a lens system in conjunction with translational displacement

Info

Publication number: WO2006136490A1
Application number: PCT/EP2006/062876
Authority: WO
Inventors: Harald Burkart
Original assignee: Thomson Licensing
Priority date: 2005-06-21
Filing date: 2006-06-02
Publication date: 2006-12-28

Abstract

An adjustment arrangement has a holding member (2) in which a tubular adjusted member (1) is movably supported. The holding member (2) has a helical slit (3) at least partially extending along its circumference. A pin (5) is rotatably mounted to the adjusted member (1) and protrudes through the helical slit (3). A movement of the pin (5) along the helical slit (3) causes a rotation and a translatory movement of the adjusted member (1). The pin (5) is further eccentrically mounted to the adjusted member (1). A rotation of the pin (5) in the helical slit (3) causes a translatory movement of the adjusted member 1). The adjustment arrangement can advantageously be used for adjusting the lens of a projection television apparatus.

Description

Fine adjustment for a lens system in conjunction with translational displacement

The invention relates to the coarse and fine adjustment of a lens system for projection television or rear-projection television.

Due to manufacturing tolerances of lens systems and the associated holding elements it is necessary, in the case of projection television or rear-projection television sets, to align the components with one another so as to obtain the best possible image quality. Easy access to the individual components that need to be adjusted is mandatory. In many cases the alignment requires additional auxiliary components such as springs, bushings or guides in order to facilitate the adjustment.

Adjustment systems known from the prior art frequently provide either a large displacement range together with quick settability, or a fine adjustment that cannot be performed quickly. For example, it is known to use an eccentrically mounted pin that converts a rotational movement into a translational movement of the corresponding counter part. The disadvantage here is that the larger the setting range required, the less accurate the achievable accuracy in case no gear reduction is present. By contrast, a relatively high setting accuracy can be achieved with the aid of a fine thread, e.g. as present in a photo lens. In this case the accuracy depends on the thread pitch, while the setting range is limited only by the thread length. In the extreme case, very many thread revolutions have to be made in order to cover the entire setting range.

It is desirable to simplify the adjustment of a lens system of projection television sets in the focusing direction.

The inventors have identified a particular challenge that resides in the relatively large possible displacement range, for example 2 mm, in relation to the required very accurate setting tolerance of, for example, ±2 μm. An adjustment arrangement according to the invention has a holding member in which a tubular adjusted member is movably supported. The holding member has a helical slit at least partially extending along its circumference. A pin is rotatably mounted to the adjusted member and protrudes through the helical slit. A movement of the pin along the helical slit causes a rotation and a translatory movement of the adjusted member. The pin is further eccentrically mounted to the adjusted member. A rotation of the pin in the helical slit causes a translatory movement of the adjusted member.

In one embodiment of the invention the helical slit has a shallow inclination and the pin has a large eccentricity.

In another embodiment of the invention the helical slit has a steep inclination and the pin has a small eccentricity.

The invention combines the advantages of the two above-named setting variants: the large setting range of the cam, or eccentric pin with the accuracy of the fine thread. The invention can advantageously be used for adjusting a lens in a projection television. To this end, in a preferred embodiment, a helical opening that has a flat pitch, corresponding to a fine thread, is provided in a holding element fitted in a fixed fashion. However, the opening is so widely shaped that an eccentric pin with an eccentricity corresponding to the setting range can be inserted. The eccentric pin is rotatably mounted to a tubular lens arrangement that is movably supported in the holding element. The tubular lens arrangement is the counterpart to the holding element. The eccentric pin is rotated for the purpose of coarse setting, and this effects a translational displacement of the tubular lens arrangement. This rotation is radial to the lens focus direction. For the purpose of fine adjustment the tubular lens arrangement to which the pin is rotatably mounted is rotated in the opening of the holding element without rotating the pin. The rotation in this case is co-axial to the lens focus direction. The co-axial rotation effects a very small translational displacement of the tubular lens arrangement to be set, in accordance with the flat or fine pitch of the helical opening. The invention will be described in the following with reference to the drawing. In the drawing,

Figure 1 shows an oblique view of the holding element and the tubular lens arrangement;

Figure 2 shows an oblique view of the holding element and the tubular lens arrangement with the pin removed;

Figure 3 illustrates the fine adjustment in a side view of the holding element and the tubular lens arrangement; and

Figure 4 illustrates the coarse adjustment in a side view of the holding element and the tubular lens arrangement.

In the figure same or similar elements are referenced with the same reference symbols.

Figure 1 shows an oblique view of the holding element 2 and the tubular lens arrangement 1 according to the invention. A helical slit 3 is cut into a tubular part of the holding element 2. A pin 5 is rotatably attached to the tubular lens arrangement 1 and protrudes through the helical slit 3. The pin 5 is mounted eccentrically to the tubular lens arrangement 1. A rotational movement of the pin around its longitudinal axis results in a rather large translatory displacement of the tubular lens arrangement 1 with respect to the holding element 2. Due to the very shallow inclination of the helical slit 3 a rotational movement of the tubular lens arrangement 1 results in a small translatory displacement of the tubular lens arrangement 1 with respect to the holding element 2.

Figure 2 shows an oblique view of a detail of the holding element 2 and the tubular lens arrangement 1. In the figure the pin 5 is not mounted to the tubular lens arrangement 1. A bearing 4 which accommodates the pin 5 can be seen through the helical slit 3. Further, the eccentric portion 6 of the pin 5 is visible.

Figure 3 illustrates the fine adjustment of the tubular lens arrangement 1 with respect to the holding element 2. The shallow inclination of the helical slit 3 is clearly visible. A movement of the pin in the direction of the arrow 7 results in a corresponding movement of the tubular lens arrangement 1 in the direction of the arrow 8.

Figure 4 illustrates the cause adjustment of the tubular lens arrangement 1 with regard to the holding element 2. A rotational movement of the pin 5 in the direction of the arrow 9 will result in a translatory movement of the tubular lens arrangement 1 in the direction of the arrow 10 due to the eccentricity of the bearing of pin 5.

The invention advantageously allows for performing a full adjustment of a projection lens system using only a single element.

Although the invention was described in the foregoing with reference to a projection television apparatus, the invention can also be used in all fields requiring a coarse/fine adjustment of parts that can be displaced by translation, for example binoculars, microscopes, screw drives, for example the lead screw of a lathe for displacement of the support.

It is also conceivable to reverse the operation of the elements, i.e. the rotation of the pin could also be used for fine adjustment and the rotational movement in the helical slit is used for coarse adjustment.

Claims

Patent claims

1. Adjustment arrangement with a holding member (2) in which a tubular adjusted member (1 ) is movably supported, characterised in that the holding member has a helical slit (3) at least partially extending along its circumference, wherein a pin (5) that is rotatably mounted to the adjusted member (1 ) protrudes through the helical slit (3), wherein a movement of the pin along the helical slit (3) causes a rotation and a translatory movement of the adjusted member (1 ), further characterised in that the pin (5) is eccentrically mounted, wherein a rotation of the pin (5) in the helical slit (3) causes a translatory movement of the adjusted member (1 ).

2. Adjustment arrangement according to claim 1 , characterised in that the helical slit (3) has a shallow inclination and the pin (5) has a large eccentricity.

3. Adjustment arrangement according to claim 1 , characterised in that the helical slit (3) has a steep inclination and the pin (5) has a small eccentricity.

4. Projection television apparatus having an adjustment arrangement according to any one of claims 1 to 3.

5. Microscope having an adjustment arrangement according to any one of claims 1 to 3.