WO1995027227A1

WO1995027227A1 - Support stand for an optical scanning module

Info

Publication number: WO1995027227A1
Application number: PCT/US1995/002469
Authority: WO
Inventors: Mining And Manufacturing Company Minnesota; Jay A. Esch; James E. Steffen; Eric J. Donaldson
Original assignee: Minnesota Mining & Mfg
Priority date: 1994-03-31
Filing date: 1995-02-28
Publication date: 1995-10-12

Abstract

A support stand (10) for an optical scanning module having a planar portion (14) and a planar portion support (18). The planar portion (14) has a first surface (15) for holding an optical scanning module and a second surface (16) for connection to at least one planar portion support (18). At least one planar portion support (18) is connected to the planar portion second surface (16), and the support stand (10) exhibits a first natural vibration frequency greater than the driving frequency of the optical scanning module mounted on the support stand (10).

Description

SUPPORT STAND FOR AN
OPTICAL SCANNING MODULE
Field of the Invention
The invention relates to radiographic or reprographic imaging of objects and more particularly to a support stand for an optical scanning module for use in flatbed swept-beam type imaging systems.

Background of the Invention
Radiographic imaging of objects, particularly useful in the medical sciences, utilizes x-ray imaging techniques to render an image onto a photoreceptive medium. The image formed is representative of the shadow cast by the object as the radiation passes through the object. In this way considerable detail can be seen of the internal structures of the object.

Reprographic imaging of objects, particularly useful in the graphic arts industry, utilizes actinic radiation to provide a reproduction of an image on a photoreceptive medium.

More recent advances in imaging technologies have realized the advantage of being read electronically.

The electronic reading provides the image data in a digital format which is readily stored, may be communicated to another over long distances, and is readily enhanced to glean additional image information from any particular area of the dynamic range.

Effective use of optical scanning systems, particularly laser optical scanning systems, often requires overcoming system vibration problems. For example, during laser scanning of a photoreceptive medium to initiate acquisition of a latent image, as disclosed in a co-pending U. S. Patent Application filed on even date herewith and presently identified as 3M
Docket No. 50134USA1A (Steffen et al.; Radiographic
Image Reader), considerable inaccuracies may be induced into a retrieved image unless certain system components are designed to minimize the effects of machine vibration.

Machine vibration is a particular problem in systems having compact arrangements of moving components, or systems using optical equipment such as rotating choppers and mirrors. Image artifacts appearing as spatially periodic variations in the spacing between scan lines on the photoreceptive medium can be caused by machine vibrations which affect the relative positions of the beam and the plane of the photoreceptive medium.

Summary of the Invention
The present invention overcomes these problems by providing a support stand for an optical scanning module which is engineered to control machine vibration. The invention utilizes novel constructions to provide a support stand with an optical scanning module mounted upon it. The invention provides a support stand having a first natural vibration frequency at a level significantly above many high precision instruments which could be mounted on the support stand. In this way, the support stand mitigates the vibrational background noise from high precision instruments minimizing interference with the data collected from these high precision instruments.

One embodiment of the invention is a support stand for an optical scanning module having a planar portion and a planar portion support. The planar portion has a first surface for holding an optical scanner assembly and a second surface for connection to at least one planar portion support. At least one planar portion support is connected to the planar portion's second surface, and the support stand with the optical scanning module mounted on it exhibits a first natural vibration frequency which is greater than the driving frequency of the optical scanning module.

Brief Description of the Drawinqs
The foregoing advantages, construction, and operation of the present invention will become more readily apparent from the following description and accompanying drawings in which:
Figure 1 is a perspective view of a support stand for an optical scanning module.

Figure 2 is a perspective view of a support stand for an optical scanning module analogous to that shown in Figure 1 but with an optical scanning module and a movable translation mechanism shown in operational configuration with the support stand.

Figure 3 is a perspective view of an alternate embodiment support stand.

Figure 4 is an end view of an alternate embodiment support stand.

Detailed Description of the Preferred Embodiments
A support stand 10 is disclosed in Figure 1, which may either be integrally formed with or simply mounted to table 12. Support stand 10 includes a planar portion or top plate 14 having a generally polygonal shape with portions that are directly supported and portions which are generally suspended or cantilevered, i. e., without direct support. Top plate 14 is shown having corner portions which are angled rather than arcuate, although the latter is within the scope of this invention provided the shape achieves the acceptable vibration mitigation criteria described below. Top plate 14 has a first surface 15 for holding an optical scanning module having a particular driving frequency and a second surface 16 for connecting with at least one planar portion support 18.

Support stand 10, with an optical scanning module mounted on it, exhibits a first natural vibration frequency which is greater than the driving frequency of the optical scanning module by itself.

Preferably, the support stand 10 can has a plurality of adjacent planar portion supports 18 connected to second surface 16 of top plate 14 and positioned to be along side faces 21 of top plate 14.

As disclosed in Figure 1, the support stand 10 can have two planar portion supports 18 arranged in an L-frame configuration. It is recognized that planar portion supports 18 may be manufactured as a unitary construction with top plate 14. The L-frame configuration preferably allows movable components of a radiographic imaging system to move under top plate 14 without contacting the planar portion supports 18.

This is accomplished by planar portion supports 18 comprising wall portions 23 defining an opening 27 suitable for allowing passage of a movable object, such as a movable translation mechanism 30 shown in Figure 2, under top plate 14 without contacting side supports 18. Returning to Figure 1, this configuration results in a corner section 31 of top plate 14 being suspended or cantilevered relative to opening 27 under top plate 14.

The support stand 10 has a generally horizontal polygonal planar portion or top plate 14 with a thickness that is variable so that the thickest part of top plate 14 is at side faces 21 where planar portion supports 18 connect to second surface 16, and the thinnest part of top plate 14 is at corner section 31.

In the embodiments shown in Figure 1, the thickness of top plate 14 at corners 36,38, and 40 is about 1.85 inches (47 mm). Top plate 14 is tapered so that the plate thickness at corner section 31 is about 1.65 inches (42.5 mm). It is recognized that other th-. cknesses may be used within the scope of this invention provided the desired vibration characteristics described below are achieved.

Using the construction and dimensions shown in
Figures 1 and 2, support stand 10 has a first natural vibration frequency of about 165 hertz. This first natural vibration frequency allows support stand 10 to be non-responsive to sources of vibration below 165 hertz in radiographic imaging systems. One such application for support stand 10 is to support a high precision laser optical scanning module, such as the optical scanning module 51 shown in Figure 2. Such scanning devices often employ rotating polygon mirrors and beam choppers each with inherent vibrational patterns. For example, optical scanning module 51 has a driving frequency of about 110 hertz. Support stand 10, with optical scanning module 51 mounted on it, has a first natural vibration frequency greater than 110 hertz.

In use, the translation mechanism 30 can be used to translate a photoreceptive medium 52 within a cassette 54 beneath the optical scanning module 51. As the photoreceptive medium 52 passes beneath, the optical scanning module 51 can direct a scanning beam (not shown) across the photoreceptive medium 52 to capture the image held within the photoreceptive medium 52. The support stand 10 is capable of controlling the vibration of the optical scanning module 51 caused by this translation of the photoreceptive medium 52 and the rotation of the scanning mirror.

In a preferred embodiment, support stand 10 includes a metal portion in which the metal is selected from a list of metals including steel, aluminum, and titanium, or other alternative metals yielding slightly different natural vibration frequencies. A composite material provides an alternative material which is lightweight but still maintains the similar strength and vibrational damping characteristics of the metals.

Useful composite materials non-exclusively include carbon graphite, fiber glass, and metal matrix materials. A laminate material construction may also be used. Laminates allow for the use of similar and dissimilar materials in the construction of support stand 10. As shown in Figure 1, the top plate 14 can have a ribbed construction 59 which uses less material and reduces the overall weight when choice of materials allows this type of construction and when the support stand 10 and optical scanning module 51 can achieve the desired vibration damping characteristics.

Another embodiment of the present invention is support stand 60 depicted in Figures 3 and 4. As shown, support stand 60 is constructed from sections of tubular steel. In this embodiment, fifteen steel tubes having four different tubular dimensions are used.

Tubes 62 and 64 run parallel to each other and their upper surfaces 66 provide support for a system component such as a high precision laser optical scanner. Tubes 62 and 64, with associated cross linking tubes 63,65,67, and 69, describe a planarlike portion 70 functionally analogous to planar portion or top plate 14 described above in relation to
Figures 1 and 2. Tubes 62,63,64,65,67, and 69 are supported by legs 76,78,80, and 81. Legs 76,78,80, and 81 are mountable to a table surface. Tube 84 is suspended from the under surface of cross member 82 and is connected to tubes 64,67, and 69. This stabilizes corner 90 of planar-like portion 70 created by tubes 62 and 64 and associated cross members 63,65,67, and 69.

Construction of either support stand 10 or support stand 60 allows for related system components to pass beneath or adjacent the support stands without inducing vibration. Furthermore, in the latter embodiment, placement of cross member 82 above upper surface 66 allows for an opening 94 bounded by the placement of vertical tube 84, cross member 82, and leg 80 for objects to pass to the side of planar-like portion 70.

The invention provides support stands engineered to control vibrations. Most high precision devices have natural vibrations that degrade data generated by these devices in the form of background noise. The invention utilizes novel constructions to provide a support stand with an optical scanning module mounted on it with a combined first natural vibration frequency at a level significantly above many high precision instruments that could be mounted on the support stand.

In this way the support stand mitigates the vibrational background noise from high precision instruments minimizing interference with the data collected from these high precision instruments.

Thus, it can be seen that there has been shown and described a novel invention as described above. It is recognized and understood, however, that there are many extensions, variations and modifications on the basic theme of the present invention beyond that shown in the illustrations and detailed description, which are within the spirit and scope of the present invention.

Claims

We claim: 1. A support stand for use in a scanning subsystem of a radiographic imaging system, comprising: a planar portion having a first surface for holding an optical scanning module having a driving frequency and a second surface for connection to at least one planar portion support; at least one planar portion support connected to the planar portion second surface; and the support stand with the optical scanning module mounted on it exhibiting a first natural vibration frequency which is greater than the driving frequency of the optical scanning module.

2. The support stand of claim 1 in which the planar portion is a tapered polygonal plate constructed so that the plate is thickest proximate the connection locations with the planar portion support.

3. The support stand of claim 2 in which the tapered plate is thinnest at a suspended corner which is not directly connected to the planar portion support.

4. The support stand of claim 3 in which the tapered plate tapers from a thickness of about 1.85 inches proximate connection locations with the planar portion support to about 1.65 inches at the thinnest suspended corner.

5. The support stand of claim 1 in which the planar portion support comprises a plurality of adjacent planar portion supports connected along side portions of the planar portion second surface.

6. The support stand of claim 5 in which the adjacent planar portion supports comprise two side supports arranged in an L-frame configuration which allows movable components of the radiographic imaging system to move under the planar portion without contacting the planar portion supports.

7. The support stand of claim 5 in which the planar portion supports comprise wall portions defining an opening suitable for allowing passage of a movable object under the planar portion without contacting the planar portion supports.

8. The support stand of claim 1 in which the support stand with the optical scanning module mounted on it has a first natural vibration frequency greater than 110 Hz.