ARRANGEMENT FOR AN IMAGE SCANNING UNIT

Abstract: The invention relates to an arrangement for an image scanning unit (1). This comprises a semiconductor capsule (2) so arranged as to generate electrical signals corresponding to an image incident upon the light-sensitive surface (2a) of the capsule and so arranged as to be connected by soldering to a circuit board (5). Also present are an optical system arranged in a holder (3) for projecting the image to be scanned onto the aforementioned light-sensitive surface (2a) and a mounting plate (4) positioned between the semiconductor capsule (2) and the circuit board (5). Finally, devices (3a, 3b, 4a) are also present for joining together the holder (3) and the mounting plate (4) and for ensuring correct mutual alignment between the semiconductor capsule (2) and the optical system.

Description: Arrangement for an image scanning unit The present invention relates to an arrangement for an image scanning unit comprising a semiconductor capsule so arranged as to generate electrical signals corresponding to an image incident upon the light-sensitive surface of the capsule and so arranged as to be connected by soldering to a circuit board, an optical system arranged in a holder for projecting the image to be scanned onto the aforementioned light-sensitive surface, a mounting plate positioned between the semiconductor capsule and the circuit board, and devices for joining together the holder and the mounting plate and for ensuring correct mutual alignment between the semiconductor capsule and the optical system. An arrangement of this kind is previously disclosed through US-A-4,594,613. The mounting plate is attached in this case to the holder for the optical system by means of screws and pins, which project outwards from the holder and interact with holes in the mounting plate in order to ensure the desired alignment between the semiconductor capsule and the optical system. The previously disclosed arrangement has a comparatively bulky construction and uses many detail components which demand a relatively long assembly time; in order to be able to fix the holder to the mounting plate with screws, or vice versa, openings are also required in the actual circuit board. Ensuring that the holder is correctly aligned relative to the semiconductor capsule, as briefly described above, means that the accuracy of the alignment may be jeopardized. The object of the present invention is to make available an arrangement of the kind referred to by way of introduction, in which elimination of the above-mentioned disadvantages has been effected and has been made possible in that the aforementioned devices, in order to ensure correct alignment between the optical system and the light- sensitive surface of the semiconductor capsule, consist in the longitudinal direction of the semiconductor capsule of a projection projecting from the holder in such a way, when the unit is assembled, that it engages between two of the contact legs of the semiconductor capsule and that, in the transverse direction of the semiconductor capsule and in a direction normal to the light-sensitive surface, the aforementioned joining devices comprise snap elements capable of interacting with one another arranged on the holder and on the mounting plate. A desired alignment accuracy tolerance between the optical system and the light-sensitive surface of the semiconductor capsule is achieved through the characteristic features of the invention in that the location of the holder is achieved by means of the semiconductor capsule itself or, rather, with two of its contact legs. In addition, a space- saving, rapid, reliable and simple joint is obtained between the holder and the mounting plate. In accordance with one particular characteristic of the invention, the snap elements in one preferred embodiment are arranged along two lines running parallel to one another and to the longitudinal edges of the semiconductor capsule and lying in areas close to them. The invention is described in greater detail below with reference to the accompanying drawing, in which Fig. 1 illustrates an exploded view of the invention in perspective view. Fig. 2a shows the arrangement in accordance with the invention installed, and Fig. 2b is a detailed view showing a projection which ensures correct alignment between the light-sensitive surface of a semiconductor capsule and an optical system, by means of which an image is projected onto the aforementioned surface. Fig. 3a shows the arrangement in accordance with the invention shown in Fig. 2a in side view, and Fig. 3b is an enlarged partial view of Fig. 3a, which shows snap elements by means of which a holder for the optical system is fixed to a mounting plate for the holder. The designation 1 is used in the drawing generally for an image scanning unit comprising a semiconductor capsule 2 with a light-sensitive surface 2a, a holder 3 for an optical system (not shown in the drawing) for projecting onto the light-sensitive surface 2a an image which is to be scanned, a mounting plate 4 and a circuit board 5. The semiconductor capsule has contact legs 2b which carry electrical signals corresponding to the image incident upon the light-sensitive surface 2a when the image scanning unit is being used, and which are intended to be connected in the conventional manner to a conductive pattern on the circuit board 5. The contact legs 2b are inserted for this purpose into holes 5a in the circuit board 5 and are soldered in place to the conductive pattern. The mounting plate 4 is so arranged as to be positioned between the semiconductor capsule 2 and the circuit board 5 in the space which is conventionally present between a circuit board and a semiconductor capsule of this kind when it is soldered in place on the circuit board. Rapid and reliable joining of the holder 3 to the mounting plate and, at the same time, accurate alignment of the optical system relative to the light-sensitive surface 2a in the transverse direction of the semiconductor capsule 2 and in a direction normal to the surface 2a are achieved in accordance with the invention by means of snap elements 3b, 4a interacting with one another arranged on the holder 3 and on the mounting plate 4 and preferably integral with them. The manner in which these snap elements 3b, 4a interact can be appreciated most clearly from Figures 3a, 3b. The holder 3 exhibits on its surface facing the semi¬ conductor capsule 2 a recess 3c into which the semi¬ conductor capsule 2 fits. When the capsule 2 is introduced into the recess 3c and rests against its bottom, the edges 3cl, 3c2 of the recess 3c form guide edges for the longi¬ tudinal edges of the semiconductor capsule 2. When the arrangement is installed, the internal surfaces of the snap elements 4a belonging to the mounting plate 4 and facing towards the contact legs 2b also touch corresponding contact legs 2b. Very stable and reliable alignment is thus achieved between the component parts of the arrangement. An image scanning unit 1 in accordance with the invention is installed as follows: first the semiconductor capsule 2 is attached to the mounting plate 4, in conjunction with which a number of the contact legs 2b of the semiconductor capsule 2, more specifically those which are situated in association with the snap elements 4a, are caused to pass through transcurrent holes 4b in the mounting plate 4. The rear surface 2c of the semiconductor capsule 2 facing away from the light-sensitive surface 2a now comes into contact with the top surface 4c of the mounting plate. The semi¬ conductor capsule 2 together with the mounting plate 4 is then assembled with the circuit board 5, whereupon the contact legs 2b are soldered in place on the circuit board 5 in the conventional manner. The holder 3 can now be installed. It is essential to make sure that the projection 3a is introduced between two selected contact legs 2b at the same time as the snap elements 3b, 4a are brought into engagement with one another. Once this has occurred, an edge area of the light- sensitive surface 2a will lie against a surface (not shown in the drawing) corresponding to the underside of the holder 3. Direct and accurate alignment of the holder, and thus of the optical system arranged in the holder, relative to the light-sensitive surface is achieved in this way.

Claims: Patent ma ns 1. Arrangement for an image scanning unit (1) comprising a semiconductor capsule (2) so arranged as to generate electrical signals corresponding to an image incident upon the light-sensitive surface (2a) of the capsule and so arranged as to be connected by soldering to a circuit board (5), an optical system arranged in a holder (3) for projecting the image to be scanned onto the aforementioned light-sensitive surface (2a), a mounting plate (4) positioned between the semiconductor capsule (2) and the circuit board (5) , and devices (3a, 3b, 4a) for joining together the holder (3) and the mounting plate (4) and for ensuring correct mutual alignment between the semiconductor capsule (2) and the optical system, characterized in that the aforementioned devices for ensuring correct alignment between the optical system and the light-sensitive surface (2a) of the semiconductor capsule (2) consist in the longitudinal direction of the semiconductor capsule of a projection (3a) projecting from the holder (3) in such a way that, when the unit (1) is assembled, it engages between two of the contact legs (2b) of the semiconductor capsule (2) and in that, in the transverse direction of the semiconductor capsule and in a direction normal to the light-sensitive surface (2a), the aforementioned joining devices comprise snap elements (3b, 4a) capable of interacting with one another arranged on the holder (3) and on the mounting plate (4) . 2. Arrangement in accordance with Patent Claim 1, characterized in that the snap elements (3b, 4a) are arranged along two lines running parallel to one another and to the longitudinal edges of the semiconductor capsule and lying in areas close to them. 3. Arrangement in accordance with Patent Claim 1, characterized in that the holder (3) exhibits on its surface facing towards the semiconductor capsule (2) a recess (3c) into which the capsule (2) fits, the edges (3cl, 3c2) of which form guide edges for the longitudinal edges of the semiconductor capsule (2) . 4. Arrangement in accordance with Patent Claim 1, characterized in that the surfaces of the snap elements (4a) belonging to the mounting plate (4) and facing towards the contact legs (2b) also touch corresponding contact legs (2b).

Inventors: KAGEBECK TOR, KAGEBECK, TOR
Applicants: ICL SYSTEMS AB, KAGEBECK TOR
Application year: 1993
Main classification: H01L31
IPC codes: H04N1, H04N5, H05K13