GB2426649A - Sleeve for mounting between a lens and sensor - Google Patents

Abstract

A camera including a photoelectric detector 113 and a window (129, fig.3) covering the photoelectric detector and characterised by a sleeve 123 between the photoelectric detector and the window, the sleeve providing an aperture (135, fig.3) through which light can pass onto the photoelectric detector and a side wall (137, fig.3) around the aperture which restricts light contacting the photoelectric detector to that which passes through the aperture and prevents any stray light reaching the photodetector. The camera may be a portable device adapted to illuminate a target object such as a bar code label on mail and further comprises LEDs 115 to illuminate the barcode. The sleeve may be made of an opaque, resilient material such as a moulded elastomer material, which can further provide mechanical shock protection should the camera be dropped.

Description

2426649

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TITLE: CAMERA AND SLEEVE FOR USE THEREIN FIELD OF THE INVENTION

5 The present invention relates to a camera and a sleeve for use therein. In particular, the invention relates to a digital camera which comprises an intelligent mail tracking imager device.

10 BACKGROUND OF THE INVENTION

Cameras for some applications involve frequent or constant use and need to be ruggedly designed and constructed to provide protection against mis-use such 15 as exposure to mechanical shock when accidentally dropped by a user. An example of such a camera is a digital camera which comprises an intelligent mail tracking imager device. Such a camera is described further later. In such a camera a photoelectric detector 20 is normally mounted behind a window. A potential weakness is the possibility of damage to the photoelectric detector when the camera is accidentally dropped.

25 SUMMARY OF THE INVENTION

According to the present invention in a first aspect there is provided a camera as defined in claim 1 of the accompanying claims.

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According to the present invention in a second aspect there is provided a sleeve as defined in claim

II of the accompanying claims.

Further features of the invention are as defined in 5 the accompanying dependent claims and are as disclosed in the embodiments of the invention to be described

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

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BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view of selected inner components of an imaging camera embodying the invention.

FIG. 2 is a cross-sectional side view of parts of the imaging camera of FIG. 1.

FIG. 3 is an enlarged perspective view of a sleeve embodying the invention of the camera of FIG. 1.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 is perspective exploded view of selected inner components of an imaging camera 100 embodying the 25 invention. The imaging camera 100 is a digital camera which comprises an intelligent mail tracking imager device. The components shown include an imaging block

III and a sleeve 123. The imaging block 111 is fastened in use by studs 107 to other constructional and

30 functional blocks (not shown) of the camera 100. The imaging block 111 incorporates active electro-optical

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transmitter and receiver components. Thus, the block 111 incorporates a photoelectric detector 113 and four light emitting cells 115. The photoelectric detector 113 may comprise an array of CMOS (complementary metal oxide 5 semiconductor) transistor cells, e.g. fabricated on a single semiconductor chip, which are scanned electronically in a known manner to receive an electronic signal representing a two dimensional optical image falling on the photoelectric detector 113. The 10 light emitting cells 115 may each comprise one or more LEDs (light emitting diodes), for example forward biased semiconductor p-n junction devices emitting in one or more colours of the visible spectrum and/or in the infra-red spectrum, preferably in the visible spectrum 15 so that a user can see illumination of a target object by light from the cells 115.

The imaging block 111 has a front face 119. The photoelectric detector 113 has an outer rim 121 which is proud of the front face 119 of the imager block 111. The 20 sleeve 123 to be described in more detail later with reference to FIG. 3 fits on the rim 113 against the front face 119.

FIG. 2 is a cross-sectional side view of parts of the imaging camera 100. This cross-section is taken on a 25 vertical plane passing through a longitudinal axis of the camera 100 indicated as axis X in FIG.l. The camera 100 includes a case 125 having an aperture 127 through which radiation passes from the cells 115 and to the photoelectric detector 113. A plane window 129 made of 30 chemically strengthened glass is retained by a rim 131 having a U-shaped cross-section attached to an inner

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face of the case 125 so that the window 129 covers and hermetically seals the inner end of the aperture 127. There is a clearance 133 between the front block 111 and the window 129 which is maintained by the sleeve 123.

5 The camera 100 also includes one or more optical lenses (not shown) in front of the window 129.

Referring now to FIG. 3, the sleeve 123 includes a ring 134 forming an aperture 135 which corresponds in diameter to the diameter of the photoelectric detector 10 113 of FIG. 1. The ring 134 has an inner side wall 137 defining an outer edge of the aperture 135. The inner side wall 137 serves as an optical baffle and minimises unwanted internal reflections caused by the clearance

133 (FIG. 1) between the window 129 and the

15 photoelectric detector 113. The inner side wall 137 of the ring 134 also fits slidably on the rim 121 of the photoelectric detector 123 (FIG. 1). The front of the ring 134 (i.e. the front as shown in FIG. 3) has an annular shaped surface 139 adjacent to the side wall 20 137. The surface 139 abuts in use against the window 129 as shown in FIG. 2. The cross-sectional area of the ring

134 increases gradually toward the rear of the ring 134. At the rear of the ring 134, the ring 134 merges with a flat flange portion 141 of the sleeve 123 which has a

25 rear surface which in use fits flush against the front face 119 of the front block 111 (FIG. 1). The flange portion 141 has an overall shape in the form of a cross which includes arms 143, 145, 147 and 149. There are gaps 151, 153, 155 and 157 formed between the arms 143, 30 145, 147 and 149 respectively. When the sleeve 123 is fitted in use against the front face 119 of the front

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block 111, the light emitting cells 115 are not covered by the sleeve 123 because the gaps 143, 145, 147 and 149 are arranged to be in front of the cells 115.

In an alternative embodiment (not shown) the arms 5 145 and 149 may extend to become flexible straps which may be wrapped around the imaging block 111 and fastened together in a manner similar to a wristwatch strap.

The sleeve 123 is opaque and made of a strong, springy, resilient material such as an elastomeric 10 material. For example, it may be made of a silicone rubber which is injection moulded into the appropriate shape. The material may optionally include filler particles or fibres to give added strength. Preferably, the sleeve 123 has the following minimum physical 15 properties: the sleeve should be a geometrically stable, well absorbed product having a high deflectability to absorb any mechanical stresses, and should meet industry standard drop, shock temperature and humidity specifications.

20 The sleeve 123 allows the clearance 133 to be maintained between the block 111 including the photoelectric detector 113 and the light emitting cells 115 whilst maintaining satisfactory optical and mechanical properties in the camera 100. Thus, the 25 sleeve 123 allows light to be emitted from the cells 115 via the window 129 and the aperture 127. This emitted light is directed via one or more lenses (not shown) at a target object (not shown) required to be illuminated, e.g. a bar code on a mail parcel or package. The sleeve 30 123 also allows light reflected from the illuminated target object to be received (via one or more lenses not

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shown) on the photoelectric detector 113 without unwanted lateral spreading or unwanted internal reflections due to the clearance 133. Such spreading or reflections if present would degrade the quality of the 5 captured image. Furthermore, the sleeve 123 provides a cushion between the front face, including the photoelectric detector 113 and light emitting cells 115, and the window 129 when the camera 100 is subjected to mechanical shock. In particular, this gives good 10 mechanical shock protection to the photoelectric detector 113. The window 129 may be a known special high strength window such as chemically strengthened glass which meets the standard drop test of a drop of a 130 grammes steel ball from a height of one metre. The 15 design of the window 129 and the provision of the sleeve 103 allows the camera 100 to meet the standard Avery severe drop test requirements involving 42 different drops onto a concrete surface from various heights of from about 0.7 metres to about 2 metres. 20 The digital camera 100 may comprise an intelligent mail tracking imager device. Light reflected from a bar code on the illuminated target object forms an image at the photoelectric detector 113 such as a CMOS array included in the camera. An image recognition processor 25 of the camera 100 (in a unit not shown attached to the imager block 111) reads the received image and electronically extracts information such as a bar code number from the image. The camera 100 may also include a wireless transmitter (not shown) connected to the image 30 recognition processor. Such a transmitter is employed to send a signal including the extracted information to a

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receiving terminal which may be nearby or remotely located, e.g. at a central facility where mail transit and delivery is tracked and recorded.

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Claims (14)

1. A camera including a photoelectric detector and a 5 window covering the photoelectric detector and characterised by a sleeve in a clearance between the photoelectric detector and the window, the sleeve providing an aperture through which radiation can pass to contact the photoelectric detector and a side wall 10 around the aperture which confines radiation contacting the photoelectric detector to that which passes through the aperture.

2. A camera according to claim 1 wherein the photoelectric detector has a rim on which part of the

15 side wall of the sleeve is slidably fitted.

3. A camera according to claim 1 or claim 2 wherein the camera includes an imager member having a face which includes a flat portion and the sleeve has a flange portion which is flush against the flat face.

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4. A camera according to claim 3 wherein the flange portion comprises arms having at least one gap between the arms.

5. A camera according to claim 4 wherein the arms extend to form flexible straps.

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6. A camera according to claim 4 or claim 5 wherein the imager member includes at least one light emitter and the at least one light emitter is arranged to enable light to be emitted through the at least one gap.

7. A camera according to claim 6 wherein the light 30 emitter comprises a semiconductor p-n junction light emitting device.

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8. A camera according to any one of the preceding claims wherein the photoelectric detector comprises an electronically scanned semiconductor device.

9. A camera according to claim 8 wherein the

5 electronically scanned semiconductor device comprises a two dimensional array of complementary metal oxide semiconductor transistors.

10. A camera according to any one of the preceding claims and substantially as described herein with

10 reference to the accompanying drawings.

11. A sleeve adapted for use as the sleeve of the camera according to any one of the preceding claims.

12. A sleeve according to claim 11 made of an opaque resilient material.

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13. A sleeve according to claim 12 wherein the resilient material comprises a moulded elastomer.

14. A sleeve according to claim 11, claim 12 or claim 13 and substantially as described herein with reference to the accompanying drawings.