Method of Assembling an Optical Device and Optical Device Assembled According to the Same

Abstract

Method of assembling an optical device in which a circuit board is provided supporting an imager, and a support is provided for supporting the circuit board. A first adhesive layer is applied to a mating region of at least one of the circuit board and the support. The circuit board is fixed to the support using at least one fastener. The first adhesive layer is compressed between the mating regions once the circuit board is fastened. The first adhesive layer is then cured for forming a stabilised imager assembly. A lens is then fixed to the stabilised imager assembly using a second adhesive layer, where fixing includes positioning the lens on the support to align its focal plane with the imager and then curing the second adhesive layer.

Claims

1. A method of assembling an optical device, comprising: providing a circuit board supporting an imager and a support for supporting the circuit board; applying a first adhesive layer to a mating region of at least one of the circuit board and the support; and fastening the circuit board to the support using at least one fastener, the first adhesive layer compressed between the mating regions after the circuit board is fastened; curing the first adhesive layer for forming a stabilised imager assembly; and fixing a lens to the stabilised imager assembly using a second adhesive layer, the fixing the lens including: positioning the lens on the support to align its focal plane with the imager; and curing the second adhesive layer.

2. A method according to claim 1, wherein at least one of curing the first adhesive layer and curing the second adhesive layer comprises heating the adhesive.

3. A method according to claim 1, wherein curing the first adhesive layer comprises curing until full strength.

4. A method according to claim 1, wherein curing the first adhesive layer comprises heating to a temperature equal to or greater than a maximum operating temperature for the optical device.

5. A method according to claim 1, wherein curing the first adhesive layer comprises heating for a duration until full cure of the adhesive.

6. A method according to claim 1, wherein the cured first adhesive layer stabilizes the interface between the mating regions in the stabilised imager assembly.

7. A method according to claim 1, wherein fixing the lens to the stabilised imager assembly comprises optical system alignment for compensating for manufacturing tolerances.

8. A method according to claim 1, wherein fastening the circuit board to the support using at least one fastener comprises fastening using a screw fastener.

9. A method according to claim 1, wherein fixing the lens to the stabilised imager assembly comprises aligning the lens based on a cured position of the imager in the stabilised imager assembly.

10. An optical device, comprising: a stabilised imager assembly comprising: a circuit board configured to support an imager; a support configured to support the circuit board; and at least one fastener configured to fasten the circuit board to the support, the fastening being stabilized by a first adhesive layer of cured adhesive compressed between mating regions of the circuit board and the support; and a lens fixed to the support by a second adhesive layer of cured adhesive in a position where a focal plane of the lens is aligned with the imager in the position stabilized by the first adhesive layer.

11. An optical device according to claim 10, wherein the adhesive is heat cured.

12. An optical device according to claim 10, wherein: the first adhesive layer is cured to full strength; and the focal plane is aligned with the imager in the position stabilized by the full strength cured first adhesive layer.

13. An optical device according to claim 10, wherein: the first adhesive layer is cured to full cure; and the focal plane is aligned with the imager in the position stabilized by the full cured first adhesive layer.

14. An optical device according to claim 10, wherein the cured first adhesive layer stabilizes the interface between the mating regions in the stabilised imager assembly.

15. An optical device according to claim 10, wherein the lens is fixed to the support for compensating for manufacturing tolerances in optical system alignment.

16. An optical device according to claim 10, wherein the at least one fastener comprises a screw fastener.

17. An optical device according to claim 16, wherein the at least one fastener comprises two screw fasteners that are fastened on opposing sides of the circuit board.

18. An optical device according to claim 10, wherein the circuit board is seated in a recess provided in a base of the support.

19. An optical device according to claim 10, wherein the lens includes a collar configured to secure the lens to a lens seat provided at a front of the support.

20. An optical device according to claim 19, wherein: the collar and the lens seat provide mating regions between the lens and the support for alignment of the lens to the imager; and the collar is fixed in place by the second adhesive layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] An illustrative embodiment will now be described with reference to the accompanying drawings in which:

[0025] FIG. 1 shows a cross-sectioned isometric view of a camera according to the illustrative embodiment; and

[0026] FIG. 2 illustrates a cross sectional view of part of the camera shown in FIG. 1.

DETAILED DESCRIPTION

[0027] FIGS. 1 and 2 show a camera according to an illustrative embodiment. The camera includes an imager assembly including an imager 10 soldered to a printed circuit board (PCB) 1. The PCB 1 is secured to a lens holder 4, which forms a support for the lens 6 and provides part of the housing for the camera assembly. In this embodiment, the lens holder 4 is formed as a metal frame for supporting other components.

[0028] The PCB 1 is seated into a recess provided in the base of the lens holder 4. Once seated, an imager mating region 2 on the PCB 1 mates with an opposing holder mating region 3 of the lens holder 4. As shown in FIG. 2, a screw 11 is used to secure the PCB 1 in its seated position on the lens holder 4. In this embodiment, two screws 11 are used on opposing sides of the PCB 1, although only one screw is visible in FIG. 2. In other arrangements, more than two screws may be used. A first layer of heat curable adhesive 9 is also provided between the mating regions 2 and 3 to stabilise the screw fixing.

[0029] The lens 6 is provided with a radial collar 7 which is used to secure to the lens 6 to a lens seat 5 provided at the front of the lens holder 4. The collar 7 fixed in place by a second adhesive layer 8. The lens seat 5 and the collar 7 provide mating regions between the lens 6 and lens holder 4 for aligning the lens 6 to the imager 10.

[0030] During assembly, a bead of adhesive is applied to the imager mating region 3 of the lens holder 4 to form the first adhesive layer 9. The PCB 1 containing the imager 10 is then fitted to the lens holder 4 and fixed in place by the screw 11. The screw 11 passes through a screw aperture in the PCB 1 and the screw's head presses the PCB 1 against the housing 4. This acts to compress the first adhesive layer 9 between the holder mating region 3 and the opposing imager mating region 2 on the surface of the PCB 1. Once the PCB 1 is mechanically fixed by the screws, the first adhesive layer 9 is heat cured until it achieves full cure and attains its full bonding properties. This thereby acts to stabilise the PCB 1 relative to the lens holder 4, and hence also stabilises the imager 10 soldered to the PCB 1.

[0031] Once the first adhesive layer 9 has fully bonded, a stabilised imager assembly 12 is formed which includes the PCB 1, the imager 10 and the lens holder 4. The lens 6 may be fixed to the lens holder 4 in an active alignment step to align the optical system. For this, a bead of adhesive is applied between the seat 5 and the collar 7 to form the second adhesive layer 8, and the position of the lens is adjusted until the focal plane of the lens 6 is optimally aligned for focussing an image onto the imager 10. The second adhesive layer 8 is then UV cured to fix the lens 6 in the aligned position relative to the lens holder 4. Thermal curing may then be used to fully cure the second adhesive layer 8 and achieve maximum bonding strength.

[0032] Importantly, because the active alignment step occurs after the imager assembly has been stabilised by the cured first adhesive layer 9, the positional stability of the imager 10 may be maintained. As such, the resultant camera assembly is less prone to defocussing arising from positional changes between the imager 10 relative to the lens 10 because the position of the PCB 1 is stabilised by its more secure fixing to the lens housing 4. This, in turn, stabilises the final optical system when subjected to thermal cycling during normal camera use.

[0033] It will be understood that the embodiment illustrated above shows an application only for the purposes of illustration. In practice, embodiments may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

[0034] In this connection, for example, whilst the above illustrative embodiment utilises heat curing for the first adhesive layer 9, it will be understood that other curing methods, such as UV curing, may be used. Furthermore, it will be understood that the first and second adhesive layers may be the same type of adhesive, or in other embodiments different adhesives may be used.