WO2009100804A1

WO2009100804A1 - Radiation guide, detector, manufacturing method

Info

Publication number: WO2009100804A1
Application number: PCT/EP2009/000319
Authority: WO
Inventors: Arthur Barlow
Original assignee: Perkinelmer Optoelectronics Gmbh & Co. Kg
Priority date: 2008-02-15
Filing date: 2009-01-20
Publication date: 2009-08-20
Also published as: DE102008009213B4; DE102008009213A1; TW200941416A

Abstract

A radiation guide (10) for a detector (20) comprises a first interfacing section (lla) for a first electro- optical component (21a), preferably a radiation source, a second interfacing section (lib) for a second electro-optical component (21b), preferably a radiation sensor, a first radiation guiding section (12a, 13a) rendering a first radiation path (14a) in relation to the first electro-optical component, and a second radiation guiding section (12b, 13b) rendering a second radiation path (14b) in relation to the second electro-optical component, wherein the first and the second radiation guiding sections are arranged such that they form the first and the second radiation paths (14a, 14b) such that they intersect at a detection region (15) outside the radiation guide.

Description

RADIATION GUIDE, DETECTOR, MANUFACTURING METHOD

The invention relates to a radiation guide and a detector and a manufacturing method according to the preamble of the independent claims.

As one example, the invention may relate to smoke detectors provided for detecting particles such as solid particles or liquid droplets in a fluid such as ambient air. It may be used for the detection of fire or undue smoking or vapour or fog or similar conditions. A type of smoke detector uses the fact that smoke particles scatter radiation. Thus, smoke can be detected by either monitoring the scattered light intensity at a specific angle of scattering (the intensity increasing when smoke is present) or by monitoring the transmitted radiation intensity (decreasing when smoke is present) for detecting the presence of smoke. US 4 103 997 discloses a smoke detector using the scattered light intensity and comprising a housing containing a light source, a light receiving element and a smoke collecting region and discrete components such as lenses or light guides to make a radiation guide for source and detector. The optical axes of the light source and of the receiving element intersect under a scattering angle of 30° to 75°. EP 0 105 199 shows a similar device. These known devices are on the one hand comparatively voluminous in structure and are, on the other hand, difficult to assemble in a precise manner so that the optical axes of the various components are properly adjusted.

The earlier filed application DE 10 2007 045 018.6 of the same applicant discloses reflective or refractive radiation guides for respectively one or both of the electro-optical components.

It is the object of the invention to provide a radiation guide, a detector and a manufacturing method thereof rendering a detector, particularly a smoke detector that is small in size and easy to assemble.

This object is accomplished by the features of the independent claims. Dependent claims are directed on preferred embodiment of the invention.

A radiation guide comprises a first interfacing section towards a first electro-optical component, preferably a radiation source such as an LED, a second interfacing section towards a second electro-optical component, preferably a radiation sensor, such as a photo-diode or another infrared detector, a first radiation-guiding section rendering a first radiation path in relation to the first electro-optical component and a second radiation-guiding section rendering a second radiation path in relation to the second electro-optical component, wherein the first and the second radiation-guiding sections are arranged such that they form the first and the second radiation paths such that they intersect at a detection region outside the radiation guide.

Such a radiation guide renders a small smoke detector, because the radiation paths may include a comparatively small scattering angle at the detection region such as 30° or less, or 25° or less, or even 20° or less. The interfacing sections render a self- alignment and integrating function, which may be rendered by moulding the radiation guide directly onto one or both of the appropriately held electro-optical components or by providing one or more recesses with form-fitting surface portions inside one or both recesses. The acute angle renders a small-sized device, and the interfacing towards the electro-optical components either by direct moulding or by providing recesses makes it easy to assemble the same, so that the object of the invention is accomplished by the above construction. Instead of or in addition to directly moulding the radiation guide onto the electro-optical components other encapsulation means or techniques may be used. Said radiation guide and components will then in effect become a single solid- state component.

A smoke detector comprises a radiation guide as above, into which the electro-optical components are fitted, and a circuitry for power supply, radiation source driving and radiation sensor signal acquisition. Besides that, the smoke detector may comprise a smoke- permeable housing surrounding the detection region and protecting it against ambient light, insects and the like. The housing may also accommodate at least a part of the radiation guide or may be attached thereto.

The radiation guide may also be applied to other detector applications using the detection of emitted radiation, and thus using a radiation source and a radiation sensor. Also such other detectors will become small and easy to assemble because radiation source and radiation sensor come close together because their respectively allocated optical paths include a small angle that may also be 0° and because the components may be moulded together in an aligned state .

In the following, embodiments of the invention will be described with reference to the attached drawings, in which

Fig. 1 is a schematic side view of a radiation guide, Fig. 2 is a sectional view of an overall smoke detector,

Fig. 3 is a schematic representation of the circuitry used in the smoke detector, and

Fig. 4 shows various views of a radiation guide. Generally speaking, in this specification same reference numerals denote same features. Features shall be deemed to be combinable with each other, also if it is not explicitly said, to the extent that technical reasons do not exclude such a combination.

The following specification relates to smoke detector applications of the invention as one preferred embodiment of the invention. But the described features may also be applicable for other detector applications. "Detector" here may mean both the qualitative and the quantitative detection of a state of interest.

In Fig. 1 reference numeral 10 denotes the radiation guide, 11a and lib denote radiation interfacing sections shown as recesses, 12a and 12b denote a first and a second radiation-guiding section, 13a and 13b denote radiation-permeable surface portions that may be dome-shaped or convex or lens-like, (also like a

Fresnel lens), 14a and 14b denote the ideal first and second radiation path as defined by the centres of the radiation interfacing sections 11 and transparent surface portions 13. 15 denotes a detection region, 16a and 16b denote first and second surfaces of the radiation guide and 17 denotes a further recess.

The radiation interfacing sections 11a and lib may be provided for electro-optical components, particularly for a radiation source 21a and a radiation sensor 21b, respectively. The radiation interfacing sections 11a and lib allow radiation transition between the radiation guide 10 and the respective electro-optical component. They may be appropriately shaped and designed surface portions of the radiation guide 10 that may be somewhat distant from the respective electro-optical components or that are partially or fully form-fitting.

Likewise, the radiation guide may directly be moulded onto the electro-optical component so that the interfacing section is the intimate connection between the electro-optical component and the material moulded onto it. The radiation interfacing sections 11a, lib may differ from each other in that either one of them is formed as a distinct recess and the other is formed by directly moulding the radiation guide onto the electro-optical component.

The electro-optical components 21a, 21b may take the form of housed components, such as the common plastic encapsulated devices of LEDs or regularly housed radiation sensors, or they may be a naked emitter semi-conductor chip (such as an LED-chip, a laser source such as a laser diode or the like) and sensor semi-conductor chip (such as a photo diode or a light dependent resistor (LDR) on a substrate) , respectively placed on connection lead-frames. In the latter case, the radiation guide 10 forms a encapsulation around source 21a and radiation sensor 21b in addition to defining the optical paths 14a and 14b.

In Fig. 1 it is assumed that the top radiation path 14a guides light from the radiation source 21a via the interfacing section 11a, the radiation guide body and the first radiation-permeable surface portion 13a thereof to the detection region 15, whereas the lower radiation path 14b guides possibly scattered light from the detection region 15 towards the radiation sensor 21b via the second radiation-permeable surface portions 13b, the radiation guide body and the interfacing section lib. The radiation paths 14a and 14b intersect at the detection region 15 under an angle α that may be less than 20° or less than 15°.

The overall shape of the radiation guide may be that of a rectangular parallelepiped with three pairs of opposing surfaces. In a more general sense, the radiation guide has at least two opposing surfaces 16a and 16b, one of them having the interfacing sections 11a and lib for the electro-optical components, the other having radiation-permeable surface portions 13a and 13b allowing radiation to pass. The intersection of the radiation paths 14a and 14b may be accomplished optically by appropriately deflecting radiation and bending it in such a way that the desired intersection is obtained. It may, however, also be accomplished by spacing the interfacing sections 11a and lib further apart from each other than the transparent surface portions 13a and 13b. The respective distances of the respective centres are denoted by d2 and dl, and thus d2 is smaller than dl, under this embodiment-

The recesses and likewise the radiation-permeable surface portions or the optical axes of the electro- optical components may be tilted compared to the vertical and horizontal direction, preferably by α/2 against the horizontal direction in Fig. 1. The radiation-permeable surface portions 13a and 13b may be lens-shaped for rendering some kind of focussing or light confinement, such as that described in the earlier filed application DE 10 2007 045 018.6 of the same Applicant, which discloses reflective or refractive radiation guides for respectively one or both of the electro-optical components. The focus needs not be at the detection region 15. The focussing effect can also be to transform a divergent light beam from the source into a more or less parallel beam towards the detection region. Focussing surface portions may be provided in such a way that they face the detection region 15, as shown in Fig. 1, and/or they may be provided in such a way that they face the electro-optical component at the interfacing section 11a, lib (not shown in Fig. 1) .

Generally speaking, focussing may be designed such that on the side of one or both of the electro-optical components the aperture of the optical path has a certain relation to the respective active or effective area of the component (LED chip active area, LED . aperture, sensor chip area, sensor aperture) . It may be such that the aperture is substantially the same as the active or effective area of the respective component. On the side of the detection region 15, the aperture may be adjusted such that the detection region has a desired size. It is noted that the detection region is defined by the spatial volume defined by the intersection of the radiation paths towards the electro-optical components.

The overall radiation guide 10 may be or comprise a cast and preferably massive body of radiation- permeable material. It may be resin material of any desired spectral characteristics. Radiation attenuation thereof should be low or reasonable, but a certain amount of radiation attenuation along the optical path may be accepted. Nevertheless, it may comprise internal hollows, e.g. for avoiding unwanted radiation attenuation. In such a body, the radiation- permeable surface portions 13a and 13b with focussing effect may be moulded integrally with the rest of the body and, thus, consist of the same material, or they may be separate parts moulded into the body.

The distance d3 of the centre of the detection region 15 from the second surface 16b may be smaller than twice the length of the radiation guide (maximum distance of the two surfaces 16a and 16b) , preferably smaller than 1.5 times said length. Said distance d3 may be smaller than 5 cm, or smaller than 4 cm, or smaller than 3 cm. The length 1 of the radiation guide may be smaller than its height h (in the direction in which the interfacing sections are distant from each other), or it may be the same size or it may be larger. The width w may be smaller than the height of the radiation guide 10. The centre distance d2 among the interfacing sections as indicated in Fig. 1 may be less than 3 cm, or less than 1 cm.

One of the recesses or both of them may have pre- shaped at least partially form-fitting surfaces. The form-fit may be provided for an electro-optical component to be accommodated in the respective recess, or it may be provided in relation to an adapter for the electro-optical component. Thus, the electro- optical component may directly be form-fitted into the respective recess, or it may be form-fitted into an adapter which, in turn, is form-fitted into the recess. And as said above, a further embodiment is to directly mould or encapsulate the naked emitter semi-conductor chip and sensor semi-conductor chip, respectively placed on connection lead-frames, using radiation guide 10, where in this case recesses 11a and lib are omitted and are indistinguishable parts of radiation guide 10. Through this feature the construction is self-aligning, so that the assembly of the overall smoke detector becomes easy. The form-fit may be provided to an extent that the translatory and rotatory degrees of freedom when placing a component are fixed as required.

A mechanical adapter may be provided between an electro-optical component and the radiation guide recess. This may be advantageous when it is desired to have a lens-shaped or dome-shaped or focussing surface portion directed towards the electro-optical component which would be difficult to mould when, at the same time, a form-fit with the immediate electro-optical component had to be made .

On an appropriate outer surface, the radiation guide may be provided with features of a surface-mountable device. Particularly, it may comprise contact pads 24 which are appropriately wired towards the electro- optical components and related circuitry. Said surface-mountable device features may be provided immediately on the radiation guide body itself or may be provided on an auxiliary body, e.g. a circuit board attached to the radiation guide body.

The radiation guide 10 may comprise a further recess 17. Said recess may be provided for accommodating therein circuit elements possibly protruding from a circuit board. Likewise it may be used for accommodating a second radiation source so that the further recess 17 may be formed and has properties like the above mentioned interfacing sections 11a and lib. Such a second radiation source may be of a spectral characteristic different from that of the first radiation source. It may have an own radiation path (not shown in Fig. 1) with same or similar features as those of the already described radiation paths 14a and 14b. The radiation back-path for radiation from said second radiation source towards the sensor may be the same as the radiation back-path for radiation from the first radiation source 21a. The first and the second radiation source may, however, also be positioned close together, so that they define or use, with sufficient accuracy in focussing and radiation-guidance, the same radiation path 14a.

Unlike as shown in Fig. 1, when two radiation sources are provided, they may be placed side by side, i.e. in Fig. 1 distant in a direction vertical to the drawing plane. Then, the respective radiation paths would include substantially the same angle α with the back- radiation path towards the sensor. It may, however, also be desired to establish different angles by providing the radiation sources and their corresponding interfacing sections distant in vertical direction in Fig. 1.

The module may be designed for accommodating either encapsulated LEDs, or it may accommodate LED chips only. Colour characteristics provided to the radiation may come directly from the emitted radiation of the LED or may come from the encapsulant of the LED (LED package) or may come from coloured portions of the radiation guide body 10. Discrete such coloured transparent parts may be moulded into the radiation guide body, or it may completely consist of appropriately coloured material.

When the radiation guide accommodates LED chips only, two or more such chips of preferably different spectral characteristics may be provided close to each other, so that they use the same optical path 14a and optical structures towards the detection region 15.

It is noted here that radiation sources of different spectral characteristics may include identical radiation emitters, but thereafter some kind of spectral differentiation somewhere in the optical path, i.e. also beyond and away from the radiation source in a technical sense. When sources of plural spectral characteristics are used, they may be driven concurrently or in an alternating manner. If they are driven in an alternating manner, signal evaluation may be done correspondingly alternately, so that alternate outputs are received. They may be processed appropriately or may be output separately.

When plural spectral characteristics are used, they may include visible light and UV radiation and IR radiation. When only one radiation source is used, it may use visible radiation and/or UV radiation and/or infrared radiation. The radiation guide 10 may further have attachment means for attaching a component to the radiation guide The attachment means may be integrally moulded elastic portions for providing a kind of snapping effect. They may be provided to attach, e.g., a circuit board or lead frame to the radiation guide body, and/or they may also be provided for attaching the radiation guide to another larger component or circuit board or mounting location.

Fig. 2A shows an overall smoke detector. It comprises the radiation guide 10 as described so far. Besides that, it comprises the electro-optical components 21a (radiation source, LED, laser light source, laser diode) and 21b (radiation sensor, infrared sensor, thermopile, photo diode) at the respective interfacing section. A circuit board or lead frame 23 may be provided and may be attached to the radiation guide 10 in an appropriate manner, e. g. by clipping or gluing the components to each other or by moulding the radiation guide onto the lead frame or circuit board 23. The circuit board may bear wiring and possibly also circuit elements for power supply, radiation source driving and sensor signal acquisition and evaluation and signal output. It further may bear the already mentioned installations for surface-mountable devices such as contact pads 24. The circuit board or lead frame 23 may be attached as shown to cover the first surface 16a. However, it may also be provided on a side surface (such as top surface or bottom surface in Fig. 2A) .

The transparent surface portions 13a and 13b are shown as surface portions of the moulding material itself. They may be formed by appropriately shaping the mould used for moulding. In another, not shown embodiment, a transparent surface portion 13a, 13b may be a surface of a separately formed body (e. g. a lens) moulded into or attached onto the radiation guide body.

The smoke detector may comprise a smoke-permeable, but radiation-shielding housing 22. The housing may surround the detection region 15 for avoiding ambient light/radiation (UV, visible, IR) leading to misdetections . The housing may shield ambient radiation in such a way that it does not reach into the back-radiation path towards the sensor, what would lead to misdetections. The housing may also accommodate at least a part or all of the radiation guide, preferably such that one surface part of the radiation guide remains accessible for electrical connectivity, or the housing may be attachable to the radiation guide. The construction may be such that substantial parts of the radiation guide slip into the housing. The housing again may have fixation parts for fixing the smoke detector to a mounting side and/or may have surface-mountable device installations as already mentioned above for the radiation guide itself, The housing may be a one part component or a multi part component .

The overall appearance of the smoke detector may be elongated in such a way that it has two ends 28 and 29. The detection region 15 may be at or close to the one end 28, whereas the other end 29 is occupied by the radiation guide and particularly the electro-optical components. The overall length L may be less than 8 cm, or less than 6 cm. The overall height H may be less than 4 cm, or less than 3 cm. The overall width may be less than 2 cm or less than 1.5 cm.

Fig. 2B shows as a partial drawing of the embodiment where the radiation guide 10 is directly moulded onto the electro-optical components 21a, 21b. They may sit on a lead frame or circuit board 23, but may likewise have only their own electrical connections accessible in the assembly without a lead frame or circuit board being provided. The interfacing sections 11a, lib are here the mechanical contact surfaces between the respective electro-optical component 21a, 21b and the material of the radiation guide 10.

Fig. 3 schematically shows a circuitry that may be used for the smoke detector. The left-hand side is the radiation source side. The right-hand side is the radiation sensor side. A power supply 31 is used for energizing a radiation source such as one LED or plural of them. In a straightforward embodiment, the radiation source may be continuously radiating, or may be intermittently radiating for saving power, when, e.g., the power source is a battery.

However, the radiation source may also be driven according to a given or set pattern. It may, e.g., have a varying intensity, the variation being made with a certain frequency. The variation may be sinusoidal or may follow a quick on/off-pattern which, itself, may again be intermittently supplied. Thus, the radiation sent towards the detection region 15 shows a certain pattern over time, and this pattern will also appear in the sensor signal. Vice versa, noise radiation will most likely not show this pattern and may, thus, be filtered out. The pattern may be a certain frequency, and on the receiving side a band pass corresponding to the driving frequency of the radiation source may be provided.

On the radiation sensor side, the sensor 21b itself is provided. It may be a photo-diode or any other kind of radiation sensor or infrared sensor. An amplifier 35 may be provided for amplifying a potentially weak sensor signal. For sensor signal evaluation, a lock-in amplifier 34 may be provided, its operation corresponding to the way how the radiation source is driven. The output signal may be evaluated in a more or less complex manner. The evaluation may be done with respect to the driving pattern used for driving the radiation source, symbolized by box 36. It is pointed out that this box 36 needs not symbolize an own component. Primarily, it shall symbolize that source and sender operate with matching characteristics, no matter how this is accomplished. However, in more complex driving installations, there may in fact be a kind of variable pattern generator that adjusts both the driving part for the radiation source and the evaluation part for the radiation sensor to operate with matching patterns.

Some kind of more or less refined output signal may finally be available at the output terminal 35. The output terminal 35 may be a single line and may be an analogue signal, but it may also be a digital signal, possibly in time-series transmission. And likewise, plural output terminals may be provided for parallel input/output, possibly digital after an AD-conversion.

Generally speaking, the smoke detector may come without a light-shielding housing and may, thus, consist of the radiation guide as its major component. This feature is particularly enabled when a more complex radiation source driving and sensor signal evaluation as described is made. The primary purpose of the housing is to shield unwanted radiation from entering the sensor. It must also be insect-proof, because otherwise insects and other little animals might enter and lead to misdetections . If a housing for radiation-shielding purposes is not provided, the detection region may be in the free space. In the mounting stated, the smoke detector may point downward from a ceiling (mounting position rotated 90° clockwise compared to Fig. 2A) . The detection region 15 may be the free space in the room to be monitored. For avoiding mis-detections in this case, a particularly adapted signal evaluation may be used. For example, the presence of smoke may only be decided if presence is detected over a certain period or repeatedly therein for avoiding misdetections due to coincidental one-time reflections.

Fig. 4a shows a modified embodiment of the radiation guide 10. Whereas in Fig. 1 the focussing portions on the second surface lβb were separate from each other, they are - in the embodiment according to Fig. 4a - so large that they "grew together" and occupy the entire second surface lβb. This increases the numerical aperture and, thus, intensity, or may allow for same intensity to use lower driving power. Thus, the lens portions or dome-shaped portions or convex portions 13a and 13b are formed such that they touch each other on the second surface lβb and preferably fully occupy it. The focussing portions may be shaped as classical lenses or as Fresnel lenses.

In Fig. 4a, the line 41 were the two dome-shaped portions 13a and 13b abut may be closer to the first surface (i.e. further to the left in Fig. 4a) than one or both of the sideways limitations 42a and 42b of the dome-shaped portions 13a and 13b.

Fig. 4b shows a plan view on the left surface in Fig. 1. The two interfacing sections 11a and lib for the electro-optical components and a third recess 17 which may be used either for circuit components or for another electro-optical component are recognizable. The shapes 11a, lib and 17 may indicate the contour of the electro-optical component moulded into the radiation guide or may indicate the rim of a distinct recess. As already said, when a second radiation source is used, the interfacing section used for it may be placed side by side with the interfacing section for the first radiation source. The width w of the radiation guide may be smaller than 2 cm, or smaller than 1 cm.

A method for manufacturing a smoke detector comprises the steps of pre-assembling the electro-optical components into a lead frame and moulding a radiation guide as described above onto said assembly. The manufacturing method may have further features as described above. The mould is shaped according to the desired shape of the radiation guide and may have alignment portions for holding in an aligned manner, prior to moulding, components to be moulded into the detector, such as the lead frame, optical filters, lens portions, and the like. Smoke is a mixture of solid particles carried in a gaseous fluid. But the detector may also be used for other mixtures. The carrying fluid may be a liquid. Likewise, the scattering particles may be droplets of a liquid in a gaseous fluid (vapour) or in another carrying liquid to which they are immiscible.

Other detector applications than smoke detectors may evaluate reflected light. They may send out radiation with known or controlled polarization or coherent radiation (laser light) or modulated radiation (AM, FM, FMCW (frequency modulated continuous wave)) . They may evaluate a radiation-related quantity such as one or more of on/off, intensity, frequency (particularly modulation, shift, beat), propagation time, polarization state, or phase. The optical axes include an angle that may be smaller than 20° or 10° or 5°. They may be parallel (0°).

Claims

Claims :

1. A radiation guide (10), comprising

a first interfacing section (lla) towards a first electro-optical component (21a), preferably a radiation source,

a second interfacing section (lib) towards a second electro-optical component (21b) , preferably a radiation sensor,

a first radiation guiding section (12a, 13a) rendering a first radiation path (14a) in relation to the first electro-optical component, and

a second radiation guiding section (12b, 13b) rendering a second radiation path (14b) in relation to the second electro-optical component,

wherein the first and the second radiation guiding sections are arranged such that they form the first and the second radiation paths (14a, 14b) such that they intersect at a detection region (15) outside the radiation guide.

2. The radiation guide of claim 1, comprising one or more appropriately shaped, preferably convex surface portions (13a, 13b) for rendering radiation convergence at the detection region and/or at one or both electro-optical components.

3. The radiation guide of one of the preceding claims, comprising a massive cast body of radiation permeable material forming said first and second interfacing sections and said first and second radiation guiding portions.

4. The radiation guide in accordance with claim 3, wherein the massive body has two opposing surfaces (16a, 16b) , wherein said first and second interfacing sections are formed in one (16a) of said surfaces, the other (16b) of said surfaces having radiation permeable surface portions (13a, 13b) for said first and second radiation paths.

5. The radiation guide of one of the preceding claims, wherein at least one of the interfacing sections comprises a recess with a form-fitting portion adapted to at least a part of the shape of the electro-optical component to be accommodated or an adapter thereof.

6. The radiation guide of one of the preceding claims, wherein at least one of the interfacing sections is formed by a moulded portion of the radiation guide adapted to or moulded onto at least a part of the shape of the electro-optical component .

7. The radiation guide of one of the preceding claims, comprising in each of the radiation paths a radiation permeable surface portion (13a, 13b), wherein the centre distance (dl) amongst said surface portions is smaller than the centre distance (d2) amongst said interfacing sections.

8. The radiation guide of one of the preceding claims, having installations (24) of a surface mountable device on an outer surface thereof.

9. The radiation guide of one of the preceding claims, comprising one or more of the following features :

• the optical axes of the first and the second radiation path include an angle (α) of less than 45°, preferably less than 30°, • the centre distance (d2) amongst the interfacing sections is less than 3 cm, preferably less than 2,5 cm,

• the distance (d3) of the centre of the detection region (15) from the second surface (16b) is less than 5 cm.

10. The radiation guide of one of the preceding claims, comprising a further recess (17) for accommodating a component, particularly a circuit element and/or a second radiation source.

11. The radiation guide of one of the preceding claims, comprising attachment means for attaching a component to the radiation guide.

12. A detector (20) comprising a radiation guide (10) in accordance with one or more of the preceding claims, a radiation source (21a) and a radiation sensor (21b) respectively mounted in relation to one of the interfacing sections (11a, lib) , and circuitry (30) for power supply (31), radiation source driving (32) and radiation sensor signal acquisition and processing (33 to 35).

13. A detector in accordance with claim 12, comprising a particle-permeable housing (22) confining the detection region (15), the housing accommodating also at least a part of the radiation guide (10) or being attached thereto.

14. A detector in accordance with claim 12 or 13, wherein the circuitry comprises a driving section

(32) for driving the radiation source with a predetermined pattern, and an evaluation section

(34) for acquiring the radiation sensor signal and evaluating it with reference to said predetermined pattern .

15. The detector in accordance with one or more of the claims 12 to 14, having an elongated outer appearance with the detection region (15) situated at the one end (28) and the electro-optical components (21a, 21b) situated at the other end (29) thereof.

16. The detector in accordance with one or more of the claims 12 to 15 wherein the radiation guide is moulded onto at least one of the electro-optical components, which may be a component without an own housing.

17. The detector in accordance with one or more of the claims 12 to 16 wherein the electro-optical components are assembled as a lead frame to which the radiation guide (10) is mounted, preferably by moulding it onto the lead frame.

18. The detector in accordance with one or more of the claims 12 to 15, comprising one or more of the following features:

• the radiation source (21a) comprises an LED,

• the radiation sensor (21b) comprises an IR sensor, particularly a thermopile,

• the driving pattern of the radiation source is an amplitude pattern over time, preferably a pattern of a set frequency,

• the detector is a smoke detector.

19. A method for manufacturing a detector, comprising the steps of

pre-assembling electro-optical components into a lead frame, and

moulding a radiation guide according to one of the claims 1 to 11 onto said assembly.