EP4187512A1 - Device and method for optically detecting a valuable or security product - Google Patents

Abstract

The invention relates to a device (200) for the optical detection of a valuable or security product (100) with a first security feature (102) which is reconstructed at a first irradiation angle and with a second security feature (104) which is reconstructed at a second irradiation angle. which deviates from the first irradiation angle, comprising: - an at least partially transparent support plate (202), - an optical detection device (204), - a partially transparent mirror (206), which has a front side (208) facing the support plate (202) and one of the support plate comprises a rear side (210) facing away from (202), - a first lighting device (212) which is set up to emit light at the first irradiation angle directly onto the support plate (202), and - a second lighting device (214) which is set up To emit light at the second irradiation angle on the back (210) of the mirror (206), whereby it is transmitted through the mirror (206) to the front (208) and thus to the platen (202). The invention also relates to a method for optical detection of a value or security product (100).

Description

The invention relates to a device for the optical detection of a valuable or security product with a first security feature that is reconstructed at a first irradiation angle and with a second security feature that is reconstructed at a second irradiation angle that differs from the first irradiation angle. The invention also relates to a method for the optical detection of such a valuable or security product.

Valuable or security products can be, for example, an identity card, another personal document, a check card, a non-personalized authorization ID such as a ticket or a means of payment, or a value or security element intended for product security.

It is known from the prior art, for example, to integrate holograms as security features in value or security products. Security features or security elements are entities that have at least one feature that makes unauthorized duplication, imitation and/or falsification of an object into which the security element is integrated more difficult. Holograms are used as security features in passports or identity cards, for example. However, they are also used in banknotes, driver's licenses, visas, other stamps, labels or tickets, credit cards, bank cards, telephone cards or the like. Volume holograms represent a special group of holograms. In a volume hologram, a diffractive structure of the hologram is stored in the volume of the holographic recording material. As Recording materials for volume holograms are used in value and/or security documents, as a rule, holographic exposure films, which are mostly provided on rolls. These exposure films are suitable for storing interference structures whose characteristic dimensions are in the range of the light wavelength of the light that is used for recording or reconstructing the hologram.

In a contact printing process, the holographic exposure film is placed in front of a master in which diffractive structures are formed which are to be "transferred" into the holographic exposure film. With this method, the diffractive structures of the master are copied into the holographic film. For this purpose, coherent light is radiated onto the master through the holographic film, which is arranged in the immediate vicinity in front of the master or in contact with the master. The diffractive structures in the master bend the light such that the diffracted light is reflected back into the holographic film. There it interferes with the coherent light that is used to illuminate the master. An interference structure is thus formed in the holographic film, which is defined by the light diffracted at the master. When the holographic film is developed and reconstructed, the reconstruction is similar to that observed when the master is illuminated. A hologram is stored in the holographic film, which is also referred to as a Denisyuk hologram and is a volume reflection hologram. It goes without saying that the incident light must have a suitable wavelength (or suitable wavelengths) and a suitable irradiation direction (or suitable irradiation directions), so that diffraction at the diffraction structure takes place in the desired manner.

In the case of value or security products, for example, the use of holographic features formed from volume holograms is suitable, since they are particularly suitable for verification when the exposed and developed holographic film is viewed perpendicularly, for example. In this case, the reconstruction light is preferably irradiated at an acute angle, for example at 45 degrees to the perpendicular. The angle between the irradiation direction of the reconstruction light and the exit direction of the generated light Volume hologram of diffracted light, which reconstructs the information of the hologram, is essentially determined during the production of the master.

In the DE 10 2007 052 952 A1 describes a security document which comprises two volume reflection holograms adjacent to one another, of which a first volume reflection hologram is formed from a more strongly scattering layer and a second volume reflection hologram is formed from a weaker scattering layer. For both slices, the intensity of the reconstruction increases the closer one approaches the angle of reflection. This security document has proven itself in practice and offers adequate protection against counterfeit products.

It is the object of the present invention to specify a device and a method that allow a partially or fully automated evaluation of a value or security product, the different optically variable security features being machine-readable.

This object is achieved with a device having the features of claim 1 and with a method having the features of claim 12. Advantageous configurations with expedient developments of the invention are specified in the dependent claims.

The device according to the invention comprises an at least partially transparent support plate on which the product of value or security can be placed. Furthermore, an optical detection device is present, the optics of which are directed at a partially transparent mirror, which comprises a front side facing the support plate and a rear side facing away from the support plate. The mirror is positioned in the beam path of the optical detection device in order to deflect a light impinging on it from the support plate on its front side in the direction of the optical detection device. In addition, there is a first lighting device which is set up to emit light directly at the support plate at the first irradiation angle. In addition, there is a second illumination device, which is set up to emit light at the second irradiation angle onto the rear side of the mirror, with it being transmitted through the mirror to the front side and thus to the support plate is let through.

This configuration has the advantage that all security features, in particular the holographic security features of the valuable or security product, can be reliably optically detected. The opening angle of the lens of the optical detection device, in particular a camera, is designed in such a way that the support plate can be fully detected. A full-area and high-contrast detection of the security features on the entire area of the value or security product is thus possible; in particular the recording of the identigram (a registered trademark of the applicant).

Holographic security features come to light or are reconstructed particularly well when they are irradiated at an angle of irradiation that corresponds or almost corresponds to the angle of incidence of the angle corresponding to the exposure of the hologram, in other words the irradiation angle is the reconstruction angle or almost the Reconstruction angle of the holographic security feature should correspond. The greater the proportion of the directed light, the more clearly the security features formed in this way become visible. In order to maximize the proportion of directed light beams, it has proven to be advantageous if the lighting devices are formed from a light-emitting diode arrangement with a plurality of light-emitting diodes which have a narrow emission angle of between 5 degrees and 15 degrees. The light-emitting diodes preferably have an emission angle of 10 degrees, which has proven to be particularly reliable for the reconstruction of the holographic security features of the value or security product.

In order to increase the proportion of directed light beams onto the support plate and the value or security product located on it, there is also the possibility that a structured light guide is assigned to the lighting devices for generating axis-parallel light.

The use of one or more Contrast enhancing films proven. These can be applied to the support plate, for example. Alternatively, the lens of the optical detection device can also be provided with such a contrast-enhancing film.

The contrast-enhancing film can be designed as an optical filter that is set up to increase the contrast via the wavelength of the incident light and/or the angle of incidence of the incident light and/or the polarization of the incident light, since wavelengths "of lower interest" can be filtered out. Depending on the emitted wavelength range, several foils can also be arranged one on top of the other in order to increase the contrast. In this case, the contrast-enhancing film is preferably a laminate of several film layers that are arranged one on top of the other. The foils or the foil layers themselves can have different optical characteristics. The contrast-enhancing film is applied, for example, in a decal process, or a contrast-enhancing coating is applied as a liquid.

A further possibility for sending light beams directed over a large area onto the support plate is that an f-theta lens or an f-theta objective is integrated in the beam path of the lighting devices.

The optical detection device is preferably an image sensor of a camera. There is a possibility that the camera is designed as a CCD camera, a NIR (near infrared) camera or a UV (ultraviolet) camera. However, the camera is preferably designed as a VIS camera that captures the light rays from the spectrum that is visible to the human eye.

Since the reconstruction of holographic security features depends not only on the reconstruction angle but also on the wavelength of the incident light, there is the possibility that the two security features will be reconstructed at different reconstruction wavelengths or reconstruction wavelength ranges. To therefore value or To be able to read security products that are equipped with holographic features that reconstruct at different reconstruction wavelengths, it has proven to be advantageous if the first illumination device is set up to emit light in one wavelength or a wavelength range, and if the second illumination device is set up To emit light in a further wavelength or a further wavelength range, which differ from those of the first lighting device.

For reading the security features of valuables or security products, it has proven to be particularly reliable if the first irradiation direction of the first lighting device is a 45-degree grazing light. Accordingly, alternatively or additionally, the second irradiation direction of the second illumination device can be 0-degree coaxial light.

The advantages, advantageous configurations and effects described in connection with the device according to the invention apply in the same way to the method according to the invention.

• Auflegen des Wert- oder Sicherheitsprodukts auf eine zumindest teiltransparente Auflageplatte,
• Entsenden von Licht durch eine erste Beleuchtungseinrichtung unter dem ersten Bestrahlungswinkel unmittelbar an die Auflageplatte sowie optisches Erfassen des Wert- oder Sicherheitsprodukts mit einer optischen Erfassungseinrichtung anhand des von der Auflageplatte ausgehenden, an einer Vorderseite eines teildurchlässigen Spiegels abgelenkten Lichts, und
• Entsenden von Licht durch eine zweite Beleuchtungseinrichtung an eine Rückseite des teildurchlässigen Spiegels, wobei das Licht durch den Spiegel zur Vorderseite transmittiert und zur Auflageplatte in dem zweiten Bestrahlungswinkel hindurchgelassen wird sowie optisches Erfassen des Wert- oder Sicherheitsprodukts mit der optischen Erfassungseinrichtung anhand des von der Auflageplatte ausgehenden, an der Vorderseite des Spiegels abgelenkten Lichts.

The method for optically capturing a valuable or security product with a first security feature that is reconstructed at a first irradiation angle and with a second security feature that is reconstructed at a second irradiation angle that differs from the first irradiation angle comprises the following steps in particular:

• Placing the value or security product on an at least partially transparent support plate,
• Sending light through a first lighting device at the first irradiation angle directly to the support plate and optically detecting the value or security product with an optical detection device using the light emitted by the support plate and deflected on a front side of a partially transparent mirror, and
• Sending light through a second illuminator to a back side of the partially transparent mirror, the light transmitting through the mirror to the front side and to the platen in the second Irradiation angle is passed and optical detection of the valuable or security product with the optical detection device based on the light emitted by the support plate and deflected on the front side of the mirror.

The value or security product with its holographic security features can also be recorded and read by machine using this method.

If several images are recorded, it is advantageous if all images of the value or security product captured by the optical capture device are combined into one common image, with which all holographic security features are then visible and can be checked.

In this context, it is advantageous if the two lighting devices are switched alternately in order to reconstruct the security features. Here, in particular, 45-degree grazing light is emitted, which ideally emerges perpendicularly from its surface of the first lighting device and impinges on the support glass. It hits the support plate at an angle of 45 degrees.

The second lighting device emits 0-degree coaxial light, which ideally exits perpendicularly with respect to its surface and impinges on the support plate. It passes through the semi-transparent mirror and hits the platen perpendicularly, i.e. at an angle of 0 degrees with respect to the surface normal of the platen.

In order to reduce the number of images to be evaluated, it has proven to be advantageous if the exposure time of the optical detection device lags behind the frequency of the alternating switching of the two lighting devices.

The value or security product provided with the multiple security features can be a value or security document or a security element, i.e. an element that is connected, for example, to an object to be protected against imitation, counterfeiting or falsification, for example a sticker, label or the like. A passport, an ID card, a driver’s license or another ID card or an access control card, a vehicle registration document, a vehicle registration document, a visa, a check, other means of payment, in particular a banknote, a check or a bank, can be used as valuable or security products -, or a credit or cash card, loyalty card, health card, smart card, company ID card, proof of entitlement, membership card or other ID document.

Preferably, the value or security product is in ID 1, ID 2, ID 3 or some other format, for example in booklet form, like a passport-like item. The valuable or security product is generally a laminate of several document layers, which are connected to one another with a precise fit under the action of heat and increased pressure. These products should meet the standardized requirements, for example ISO 10373, ISO/IEC 7810, ISO 14443.

The product layers preferably consist of a carrier material that is suitable for lamination. However, the product of value or security can preferably be formed from a polymer selected from a group comprising polycarbonate (PC), in particular bisphenol A polycarbonate or a polycarbonate formed with a geminally disubstituted bis(hydroxyphenyl)cycloalkane, polyethylene terephthalate (PET), their derivatives, such as glycol-modified PET (PETG), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polyimide (PI), polyvinyl alcohol (PVA), polystyrene (PS) , polyvinylphenol (PVP), polypropylene (PP), polyethylene (PE), thermoplastic elastomers (TPE), in particular thermoplastic polyurethane (TPU), acrylonitrile-butadiene-styrene copolymer (ABS) and derivatives thereof, and/or paper and/or cardboard and/or glass and/or metal and/or ceramic. In addition, the product can also be made of several of these materials. It preferably consists of PC, PVC and PET. The polymers can be either filled or unfilled. In the latter case, they are preferably transparent or translucent. If the polymers are filled, they are opaque. The above information relates both to films to be bonded together and to liquid formulations that are applied to a preliminary product, such as a protective or top coat. The product is preferably made from three to twelve, preferably four to ten films. The films can also carry printed layers. A laminate formed in this way can finally be coated on one or both sides with the protective or top coat or with a film. In particular, the foil can be a volume hologram, a foil with a surface hologram (for example a kinegraphic element) or a scratch protection foil. Overlay layers formed in this way protect a security feature arranged underneath and/or give the document the required abrasion resistance.

Figur 1

eine schematische Seitenansicht auf eine Vorrichtung zur optischen Erfassung eines Wert- oder Sicherheitsprodukts, welches auf die Auflageplatte aufgelegt ist,

Figur 2

eine Draufsicht auf ein Wert- oder Sicherheitsprodukt in Form einer Identitätskarte, bei der die ersten Sicherheitsmerkmale aufgrund der Beleuchtung unter dem ersten Bestrahlungswinkel rekonstruieren, und

Figur 3

eine der Figur 2 entsprechende Darstellung des Wert- oder Sicherheitsprodukts, bei der die zweiten Sicherheitsmerkmale rekonstruieren, da sie unter dem zweiten Bestrahlungswinkel bestrahlt werden.

The present invention is explained in more detail below with the aid of figures, the examples shown being merely exemplary in nature and not representing any limitation with regard to the scope of the invention described. They show in detail:

figure 1

a schematic side view of a device for the optical detection of a product of value or security, which is placed on the support plate,

figure 2

a plan view of a product of value or security in the form of an identity card, in which the first security features are reconstructed due to the illumination at the first irradiation angle, and

figure 3

one of the figure 2 corresponding representation of the product of value or security, in which the second security features reconstruct, since they are irradiated at the second irradiation angle.

In the Figures 2 and 3 a value or security product 100 is shown which is shown as an example in the form of an identity card, which has been assembled, for example, as a laminate of several internal polymer layers. For example, the polymer layers can consist of PC and/or PET. The individual layers can be unfilled or filled with fillers. In the latter case they are opaque, otherwise transparent. The plies may preferably be bonded together to form a monolithic block that is practically impossible to split.

It can be seen that the identity card is equipped with security features 102, 104, which are in the form of an identigram (a registered trademark of the applicant). These form individual volume reflection holograms, the arrangement, the size and the shape being selected purely by way of example, so that other arrangements, sizes or dimensions of the security features 102, 104 are also possible.

Based on Figures 2 and 3 it can be seen that the product of value or security 100 has an upper side which is opposite an underside. The face or portrait of the card holder and some data fields containing personal or document-related content are located on the top.

In the view figure 2 the first security features 102 of the identity card are visible, since this valuable or security product 100 is irradiated from a first irradiation angle in such a way that the first security features 102 are reconstructed. In the present case, the valuable or security product 100 is irradiated with 45-degree grazing light from a first lighting device 212 .

In figure 3 second security features 104 are visible, since the value and security product 100 is illuminated at a second irradiation angle in such a way that the second security features 104 are reconstructed. In this case, the irradiation takes place with a second illumination device 214 which emits a 0-degree coaxial light onto the upper side of the valuable or security product 100 .

To the value or security product 100, in particular the identity card after the Figures 2 and 3 to be able to be read out by machine, a device 200 is used, which in figure 1 is shown.

figure 1 shows a device 200 for the optical detection of a value or security product 100 with a first security feature 102, which reconstructs at a first irradiation angle, and with a second security feature 104, which reconstructs at a second irradiation angle, which differs from the first irradiation angle. The device 200 comprises an at least partially transparent support plate 200 on which the value or security product 100 can be placed. The support plate 202 is preferably formed from transparent glass, so that it does not only appear partially transparent. There is also an optical detection device 204, in the present case in the form of a camera, whose lens uses a relatively small camera opening angle, as a result of which the longest possible optical path is created. The length of the optical path is designed in such a way that the support plate 202 is captured completely under the opening angle of the camera. This is advantageous because the security features 102, 104 excited by the illumination are only visible within a limited angular range perpendicular to the surface. If this angle is exceeded, the contrast of the security features 102, 104 decreases and they are no longer so clearly visible in the edge areas.

The value or security product 100 is detected by the optical detection device 204 using a partially transparent mirror 206 . This partially transparent mirror 206 comprises a front side 208 facing the support plate 202 and a rear side 210 facing away from the support plate 202. It is thus positioned in the beam path of the optical detection device 204 in order to prevent light impinging on it from the support plate 202 on its front side 208 in the direction of the optical Deflect detection device 204.

In order to ensure that the two security features 102, 104 are reliably reconstructed, the two lighting devices 212, 214 are present, which emit light that is directed as strongly as possible. Such a highly directional light comes about, for example, in that the lighting devices 212, 214 are formed from a light-emitting diode arrangement with a plurality of light-emitting diodes which have a narrow beam angle of between 5 degrees and 15 degrees, in particular a beam angle of 10 degrees. In order to ensure that the light is as parallel as possible to the axis, the lighting devices 212, 214 can also be provided with a structured light guide. The lighting devices 212, 214 or also the support plate 202 or also the lens of the optical detection device 204 can be covered with at least one contrast-enhancing film in order to make the holographic security features 102, 104 more clearly visible. The beams of the two illumination devices 212, 214 can also be aligned by using an f-theta lens or an f-theta objective in the beam path of the illumination devices 212, 214. There is the possibility that the two lighting devices 212, 214 also emit light from a different wavelength range or different wavelengths.

The first illumination device 212 is set up to emit light at the first irradiation angle directly onto the support plate 202, with the second illumination device 214 being set up to emit light at the second irradiation angle onto the rear side 210 of the mirror 206, with this passing through the mirror 206 to the Front 208 is transmitted and thus passed to the platen 202.

In the present case, the first illumination device 212 emits 45-degree grazing light 216, as a result of which the first security features 102 are reliably reconstructed. The light rays thus impinge on the platen 202 at an angle of 45 degrees with respect to the surface normal of the platen 202 .

In the present case, the second illumination device 214 emits 0-degree coaxial light 218, which impinges on the support plate 202 at an angle of 0 degrees with respect to the surface normal of the support plate 202.

• Auflegen des Wert- oder Sicherheitsprodukts auf die transparente Auflageplatte 202,
• Entsenden von Licht durch die erste Beleuchtungseinrichtung 212 unter dem ersten Bestrahlungswinkel unmittelbar an die Auflageplatte 202 sowie optisches Erfassen des Wert- oder Sicherheitsprodukts 100 mit der optischen Erfassungseinrichtung 202 anhand des von der Auflageplatte 202 ausgehenden, an der Vorderseite 208 des teildurchlässigen Spiegels 206 abgelenkten Lichts, und
• Entsenden von Licht durch die zweite Beleuchtungseinrichtung 214 an die Rückseite 210 des teiltransparenten Spiegels 206, wobei das Licht durch den Spiegel 206 zur Vorderseite 208 transmittiert und zur Auflageplatte 202 in dem zweiten Bestrahlungswinkel hindurchlassen wird sowie optisches Erfassen des Wert- oder Sicherheitsprodukts mit der optischen Erfassungseinrichtung 204 anhand des von der Auflageplatte 202 ausgehenden, an der Vorderseite 208 des Spiegels 206 abgelenkten Lichts.

In order to optically detect the product of value or security 100, in particular, the following steps were taken:

• Placing the value or security product on the transparent support plate 202,
• Transmission of light by the first illumination device 212 at the first irradiation angle directly to the support plate 202 and optical detection of the valuable or security product 100 with the optical detection device 202 using the light emanating from the support plate 202 and deflected on the front side 208 of the partially transparent mirror 206, and
• Transmission of light by the second illumination device 214 to the rear side 210 of the partially transparent mirror 206, the light being transmitted through the mirror 206 to the front side 208 and to the support plate 202 in the second irradiation angle, and optically detecting the valuable or security product with the optical detecting device 204 based on the light emitted by the support plate 202 and deflected on the front side 208 of the mirror 206 .

The images of the value or security product 100 captured by the optical capture device 204 can be combined into a common image. The generation of individual images is also possible and is advantageous for an evaluation of the holographic security features 102, 104.

In order to reconstruct all security features 102, 104, the two lighting devices 212, 214 are preferably switched alternately.

In order to only have to record a single image in which all security features 102, 104 are visible, there is the possibility that the exposure time of the optical detection device 204 lags behind the frequency of the alternating switching of the two lighting devices 212, 214.

The presently presented invention thus offers a solution for the optical examination of the holographic security features 102, 104, in particular the identigram (a registered trademark of the applicant) in part or fully automated way. The mutual arrangement of the constituents of the present device 100 results in a particularly compact design and the available installation space in document checking devices is used sensibly.

REFERENCE LIST

100

value or security product

102

first security feature

104

second security feature

200

contraption

202

support plate

204

optical detection device

206

semi-transparent mirror

208

front

210

back

212

first lighting device

214

second lighting device

216

45 degree side light

218

0 degree coaxial light

Claims (15)

Device (200) for the optical detection of a value or security product (100) with a first security feature (102), which is reconstructed at a first irradiation angle, and with a second security feature (104), which is reconstructed at a second irradiation angle, which differs from the first Irradiation angle differs, comprising: - an at least partially transparent support plate (202) on which the value or security product (100) can be placed, - an optical detection device (204), - a semi-transparent mirror (206), which comprises a front side (208) facing the support plate (202) and a back side (210) facing away from the support plate (202), and which is positioned in the beam path of the optical detection device (204) in order to of the support plate (202) to deflect light striking it on its front side (208) in the direction of the optical detection device (204), - a first lighting device (212) which is set up to emit light at the first irradiation angle directly onto the support plate (202), and - A second illumination device (214) which is set up to emit light at the second irradiation angle onto the back (210) of the mirror (206), it being transmitted through the mirror (206) to the front (208) and thus to the support plate ( 202) is allowed to pass. Device according to Claim 1, characterized in that the lighting devices (212, 214) are formed from a light-emitting diode arrangement with a plurality of light-emitting diodes which have a narrow emission angle of between 5 degrees and 15 degrees. Device according to Claim 1 or 2, characterized in that a structured light guide is associated with the lighting devices (212, 214) for generating axis-parallel light. Device according to one of Claims 1 to 3, characterized in that the support plate (202) is covered with at least one contrast-enhancing film. Device according to Claim 4, characterized in that the contrast-enhancing film is in the form of an optical filter which is set up to intensify the contrast via the wavelength of the incident light. Device according to Claim 4 or 5, characterized in that the contrast-enhancing film is in the form of an optical filter which is set up to intensify the contrast via the angle of incidence of the incident light. Device according to one of Claims 4 to 6, characterized in that the contrast-enhancing film is in the form of an optical filter which is set up to intensify the contrast via the polarization of the incident light. Device according to one of Claims 4 to 7, characterized in that the contrast-enhancing film is a laminate of a plurality of film layers one on top of the other. Device according to Claim 8, characterized in that the film layers have different optical characteristics. Device according to one of Claims 1 to 9, characterized in that an f-theta lens or an f-theta objective is integrated into the beam path of the lighting devices (212, 214). Device according to one of Claims 1 to 10, characterized in that the first irradiation direction of the first illumination device (212) is 45-degree grazing light and/or the second irradiation direction of the second illumination device (214) is 0-degree coaxial light. Method for the optical detection of a value or security product (100) with a first security feature (102), which is reconstructed at a first irradiation angle, and with a second security feature (104), which is reconstructed at a second irradiation angle which differs from the first irradiation angle, including the steps: - placing the value or security product (100) on an at least partially transparent support plate (202), - Transmission of light by a first lighting device (212) at the first irradiation angle directly to the support plate (202) and optical detection of the value or security product (100) with an optical detection device (204) based on the emanating from the support plate (202), light deflected at a front side (208) of a partially transparent mirror (206), and - Sending light through a second illumination device (214) to a rear side (210) of the partially transparent mirror (206), the light being transmitted through the mirror (206) to the front side (208) and to the platen (202) in the second irradiation angle and optically detecting the product of value or security (100) with the optical detecting device (204) using the light emitted by the support plate (202) and deflected on the front side (208) of the mirror (206). Method according to Claim 12, characterized in that all images of the value or security product (100) captured by the optical capture device (204) are combined into a common image. Method according to Claim 12 or 13, characterized in that the two lighting devices (212, 214) are switched alternately to reconstruct the security features (102, 104). Method according to Claim 14, characterized in that the exposure time of the optical detection device (204) lags behind the frequency of the mutual switching of the two lighting devices (212, 214).

Images