CN1116453A - Diffraction viewing device - Google Patents

Abstract

A viewing device to aid in authenticating an optical surface (100). The device includes a laser diode (101) which produces a beam of light (103). The device includes a viewing screen (107) which receives a diffracted image produced by the beam (103) illuminating the surface (100). The device further includes a lens system (102) which causes the diffracted beam to be focused on the viewing screen (107).

Description

Diffraction observation device

The present invention relates to a device for helping to discriminate the authenticity of a diffractive surface attached to an object, thereby assisting in the discrimination and identification of the origin of the object.

The present invention relates to optical counterfeiting and identification technology, more specifically but not exclusively, to the application of the technology to credit cards, ID cards, banknotes, checks and various types of products. More specifically, the present invention relates to devices that aid in the authenticity and identification of diffractive surfaces.

Diffraction images can be used to visually (and electronically) confirm the authenticity of a diffractive surface. A disadvantage of using a collimated laser beam to produce such a diffraction image is that such a beam may not produce a sharp, clear diffraction image, which may not provide a distinction between a true optical diffractive surface and the use of holographic reconstructions (sometimes called The ability to fake surfaces made for holographic replication) technology.

The object of the present invention is to overcome or improve above-mentioned shortcoming substantially.

An apparatus for assisting in authenticating an optical surface capable of producing a projected image from an incident beam of light is disclosed, said apparatus comprising:

a base;

a laser light source mounted on the substrate for providing a light beam and projecting the light beam along a predetermined path, the laser light source being used for illuminating the above-mentioned optical surface to generate a diffracted light beam;

an imaging surface mounted on the above-mentioned substrate for receiving the above-mentioned diffracted light beam from the above-mentioned optical surface, so that a projected image is received on the above-mentioned imaging surface; and

An optical lens system placed along the above-mentioned path, its layout is such that when a reflector is placed on a preferred position on the above-mentioned optical surface along the above-mentioned path to guide the above-mentioned light beam to the above-mentioned imaging surface, the above-mentioned optical lens system can take the above-mentioned The light beam is focused on the above-mentioned imaging plane.

The imaging surface preferably consists of a light-transmissive image receiving element such that said image thereon can be viewed from either side of said element.

A preferred embodiment of the invention will now be described by way of non-limiting example with reference to the accompanying drawings, in which,

Figure 1 is a schematic diagram of an observation device;

Fig. 2 is the schematic diagram of the light spot that is produced on an optical surface by a preferred embodiment of Fig. 1 viewing device;

Figure 3 is a schematic diagram of a hand-held viewing device employing the viewing technique used by the device of Figure 1;

It should be noted that the laser diode and lens system shown in Figures 1 and 3 are internal components of the device and are shown for clarity.

In FIG. 1 , a device for observing an optical surface 100 is schematically shown, wherein FIG. 1( a ) is a side view, and FIG. 1( b ) is a top view. The design of the optical surface 100 is such that under the correct illumination a projected image will be produced by the process of optical diffraction.

The output of laser diode 101 passes through lens system 102 to produce beam 103 . Light beam 103 is reflected by mirror 104 onto optical surface 100 . The effect of the reflector 104 is to facilitate the arrangement and casing of the laser 101 and the lens system 102 on the one hand, and on the other hand to make the light beam 103 have an optimal incident direction on the optical surface 100: in this case, it is slightly deviated from the normal incident direction direction.

Optical surface 100 causes the specularly reflected portion of incident beam 103 to become beam 105 and the diffracted portion of incident beam 103 to become diffracted beam 106 . Mirror 104 is positioned such that light beam 103 is not perpendicular to optical surface 100 . The incident beam 103 and the specularly reflected beam 105 are thus separated by an angle.

Beams 105 and 106 are intercepted by a viewing screen 107 . The reflected beam 105 produces a spot 108 on the viewing screen 107 and the diffracted beam 106 produces one or more images 109 (depending on the design of the optical surface 100 ) on the viewing screen 107 . A single image 109 is depicted in FIG. 1 . Both spot 108 and image 109 can be seen from above the viewing screen, for example from position 110 . The best viewing position for image 109 is when the observer is located at position 110 and looks in a direction close to the return direction of diffracted beam 106 , as shown in FIG. 1 . It should be noted that optical surface 100 may produce diffracted beams other than beam 106, thereby producing diffracted images other than image 109 - for example in typical cases optical surface 100 will produce a high order diffracted image of a conjugate image to image 109 . However, only image 109 is intercepted by viewing screen 107 in the layout shown in FIG. 1 . Since the images produced by the optical surface 100 usually appear in conjugate pairs, the screen 107 is generally placed such that it can only receive images in a half-plane above the optical surface 100 and parallel to the surface. Viewing screen 107 is preferably designed such that it scatter diffracted beam 106 so that image 109 can be seen over a range of viewing angles on either side of viewing screen 107 .

The viewing device shown in FIG. 1 may be hand-held, so it may not be positioned against the optical surface 100 . The positioning of the image 109 on the viewing screen 107 depends on the relative orientation between the viewing device and the optical surface 100 . The viewing screen 107 includes an alignment point 111 to aid in the alignment of the viewing device relative to the optical surface 100, and proper alignment is achieved when the light spot 108 falls on the alignment point 111.

Proper focusing of beam 103 is important to obtain a sharp diffraction image 109 on viewing screen 107 . The arrangement of the lens system 102 should preferably be such that the light beam 103 is well focused on the viewing screen 107 when a flat mirror is used instead of the optical surface 100 . It should be appreciated that the viewing device shown in Figure 1 may be part of a hand-held device and thus the distance between the device and the optical surface 100 may vary. In this case the scope of the working distance between the viewing device and the optical surface should be determined, and the layout of the lens system 102 should be such that when the optical surface 100 is replaced by a flat mirror, the beam 103 is just focused at the maximum working distance on the viewing screen 107 . For example, above this maximum working distance, the image 109 will become larger and less sharp (ie, the ratio of image edge blur range to image size increases), and thus will exhibit significant degradation. As another example, at less than the maximum working distance, the image 109 will be smaller and less sharp, but the reduction in size will tend to mask the loss of image clarity, making the image acceptable to the naked eye.

The light beam 103 will create a spot on the optical surface 100 . FIG. 2 is a schematic diagram of a light spot 200 on the optical surface 100 viewed from above the optical surface 100 . Due to the nature of laser diode 101, unless corrective optics are used in lens system 102, spot 200 generally assumes an elliptical shape. In some embodiments, the optical surface 100 may be composed of a repeating pattern of some basic units 201 , as shown in FIG. 2 . Each of these elements 201 contains an optical surface capable of producing a diffractive image 109 . Cell 201 in Figure 2 is square, but it should be appreciated that other cell shapes are possible. In such an embodiment, it is preferable that the length of one or both elliptical axes of the elliptical spot 201 be close to the characteristic size of the unit 201 . FIG. 2 shows a typical example, where an elliptical light spot 200 has been aligned with a unit 201 , and the length of the minor axis of the ellipse is close to the side length of a square unit 201 . This condition may be important to the requirement to ensure that no more than one row or column of cells are fully illuminated at any one time.

In order to simultaneously meet the focusing requirements of the beam 103 and the geometrical characteristics of the spot 200 on the optical surface 100, it may be necessary to either place the lens system 102 close to the laser 101, or limit the beam 103 with a diaphragm, or take both measures at the same time.

The viewing device of FIG. 1, which preferably satisfies the optical conditions described in connection with FIG. 2, can be used in a hand-held device. FIG. 3 shows a top view of the device. Laser 101 , lens system 102 , mirror 104 and viewing screen 107 (including alignment point 111 ) are all mounted on the head of handheld viewing device 300 . The battery for driving the laser (and any associated electronic circuitry including, for example, surge protection circuitry) may be housed within the handle portion 301 of the device 300 . An on-off button switch 302 located on the side of the handle 301 controls the power of the laser 101 and any related circuits. When the viewing device 300 is in the correct position over the optical surface 100 and the laser 101 is powered on, a reflected spot 108 and one or more diffraction images 109 are produced on the viewing screen 107 .

Optical surface 100 may be part of a label that also bears a barcode (or other machine-readable information). Accordingly, handheld viewing device 300 preferably also includes means for reading barcodes or other forms of machine-readable information.

For example, in a preferred embodiment, device 300 may comprise a bar code reading device with a bar code reading head 303 housed within the device so that device 300 may be conveniently used as both a viewing device and a bar code reader, e.g. Figure 3 shows. The bar code reading function can be operated either by the push button switch 302 or by a separate button. The device 300 can store the barcode information itself for subsequent extraction, or display the barcode information, or output the barcode information through some connection (such as cable connection, infrared connection, radio frequency connection, etc.) when reading.

It should be appreciated that some changes to the design shown in Figure 1 are possible.

For example, laser diode 101 and optical lens system 102 may be arranged to produce output beam 103 directed toward optical surface 100 without using mirror 104 .

The embodiment described here uses a planar viewing screen 107 . It should be appreciated, however, that a curved viewing screen could be used in its place to minimize distortion of the diffraction image(s) 109 .

The techniques described here can be used with both handheld viewing devices as shown in Figure 3, as well as tabletop viewing devices. In the case of a tabletop viewing device, the device may contain means such as a slot or some kind of receptacle to receive the object with the optical surface 100 and thereby make the optical surface 100 on the object relative to the incident light beam 103 position. For example, where the optical surface 100 is attached to a card, the tabletop viewing device may have a slot or "picture frame" locating corner to accommodate the card and help position the card so that the optical surface on the card 100 is correctly positioned relative to the incident beam 103 described above.

Claims (12)

1, the finder of the true and false of an other optical surface is debated in a kind of help, and this surface is suitable for producing a projected image with an incident beam, and said apparatus comprises:

A substrate;

One is installed in this suprabasil LASER Light Source, is used to provide a light beam, and makes this light beam along predetermined path projection, and the above-mentioned LASER Light Source above-mentioned optical surface that is used for throwing light on is to produce a diffracted beam;

One is installed in above-mentioned suprabasil imaging surface, is used for receiving the above-mentioned diffracted beam from above-mentioned optical surface, makes to receive image projected on above-mentioned imaging surface; And

An optical lens system of placing along above-mentioned path, its layout makes, when placing a catoptron with the above-mentioned imaging surface of above-mentioned beam direction the time on the preferred positions of above-mentioned path at above-mentioned optical surface, above-mentioned optical lens system can focus on above-mentioned light beam on the above-mentioned imaging surface.

2, according to the device of claim 1, wherein above-mentioned imaging surface is made up of an image receiving element that can see through light, makes it possible to observe on said elements above-mentioned image.

3, according to the device of claim 2, wherein above-mentioned image receiving element is frosted.

4, according to claim 1,2 or 3 device, wherein above-mentioned image receiving element has an alignment portion, and this part is used for by the above-mentioned beam lighting through above-mentioned mirror reflects, to help the aligning of this device.

5, according to the device of claim 1, it also comprises one along the reflecting surface of above-mentioned road through laying, make above-mentioned path form, and above-mentioned first tilt with respect to above-mentioned second portion by first from above-mentioned light source to above-mentioned reflecting surface and second portion from above-mentioned reflecting surface to above-mentioned precalculated position.

6, according to claim 5 device, wherein above-mentioned first is an acute angle with respect to the pitch angle of above-mentioned second portion.

7, according to claim 6 device, wherein above-mentioned imaging surface is made up of an image receiving element, and above-mentioned image receiving element is made by material that can printing opacity.

8, according to the device of claim 7, wherein above-mentioned image receiving element is frosted.

9, according to claim 3 or 8 devices, wherein said apparatus can be handed.

10,1,2 or 3 device as requested, wherein above-mentioned optical lens system can produce a hot spot on above-mentioned optical surface, and this hot spot has predetermined geometrical property (size, shape etc.).

11, according to the device of claim 10, the geometric properties of wherein above-mentioned characteristic and above-mentioned optical surface is relevant.

12, a kind of finder, the illustrated device of Fig. 1 to Fig. 3 is identical with reference to the accompanying drawings with front here in essence for it.

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