Device for direct optical recording of skin impressions and documents

Abstract

Device for direct optical recording of safety-relevant objects, such as at least skin impressions, comprising a layer sequence: - a top layer (401) with a bearing surface (102) for a safety-relevant object (101, 105), - an aperture layer with non-transparent and transparent areas (304) to limit the angles of incidence of light that is remitted from the object (101, 105) through the contact surface (102) into the layer sequence, - a sensor layer (406) with pixels (307) arranged in a two-dimensional grid, each of which has a light-sensitive element (303) and a transparent transmission area (304), wherein the light-sensitive elements (303) can only detect light coming from the direction of the contact surface (102) and each light-sensitive element (303) of the sensor layer (406) is assigned exactly one aperture of the aperture layer, - a substrate (407) as the carrier of the layer sequence and - an illumination layer (409) for emitting illumination light (201) which illuminates the object (101, 105) through the support surface (102), characterized by the fact that - the aperture layer is designed as a contrast aperture layer (403) with contrast apertures (301) for a predominant transmission of light that is remitted from parts of the object (101, 105) resting on the support surface (102) without an air gap (106), wherein ◯ each contrast aperture (301) is designed as a non-transparent area of ​​the contrast aperture layer (403) and has a distance to the associated light-sensitive element (303) that is defined by means of a spacer layer (404) of selectable thickness between sensor layer (406) and contrast aperture layer (403), and ◯ the contrast diaphragm (301) located at a distance from the light-sensitive element (303) has a non-transparent area above the light-sensitive element (303) that is at least as large as an active area (305) of the light-sensitive element (303) and is arranged such that reflected light (204) falling on the light-sensitive element (303) at small angles of incidence from both object parts (103) resting without an air gap (106) and object parts (104) resting with an air gap (106) is largely blocked for the light-sensitive element (303) by means of the non-transparent contrast diaphragm (301), and only an excess of reflected scattered light (204) from parts (103) of the object (101) resting without an air gap (106) in a differential angle range (207) with large angles of incidence is detected in the light-sensitive element. (303) is permitted and - the illumination layer (409) contains a large number of point light sources (306), which emit in the direction of the contact surface (102) in such a limited angular range in order to suppress total internal reflection at the contact surface (102) of the top layer (401).

Description

[0001] The invention relates to a device for the optical direct recording of security-relevant objects, such as at least skin prints, in particular for recording papillary lines of fingerprints or handprints for personal identification, skin areas for medical purposes, textiles and foodstuffs, as well as for position detection of fingers on displays (e.g. for mobile devices), and optionally for recording documents (e.g. passports, driver's licenses and any other identification documents, such as tickets, boarding passes, etc.).

[0002] There are various methods for capturing skin impressions for identification purposes. Optical fingerprinting is widely used for this purpose.

[0003] In conventional, state-of-the-art fingerprint systems, fingerprints are captured using the principle of frustrated total internal reflection (FTIR). The devices used for this purpose employ lens-based optics for imaging and a prism into which light is coupled at an angle, causing it to be totally reflected internally at its surface. When a finger is placed on the surface, light is coupled out of the prism and into the finger at the points where the papillary lines (ridges of skin) touch the surface. Imaging the prism surface produces an (inverse) image of the papillary lines: light reaches the sensor at the points where the papillary troughs (valleys of skin) are located. Only very small amounts of the light backscattered from the ridges reach the sensor at the points where they are located.

[0004] By utilizing the FTIR principle, a very high brightness contrast is achieved between skin peaks and troughs. In practice, contrast values ​​of over 90% are achieved. However, the disadvantages of prism-based devices are the size and weight of the massive prism used, as well as the susceptibility of the overall optical system to misalignment.

[0005] The trend toward smaller, lighter fingerprint scanners has led to the development of a new class of compact, portable systems that also allow for high-quality (FBI-compliant) optical capture of fingerprints without prisms or lens-based optics. Compared to the classic prism systems described above, these systems use large sensors onto which the skin area to be scanned is placed—almost directly. An image is generated without conventional imaging and without size scaling (magnification factor 1.0). These systems are often referred to as direct scanners, and hereafter as direct sensors.

[0006] Depending on the design of the sensor used and its illumination, images can be generated in which either the skin valleys appear bright (FTIR principle) or the skin peaks appear bright (non-FTIR principle). The image formation is determined by the angular spectrum of the illumination used, as well as the thickness and refractive index of the optical layer located between the sensor and the skin surface.

[0007] In an FTIR direct imager, the illumination ideally consists exclusively of light angles that are totally reflected internally at the contact surface. Thus, at the skin's troughs, 100% of the light striking the contact surface is reflected back towards the sensor. At the points where the skin ridges touch the contact surface, some of the illumination couples into the skin and is scattered (disturbed total internal reflection). The diffusely backscattered light from the skin surface amounts to approximately 40%. This portion of the backscattered light is also detected due to the large opening angle (of 180°) of the individual light-sensitive sensor elements. Therefore, for direct scanners based on the FTIR principle, a maximum Michelson contrast of the following results: Km=100%−40%100%+40%≈43%.

[0008] In a direct scanner that does not operate on the FTIR principle, the illumination ideally contains no illumination angles that are totally reflected internally at the contact surface. A skin area placed on the scanner is illuminated through the contact surface, and the diffusely backscattered light is detected by the light-sensitive elements. The skin peaks appear brighter in the image than the skin valleys; the image is therefore inverted compared to FTIR systems. This is because additional refractive index transitions occur when detecting the light backscattered from the skin valleys. The light travels from the skin surface (n ≈ 1.3) into an air region (n = 1.0) in the skin valley and then into the uppermost layer (n ≈ 1.5) of the direct scanner. Scatter simulations show that approximately 20% of the incident light is reflected in the skin valleys, and approximately 40% in the skin peaks. The maximum Michelson contrast for these systems is therefore only approximately: Km=40%−20%40%+20%≈33%.

[0009] Neither of the two described direct scanning principles can generate contrast values ​​comparable to those of classic prism-based devices without further measures, since there is no classic optical imaging channel and therefore all unwanted stray light is detected, as the opening angle of the light-sensitive elements of the direct scanners is almost 180° without additional effort.

[0010] The low base contrast compared to FTIR systems with prisms makes direct scanners less robust against unfavorable recording conditions, such as strong ambient light or different skin types.

[0011] In the prior art, a first group of solutions with contrast-enhancing elements is known from US 2017 / 0161540 A1, US 2017 / 0161543 A1, US 2017 / 0161544 A1, US 2017 / 0169273 A1, US 2017 / 0372113 A1 and WO 2018 / 004243 A1, in which the light-sensitive elements can selectively detect only a desired angular range by using angle-selective elements. However, these solutions have the disadvantage that the desired angular range can only be limited by several layers or by curved or prismatically stepped surfaces, which makes the production of such direct image sensors complex and expensive, or additional polarization layers for interference suppression reduce the signal intensity.

[0012] Another approach to solving the contrast problem involves receiving light from the skin valleys by preferentially detecting light from small opening angles near the surface normal of the contact area, thanks to the pinhole-like nature of angle-selective elements, as described, for example, in WO 2017 / 045130 A1, WO 2017 / 063119 A1, US 2017 / 0017824 A1, and US 2016 / 0224819 A1. In such designs, the Michelson contrast of the recorded biometric objects can never reach nearly 100%, since some of the reflected light from the skin peaks is constantly being detected.

[0013] Against this background, the invention aims to generate brightness differences between skin peaks and valleys in direct sensors for capturing skin impressions, comparable to those of classic FTIR systems with prisms (contrast above 90%). The solution should be uncomplicated and easy to manufacture. In an extended application, the same direct sensor should also be able to capture documents with sufficiently high contrast.

[0014] The task is described in a device for the direct optical recording of safety-relevant objects, such as at least skin impressions, comprising a layer sequence containing a cover layer with a contact surface for a safety-relevant object, an aperture layer with non-transparent and transparent areas for limiting the angles of incidence of light that is remitted from the object through the contact surface into the layer sequence, a sensor layer with pixels arranged in a two-dimensional grid, each pixel having a light-sensitive element and a transparent transmission area, wherein the light-sensitive elements can only detect light coming from the direction of the contact surface and each light-sensitive element (303) of the sensor layer (406) is assigned exactly one aperture of the aperture layer, a substrate as a support for the layer sequence and an illumination layer for emitting illumination light.The problem of illuminating the object through the contact surface is solved by designing the aperture layer as a contrast aperture layer with contrast apertures for a predominant transmission of light that is directly remitted from parts of the object resting on the contact surface without an air gap, wherein each contrast aperture is designed as a non-transparent area of ​​the contrast aperture layer and has a distance to the associated light-sensitive element that is defined by means of a spacer layer of selectable thickness between the sensor layer and the contrast aperture layer, the contrast aperture assigned to each light-sensitive element at a distance from the light-sensitive element has a non-transparent area above the light-sensitive element that is at least as large as an active area of ​​the light-sensitive element and is arranged such that remitted light,that, at small angles of incidence, both from object parts resting without an air gap and from object parts resting with an air gap, falls onto the light-sensitive element, is largely blocked by the non-transparent contrast diaphragm for the light-sensitive element, and only an excess proportion of remitted scattered light from parts of the object resting without an air gap in a differential angle range with large angles of incidence is permitted for detection in the light-sensitive element; and that the illumination layer contains a multitude of point light sources that emit in the direction of the contact surface in such a limited angular range as to suppress total internal reflection at the contact surface of the top layer.

[0015] Advantageously, the respective contrast aperture is arranged above the light-sensitive element in such a way that - viewed from the direction of the contact surface - an active area of ​​the light-sensitive element is covered by at least 75%, preferably at least 90%.

[0016] In another practical variant, the respective contrast aperture is arranged above the light-sensitive element in such a way that - viewed from the direction of the contact surface - the active area of ​​the light-sensitive element is completely covered.

[0017] For a space-saving design of the direct sensor according to the invention, it proves advantageous that the top layer is designed as the transparent substrate for the entire layer sequence.

[0018] In another preferred design variant, the respective contrast aperture above the light-sensitive element is configured such that it projects beyond the active area of ​​the light-sensitive element in at least two directions of the pixel grid offset by 90°. In particular, the contrast aperture can have a geometrically similar surface parallel to the active area of ​​the light-sensitive element, with the same orientation in the sense of a central projection. Preferably, selected surfaces for the contrast aperture and the active area of ​​the light-sensitive element are rectangles, squares, ellipses, or circles.

[0019] For objects with varying requirements, it is advantageous if the contrast aperture and the active area of ​​the light-sensitive element have parallel geometric surfaces with different shapes. The contrast aperture and the active area can be different shapes, such as rectangles, squares, ellipses, or circles.

[0020] To improve the contrast and resolution of skin prints, the surfaces of the contrast apertures advantageously have a protrusion relative to the active areas of the light-sensitive elements, the size of which is adjusted depending on the refractive index of the cover layer, the distance of the contrast apertures above the light-sensitive elements, and the shape of the contrast aperture and the active area of ​​the light-sensitive element.

[0021] To enable different shooting modes for photographing various objects, it proves advantageous for the contrast diaphragm layer to have two or more different contrast diaphragms arranged alternately and offset from each other in a grid corresponding to the pixel grid over the active areas of the light-sensitive elements. This is particularly useful for photographing a variety of objects, ranging from fingers with different skin types, such as normal and moist or light and dark skin, to documents of various types.

[0022] In order to achieve higher resolution recordings and improve the recording of documents as security-relevant objects, the contrast aperture advantageously has an equal protrusion relative to the active area of ​​the light-sensitive element in three directions offset by 90° within the contrast aperture layer, and a smaller protrusion, which can approach zero, in a fourth direction offset by 90°.

[0023] In a further improved variant, in which the recording with the same increased resolution in two dimensions is achieved and the recording of documents can be improved, the contrast diaphragm expediently has an equal protrusion to the active area of ​​the light-sensitive element in two directions offset by 90° within the contrast diaphragm layer and a smaller protrusion, which can approach zero, in two directions opposite to the two directions offset by 90°.

[0024] The spacing of the contrast apertures above the light-sensitive elements is advantageously selected in a range between 10 nm and 1 mm. Preferably, the spacing is set in a range of 0.5 µm to 50 µm, with the spacing being particularly preferably achieved by setting a layer thickness between 1 µm and 10 µm.

[0025] The illumination layer is advantageously configured as a large-area backlight coupled to the layer sequence below the sensor layer via an intermediate layer or an air gap. The large-area illumination layer is preferably a display, which is preferably coupled to the bottom layer of the layer sequence via an air gap. The bottom layer can either be a transparent substrate or, if the top layer is configured as a substrate, it can be the sensor layer.

[0026] In an alternative design, the illumination layer can advantageously be configured as point light sources arranged singularly within the sensor layer, offset in the pixel transmission areas, and equipped with beam-limiting apertures. These point light sources can be in the form of LEDs, OLEDs, or QLEDs within the sensor layer.

[0027] In a particularly advantageous design, the contrast diaphragm layer is configured to allow a predominant transmission of light reflected from parts of the object resting on the support surface without an air gap, and an additional, small proportion of light reflected from parts of the object resting on the support surface with an air gap, wherein the respective associated contrast diaphragm is arranged above the light-sensitive element such that – viewed from the direction of the support surface – the active area of ​​the light-sensitive element is completely covered, and the contrast diaphragm has a recess within an area covering the active area such that an additional small proportion of predominantly perpendicularly incident light can be received in the area of ​​the recess in order to improve the contrast when photographing documents.

[0028] In a suitable design of the contrast diaphragm, the recess is preferably a recess in the form of a circular hole, oblong hole, slot, notch, sector or other shaped cutout within the surface of the contrast diaphragm covering the active area of ​​the light-sensitive element.

[0029] In another advantageous design of the contrast aperture, the recess is a cutout in the form of a circular hole, oblong hole, slot, notch, sector or other shaped cutout, provided it is located in a projection of the contrast aperture towards the active area.

[0030] The invention is based on the fundamental idea that when capturing objects for personal identification, such as fingerprints, handprints, or footprints, the biometric features, specifically the papillary lines, can be captured in different ways. With direct optical sensors for capturing skin prints, the papillary lines are in direct contact with the sensor's contact surface, with the contrast between skin ridges and troughs arising from their differing refractive index transitions at the contact surface. Crucial for achieving the FBI's quality standards (according to EBTS Appendix F) is the contrast between the papillary ridges (skin ridges) and papillary troughs (skin valleys) of the skin print. A theoretical maximum contrast for a direct optical sensor with diffuse illumination, which according to the formula mentioned above can only reach 33%, is clearly too low, considering that high contrast is the primary requirement for high image quality.Although FBI-compliant images can be produced with a base contrast of 50% under ideal conditions, a higher base contrast in the unprocessed image offers reserves that ensure the required high image quality even under poor conditions (dry or moist skin, dark skin types, ambient light or a dirty surface).

[0031] The invention solves the problem of insufficient contrast inherent in direct sensors by means of a new detection principle of optical recording.

[0032] The basic principle is that the backscattered (remitted) light from the object resting on the contact surface is detected, and the possibility is exploited that, on the path from the contact surface of the device to the light-sensitive elements of a large-area sensor layer, the remitted light, or a portion thereof, can be modified by angle-selective elements. According to the invention, the opening angle of the light-sensitive elements is changed in such a way that the detection of certain angular ranges of the remitted light from the object is favored or prevented.In particular, scattered light components remitted from both different skin areas, the skin peaks and the skin valleys, within the same angular range are not permitted for detection. This allows for higher contrast by using only the excess portion of the scattered light originating from the skin peaks, which enters the direct image sensor as remitted light at larger angles, for signal acquisition. This is achieved by blocking (shading) the scattered light remitted from the skin areas that strikes the light-sensitive elements at small angles of incidence using a contrast diaphragm that essentially covers the center of each light-sensitive element.

[0033] The invention makes it possible to improve the brightness differences between skin peaks and valleys in direct scanners for capturing skin impressions to such an extent that they are comparable to those of classic FTIR systems with prisms (contrast over 90%). The invention also solves the extended problem of capturing documents with sufficiently high contrast using the same direct sensor.

[0034] The invention will be explained in more detail below using exemplary embodiments. The drawings show: Fig. 1: a basic structure of the device according to the invention for taking skin impressions, Fig. 2a: a side view (sectional view) of a preferred embodiment of the device according to the invention, in which the illumination layer is integrated into the sensor layer in the form of a plurality of point light sources, Fig. 2b: a side view (sectional view) of a further embodiment of the device according to the invention, in which the illumination layer in the form of a plurality of point light sources is integrated into the sensor layer and the cover layer simultaneously represents the substrate for the layer sequence, Fig. 3: a side view (sectional view) of another preferred embodiment of the device according to the invention, in which the illumination layer is coupled to a display as backlighting below the substrate, Fig. 4a: a schematic representation of the critical angles for grazing light incidence for the different media transitions of skin ridge and skin valley at the contact surface as the interface, Fig. 4b: a schematic representation of the superposition of the different critical angles for the entry of scattered light from the skin peak and skin valley into the cover layer, stylized at one point on the contact surface to illustrate the range of the difference angles, Fig. 5: a side view (as a schematic sectional representation) of the device according to the invention in an embodiment for receiving a document which is illuminated by point light sources contained in the sensor layer, Fig. 6: a schematic section of the device according to the invention with light-sensitive elements without a diode aperture layer and with a fully covering contrast aperture for receiving a document which is illuminated from below the sensor layer with an illumination layer as background light, Fig. 7a: a top view of a first embodiment of a light-sensitive element with diode aperture and contrast aperture, Fig. 7b: a side view as a sectional representation of the embodiment of Fig. 7a, Fig. 8a: a top view of the light-sensitive element analogous to Fig. 7a when using a square contrast aperture with a defined symmetrical overhang relative to an active area left free by the diode aperture, Fig. 8b: a top view of the light-sensitive element in a second embodiment of a square contrast aperture, in which the projection in one direction is reduced by a recess, Fig. 8c: a top view of the light-sensitive element in a third embodiment of a circular contrast aperture over a circular active area, in which the uniform overhang in one direction is interrupted by a sector-shaped recess and the active area is not completely covered, Fig. 8d: a top view of the light-sensitive element in a fourth embodiment of a square contrast aperture over a square active area, in which the uniform overhang for two orthogonal directions is interrupted by a right-angled sector-shaped recess and the active area is not covered to approximately 25%, Fig. 9: Top views of further preferred embodiments of the device according to the invention with different configurations of contrast aperture and active area of ​​the light-sensitive elements and Fig. 10: a side view and a top view of a mobile device in which the device according to the invention is integrated.

[0035] In Fig. Figure 1 schematically shows the layer sequence of a device for the direct optical recording of security-relevant objects (hereinafter referred to as: direct optical sensor) in a cross-sectional view. Security-relevant objects are skin areas, such as a fingerprint 101, hand or footprints, as well as documents 105 (only in Fig. 5, Fig. 6 and Fig. 10) for the identification of persons, such as identity card, passport, driver's license, credit or business card.

[0036] In Fig. Figure 1 schematically depicts a finger 101 with several skin ridges 103 and skin valleys 104, which is placed on the contact surface 102 of the direct optical sensor. The contact surface 102 is usually formed by the outer surface of a resistant transparent cover layer 401, on which several fingers 101 can be placed simultaneously. For optical detection of the placed finger 101, in Fig. Figure 1 shows the sensor structure schematically using three pixels 307, each consisting of a light-sensitive element 303 and a transparent transmission area 304. An example of a possible light path for illumination light 201 is directed from one of the transmission areas 304 to the underside of the finger 101 towards the contact surface 102. This path leads to a point-like conversion into scattered light 202 in the object placed on the finger 101. Scattered light 203 directed towards the contact surface 102 enters the direct sensor as reflected light 204, which can be received by a light-sensitive element 303 under certain conditions.

[0037] The device according to the invention comprises, coming from the direction of the finger 101, a cover layer 401 with the contact surface 102 for the objects to be received, a contrast aperture layer 403, a spacer layer 404, a sensor layer 406 and a substrate 407.

[0038] Substrate 407 forms the basis for the layer sequence of the direct optical sensor. Conductors, semiconductors, and insulators are applied to substrate 407 using photolithographic processes, known in the prior art as TFT (thin-film transistor) technology. Alternatively, the direct optical sensor can also be manufactured using printing processes, for example, screen printing. Substrate 407 preferably consists of a transparent material, such as plastic or glass, to allow the transmission of illumination light 201, which, coming from the direction of the transmission areas 304 of the pixels 307 of the sensor layer 406, passes through the entire layer sequence and the contact surface 102, illuminating the object, the finger 101, or the document 105.

[0039] Supported by the substrate 407 is a sensor layer 406, which has pixels 307 arranged in a regular two-dimensional grid. Each pixel 307 has a photosensitive element 303 for converting light into electrical signals and, in this embodiment, a transparent transmission area 304 for transmitting illumination light 201 from below the substrate 407. The photosensitive elements 303 are photodiodes designed such that they cannot detect light from below, from the direction of the substrate 407. This is achieved by means of an aperture made of an opaque material on the underside of the photodiode, as is known and customary in the prior art. The photosensitive elements 303 typically have an opening angle of approximately 180° and are designed to detect light of a predetermined wavelength range from the direction of the contact surface 102.Preferably, the pixels 307 detect a wavelength range in the visible radiation spectrum between 380 and 780 nm. For the purpose of capturing FBI-compliant images, the sensor layer 406 preferably has a center-to-center spacing of the light-sensitive elements 303 of ≤ 50.8 µm, which corresponds to a resolution of 500 ppi (pixels per inch) or more.

[0040] The transmission areas 304 between the light-sensitive elements 303 consist of a material that is at least partially transparent to the illumination light 201. Preferably, transparent coating materials, such as silicon dioxide or aluminum oxide, are used, which are adapted to the thickness of the light-sensitive elements 303 during the coating process. This flattens the sensor layer 406 before the next coating step.

[0041] In most applications of the direct optical sensor, it is advantageous to define and limit the effective area of ​​the light-sensitive elements 303 and, to a lesser extent, also to restrict the aperture angle in order to adjust the light sensitivity to the level required for the application, while simultaneously realizing the largest possible light-sensitive element 303 for a better signal-to-noise ratio. In this case, a diode aperture layer 405, consisting of transparent and opaque areas, is arranged above the sensor layer 406. The opaque areas of the diode aperture layer 405 form diode apertures 302, which shade a portion of the area from the edge of the light-sensitive elements 303. The portion of the light-sensitive element 303 not covered by the diode aperture 302 forms a precisely defined active area 305 in which light can still be detected.Each light-sensitive element 303 is assigned exactly one diode aperture 302, which defines the active area 305 of the light-sensitive element 303 and the pixel 307. The transparent areas of the diode aperture layer 405 between the diode apertures 302 coincide in area with the transmission areas 304 of the sensor layer 406 and preferably consist of the same material as the transmission areas 304.

[0042] Above the diode aperture layer 405 is a transparent spacer layer 404, which establishes a defined distance between the active area 305 of the photosensitive elements 303 and the contrast aperture layer 403. The spacer layer 404 has a thickness between 0.01 and 1000 µm. Preferably, the thickness of the spacer layer 404 is between 0.5 µm and 50 µm, particularly preferably in the range of 1 to 10 µm. The spacer layer 404 consists of a transparent organic or inorganic material, preferably an organic material, to achieve better leveling properties and greater layer thicknesses.

[0043] Above the spacer layer 404 is a contrast aperture layer 403, which has transparent areas and opaque contrast apertures 301. Each light-sensitive element 303 of the sensor layer 406 is assigned exactly one contrast aperture 301 within the contrast aperture layer 403. The contrast apertures 301 cover substantial areas of the active area 305 of the light-sensitive elements 303 and areas of the diode apertures 302. The contrast apertures 301 restrict the angles of incidence of scattered light 203, which is reflected from the finger 101 via the contact surface 102 into the direct sensor, for the active areas 305 of the light-sensitive elements 303.The contrast diaphragms 301 are designed for preferential transmission of stray light 203, which is directly reflected from parts of the finger 101 resting on the support surface 102 without an air gap 106 and enters the active areas 305 of the light-sensitive elements 303 as reflected light 204 at a large angle of incidence. An explanation of the limitation of the angles of incidence of reflected light 204 detectable by the light-sensitive elements 303 follows. Fig. 4a and Fig. 4b described.

[0044] To effectively block reflected light 204, non-transparent materials are required for the diode apertures 302 and the contrast apertures 301. Aperture materials that are suitable for photolithographic coating processes due to their good structuring properties are preferred; for example, metals such as chromium, aluminum, gold, molybdenum, copper, silver, and silicon. However, due to the reflective properties of these materials, undesirable reflections can occur on the surfaces of the diode apertures 302 and contrast apertures 301, which can reduce contrast, increase noise, or produce double images. Therefore, absorbing organic materials, such as polytetrafluoroethylene, and absorbing inorganic materials, such as diamond-like carbon layers, black chromium, copper indium disulfide, or materials with a special microstructure, are primarily used.Materials that can be applied as diode apertures 302 and contrast apertures 301 using printing processes, e.g., screen printing, are particularly preferred, as they are quick, flexible, and cost-effective to produce. Organic materials are primarily used for this purpose in printing processes.

[0045] Above the contrast aperture layer 403 is the cover layer 401, which protects the direct optical sensor from mechanical and chemical stresses and whose outer surface forms the contact surface 102 for objects such as the finger 101 or the document 105. The cover layer 401 has a thickness in the range of 1 µm to 10 mm, preferably 10 µm to 1000 µm, and particularly preferably 50 µm to 200 µm. A cover layer 401 that is as thick as possible is advantageous to ensure particularly good mechanical and chemical protection. However, the cover layer 401 should still be thin enough to allow for easy integration of the direct sensor into mobile devices where a low overall thickness is desirable. For user-friendliness, cover layers 401 are made of plastic, which can be removed and replaced by the user without leaving any residue. Hard cover layers 401 are particularly preferred, e.g., B. made of glass, chemically tempered glass, quartz glass, sapphire or ceramic.

[0046] The transparent areas of all layers in the layer sequence of the device according to the invention preferably have similar optical properties (in particular, similarly matched refractive indices) in order to minimize reflection losses at the interfaces between the layers. Preferably, the refractive indices of all transparent layers are n = 1.5 ± 0.2.

[0047] To reduce reflection losses between the top layer 401 and the contrast aperture layer 403, an adhesive layer 402 (not in Fig. (1 shown), which has a refractive index n = 1.5 ± 0.2, is provided, which optically couples or bonds the top layer 401 to the underlying layer sequence. Preferably, the adhesive layer 402 is an optically transparent adhesive (LOCA - liquid optical clear adhesive) or an optically transparent double-sided adhesive film (OCA - optical clear adhesive). Particularly preferred transparent adhesives are based on acrylates, epoxies, and silicones.

[0048] To suppress the detection of interfering ambient light, one or more spectral filter layers 411 (in Fig. (1 not shown) can be integrated into the layer sequence of the direct sensor. This allows the ambient light protection required by some users to be achieved, where the direct sensors must also function in direct sunlight. To prevent saturation of the light-sensitive elements 303 by ambient light, one or more full-surface spectral filter layers 411 can be embedded between the light-sensitive elements 303 and the contact surface 102 (only in Fig. (2b shown). Such a spectral filter system can be applied as a continuous layer system over the entire surface of the direct sensor. The spectral filter layer 411 is designed such that ambient light is preferably absorbed or reflected and at least a portion of the illumination light 201 is transmitted.

[0049] A structured spectral filter layer 412 is preferred (only in Fig. 3) provided with transparent and absorbing areas, wherein the absorbing areas are located at least above the active areas 305 of the photosensitive elements 303. Preferably, the absorbing areas are arranged such that no portion of the illumination light 201 is absorbed by the structured spectral filter layer 412.

[0050] The spectral filter layer 411 or 412 is located between the sensor layer 406 and the cover layer 401, particularly preferably between the sensor layer 406 and the contrast aperture layer 403. The cover layer 401 itself can also be designed as a spectral filter layer 411 (not shown) (e.g., colored glass). Another embodiment is to design the light-sensitive elements 303 to be wavelength-selective only for the wavelength of the illumination light 201. All measures can also be combined with one another.

[0051] Possible methods for implementing spectral filters include, for example, absorbing organic and inorganic dyes and particles, resonant metal nanoparticles (plasmonic filters), and interference filters. If a liquid adhesive is used to bond the top layer 401 to the contrast aperture layer 403, the ambient light blocking can also be integrated into this; the spectral filter layer 411 would then be implemented in the adhesive layer 402 (not shown). The spectral filter layer 411 or 412 is preferably only transparent to wavelengths or wavelength ranges that cannot penetrate the object placed on it, finger 101 or document 105. The narrower the transmission band of the spectral filter layer 411 or 412, the better the ambient light (e.g., sunlight) is blocked. Of course, it is also possible to combine several spectral filters or to use the spectral filter layer 411 or 412 in conjunction with other spectral filters.412 to be designed so that it is selective for several wavelength ranges.

[0052] If an object, finger 101 or document 105, placed on the contact surface 102, is illuminated by the illumination light 201 from the direction of the transmission areas 304 of the sensor layer 406, the illumination light 201 passes through at least the transmission area 304 of the sensor layer 406, the diode aperture layer 405, the spacer layer 404 and the contrast aperture layer 403 as well as the cover layer 401. All layers of the direct sensor are transparent to at least a portion of the illumination light 201.

[0053] Is an object, for example a finger 101, as in Fig. As shown in Figure 1, with the contact surface 102 in contact and ready to receive light, illumination 201 penetrates through the transparent areas of the device, across the contact surface 102, and towards the finger 101. Upon striking the finger 101 resting on the contact surface 102, the illumination 201 is coupled into the finger 101 and scattered there. Due to multiple scattering, the direction of the scattered light 202 is stochastic. A portion of the scattered light 202 travels as scattered light 203 towards the contact surface 102 and enters the surface layer 401 there as reflected light 204 via the papillary ridge (skin ridge 103) on the contact surface 102. From there, the remitted light 204 penetrates the further layer sequence and is finally absorbed in the active area 305 of the light-sensitive elements 303, whereby the detected light intensity is converted into an electrical signal and subsequently into a grayscale image.A similar process occurs in the skin valleys 104, from which scattered light 203 initially couples out into the air gap 106 of the skin valleys 104 and subsequently enters the top layer 401 as remitted light 204 via the contact surface 102. Due to the additional optical transition for remitted light 204 from the skin valleys 104, there is a greater light loss than with the skin peaks 103, which lie on the surface without an air gap 106. This greater light loss is detected by the light-sensitive elements 303 and displayed as a contrast between the skin peaks 103 and the skin valleys 104.

[0054] The angular spectrum of the incident direction of the reflected light 204 is stochastic due to multiple scattering in the finger 101. Several possible directions result, whereby the sum of all possible light paths of the reflected light 204 refracted into the cover layer 401 (at the contact surface 102) describes a light cone. In the cover layer 401, two critical angles 205 and 206 are established (only in Fig. 4a and Fig. 4b) of the reflected light 204 is defined by the refractive index transition between the skin peak 103 and the cover layer 401 or between the air gap 106 and the cover layer 401. The proportion of the reflected light 204 that is captured by the active areas 305 depends on the positioning and design of the contrast diaphragm layer 403, which restricts the light path of the reflected light 204.

[0055] In Fig. 2a and Fig. 2b The illumination light 201 is emitted by point light sources 306, such as LEDs, OLEDs, QLEDs or LCDs, and diffusely illuminates the placed finger 101, meaning that the illumination light 201 is emitted in all directions. Individual point light sources 306 are not directly assigned to a light-sensitive element 303; that is, a light-sensitive element 303 detects reflected light 204 from the sum of several point light sources 306.

[0056] In Fig. 2a shows a preferred embodiment of the device schematically in a side view. An illumination layer 409 (made of Fig. 1) for emitting illumination light 201 is integrated into the sensor layer 406. The point light sources 306 are arranged within the sensor layer 406, offset from the light-sensitive elements 303, in the transmission areas 304 of the pixels 307 and emit diffuse illumination light 201 into the upper hemisphere towards the contact surface 102. To prevent total internal reflection at the contact surface 102 of the top layer 401, means for collimating the illumination light 201 from the point light sources 306 or further beam-limiting apertures (not shown) can be used. This can be achieved, for example, by a suitable design of the diode apertures 302 and / or the contrast apertures 301 in the diode aperture layer 405 or contrast aperture layer 403, respectively.

[0057] Furthermore, as already described above, there is no direct assignment of point light source 306 and light-sensitive element 303, since the light cones of the point light sources 306 can overlap in the contact surface 102 and multiple scattering occurs in the finger 101 before the remitted light 204 entering the cover layer 401 is detected.

[0058] One advantage of the embodiment of Fig. 2a is that the substrate does not necessarily have to be transparent, since the point light sources 306 for emitting the illumination light 201 are arranged above the substrate 407. Furthermore, integrating the illumination into the sensor layer 406 results in a thinner device, which is particularly advantageous for mobile applications. The complete integration of such a device into a mobile device (e.g., mobile phone, tablet, etc.) is possible, where the direct optical sensor is integrated into the entire surface of the display and an object (e.g., finger 101 or document 105) can be captured with high image quality across the entire display area of ​​the mobile device. Such an embodiment of the invention is described in Fig. 10 shown.

[0059] In another embodiment of the device for direct optical recording of safety-relevant objects, as in Fig. 2b shows the top layer 401 with the contact surface 102 simultaneously forming a transparent substrate 407 for the layer sequence. The substrate 407, originally located under the sensor layer 406, is applied to the substrate 407 as shown in Fig. 1 and Fig. As shown in Figure 2a, the substrate 401 is omitted. The cover layer 401 is present as a substrate 407, and the contrast aperture layer 403 is applied first, followed, if necessary, by a spectral filter layer 411. Subsequently, the spacer layer 404, diode aperture layer 405, and sensor layer 406 are applied sequentially. This has the advantage of reducing the overall thickness and manufacturing costs of the device because a separate substrate 407 or cover layer 401, as well as an adhesive layer 402 and the associated joining process, are not required. Application scenarios for this embodiment can be found in mobile devices where a low thickness is advantageous and the back of the sensor layer 406 is encapsulated by the device frame or a simple and inexpensive alternative, such as a plastic film.

[0060] In Fig. Figure 3 schematically shows a preferred embodiment of the device in a side view, in which the illumination layer 409 is a display located beneath the substrate 407. Preferably, an air layer 408 is located between the illumination layer 409 and the substrate 407 to restrict the angular spectrum of the illumination light 201 through the optical transition from air to the substrate 407. Instead of air, the display can, in principle, also be optically coupled to the substrate 407 via another adhesive layer (not shown), but the advantage of angular restriction is then no longer present.

[0061] Preferably comes in Fig. 3. An illumination layer 409 in the form of a display with individually controllable point light sources 306 (not shown) is used, whereby an object, finger 101, or document 105 placed on the support surface 102 can be illuminated in a structured manner. A display that emits illumination light 201 with different wavelengths in the visible spectral range is particularly preferred, allowing helpful, color-highlighted information to be displayed to the user. User guidance for more intuitive use of the direct sensor can thus be integrated. The resolution of the point light sources 306 of the backlight or the display can be between 100 and 1000 ppi, preferably in the range of 300–500 ppi.

[0062] The additional air layer 408 causes the diffuse illumination light 201 to be refracted at the interface between the air layer 408 and the substrate 407 upon entering the substrate 407. As described above, this leads to a restriction of the angular spectrum of the illumination light 201. This has the advantage that the illumination light 201 is not totally reflected at the surface of the top layer 401, which would otherwise lead to a reduction in contrast.

[0063] In Fig. Figure 4a illustrates the inventive principle of contrast enhancement. The critical angles 205 and 206 for grazing incidence of light at the contact surface 102, which represents an interface for two different media or refractive index transitions between skin ridge 103 (direct skin contact) and skin trough 104 (air gap 106), are shown schematically in a cross-sectional view. As described above, scattering in the object resting on the contact surface 102 results in several possible light paths for the reflected light 204, the sum of all light paths describing a light cone with a defined critical angle 205 or 206. The critical angles 205 or 206 describe the respective angle of the reflected light 204 after refraction at the interface of the two materials mentioned above for grazing incidence and depend on the optical properties of the two materials (skin, air) from which the light originates and the material (e.g.,glass), into which the different light components are reflected.

[0064] The critical angle 205 for the transitions from air to the cover layer 401 and the critical angle 206 for the transitions from skin to the cover layer 401 are shown schematically. In both cases, the cover layer 401 is the optically denser medium, which is why the light is refracted towards the normal 208 of the contact surface 102. The angular spectrum of the reflected light 204 is restricted. For further calculations, a cover layer 401 made of glass with a refractive index of n = 1.517 (refractive index of BK7 glass) and the skin with n = 1.376 (refractive index of the cornea) are assumed as examples. Between the skin peaks 103, there is air with n = 1 in the skin valleys 104. The refractive index applies to a wavelength of 600 nm. Due to the refraction of light at the contact surface 102, the reflected light 204 describes a light cone with a defined angular range between the normal 208 of the contact surface 102 and the critical angle 205 or 206.A first type of reflected light cone 204 for the transition from skin to glass has a critical angle 206 of approximately 65°, and a second type of reflected light cone for the transition from air to glass has a critical angle 205 of approximately 41°. If both types of reflected light cones are fully detected by the light-sensitive elements 303 (without additional apertures), this results in low contrast between the skin peaks 103 and the skin valleys 104, since the first and second types of reflected light cones differ only slightly in their energy content. To better distinguish the detection of the two types of reflected light cones 204 and thus increase the contrast between the skin peaks 103 and the skin valleys 104, the contrast apertures 301 partially or completely block the portion of the angular range encompassed by both types of reflected light cones, according to the invention.This increases the relative proportion of the angular areas that only occur at the transition from skin mountain 103 to cover layer 401 during detection.

[0065] Fig. Figure 4b shows the difference angle range 207 in a schematic sectional view. The difference angle range 207 describes an angular range of the reflected light 204 that is reflected exclusively from the skin ridges 103 resting on the support surface 102 into the cover layer 401. This means that, for example, no light is reflected in the difference angle range 207 that couples into the cover layer 401 from the air gap 106 in the skin valley 104.

[0066] The purpose of the contrast diaphragm layer 403 according to the invention is to restrict the angular range of the light-sensitive elements 303 in which they can detect the reflected light 204, such that the type of light cone with the smaller critical angle 205 (approx. 41° with BK7 as the cover layer 401), which arises at the interface between the air gap 106 in the skin valley 104 and the cover layer 401, can only be detected to a small extent or not at all by the light-sensitive elements 303. The light 204 reflected from the skin valleys 104 is almost completely blocked, whereas only a portion of the reflected light 204 from the skin peaks 103 is blocked. This applies to the angles between 0° and the critical angle 205 for the air-glass interface (41°). The contrast aperture 301 is preferably arranged such that predominantly reflected light 204 from the light-sensitive elements 303 is detected at angles of incidence of approximately 41° to the perpendicular 208 of the contact surface 102. As shown from Fig. 4a and Fig. 4b can be derived, thereby detecting only remitted light 204 that has been remitted from the skin peaks 103 into the layer sequence. This significantly increases the contrast between skin peaks 103 and skin valleys 104, since the interfering remitted light 204 from the skin valleys 104 is blocked and not detected.

[0067] The design, in terms of shape and position, of the contrast apertures 301 is freely selectable within wide limits and represents merely an additional coating and structuring process step or printing process in the manufacture of the direct optical sensor. Such a process step can be easily integrated into the production of the layer sequence, thereby improving the contrast of the captured skin impressions.

[0068] The high-contrast recording of moist fingers 101, so-called "water rejection," remains a problem for direct optical sensors. This is because skin and water have similar refractive indices in the visible spectrum, namely 1.376 for skin and 1.33 for water, meaning that the critical angles 205 and 206 of the reflected light 204 in both cases are very close. In another embodiment, the high-contrast recording of moist fingers 101 is achieved by completely blocking the reflected light 204 from the interface between water (n = 1.33) and the top layer 401 (e.g., BK7 glass with n = 1.517) by means of a suitably designed contrast aperture 301. In this case, the contrast aperture 301 completely restricts the detection of reflected light 204 up to a corresponding critical angle of the water-to-glass transition (not shown). This angle is approximately...61° (for BK7), while the differential angle range 207 can still be detected. This means that the light cone reflected from the overlying skin ridges 103 has the larger critical angle 206 of approximately 65°, and reflected light 204 is still detected. However, a large portion of the reflected light 204 from the overlying skin ridges 103 is also blocked, and the signal-to-noise ratio decreases. To compensate for this, the illuminance of the illumination light 201 can be increased, for example.

[0069] For this or similar special cases, in a preferred embodiment, two or more differently designed contrast apertures 301 are integrated into one and the same direct optical sensor to enable contrast-optimized imaging of, for example, normal fingers 101, wet fingers 101, and documents 105 with the same device. The designs of the different contrast apertures 301 are optimized for contrast-optimized imaging of objects or in different application scenarios and are arranged alternately in the layer sequence. It is also possible to design certain light-sensitive elements 303 with associated contrast apertures 301 as a sunlight sensor, for example, for detecting the intensity of ambient light. A large protrusion 501 (not shown, see [reference]) Fig. 7a,b) of the contrast aperture 301 to the active area 305 ensures that no oversaturation of the light-sensitive element 303 occurs even at very high ambient light intensity, making it measurable.

[0070] Are different contrast apertures 301 integrated into a direct optical sensor (as in Fig. (5 shown) and because the layer sequence is optimized for different imaging scenarios, the resolution for each individual imaging scenario is consequently reduced, as fewer pixels (ppi) are available per imaging scenario. This can be compensated for by using optical direct sensors with higher resolution (ppi).

[0071] In a process that utilizes two different contrast apertures 301 on the same direct optical sensor, a first image is acquired using a first contrast aperture arrangement designed for high-contrast imaging of normal skin areas (blocking reflected light 204 in a light cone up to an angle of 41° to the perpendicular 208 of the contact surface 102) and a first illumination intensity 201. An image evaluation algorithm assesses the contrast between skin peaks 103 and skin valleys 104. If the contrast value falls below a minimum threshold, a second image is acquired using a second contrast aperture arrangement designed for high-contrast imaging of moist skin areas (blocking reflected light 204 in a light cone up to an angle of 61° to the perpendicular 208 of the contact surface 102) and a second illumination intensity 201. The second image is stored and used for further processing, e.g., B.The data is transmitted to the electronics of a device with the optical direct sensor for comparison with a stored fingerprint. The second luminous intensity of the illumination light 201 is greater than the first luminous intensity of the illumination light 201 in order to ensure a good signal-to-noise ratio, since more light paths of the reflected light 204 are restricted in the second contrast aperture arrangement.

[0072] The inclusion of documents 105 (passports, business cards, driver's licenses, etc.), as they appear in Fig. 5 and Fig. As shown in Figure 6, this poses special challenges for the contrast aperture layer 403, since there is always a thin air gap 106 between the document 105 and the support surface 102, because the surface of a document 105 is not optically coupled to the support surface 102.

[0073] In Fig. 5 is a schematic side view of the device according to Fig. 2a is shown, with the difference that a document 105 instead of a finger 101 lies on the support surface 102 and is picked up.

[0074] The generation of the illuminating light 201 is carried out in this example as in Fig. 2a also consists of point light sources 306, which are arranged within the pixel grid of the sensor layer 406 in the transparent transmission areas 304. To prevent total internal reflection at the contact surface 102 of the top layer 401, the point light sources 306 are equipped with beam-limiting or collimating devices (not shown). When the document 105 is illuminated with illumination light 201, scattering occurs at the surface of the document 105. The light backscattered towards the top layer 401 passes through the air gap 106 between the document 105 and the top layer 401 and enters the layer sequence of the direct sensor via the contact surface 102 as reflected light 204. Due to the air gap 106, the critical angle 205 of the reflected light cone is approximately 41° (when using BK7 as the top layer 401).If the contrast apertures 301 were designed exclusively for the contrast-optimized recording of fingerprints, no documents 105 could be recorded, since reflected light 204 with angles < 41° to the perpendicular 208 of the contact surface 102 would be completely blocked by the contrast aperture 301.

[0075] As described above and in Fig. As shown in Figure 5, the direct optical sensor can have various contrast apertures 301 arranged side by side for specific recording scenarios. In this case, the contrast apertures 301 are alternately arranged side by side for the high-contrast recording of both skin prints (e.g., finger prints 101) and documents 105.

[0076] Furthermore, the sensor electronics can be controlled (only in Fig. (10 shown) between the recording modes using differently designed contrast apertures 301 to read out only half of the light-sensitive elements 303, depending on whether a document 105 or a finger 101 is being recorded.

[0077] In another embodiment, an additional infrared diode and an infrared sensor are used to check before recording whether a finger 101 or a document 105 is approaching the recording surface 102 and the respective recording mode is selected by controlling the corresponding light-sensitive elements 303.

[0078] An image can also be taken with each of the different configurations of the contrast apertures 301. Combining both images is helpful for a liveness detection method, since forgeries interact with the surface differently than, for example, a living finger 101. For instance, when fingerprints printed on paper or foil are placed on the surface, there is no optical coupling with the contact surface 102 (similar to when a document 105 is photographed). The contrast aperture 301, optimized for fingerprints, will therefore prevent the capture of contrast-enhancing reflected light 204. This makes circumventing liveness detection (so-called antispoofing) with a forgery using a fingerprint printed on paper or foil significantly more difficult compared to the solutions described in the prior art, which primarily detect the skin valleys 104.

[0079] A preferred embodiment of the contrast aperture 301 for high-contrast imaging of various objects, fingers 101 and documents 105, is to create a defined passage for a small portion of the reflected light 204 from the interface between air and the cover layer 401, so that this portion is detected by the light-sensitive elements 303. This can be achieved, as shown in Fig. 5 can be seen, achieved by a contrast aperture 301, which has no or only a minimal overhang 505 (not shown here, see e.g. Fig. 8b) to the active area 305 of the light-sensitive element 303.

[0080] In a particularly preferred embodiment, the projection 501 of the contrast aperture 301 is optimized for the high-contrast recording of skin areas and at the same time a hole 507 [not shown here, see but Fig. 9, Partial view (l)] above the active area 305 of the light-sensitive element 303 in the contrast aperture 301, which additionally enables the capture of documents 105. An advantage of this embodiment is that the resolution of the document capture is high, since only reflected light 204 is detected, which strikes the light-sensitive element 303 perpendicularly. This prevents information from one object point from being detected in several light-sensitive elements 303. The small opening in the contrast aperture 301, which is in Fig. 9 (l) is only shown as hole 507, can instead also be in the form of a square or other equilateral polygons or slots, preferably in a crossed position relative to each other.

[0081] As described above, the diode aperture layer 405 defines the size and shape of the active area 305 of the photosensitive element 303 by covering peripheral parts of the photosensitive element 303 with the diode aperture 302.

[0082] Another design of the direct sensor with adaptations for document capture 105 is in Fig. Figure 6 is shown as a schematically abbreviated section. Two light-sensitive elements 303 are shown, which, unlike in Fig. 5 do not have a diode aperture layer 405 and are therefore shaded by a completely covering contrast aperture 301. In this case, the illumination of the document 105 is provided by an illumination layer 409, which emits diffuse illumination light 201. This light is collimated and aligned by the air layer 408 present between the substrate 407 and the substrate 407 in the direction of the contact surface 102 of the cover layer 401 to such an extent that at least total internal reflection at the contact surface 102 is avoided. The illumination light 201 illuminates the document 105 in the same way as in the previous case. Fig. 5 described, and scattering occurs at the surface of document 105. The scattered light 203 passes through the air gap 106 between document 105 and cover layer 401, enters the cover layer 401 via the contact surface 102 and, due to the air gap 106, is largely blocked by the contrast aperture 301 as remitted light 204 with a critical angle 205 of approximately 41° in the layer sequence. As a result of a minimal overhang 505 of the contrast aperture 301 relative to the unrestricted light-sensitive element 303 (i.e., with a large active area 305 of the light-sensitive element 303), only scattered light components that occur almost parallel to the perpendicular 208 of the contact surface 102 are blocked, and all obliquely incident reflected light 204 can be recorded pixel by pixel by the sensor layer 406 to capture the document 105.

[0083] In this example, the active area 305 is exactly the same size as the light-sensitive element 303. In a preferred embodiment, see Fig. 6, the contrast aperture 301 shades the light-sensitive element 303 so that no light is detected which is remitted orthogonally to the contact surface 102 into the layer sequence, thus enabling the recording of both documents 105 and skin prints.

[0084] A smaller contrast aperture 301 would, for the reasons already described above, lead to a deterioration of the contrast between skin peaks 103 and skin valleys 104. A larger contrast aperture 301 with a defined overhang 501 to the active area 305 is also not recommended in this case, since this would cause the transmission areas 304 of the sensor layer 406 to be overlapped by the non-transparent contrast aperture 301, and the light path of the illumination light 201 on its way to the contact surface 102 would be partially blocked.

[0085] In Fig. Figure 7a schematically illustrates an embodiment of diode aperture 302, active area 305, and contrast aperture 301 for contrast-enhanced recording of skin impressions in a top view. Fig. In the corresponding top view in Figure 7a, the active area 305 is shown with a dashed line. The contrast aperture 301 and the diode aperture 302 are shown with solid lines, with the contrast aperture 301 also having hatching. Where the arrangement of the contrast aperture 301 and diode aperture 302 and the active area 305 exhibits symmetries, corresponding axes of symmetry 506 are shown. An example is shown in Fig. 7a A possible axis of symmetry 506 of the depicted arrangement is shown as a dashed line. The arrangement can be uniquely described in the top view via the xy-plane. The layer sequence of Fig. 7a is described by the yz-plane and is based on the explanations to Fig. 1 in Fig. 7b is shown in a section through the yz-plane as a side view. Fig. Figure 7b shows an additional adhesive layer 402, with which the optical coupling of the cover layer 401 to the underlying layer sequence of the device is carried out by adapted refractive index transitions.

[0086] Further advantageous and particularly preferred embodiments of the contrast aperture 301 and the active area 305 are presented and described below. The layer sequence corresponds to one of the [references to be added]. Fig. 1, Fig. 2a, Fig. 2b, Fig. 3, Fig. 5, Fig. 6 or Fig. The configurations described in 7a are therefore not shown in the following figures, which is why side views are omitted. The embodiments in Fig. 8a to 8d and in Fig. 9. Partial figures (a) to (o) are shown in top view and define, by means of the dashed and solid lines, the unique assignment between the active area 305, limited by the diode aperture 302, and the contrast aperture 301. The embodiments differ in their symmetry, the orientation of the contrast aperture 301 and the active area 305 relative to each other, the geometric shapes and sizes of the surfaces, as well as additional structuring.

[0087] In Fig. Figures 8a-d schematically depict four embodiments of the contrast aperture 301 and the active area 305 in a top view of a light-sensitive element 303 of the direct optical sensor. In all embodiments, the diode aperture 302 and the contrast aperture 301 are shown with solid lines, the active area 305 with a dashed line, and the axes of symmetry 506 with dashed-dotted lines. The contrast aperture 301, which also has hatching, has in all embodiments at least the same area as the active area 305 and at most the same area as the diode aperture 302 or the light-sensitive element 303.

[0088] Fig. Figure 8a shows a square contrast aperture 301 and a square active area 305. The surface shapes are geometrically identical. Furthermore, the surfaces are arranged parallel with the same orientation in the sense of a central projection, meaning that the contrast aperture 301 lies symmetrically over the active area 305. The projection 501 of the contrast aperture 301 is larger than in Fig. 1 and are of the same size in both dimensions of the pixel grid (x and y dimensions). This means that the contrast aperture 301 has an equally large projection 501 on each of the four sides of the square active area 305. The embodiment in Fig. 8a also has four axes of symmetry 506, around which the arrangement can be mirrored.

[0089] In Fig. In section 8b, contrast aperture 301 and active area 305 also have geometrically similar surface shapes. Geometrically similar surface shapes include, for example, squares and rectangles, or circles and ellipses. Fig. 8b the contrast aperture 301 also has a recessed sector in the form of a notch 502. The notch 502 is defined by the notch angle 503 and the notch depth 504, which results in a reduced minimum projection 505 of the contrast aperture 301 to the active area 305 at the position of the notch 502.

[0090] Fig. Figure 8c shows a round contrast aperture 301 with a recessed sector in the form of a notch 502 and an active area 305 with a circular surface. In this arrangement, the projection 501 is the same size at all points except for the recessed sector, due to its circular shape. As in Fig. 8b The notch 502 is defined by the notch angle 503 and the notch depth 504, which can be freely selected when manufacturing such an embodiment. In this case, no minimal projection 505 remains at the position of the notch 502, but rather a portion of the active area 305 is left uncovered, allowing reflected light 204 to enter perpendicularly in this area, which can be used to receive documents 105 as security-relevant objects.

[0091] Both in Fig. 8b as well as in Fig. 8c and Fig. In 8d, the arrangement has only one axis of symmetry 506 with respect to the notch 502.

[0092] In Fig. Figure 8d shows a further embodiment of the invention, which is a modification compared to Figure 8d. Fig. 8b and Fig. 8c represents. Here, the recessed sector is shown with a square contrast aperture 301 over a square active area 305. As in Fig. In 8c, the notch 502 is removed up to and including the active area 305, thus eliminating the otherwise uniform protrusion 501 in all directions, such that the area of ​​the contrast aperture 301 and the area of ​​the cover of the active area 305 are reduced by one quarter. This design of the light-sensitive element 303, viewed from the direction of the contact surface 102, is particularly suitable for taking high-contrast images of both skin prints (e.g., fingers 101) and documents 105 by covering approximately 75% of the active area 305. The portion of the reflected light 204 that strikes the active area 305 orthogonally to the contact surface 102 can therefore be detected for the purpose of capturing documents 105.

[0093] Fig. Figure 9 shows in its partial figures (a) to (o) preferred embodiments for the design of the contrast apertures 301 and the active area 305. These are shown only in top view, since the layer sequence is the same as in Fig. 1. In all embodiments, the contrast aperture 301 and the diode aperture 302 are represented by a solid line, the active area 305 by a dashed line, and the axes of symmetry 506 by a dashed-dotted line. The contrast aperture 301, which additionally features hatching, has in all embodiments at least the same area as the active area 305 and at most the same area as the diode aperture 302 or the light-sensitive element 303.

[0094] In Fig. Figure 9 shows partial illustration (a) the same embodiment of the contrast aperture 301, which is already shown in Fig. As shown in Figure 8a and described above, the larger the projection 501 of the contrast diaphragm 301 is selected, the smaller the angular range of the reflected light 204 that is detected in the active area 305. This means that a certain portion of the reflected light 204 is not detected, with the light 204 reflected from air into the layer sequence being blocked more strongly than light reflected from skin into the layer sequence. This significantly improves the contrast between skin peaks 103 and skin valleys 104. To achieve the problem according to the invention and to optimize the contrast between skin peaks 103 and skin valleys 104, the projection 501 of the contrast diaphragm 301 is increased in a particularly preferred embodiment until only reflected light 204 with angles larger than the critical angle 205 from the air-glass interface (approx. 41°) can be detected.The required overhang 501 depends primarily on the refractive index of the cover layer 401 and the thickness of the spacer layer 404. The refractive index of the cover layer 401 defines the critical angle 205 or 206 of the reflected light 204. The required overhang 501 for blocking reflected light from 0° up to a certain critical angle 205 to the perpendicular 208 of the contact surface 102 becomes smaller the thinner the spacer layer 404 is. For example, if the refractive index of the cover layer 401 is n = 1.517 (BK7 glass) and the thickness of the spacer layer 404 is d = 10 µm, a minimum overhang 505 of 8.7 µm is necessary to block remitted light 204 at angles < 41° to the normal 208 of the contact surface 102 and thus not detect light from the skin valleys 104.

[0095] This is calculated using the following formula a=d⋅tan α, where a is the minimum overhang 505 and α denotes the angle of the remitted light 204 to the perpendicular 208 of the support surface 102.

[0096] To determine the minimum superelevation 505 for high-contrast imaging of moist fingers 101, only the critical angle of reflected light 204 from the water interface to the top layer 401 (α = 61°) needs to be entered into the formula described above. Under the same conditions as above (d = 10 µm and n = 1.517), a required superelevation 501 of α = 18 µm results to restrict and prevent detection of the light paths of the light 204 reflected from water into the layer sequence from 0° to the corresponding critical angle of 61° to the perpendicular 208 of the contact surface 102.

[0097] One advantage of direct optical sensors is their ability to capture both skin prints (e.g., from fingers 101) and documents 105. Since a placed document 105 does not form an optical coupling with the contact surface 102, and there is usually an air gap 106 between the document 105 and the contact surface 102, the reflected light 204 from a document 105 has a critical angle 205 of approximately 41°. If the active area 305 can no longer detect reflected light 204 from the air-glass interface due to the contrast aperture 301, documents 105 cannot be captured with such a direct sensor. Consequently, it is helpful to choose the design of the contrast aperture 301 in such a way that at least some of the reflected light 204 from the air-glass interface can still be detected in order to still allow the recording of documents 105, such as passports, driving licences, business cards, etc.

[0098] This shows that the specific application defines the actual design of the contrast aperture 301, for example, to enable the recording of various security-relevant objects, including documents 105, to efficiently design the image formation processes with regard to the required light intensity of the illumination 201, or to optimize the contrast for recording a specific object. For example, if the projection 501 of the contrast aperture 301 is made of Fig. 9, partial figure (a) is chosen such that the critical angle 206 from the skin-glass interface (approx. 65°) can just be detected. While the contrast when recording skin impressions is very good, the overall detectable light intensity per light-sensitive element 303 is greatly reduced. To compensate for the loss of light intensity and improve the signal-to-noise ratio, the light intensity of the illumination light 201 must therefore be increased. However, particularly in the field of mobile applications, an efficient, energy-saving design of the device is advantageous, for example, to increase the battery life of a device with the device according to the invention.

[0099] In Fig. Figures 9 (b), (c), and (d) schematically illustrate further embodiments of contrast apertures 301 and active areas 305. Figures (b), (c), and (d) depict embodiments in which round (preferably circular) surfaces are used for both the contrast aperture 301 and the active area 305, but also square or similar surface shapes of the contrast aperture 301 are combined with round (circular) surfaces of the active area 305 or vice versa, as shown in Figure 9. Fig. 9 shown in sub-figures (c) and (d).

[0100] In sub-figure (b) of Fig. Figure 9 shows a particularly preferred embodiment in which both the active area 305 and the contrast aperture 301 are round, and thus the overhang 501 is parallel to the sensor layer 406 in all directions, and therefore the light blocking is the same in all directions.

[0101] In mobile applications (e.g., use in mobile phones, tablets, etc.), there is also a need for sufficiently thick cover layers 401, as these guarantee improved mechanical and chemical protection for the direct sensor. However, increasing the distance between the sensor layer 406 and the contact surface 102, for example by using a thicker cover layer 401, results in information from a single object point being detected simultaneously in several light-sensitive elements 303. This leads to a reduction in contrast and resolution. Since in the solution according to the invention light 204 emitted from the skin mounds 103 is preferably detected, i.e. light from the difference angle 207 between the critical angle 205 of the air-surface layer transition (41° for BK7) and the critical angle 206 of the skin-surface layer transition (65° for BK7), the same object information already reaches at least two light-sensitive elements 303 from an object-to-sensor distance of less than 25 µm.

[0102] In a preferred embodiment of the contrast aperture 301, as described in Fig. As can be seen in partial figure (e), increasing the thickness of the cover layer 401 simultaneously achieves high contrast and high resolution. The contrast diaphragm 301 is arranged such that only a portion of the light cone of the scattered light 203 generated by the skin is detected as reflected light 204 in the active area 305 of the photosensitive element 303. For this purpose, the contrast diaphragm 301 is arranged asymmetrically as a rectangle above the active area 305.The contrast aperture 301 has such a large overhang 501 in three directions that the light 204 (not shown here) reflected from the finger 101, which would fall on the active area 305 from three directions, is completely blocked, and shows a minimal overhang 505 in a fourth direction of the pixel grid (which can also approach zero), so that only obliquely incident light from the fourth direction can pass through the contrast aperture 301 at the minimal overhang 505 and is detected in the active area 305 of the light-sensitive element 303.

[0103] Here too, as described above, the more light paths are restricted in favor of good contrast and resolution, the greater the illuminance of the illumination light 201 must be to achieve a good signal-to-noise ratio. For this reason, it can be advantageous if the contrast aperture 301 has no or only a minimal projection 505 in one direction, as shown in partial figure (e) of Fig. 9 illustrated.

[0104] Fig. Figure 9 shows a preferred embodiment in which the contrast aperture 301 has a large projection 501 only in two directions of the pixel grid offset by 90°, so that no light reaches the active area 305 from these directions. In the other two directions, the contrast aperture 301 has a minimal projection 505, which can approach zero. The advantage of this embodiment is that the resolution or the CTF (contrast transfer function) is improved equally well in the vertical and horizontal directions.

[0105] Partial image (g) of Fig. Figure 9 shows an embodiment in which the shape and area of ​​the active area 305 define the projection 501 of the contrast aperture 301. The active area 305 has been reduced to a specific area where reflected light 204 can still strike every point of this area. By reducing the area of ​​the active area 305, the detection of interfering stray light 203 propagating between the diode aperture 302 and the contrast aperture 301 is reduced. This leads to a further improvement in contrast.

[0106] The contrast aperture 301 and the active area 305 can, in principle, have a free shape and do not necessarily have to be a square, rectangle, or circle. Further preferred variants of the arrangement of contrast apertures 301 are described in Fig. 9 shown in the partial figures (h), (i), (j), (k) and show that the contrast apertures 301 may also have recesses in the form of notches 502 (slits, slots or similar).

[0107] In Fig. Figure 9 shows a partial figure (h) of an embodiment in which the contrast aperture 301 is designed such that it has a large projection 501 in three directions offset by 90° within the contrast aperture layer 403 and a minimal projection 505 in the fourth direction, which is described by a notch 502 with a defined notch angle 503 and a defined notch depth 504. The smaller the notch angle 503, the more the resolution is improved, since a smaller angular range of the reflected light 204 is detected. The larger the notch depth 504 or the smaller the minimal projection 505, the greater the detected light intensity, but the additional absorption of scattered light 203 from the skin areas (skin valleys 104) in contact with the aperture 106 also reduces the contrast between skin peaks 103 and skin valleys 104.

[0108] The partial images (i), (j), (k) of Fig. Figure 9 shows particularly preferred embodiments with square or round surface shapes, in which the contrast aperture 301 has a notch 502 above a corner of the light-sensitive element 303. The advantage of these embodiments is that the resolution is improved uniformly in two dimensions (x and y dimensions of the pixel grid), since the axis of symmetry 506 of the arrangement runs at exactly 45° in the xy plane of the pixel grid. Resolution and contrast can be significantly improved with such embodiments. In a simplified design of Fig. Figure 9, sub-figure (k), describes the recess as the surface shape of a slice of cake, as already shown in Figure 9 as a geometrically complete circular sector. Fig. Figure 8c shows the notch 502 in subfigure (k) of the diagram. Fig. 9 does not extend beyond the active area 305, leaving a minimal overhang 505 (not shown here) of the contrast aperture 301, and the active area 305 is completely covered. The pie-slice-shaped recess is then defined by a notch depth 504 (only in Fig. 8b-8d) described, which in partial figure (k) corresponds approximately to half the radius of the contrast aperture 301. An advantage of such a design is the simple geometry and improved contrast in skin images, whereas the design of the notch 502 according to Fig. 8c with a notch depth of 504, which opens part of the coverage of the active area 305, enables high contrast image capture of both fingers 101 and documents 105.

[0109] In the partial illustration (l) of Fig. Figure 9 shows a contrast aperture 301 with a hole 507 above the active area 305. As described above, the contrast aperture 301 can have recesses, for example holes 507 or slots 508, to detect portions of reflected light 204 from the interface between air and the cover layer 401 and to enable high-resolution imaging of documents 105. The position of the local recess on the contrast aperture 301 above the active area 305 is arbitrary. This recess primarily serves to enable high-resolution and high-contrast imaging of documents 105 without significantly impairing the contrast of a skin area of ​​a finger 101 imaged with the same configuration. Naturally, the embodiment shown in partial figure (1) can also be combined with the previously described embodiments of the contrast apertures 301.

[0110] Furthermore, a recess in the contrast aperture 301, such as a slit 508 or a hole 507, can be used in other configurations to homogenize the illumination of the active areas 305 of the light-sensitive elements 303, as shown in Fig. 9 shown in the sub-figures (m), (n), (o).

[0111] During aperture manufacturing, for example using photolithographic processes, production tolerances can occur, causing variations in the positioning between the contrast aperture 301 and the active area 305. To compensate for the resulting inconsistencies in the sensitivities of the pixels 307 relative to each other, a large distance between the contrast aperture 301 and the active area 305 is advantageous, achieved by means of a thick spacer layer 404. The spacer layer 404 therefore preferably has a thickness between 0.5 µm and 50 µm; a thickness in the range of 1 µm to 10 µm is particularly preferred, as mentioned above. However, longer processing times must be planned for a thicker spacer layer 404, which is why this approach can be expensive.

[0112] Further measures to compensate for positional inaccuracies of the aperture layers, contrast aperture layer 403 and diode aperture layer 405, arising during the manufacturing process, are described in Fig. 9 shown in partial figures (m), (n), (o) and lead to improved insensitivity to positional deviations of the aperture layers. These arrangements show recesses as hole 507 or slot 508, which – unlike partial figure (l) of Fig. 9 - not located above the active area 305. The active area 305 therefore only detects light that enters obliquely through the recesses of the contrast aperture 301. The arrangement of the contrast apertures 301 defines a first minimum angle and a second maximum angle of the reflected light 204, between which reflected light 204 can be detected in the active area 305. Preferably, the recessed area of ​​the contrast aperture 301 is designed such that only reflected light 204 with angles between 60° and 35° to the perpendicular 208 of the support surface 102, and particularly preferably between 55° and 51°, is detected. This makes the sensitivity of the photosensitive elements 303 more uniform if manufacturing inaccuracies are present. As described above, this can also be implemented with different geometric surface shapes of the contrast aperture 301, the active area 305 and the recess of the contrast aperture 301.

[0113] The contrast panels 301, which are in Fig. 9, shown in the sub-figures (m), (n), allow slightly additional angles of incidence from which light can be detected and limit these to a narrow area along the drawn axis of symmetry 506, thereby achieving an additional contrast and resolution-enhancing effect for document 105.

[0114] Those skilled in the art will recognize that, in addition to the described embodiments, further possible arrangements exist to solve the problem according to the invention. Any combination of the different embodiments allows the optimization of the device for certain application scenarios not described here.

[0115] To achieve a contrast-enhancing effect when capturing skin prints, the active area 305 of the light-sensitive element 303 – viewed from the direction of the contact surface 102 – must be at least 60% covered by the respective associated contrast aperture 301. For a significant improvement in contrast when capturing skin prints, this coverage should be at least 75%, preferably 90%. With complete coverage (100%), the contrast when capturing skin prints is further improved, while the capture of documents 105 is still possible with sufficient quality. If there is a protrusion 501 of the contrast aperture 301 onto the active area 305, the contrast of skin prints is optimized, but documents 105 can no longer be captured with sufficient quality without further measures (at least singular cutouts).

[0116] In Fig. Figure 10 schematically illustrates the complete integration of the device according to the invention into a mobile device in side and top views. A mobile device can be, for example, a mobile phone 308 or a tablet, into which—in addition to an electronic layer 410 with the usual electronic components (e.g., Wi-Fi, battery, RFID, USB, CPU, etc.)—the device according to the invention is integrated, whereby the top surface of the mobile phone 308 is sealed with the cover layer 401 of the device according to the invention, and objects placed on the resulting contact surface 102, such as one or more fingers 101 and / or a document 105, can be captured in high quality, i.e., with good contrast (> 50%) and high resolution (≥500 ppi).For high-quality images, the corresponding embodiments of the contrast aperture 301 described above are used in combination with suitably designed active areas 305 of the light-sensitive elements 303.

[0117] The integration of the direct optical sensor with the layer sequence already described in the previous figures takes place on areas of the display surface of the mobile device, and particularly preferably on the entire display surface. For this purpose, the display for showing user information and emitting illumination light 201 is located below the layer sequence of the direct optical sensor. Particularly preferably, the display is implemented in the form of point light sources 306, which are integrated into the sensor layer 406 between the light-sensitive elements 303. All explanations relating to the drawings are provided below. Fig. 2a, Fig. 2b and Fig.5 are applicable and relevant. Due to the reduced thickness of the layer sequence of the direct optical sensor achievable with this design variant, the mobile phone 308, selected as an exemplary representative of any mobile device, can also be implemented in a flat design overall. Reference symbol list 101 fingers 102 contact area 103 Skin ridge (papillary ridge) 104 Skin valley (papillary valley) 105 documents 106 Air gap (in the skin valley, under document) 201 Lighting light 202 Stray light 203 Scattered light in the direction of the contact surface 204 (remitted) light 205 Limit angle (air-to-surface layer) 206 Critical angle (skin-to-cover layer) 207 Differential angle range 208 Perpendicular to the bearing surface 301 Contrast aperture 302 Diode aperture 303 light-sensitive element 304 Passage area 305 active area 306 Point light source 307 pixels 308 mobile phone 401 Top layer 402 Adhesive layer 403 Contrast aperture layer 404 spacer layer 405 Diode aperture layer 406 Sensor layer 407 Substrat 408 Air layer 409 Illumination layer 410 Electronic layer 411 (full-surface) spectral filter layer 412 (structured) spectral filter layer 501 Overhang 502 Notch 503 Notch angle 504 Notch depth 505 minimum overhang 506 Axis of symmetry 507 holes 508 slots

Claims

Device for direct optical recording of security-relevant objects, such as at least skin impressions, comprising a layer sequence: - a cover layer (401) with a contact surface (102) for a security-relevant object (101, 105), - an aperture layer with non-transparent and transparent areas (304) for limiting the angles of incidence of light that is remitted from the object (101, 105) through the contact surface (102) into the layer sequence, - a sensor layer (406) with pixels (307) arranged in a two-dimensional grid, each pixel having a light-sensitive element (303) and a transparent transmission area (304), wherein the light-sensitive elements (303) can only detect light coming from the direction of the contact surface (102) and each light-sensitive element (303) of the sensor layer (406) is assigned exactly one aperture of the aperture layer.- a substrate (407) as a carrier of the layer sequence and - an illumination layer (409) for emitting illumination light (201) which illuminates the object (101, 105) through the contact surface (102), characterized in that - the aperture layer is designed as a contrast aperture layer (403) with contrast apertures (301) for a predominant transmission of light which is reflected from parts of the object (101, 105) resting on the contact surface (102) without an air gap (106), wherein ◯ each contrast aperture (301) is designed as a non-transparent area of ​​the contrast aperture layer (403) and has a distance to the associated light-sensitive element (303) which is defined by means of a spacer layer (404) of selectable thickness between the sensor layer (406) and the contrast aperture layer (403),and◯ the contrast diaphragm (301) assigned at a distance from the light-sensitive element (303) has a non-transparent area above the light-sensitive element (303) which is at least as large as an active area (305) of the light-sensitive element (303) and is arranged such that reflected light (204), which falls on the light-sensitive element (303) at small angles of incidence from both object parts (103) resting without an air gap (106) and object parts (104) resting with an air gap (106),by means of the non-transparent contrast diaphragm (301) for the light-sensitive element (303) is largely blocked and only an excess proportion of remitted scattered light (204) from parts (103) of the object (101) resting without an air gap (106) is permitted for detection in the light-sensitive element (303) within a differential angle range (207) with large angles of incidence, and the illumination layer (409) contains a plurality of point light sources (306) which emit in the direction of the contact surface (102) within such a limited angular range as to suppress total internal reflection at the contact surface (102) of the cover layer (401). Device according to claim 1, characterized in that the associated contrast aperture (301) is arranged above the light-sensitive element (303) such that, viewed from the direction of the support surface (102), an active area (305) of the light-sensitive element (303) is covered to at least 75%, preferably at least 90%. Device according to claim 1, characterized in that the associated contrast aperture (301) is arranged above the light-sensitive element (303) such that, viewed from the direction of the support surface (102), the active area (305) of the light-sensitive element (303) is completely covered. Device according to one of claims 1 to 3, characterized in that the top layer (401) is designed as the transparent substrate (407) for the entire layer sequence. Device according to one of claims 1 to 4, characterized in that the contrast aperture (301) above the light-sensitive element (303) is designed such that the contrast aperture (301) has a projection (501) towards the active area (305) in at least two directions of the pixel grid offset by 90°. Device according to one of claims 1 to 5, characterized in that the contrast aperture (301) has a geometrically similar surface parallel to the active area (305) of the light-sensitive element (303) with the same orientation in the sense of a central projection. Device according to one of claims 1 to 5, characterized in that the contrast aperture (301) and the active area (305) of the light-sensitive element (303) have parallel, geometric surfaces with different shapes. Device according to one of claims 1 to 7, characterized in that the surfaces of the contrast apertures (301) have a projection (501) relative to the active areas (305) of the light-sensitive elements (303), the size of which is adjusted depending on the refractive index of the cover layer (401), the distance of the contrast apertures (301) above the light-sensitive elements (303) and the shape of the contrast aperture (301) and the active area (305) of the light-sensitive element (303). Device according to one of claims 1 to 8, characterized in that the contrast aperture layer (403) has two or more different contrast apertures (301) alternately and offset from each other in a grid corresponding to the pixel grid over the active areas (305) of the light-sensitive elements (303) in order to be able to realize different recording modes for recordings of different security-relevant objects. Device according to one of claims 5 to 9, characterized in that the contrast aperture (301) has an equal protrusion (501) relative to the active area (305) of the light-sensitive element (303) in three directions offset by 90° within the contrast aperture layer (403) and a smaller protrusion (505), which can approach zero, in a fourth direction offset by 90°, in order to achieve a higher resolution image and to improve the image capture of documents (105) as security-relevant objects. Device according to one of claims 5 to 9, characterized in that the contrast aperture (301) has an equal protrusion (501) to the active area (305) of the light-sensitive element (303) in two directions offset by 90° within the contrast aperture layer (403) and a smaller protrusion (505), which can approach zero, in two directions opposite to the two directions offset by 90°, in order to achieve a recording with the same increased resolution in two dimensions and to improve the recording of documents (105) as security-relevant objects. Device according to one of claims 1 to 11, characterized in that the distance between the contrast apertures (301) above the light-sensitive elements (303) is adjustable in a range from 0.5 µm to 50 µm. Device according to one of claims 1 to 12, characterized in that the illumination layer (409) is designed as a large-area backlight coupled to the layer sequence below the sensor layer (406) with an intermediate layer or an air layer (408). Device according to one of claims 1 to 12, characterized in that the illumination layer (409) within the sensor layer (406) is designed as point light sources (306) arranged singularly offset in the transmission areas of the pixels (307) and equipped with beam-limiting apertures. Device according to one of claims 1 to 14, characterized in that the contrast aperture layer (403) is designed for a predominant transmission of light that is reflected from parts (103) of the object (101) resting on the support surface (102) without an air gap (106), and an additional, small proportion of light that is reflected from parts (104) resting on the support surface (102) with an air gap (106).105) of the object (101, 105) is formed, wherein the respective associated contrast aperture (301) is arranged above the light-sensitive element (303) such that - viewed from the direction of the support surface (102) - the active area (305) of the light-sensitive element (303) is completely covered, and the contrast aperture (301) has a recess (502, 507, 508) within an area covering the active area (305) such that in the area of ​​the recess (502, 507, 508) an additional small proportion of predominantly perpendicular incident light can be received in order to improve the contrast when taking pictures of documents (105). Device according to claim 15, characterized in that the recess in the contrast aperture (301) is a recess (502, 507, 508) in the form of a circular hole, oblong hole, slot, notch, sector or other shaped cutout within the surface of the contrast aperture (301) covering the active area (305) of the light-sensitive element (303). Device according to claim 15, characterized in that the recess (502, 507, 508) in the contrast aperture (301) is a recess (502, 507, 508) in the form of a circular hole, oblong hole, slot, notch, sector or other shaped cutout provided in a projection (501) of the contrast aperture (301) to the active area (305).

Images