Optical image recording device

Abstract

An optical image acquisition device (1) is described comprising an image acquisition unit (6, 6a, 6b, 6c) designed for capturing images of an object (4) arranged on the surface of a microscope slide (3), and an illumination unit comprising several illumination elements (5) oriented to illuminate the surface of the object (4). The illumination elements (5) are arranged on a circumference that at least partially surrounds the object (4), with each illumination element (5) having a beam angle orientation of the light incident on the surface of the microscope slide (3) that differs from that of the other illumination elements (5).

Description

[0001] The invention relates to an optical image recording device with an image recording unit designed for recording images of an object arranged on a surface of a slide, and with a lighting unit having several lighting elements oriented to illuminate the surface of the object.

[0002] DE 10 2008 027 904 A1 discloses a device for detecting surface defects of a curved surface of an object with an image acquisition device and a lighting device, which is controllable in such a way that the object can be subjected to controlled area-specific dark-field illumination.

[0003] DE 42 04 843 A1 discloses a method for determining the volume, shape, and weight of illuminated objects, such as fish, arranged on a conveyor belt. A first series of images of the fish's outline is captured with a camera while the fish passes under the camera. Simultaneously with the capture of the first series of images, a second series of reflected images of the fish's outline is captured from a direction substantially perpendicular to both the capture direction of the first series of images and the direction of movement of the conveyor belt. Subsequently, the volume of the fish and / or its weight is calculated in a microprocessor based on the received image data and previously input data.The device designed for this purpose has a mirror that is arranged to the side of the conveyor belt in such a way that the camera captures the same section of the conveyor belt with the reflected images as it is directly aimed at.

[0004] Based on this, the object of the present invention is to create an improved optical image recording device.

[0005] The problem is solved by the optical image acquisition device with the features of claim 1. Advantageous embodiments are specified in the dependent claims.

[0006] It is proposed that the lighting elements be arranged on a perimeter that at least partially surrounds the object, with each lighting element having a beam angle orientation of the light impact angle on the object surface or the surface of the microscope slide that differs from the other lighting elements.

[0007] When illuminating curved objects (e.g., fish), it is essential to achieve the most uniform illumination possible across the body. Therefore, the geometric shape of the lighting system is designed to closely resemble the shape of the object, for example, tunnel-like. With conventional lighting, wet objects typically produce undesirable reflections. Curvature of the body further exacerbates these reflections. Since these reflection areas contain no intensity information in the images captured by the camera system due to overexposure, rendering them unusable for further image analysis, reflections should be suppressed as much as possible. This can be achieved through a special arrangement of individual lighting segments adapted to the shape of the object, e.g.,As a lighting tunnel with an integrated recess for the image-capturing camera system, and with diffused lighting, it is possible to almost completely avoid the formation of reflections in the camera images. The diffused lighting can be achieved by surface-illuminating lamp segments (LED panels with a diffuser disc).

[0008] A lighting element can have one or more light sources, such as a light-emitting diode or a group of light-emitting diodes (LEDs), which are arranged, for example, in a row or matrix.

[0009] The different beam angle orientations can be aligned according to the outline of a specific object type for illumination and image capture. This largely avoids reflections.

[0010] The image acquisition device can have a tunnel-shaped housing that at least partially surrounds the surface of the slide and any object placed on it. The illumination elements can be arranged adjacent to each other on the inner wall surfaces of the tunnel-shaped housing. This allows for illumination adapted to a curved surface with extensive shielding from ambient light.

[0011] The lighting elements can form the wall surfaces of the tunnel-shaped housing along its radially outward-facing perimeter. The image acquisition elements can be arranged within these wall surfaces of the tunnel-shaped housing.

[0012] A group of lighting elements can form a common lighting intersection point. This focuses the lighting onto a single point and ensures different angles of incidence, largely avoiding unwanted reflections.

[0013] The lighting elements can be fanned out onto the surface of the slide to emit light at different beam angles.

[0014] The inner wall of the tunnel-shaped housing can have individual lighting elements arranged side by side and spaced apart from each other, and offset from each other in the beam angle to the object or to the surface of the slide.

[0015] Several lighting elements can be combined in a single lighting panel. This allows for larger wall areas to be covered with lighting elements contained within a single module, which emit light onto a curved surface at different angles of incidence.

[0016] At least one of the lighting elements can be designed for diffuse illumination. It is advantageous if the areas between the lighting elements and the entrance surfaces to the tunnel of the tunnel-shaped housing are equipped on their inner surfaces with elements that reflect well light towards the object.

[0017] The lighting elements or lighting panels can each form a module consisting of a light source, control electronics, cooling unit and cover disc, for example a diffuser disc and / or polarizing filter.

[0018] The lighting elements can be controlled independently of each other. This allows the lighting itself to be adapted to changing conditions during transport of the curved object beneath the lighting element, e.g., variations in the object's height and contour, in order to counteract disruptive reflections. It is advantageous if the lighting elements can be reprogrammed to suit the situation during measurement.

[0019] There can be several groups of lighting elements, each group designed to illuminate the object with at least one specific wavelength that differs from the specific wavelengths of the other groups. This allows the lighting to be adapted to the prevailing conditions by using different wavelengths, in order to compensate for adverse lighting effects.

[0020] The lighting elements can be arranged in a radius of at least 180° to 360° around the microscope slide.

[0021] The image acquisition unit can be a line scan camera or a recording technique that captures only one or a few lines per image. This image acquisition unit can be aligned with its field of view or recording field through a gap between lighting elements or panels, or positioned within that gap. Alternatively, the image acquisition unit could be a matrix camera configured to read out a region of interest (ROI), where a single line can be read out as the ROI.

[0022] Each image acquisition unit can be assigned a laser triangulation sensor whose laser plane coincides with the acquisition plane of a line captured by the image acquisition unit. It is advantageous if the illumination elements and the laser planes for the triangulation sensors can be controlled independently of each other.

[0023] The slide can, for example, be a conveyor belt on which the objects are transported in one direction under the lighting units and the image acquisition unit.

[0024] The optical image recording device can be set up for use in the quality inspection of fish or meat products conveyed on the conveyor belt as objects.

[0025] The conveyor belt can have a conveyor belt gap, wherein in the area of ​​the conveyor belt gap a first group of upper lighting elements, which are arranged to illuminate the top of the conveyor belt carrying the object, and a second group of lower lighting elements, which are arranged to illuminate the underside of the conveyor belt, which is opposite the top of the conveyor belt carrying the object, are arranged and the first group is offset relative to the second group in the longitudinal direction of the conveyor belt.

[0026] This staggered lighting arrangement with upper and lower lighting elements is suitable for a 360° camera lighting system. The lighting tunnel can consist of upper and lower halves of lighting elements with intermediate viewing slots for the image acquisition units, such as line scan cameras. These camera-lighting system halves are not arranged vertically one above the other at the belt gap, but rather offset along the conveyor belt. They can be offset from each other in such a way that the upper half of the camera-lighting tunnel is positioned directly in front of the belt gap, allowing a camera view of the conveyor belt. This achieves better and easier segmentation of the object against the background of the conveyor belt than against the belt gap itself, thanks to lighting that extends into the gap.The lower half of the camera lighting tunnel is positioned centrally beneath the belt gap and receives a brightly illuminated background from the upper tunnel lighting, as seen by the lower camera(s). The viewing planes of the upper and lower camera units are thus parallel to each other along the conveyor belt at the edge of the belt gap. To prevent contamination and facilitate the drainage of dirty and cleaning water, the lower half of the tunnel lighting can be divided in the center at the bottom to create a drainage channel.

[0027] When using a surround-view camera lighting system, care should be taken to integrate mechanisms, especially for the areas below the conveyor belt, particularly in the case of a belt gap, that both prevent or minimize contamination and enable or include cleaning.

[0028] The conveyor belt can have a conveyor belt gap, wherein in the area of ​​the conveyor belt gap a first image acquisition unit for capturing images of the top of the conveyor belt carrying the object and a second image acquisition unit for capturing images of the underside of the conveyor belt, which is opposite the top of the conveyor belt carrying the object, are arranged and the first image acquisition unit is offset relative to the second image acquisition unit in the longitudinal direction of the conveyor belt.

[0029] By adjusting the lamp design or the orientation of the lighting units, reflections caused by the shape of the body (e.g., curvature), surface texture, moisture, or scales in fish can be largely prevented.

[0030] Light-emitting diodes (LEDs) can be used as light sources. The wavelengths can be individually selected (e.g., ultraviolet (UV) range, visible range up to the infrared range).

[0031] The lighting elements, especially LEDs, can be arranged in lighting panels. The arrangement can be, for example, across the entire surface or only along the edges of the lighting panels, i.e., with side lighting.

[0032] Diffuse lighting is advantageous, for example, through a suitable arrangement of LEDs and a diffuser disc in the emission area of ​​the LEDs.

[0033] A lighting tunnel can be composed of several individual lighting segments (panels) which form (interior) wall surfaces of the lighting tunnel.

[0034] The overall shape as a lighting tunnel also facilitates the shielding of ambient light. Side shielding panels can also be used for this purpose.

[0035] Each individual lighting panel represents a complete system in itself. A diffuser disc, the lighting elements (e.g., LEDs), control electronics, and cooling can form a single module.

[0036] Cooling of the lamps may be necessary. For this purpose, enhanced cooling (e.g., water cooling) may be used when employing LEDs that generate very hot temperatures (from near-infrared to infrared).

[0037] The geometric shape of the lighting system is adapted to the object's shape, for example, in the case of fish. A curved lighting fixture is thus adapted to the object's preferred curvature. However, the geometric shape of the lighting system can also be adapted to other object shapes.

[0038] The width and height of the lighting tunnel can be adjusted to the width of the conveyor belt, and the height can be adjusted to accommodate the necessary camera distance (according to resolution requirements). A cutout for the camera (centered at the top, for top-down camera viewing) can be provided in the lighting tunnel.

[0039] The power of the individual lighting elements or LEDs can be variably controlled, thus enabling brightness adjustment to light / dark areas of the object, e.g., the belly / back of a fish, as well as brightness adjustment to the specific geometric shape of the object.

[0040] A key advantage is the ability to control individual LED groups of the same wavelength, or, in the case of a combination of LEDs of different wavelengths, to determine the switching time, duration, and intensity. This is particularly useful, for example, when taking sequential camera shots at different wavelengths.

[0041] The individual control of the lighting segments to adjust the brightness to the object can be automated. For example, brightness sensors at the tunnel entrance can be used, or the camera itself can be used for control. This control system can interact with an evaluation / control unit for feedback, for example, to reduce the intensity in case of overexposure.

[0042] Since the spectra of currently available LEDs in the near-infrared to infrared range are highly temperature-dependent (i.e., the position and intensity of the spectra shift depending on the temperature), stabilization corrections should be implemented. Firstly, the LEDs can be kept at a constant operating temperature by means of adjustable heating / cooling (e.g., water cooling). Temperature sensors can be used inside the lamp for this purpose. Secondly, the intensity values ​​measured by the camera in the image captures can be corrected after the fact if the temperature inside the lamp at the time of each image capture is known (e.g., measured with built-in temperature sensors).Separate camera recordings can be made – technically, as well as for applying white balance to the camera using a white balance plate within the camera's field of view – to generate reference data at different temperatures. The expected temperature range depends heavily on the ambient temperature. A coupled control system can be used for both the lamp, which heats up along a defined characteristic curve with specified start and end temperatures, and the camera, which takes successive images at defined intervals. This temperature-dependent reference data can then be applied to the image data from a standard camera measurement in the form of a pixel-precise correction calculation, based on the temperature present at each image capture.

[0043] To further reduce reflections, polarized light can also be used. Polarizing filters can be placed in front of the lamp panels and the camera lenses.

[0044] A waterproof enclosure for the entire tunnel lighting system is advantageous. This can optionally be supplemented with a bottom-mounted glass panel for easier cleaning.

[0045] Tunnel lighting can be used at conveyor belt transitions or on transparent conveyor belts and can be extended to a 360° illumination loop, thus enabling illumination of the object transported on the belt from all sides. Depending on the number of cameras used in the system for all-around viewing, corresponding recesses for the cameras would need to be provided in the lighting tunnel.

[0046] With a lighting rotation of up to 360°, the lighting elements located directly under the conveyor belt could be installed openly so that cleaning and dirty water can drain downwards during cleaning and operation.

[0047] Depending on the task, the lamp elements can have suitable openings so that cameras can see through the lighting group to record the illuminated object.

[0048] The use of line scan cameras has the advantage that, due to their line-by-line recording technique, they only require narrow slits through or within the lighting elements as viewing windows. Lasers can also shine through these slits to integrate a triangulation system, enabling the creation of cross-sectional profiles of the object. With appropriate control, these triangulation units and camera units, along with their associated lighting units, can be controlled separately. This ensures that the lights and lasers do not interfere with each other. Furthermore, the upper and lower camera / light unit(s) can be controlled alternately to counteract unwanted optical interactions.

[0049] It is particularly advantageous if an upstream sensor is arranged at the tunnel inlet of the tunnel-shaped housing, which is designed to detect different brightness levels of the object in relation to the transport direction of the object, so that the lighting elements can be appropriately reprogrammed before the object reaches the line plane of the image extraction device.

[0050] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings. These show: Fig. 1 - Sketch of an optical image recording device with a tunnel-shaped housing and 180° tunnel illumination; Fig. 2 - Perspective side view of the optical image recording device Fig. 1; Fig. 3 - Sketch of an optical image recording device with a tunnel-shaped housing and 360° tunnel illumination; Fig. 4 - Sketch of an optical image recording device with a tunnel-shaped housing and 360° tunnel illumination with a conveyor belt and upper and lower illumination elements offset to a conveyor belt gap.

[0051] Fig. Figure 1 shows a sketch of an optical image acquisition device 1 with a tunnel-shaped housing 2 and a 180° tunnel illumination. The tunnel-shaped housing 2 is placed on a slide 3, such as a table as shown or a conveyor belt, and is configured to illuminate a curved object 4 arranged on the slide 3.

[0052] The tunnel-shaped housing 2 has several lighting elements 5 directed towards the surface of the object, as well as an image acquisition unit 6 directed towards the slide 3, which can, for example, be designed as a line scan camera. To shield against ambient light, the sides of the tunnel-shaped housing 2 can be covered with side walls 7. A recess 8 in the side walls 7 adjacent to the slide 3 can be used to guide the object 4 into the interior of the housing 2 or to allow it to protrude from the housing 2.

[0053] It is evident that the tunnel-shaped housing 2 has a curved outer contour, which can be, for example, parabolic. The lighting elements 5 are aligned and arranged according to the fundamental curved shape of the object's surface, with a curved beam plane defined by all the lighting elements 5, so that they emit light onto the object surface or the surface of the substrate 3 at different angles of incidence to one another. The central beam of each lighting element 5 should strike the surface of the object 4 as perpendicularly as possible (90° ±20°).

[0054] Fig. Figure 2 shows a perspective side view of the optical image recording device 1. Fig. 1.

[0055] It becomes clear that the lighting elements 5 are arranged as planar lighting panels in the space between the opposing side walls 7 and form the inner walls of the tunnel-shaped housing 2. The lighting elements 5, arranged side by side – possibly at a distance from each other – are positioned at different angles of their respective emission planes to the surface plane of the specimen support 3. The distances to the object 4 can also vary and increase towards the raised tip of the housing 2.

[0056] The image acquisition unit 6 is installed in a space between two lighting elements 5. It has a lens 9 that is aligned with the surface of the microscope slide 3 and the object 4 lying on it.

[0057] Fig. Figure 3 shows a sketch of an optical image recording device 1 with a tunnel-shaped housing 2 and 360° tunnel illumination.

[0058] It can be seen that a housing frame 10 is formed at an angle of more than 180°, for example, as a 7-sided polygon with a gap in the lower part of an otherwise 360° frame, as shown. The housing frame carries a planar lighting panel 11 on each straight section, which has several spaced-apart lighting elements 5 on a single beam plane. These lighting elements 5 emit light in a fan shape into a common illumination intersection point S. Due to the lighting panels 11 being distributed around the circumference of the housing frame 10 and the lighting elements 5 being arranged on a common beam plane of each lighting panel 11, the beam angles are aligned according to the outline of an object 4 with a curved surface positioned at the illumination intersection point S for illumination and image acquisition.

[0059] It can be seen that several image acquisition units 6a, 6b, 6c are arranged distributed around the circumference and aligned with their image acquisition angle towards the illumination intersection point S. Image acquisition units 6c can optionally be integrated as a module component into an illumination panel 11.

[0060] The lighting panels 11 can have diffuser discs arranged on the emission surface of the lighting panels 11.

[0061] Since the spectra of the light sources, especially LEDs in the near-infrared to infrared range, are temperature-dependent, it is advantageous to ensure a constant operating temperature. For this purpose, a cooling system can be provided, in which hoses 12a, 12b supply the cooling medium to the lighting elements 5. Coolant, preferably a fluid or gaseous cooling medium such as water, is supplied to the lighting elements 5 via a coolant supply line 12a and, after absorbing heat, is discharged via coolant outlets 12b. The hoses 12a, 12b can be connected to a pump for this purpose. A ring main with an intermediate heat exchanger can be provided to cool the heated coolant discharged via the coolant outlet 12b and then return it to the lighting units 5 via the coolant supply line 12a.

[0062] Fig.Figure 4 shows a sketch of an optical image acquisition device 1 with a tunnel-shaped housing 2 and 360° tunnel illumination, including a conveyor belt 13 with a conveyor belt gap 14. An upper, first image acquisition unit 6a, with its fan-shaped narrow detection angle 16a, is directed through a first gap 15a in the cylindrical housing 2, or through the illumination elements 5 arranged on the inner wall of the housing 2, onto the surface of the conveyor belt in an area adjacent to the conveyor belt gap 14. A lower, second image acquisition unit 6b, with its fan-shaped narrow detection angle 16b, is directed onto the underside of the conveyor belt 13 in the area of ​​the conveyor belt gap 14 to capture images of the underside of the object 4 being conveyed over the conveyor belt gap 14 on the conveyor belt 13.The conveyor belt gap is illuminated from above and below by the lighting elements 5 arranged on a 36° beam plane.

[0063] The upper group of upper lighting elements 5a, arranged laterally within the inner circumference of the housing 5 next to the first gap 15a, is offset relative to the lower group of lower lighting elements 5b in the transport direction T of the conveyor belt 13 and aligned with the conveyor belt gap 14. This achieves better and easier segmentation of the object 4 against the background of the conveyor belt 13 while significantly reducing the risk of reflections. The second (lower) image acquisition unit 6b sees a brightly illuminated background due to the illumination of the conveyor belt gap 14 from above by the upper lighting elements 5a. Reference symbol list 1 optical image recording device 2 tunnel-shaped housings 3 slides 4 curved object 5 lighting elements 6 Image acquisition unit 6a,b,c Image acquisition units 7 Side wall 8 recess 9 lens 10 housing frames 11 Lighting panels 12a Hose line / coolant supply line 12b Hose line / coolant drain 13 Conveyor belt 14 conveyor belt gap 15a first space 15b second space 16a,b Detection angle S Lighting intersection T Transport direction QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2008 027 904 A1

[0002] DE 42 04 843 A1

[0003]

Claims

Optical image acquisition device (1) with an image acquisition unit (6, 6a, 6b, 6c) designed for capturing images of an object (4) arranged on a surface of a microscope slide (3), and with an illumination unit having several illumination elements (5) oriented to illuminate the surface of the object (4), characterized in that the illumination elements (5) are arranged on a circumference that at least partially surrounds the object (4), wherein the illumination elements (5) are each oriented with a beam angle orientation of the light incident angle on the surface of the microscope slide (3) that differs from the other illumination elements (5). Optical image recording device (1) according to claim 1, characterized in that the different beam angle orientations are aligned according to the outline contour of an object type specified for illumination and image recording. Optical image acquisition device (1) according to claim 1 or 2, characterized in that the image acquisition device (1) has a tunnel-shaped housing (2) which at least partially surrounds the surface of the slide (3) and an object (4) arranged thereon, and the illumination elements (5) are arranged adjacent to each other on inner wall surfaces of the tunnel-shaped housing (2). Optical image recording device (1) according to claim 3, characterized in that the illumination elements (5) form wall surfaces of the tunnel-shaped housing (2) on the radially outwardly extending circumference of the tunnel-shaped housing (2). Optical image recording device (1) according to one of the preceding claims, characterized in that a group of illumination elements (5) form a common illumination intersection point (S). Optical image recording device (1) according to one of the preceding claims, characterized in that the illumination elements (5) are fan-shaped for emitting light at different beam angles onto the surface of the object carrier (3). Optical image recording device (1) according to one of the preceding claims, characterized in that the inner wall of the tunnel-shaped housing (2) has individual illumination elements (5) arranged next to each other and spaced apart from each other and offset from each other in the beam angle to the object (4) or to the surface of the object carrier (3). Optical image recording device (1) according to one of the preceding claims, characterized in that several lighting elements (5) are combined in a lighting panel (11). Optical image recording device (1) according to one of the preceding claims, characterized in that at least one of the illumination elements (5) is designed for diffuse illumination. Optical image recording device (1) according to one of the preceding claims, characterized in that the areas between the lighting elements (5) and the entry surfaces into the tunnel of the tunnel-shaped housing (2) have reflective elements on their inner sides in the direction of the object (4). Optical image recording device (1) according to one of the preceding claims, characterized in that the lighting elements (5) or lighting panels (11) with lighting elements (5) each form a module consisting of a light source, control electronics, cooling unit and cover disc, for example a diffuser disc and / or polarizing filter. Optical image recording device (1) according to one of the preceding claims, characterized in that the lighting elements (5) can be controlled independently of each other. Optical image acquisition device (1) according to claim 12, characterized in that the illumination elements (5) can be reprogrammed to suit the situation during measurement operation. Optical image recording device (1) according to one of the preceding claims, characterized in that several groups of illumination elements (5) are provided, each group being designed to illuminate the object (4) with at least one specific wavelength which differs from the specific wavelength of the other groups. Optical image recording device (1) according to one of the preceding claims, characterized in that the illumination elements (5) are arranged distributed in a circumference in the range of at least 180° to 360° around the object carrier (3). Optical image acquisition device (1) according to one of the preceding claims, characterized in that the image acquisition unit (6, 6a, 6b, 6c) is a line scan camera or a matrix camera designed to read out a line as a selected image area (ROI). Optical image acquisition device (1) according to claim 16, characterized in that each image acquisition unit (6, 6a, 6b, 6c) is assigned a laser triangulation sensor whose laser plane coincides with the recording plane of the line. Optical image acquisition device (1) according to claim 17, characterized in that the illumination elements (5) and the laser planes for the triangulation sensors can be controlled independently of each other. Optical image recording device (1) according to one of the preceding claims, characterized in that the object carrier (3) is a conveyor belt (13). Optical image recording device (1) according to claim 19, characterized in that the optical image recording device (1) is configured for use in the quality inspection of fish or meat products conveyed on the conveyor belt (13) as objects (4). Optical image recording device (1) according to claim 19 or 20, characterized in that the conveyor belt (13) has a conveyor belt gap (14), wherein in the area of ​​the conveyor belt gap (14) a first group of upper lighting elements (5a), which are arranged to illuminate the upper side of the conveyor belt (13) carrying the object (4), and a second group of lower lighting elements (5b), which are arranged to illuminate the underside of the conveyor belt (13) opposite the upper side of the conveyor belt (13) carrying the object (4), are arranged and the first group of upper lighting elements (5a) is offset relative to the second group of lower lighting elements (5b) in the transport direction (T) of the conveyor belt (13). Optical image acquisition device (1) according to one of claims 19 to 21, characterized in that the conveyor belt (13) has a conveyor belt gap (14), wherein in the area of ​​the conveyor belt gap (14) a first image acquisition unit (6a) for capturing images of the upper surface of the conveyor belt (13) carrying the object (4) and a second image acquisition unit (6b) for capturing images of the underside of the conveyor belt (13), which is opposite the upper surface of the conveyor belt (13) carrying the object (4), are arranged and the first image acquisition unit (6a) is offset relative to the second image acquisition unit (6b) in the transport direction (T) of the conveyor belt (13). Optical image recording device (1) according to one of the preceding claims, characterized in that a sensor system is located at the tunnel inlet of the tunnel-shaped housing (2), which is configured to detect different brightness levels of the object (4) with respect to a transport direction of the object (4), whereby the lighting elements (5) can be reprogrammed appropriately before the object (4) reaches the line plane.

Images