Camera system with athermalised focus

Abstract

The invention relates to a camera system (1) having an athermalised focus of the optical path, comprising a lens element (2), a printed circuit board (7), an image sensor (4) which is attached to the printed circuit board (7), a housing (3) in which the printed circuit board (7) with the image sensor (4) and a part of the lens element (2) is arranged, wherein the printed circuit board (7) is connected to the housing (3) by at least one fastening means (6), wherein at least one spacer (5) is arranged between the printed circuit board (7) and the housing (3), wherein the at least one fastening means (6) fixes the printed circuit board (7) and the spacer (5) in the housing (3) and wherein the spacer (5) is made of a material which has a variable coefficient of thermal expansion.

Description

[0001] Camera system with athermalized focus

[0002] The invention relates to a camera system with an athermalized focus of the optical path.

[0003] For stability and cost reasons, fixed-focus cameras are typically used in ADAS applications. The problem here is that the thermal expansion of the housing and the shifting of the lens's image plane are not perfectly matched for all ambient temperatures. This leads to image degradation. Consequently, the ADAS system or algorithm cannot utilize the camera's full capabilities. This could result in reduced system availability and / or lower system performance (false detections, no object detections, etc.).

[0004] Typical remaining mismatches between the perfect and real image plane range from single digits to double digits in pm.

[0005] Current solutions adapt the lens behavior to the housing expansion as closely as possible (by changing glass materials, designing the lens, or using spacers within the lens). Furthermore, elements are attached to or integrated into the circuit board (structures, counterweights, etc.).

[0006] It is therefore an object of the present invention to provide a camera system which has an athermalized focus.

[0007] This problem is solved by the subject matter of claim 1.

[0008] Further advantageous embodiments and configurations are the subject of the dependent claims.

[0009] According to the invention, a camera system with an athermalized focus is proposed, comprising a lens element, a printed circuit board, an image sensor mounted on the printed circuit board, and a housing in which the printed circuit board with the image sensor and a part of the lens element are arranged, wherein the printed circuit board is connected to the housing by at least one fastening means. Furthermore, at least one spacer is arranged between the printed circuit board and the housing, wherein the at least one fastening means fixes the printed circuit board and the spacer in the housing, and wherein the spacer is made of a material having a variable coefficient of thermal expansion. The camera system is preferably a fixed-focus camera, in particular a monocular camera oriented in the direction of travel of the vehicle or a camera of a surround-view system.The multiple spacers can advantageously compensate for the influence of temperature on the focus of the camera system.

[0010] In a particularly preferred embodiment, the fastener and the spacer are made of the same material. This is especially advantageous because it ensures that the connection is not damaged by temperature changes and the associated contraction or expansion of the spacer, since the fastener changes to the same extent.

[0011] The material is particularly preferred if it is electrically and thermally conductive.

[0012] In another preferred embodiment, the fastening element for fixing the circuit board and the spacer is pressed into the housing. This creates an advantageously stable, positive-locking connection.

[0013] It is particularly preferred that an adhesive component is also used and / or the fastener is heated when pressing it in. Using an additional adhesive component increases the stability of the connection.

[0014] In another preferred embodiment, the material is selected from polyethylene, zinc, aluminum, nickel, iron, or Invar. Invar is the name for an iron-nickel alloy with a very low coefficient of thermal expansion. For example, Polystone EL, a high-density polyethylene, was used as the polyethylene in the tests.

[0015] These materials have proven particularly advantageous with regard to their coefficients of thermal expansion and the possible compensation options. The following table shows the results of the change in thickness of the respective materials at different temperatures.

[0016] Further advantageous embodiments are shown in the drawings. These show:

[0017] Fig. 1: a schematic representation of a camera system according to one embodiment of the invention.

[0018] Figure 1 shows a schematic representation of a camera system according to an embodiment of the invention. The camera system 1 shown here comprises a lens 2, a housing 3, an image sensor 4, a spacer 5, and mounting means 6. The image sensor 4 is mounted on a circuit board 7. The circuit board 7 with the image sensor 4 is arranged in the housing 3. Between the circuit board

[0019] A spacer 5 is arranged between the circuit board 7 and the housing 3. The circuit board 7 is further secured in the housing 3 by means of fastening elements 6. The image sensor 4 is mounted on a side 7a facing the lens 2. The fastening elements 6 extend through the circuit board 7 at its edge. From a side 7b facing away from the lens 2, the fastening elements 6 pass through the circuit board 7 towards the housing 3. The spacers 5 are therefore located at the edge on the side 7a facing the lens 2, between the circuit board 7 and the housing 3. The housing 3 can, for example, be cylindrical or cuboid in shape.

[0020] Reference symbol list

[0021] 1 camera system

[0022] 2 lenses

[0023] 3 Housing 4 Image sensor

[0024] 5 spacers

[0025] 6 Fasteners

[0026] 7 printed circuit board

[0027] 7a Side of the circuit board facing the lens 7b Side of the circuit board facing away from the lens

Claims

Patent claims 1. Camera system (1) with an athermalized focus of the optical path comprising a lens element (2), a printed circuit board (7), an image sensor (4) mounted on the printed circuit board (7), a housing (3) in which the printed circuit board (7) with the image sensor (4) and a part of the lens element (2) is arranged, wherein the printed circuit board (7) is connected to the housing (3) by at least one fastening means (6), characterized in that at least one spacer (5) is arranged between the printed circuit board (7) and the housing (3), wherein the at least one fastening means (6) fixes the printed circuit board (7) and the spacer (5) in the housing (3) and wherein the spacer (5) is made of a material which has a variable coefficient of thermal expansion.

2. Camera system according to claim 1, characterized in that the fastening means (6) and the spacer (5) are made of the same material.

3. Camera system according to claim 1, characterized in that the material is electrically and thermally conductive.

4. Camera system according to claim 1, characterized in that the fastening means (6) for fixing the circuit board (7) and the spacer (5) is pressed into the housing.

5. Camera system according to claim 4, characterized in that an adhesive component is additionally used and / or the fastening element (6) is heated when pressing in the fastening element (6).

6. Camera system according to claim 1, characterized in that the material is selected from polyethylene, zinc, aluminium, nickel, iron or Invar.

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