Vehicle interior lighting

Abstract

Vehicle interior lighting system (1) with an arrangement of RGB LED units controlled by a computer unit, characterized in that a driver circuit (3) with a Manchester codec (5) is assigned to each predetermined number of RGB LED units, that the driver circuits (3) are connected to the computer units in a series circuit, that a signal sent by the computer unit is converted into a Manchester-coded signal in a first driver circuit (3) directly connected to the computer unit, and the further driver circuits (3) send and receive Manchester-coded signals, and that, depending on a calibration of the RGB LED units, control signals for the assigned RGB LED units are generated in each driver circuit (3) so that they emit light within a target color space.

Description

The invention relates to a vehicle interior lighting system. Such vehicle interior lighting systems comprise RGB LED units arranged in strips with multiple red, blue, and green light-emitting LEDs (light-emitting diodes). Each RGB LED unit is connected to a control module, with each control module being a system-on-a-chip (SoC) module. The individual control modules are connected to a computing unit in the form of a microcontroller. The microcontroller communicates with the SOC modules via a CAN bus or LIN bus. It is also common practice to implement a coding unit on the microcontroller as a software module, which generates Manchester-coded signals that are then sent to the control modules. The Manchester-encoded signals are transmitted to the control modules, which calibrate the connected RGB LED units, thus specifying a particular color tone for the RGB LED units. The generation of Manchester-coded signals performed in the microcontroller requires complex software modules, leading to an undesirable increase in the manufacturing and development costs of the microcontroller. This also includes the hardware costs for the individual SoC modules. The software complexity of the microcontroller is further increased by the fact that all calculations for calibrating the RGB LED units are performed centrally in the microcontroller. Furthermore, a disadvantage is that the color tones are only set once before the vehicle's interior lighting system is put into operation using the calibration calculations. Fluctuations in the color tones of the RGB LED units that occur during operation, especially due to environmental influences, cannot be compensated for. The invention is based on the objective of providing a vehicle interior lighting system of the type mentioned above, which has high functionality at low manufacturing costs. The features of claim 1 are provided to solve this problem. Advantageous embodiments and expedient further developments of the invention are described in the dependent claims. The invention relates to a vehicle interior lighting system with an arrangement of RGB LED units controlled by a computer unit. A driver circuit with a Manchester codec is assigned to each predetermined number of RGB LED units. The driver circuits are connected to the computer units in series. A signal sent by the computer unit is converted into a Manchester-coded signal in a first driver circuit directly connected to the computer unit. The subsequent driver circuits send and receive Manchester-coded signals. Depending on the calibration of the RGB LED units, control signals are generated in each driver circuit for the assigned RGB LED units, causing them to emit light within a target color space. The vehicle interior lighting system according to the invention comprises a multiple arrangement of RGB LED units. Each RGB LED unit comprises a red light-emitting LED, a green light-emitting LED, and a blue light-emitting LED. These RGB LED units illuminate the interior of a motor vehicle in a specific color. The RGB LED units are conveniently grouped in the form of strips, with the term strips encompassing any kind of chain or bead structure. According to the invention, the vehicle interior lighting system has a multiple arrangement of driver circuits, wherein a multiple arrangement of RGB LED units, in particular a strip of RGB LED units, is connected to each driver circuit. The driver circuits are connected in series to a computing unit, which is preferably formed by a microcontroller integrated in the motor vehicle. Advantageously, the driver circuits are formed from hardware circuits. The driver circuits form compact, cost-effective computer structures. In particular, it is advantageous that no SoC modules need to be integrated into the driver circuits, which significantly reduces the hardware complexity of the vehicle interior lighting system according to the invention. According to the invention, the RGB LED units are controlled such that they emit visible light within a predetermined target color space. To achieve this, the individual driver circuits are controlled with Manchester-coded signals. According to the invention, a Manchester codec is integrated into each driver circuit. The Manchester codec integrated into a driver circuit is designed for encoding and decoding Manchester-coded signals. Advantageously, the Manchester codecs are formed in the driver circuits of hardware circuits, whereby the Manchester codecs of the driver circuits are identically designed. The hardware circuits form compatible, cost-effective units by which the encoding and decoding of Manchester-coded signals can be performed. According to the invention, a signal sent by the computer unit, in particular the microcontroller, is converted into a Manchester-encoded signal in a first driver circuit directly connected to the computer unit by means of the Manchester codec integrated therein. This signal is then forwarded to the subsequent driver circuits, using their integrated Manchester codecs for this purpose. Since the computer unit sends signals that are not Manchester-coded, no complex software for generating Manchester-coded signals needs to be integrated into the computer unit. This allows the computer unit, and especially the microcontroller, to have a simple design. Therefore, a microcontroller that is standard in vehicles can be used as the computer unit to control the driver circuit without complex modifications. In particular, no Manchester codec needs to be implemented in the computer unit itself. The computer unit thus sends uncoded signals, in particular SPI (serial peripheral interface) signals, which are standard signals for communication between electronic units in motor vehicles. The generation of control signals for the RGB LED units takes place in the driver circuits, depending on calculations performed in the computer unit to optimize the color space of the individual RGB units. This represents an efficient and cost-effective decentralized computer architecture that enables fast and precise adjustment of the RGB LED units to emit light in the target color space. According to the invention, the individual RGB LED units or strips of RGB LED units are calibrated to adjust the light emitted by the RGB LED units to the target color space. Preferably, the target color space is specified in the computer unit, which is advantageously transformed into the CIE-1931 color coordinate system. The parameters of the RGB LED units, which are available in individual coordinate systems, are transformed into the CIE-1931 color coordinate system and aligned with the target color space. This adjustment is achieved by changing, in particular expanding, the respective color spaces of the individual bands of RGB LED units. These calculations are performed in the computer unit. Since the color spaces of the individual bands of RGB LED units are transformed into the CIE-1931 color coordinate system, which, unlike individual three-dimensional color spaces, is only two-dimensional, the adjustment of the color spaces of the individual bands of RGB LED units requires little computing time and can therefore be carried out quickly. For the purpose of comparison, output control instructions can be derived, particularly in the computer unit, with which the color space adjustments of individual bands of RGB LED units are compared against each other, so that in particular an intersection of individual color spaces is obtained, in which a cooperative adjustment of the color spaces of all bands of RGB LED units is enabled. For the color space adjustments to be carried out to the target color space, control commands are generated in the individual driver circuits, by means of which the red, green and blue LEDs of the respective band of RGB LED units are controlled in order to carry out the color space adjustments accordingly. Advantageously, in the driver circuits for the individual RGB LED units, PWM (pulse width modulation) signals are generated as control signals, by means of which the parameters of the RGB LED units are optimized with regard to the target color space. The optimization of the parameters of RGB LED units to the target color space is particularly advantageous when it is carried out exclusively or predominantly in the red wavelength range. This simplified method for color space adjustment is based on the understanding that the human eye is most sensitive in the red wavelength range. Therefore, color space changes in the red wavelength range are perceived much more strongly than in the blue and green wavelength ranges. By adjusting the color space only in the red wavelength range, the user experiences little to no loss of quality, but the adjustment process is significantly simplified, resulting in a considerably reduced processing time. A significant advantage of the invention is that the RGB LED units are continuously calibrated during its operation, i.e., the calibration is not limited to the commissioning phase of the vehicle interior lighting system. This makes it possible to compensate for environmental influences during operation by calibrating the RGB LED units. Such environmental influences include ambient light and temperature. In particular, it is also possible that the calibration of the RGB LED units is carried out according to customer-specific requirements. In order to make the color space adjustments of the individual bands of RGB LED units, it is necessary to know the current color behavior of the individual bands of RGB LED units. This is done in a learning process in which, according to the invention, the individual LED strips are measured with a redundant camera system. Advantageously, the redundant camera system features a grayscale camera and a color camera, whose fields of view are arranged in an overlapping manner. It is particularly advantageous that the camera system, arranged in a fixed position, completely captures a band of RGB LED units. Therefore, the camera system does not need to be moved along the strip of RGB LED units. Instead, the camera system can be positioned in a fixed position relative to the strip to capture the entire strip. The measurement of each band of RGB LED units is advantageously performed by determining the vignetting coefficient of an image using a grayscale camera. The corresponding image from the color camera is then corrected using this vignetting coefficient. Based on these corrected images from the color camera, the chromaticity of the RGB LED unit band is determined. A key advantage is that the parameters of RGB LED strips can be determined in the respective customer application. The learning process therefore does not need to be carried out in the development process of the vehicle interior lighting system, but can be carried out by the customer himself in the application. The invention is explained below with reference to the drawings. They show: Fig. 1: Schematic representation of electronic components of the vehicle interior lighting system according to the invention. Fig. 2: Circuit example of a driver circuit of the arrangement according to Fig. 1. Fig. 3: Overview of a redundant camera system for acquiring parameters of a band of RGB LED units. Fig. 4: Detailed representation of the arrangement according to Fig. 3. Fig. 5: Schematic representation of coordinate transformations of color spaces of individual RGB LED units. Fig. 6: CIE 1931 coordinate representation of a color space of an RGB LED unit. Fig. 7: Color space distribution of two bands of RGB LED units. Fig. 1 schematically shows the structure of electronic components of the vehicle interior lighting system 1 according to the invention. The vehicle interior lighting system 1 comprises a computing unit in the form of a microcontroller 2 present in a motor vehicle. An arrangement of driver circuits 3 in series is connected to this microcontroller 2. Figure 1 shows four driver circuits 3, although generally a different, and in particular a higher, number of driver circuits 3 is provided. Each driver circuit 3 is connected to an arrangement of RGB LED units, in particular an RGB strip 4 with several RGB LED units as schematically shown in Figures 3 and 4. Each RGB LED unit has a red light-emitting LED, a green light-emitting LED, and a blue light-emitting LED. Each driver circuit 3 contains a Manchester codec 5, which is configured for encoding and decoding Manchester-coded signals. The Manchester codecs 5 are identical in this case. The microcontroller 2 does not contain a Manchester codec 5. In Manchester encoding, the bits of a data stream are determined by the directions of the transitions from a high-voltage signal to a low-voltage signal and vice versa. In the arrangement shown in Fig. 1, the microcontroller 2 sends uncoded signals, in particular SPI signals, via line 6a to the first driver circuit 3, which is directly connected to the microcontroller 2. Manchester-coded signals are generated there using the Manchester codec 5. The driver circuits 3 are connected via lines 7a and 7b for bidirectional data exchange of Manchester-coded signals. Uncoded signals are read back from the first driver circuit 3 to the microcontroller 2 via line 6b. Fig. 2 shows an example of the structure of a driver circuit 3. The driver circuit 3 has a logic core 8 as its central processing core. Timer signals 9 and authentication signals 10 are fed to the logic core 8. In addition, data or parameter values ​​from external units 12, such as temperature sensors, are read into the logic core 8 via an analog-to-digital converter 11. The logic core 8 is coupled to the Manchester codec 5, which has a differential transceiver 13a for processing input signals 14 and a differential transceiver 13b for generating output signals 15, with switching contacts 16 controlled by the logic core 8 being prior to this. A first register 17a is connected to the logic core 8, and a driver 18a for a red light emitting LED is connected to it, with the driver 18a being led to an output stage 19a. Furthermore, a second register 17b is connected to the logic core 8 and a driver 18b for a green light emitting LED is connected to it, with the driver 18b being led to an output stage 19b. Finally, a third register 17c is connected to the logic core 8, and a driver 18c for a blue light-emitting LED is connected to it, with the driver 18c being led to an output stage 19c. The drivers 18a to 18c and the output stages 19a to 19c output control signals in the form of PWM (pulse width modulation) signals to dim the red, green and blue LEDs in a predetermined way and thus define the color behavior of the RGB LED units, especially of RGB band 4. Before commissioning, the color properties and brightness of RGB bands 4 used for the vehicle interior lighting system 1 are determined. For this purpose, a redundant camera system 20 is used, as shown in Fig. 3 and Fig. 4. The camera system 20 comprises a grayscale camera 21 and a color camera 22, which are arranged stationary such that their fields of view 23a, 23b overlap in an area C. Both cameras have image sensors with a matrix-shaped arrangement of pixels in the form of CCD or CMOS elements. The fields of view 23a, 23b are dimensioned such that an RGB band 4 can be completely captured without having to move the camera system 20. In a first step, the gray value distribution of the pixels of the grayscale camera 21 is evaluated. From this, a vignetting coefficient is determined, which is a measure of image distortion in the edge region of the grayscale camera 21. This vignetting coefficient is used to correct the color images of the color camera 22, so that the edge distortions in the color images are eliminated or greatly reduced. The chromaticities, i.e., color properties of the light emitted by individual RGB bands 4, are then detected using the color images from the color camera 22. This allows manufacturing-related variations in the color properties of RGB bands 4 to be accurately detected and used for the control of the RGB bands 4 according to the invention by means of the driver circuit 3. The color behavior of the RGB bands 4 can be specified by a target value specification of a color space of an ideal RGB LED unit with a red, green and blue light emitting LED. This takes place in the computing unit, i.e., in the microcontroller 2. Figure 5 (top left) shows a color space of an RGB LED unit in the standard CIE 1931 color coordinate system. Figure 5 (top right) shows the ideal color space of the RGB LED unit with a triangle. Fig. 5 shows the color spaces of the individual RGB LED units of the RGB bands 4 of the vehicle interior lighting system 1 in the coordinates of the individual RGB LED units. Fig. 6 shows the projection of a coordinate system X1, Y1, Z1 of an RGB LED unit onto the XY plane of the CIE 1931 color coordinate system. The triangle again denotes the ideal color space of the RGB LED unit with the target color at its center. By transforming the three-dimensional coordinate system of the RGB LED units into the two-dimensional CIE-1931 color coordinate system, data reduction is achieved, thus shortening the computing time for subsequent calculations to be performed in the computing unit. In the respective driver circuit 3, depending on the current color behavior of the RGB LED units, in particular of the RGB band 4, the control signals, i.e. pulse width modulation signals, are generated with which the red, green and blue LEDs of the RGB band 4 are controlled, depending on the current color behavior of the RGB LED units, in particular of the RGB band 4, and the ideal color behavior preferably specified in the microcontroller 2 (as shown in Fig. 5 and Fig. 6). Without the coordinate transformations of the individual RGB LED units illustrated in Fig. 5, their non-ideal color behavior exists in their individual coordinate systems, meaning that controlling the individual red and green LEDs based on this would not result in ideal color behavior for the RGB LED unit. This is only possible through transformation into the CIE 1931 color coordinate system, where the target color space and target color for the ideal RGB LED unit are defined. The procedure for adjusting the color behavior of the RGB LED units is as follows. First, a target value, i.e., the target color or color space, is specified via microcontroller 2. This can be done according to customer-specific requirements. The microcontroller 2 performs the calculations to optimize the color behavior of the individual RGB LED units. In particular, the coordinate transformations of the RGB LED units, i.e. the RGB bands 4 into the CIE-1931 color coordinate systems, take place in the computer unit. There, it is determined whether and in which direction the current color space of the RGB LED unit exceeds the target color space. A corrective measure is only advantageous if the deviation from the target color space lies in the red wavelength range, since the human eye is most sensitive in the red wavelength range. Depending on the registered exceedance of the target color space for a current color space of an RGB LED unit, control commands in the form of pulse width modulation signals are generated in the logic core 8 of the associated driver circuit 3, with which the red, green and blue LEDs of the RGB LED unit are selectively controlled in order to change the current color space so that it at least approximately matches the target color space. Fig. 7 schematically shows the cooperative effect when several (in the illustrated case two) RGB bands 4 are simultaneously optimized with regard to their color behavior. Figure 7 shows the color space for the RGB LED units, where points 1 and 2 represent the color distributions of two RGB LED units. SO3 indicates the color space available for joint optimization of the color behavior of the two RGB LED units, whereas SO1 and SO2 are not available for this purpose. Simulations are used to determine and define the SO3 area, and in particular point 3, which represents the optional color distribution for both RGB LED units. This makes it possible to optimize all RGB bands 4 of the vehicle's interior lighting system 1 simultaneously. According to the invention, this calibration and optimization of the color spaces of the individual RGB bands 4 is carried out not only before the vehicle interior lighting system 1 is put into operation, but also during its entire operating period. This allows environmental influences such as temperature fluctuations or changing ambient light conditions to be continuously compensated for during the operation of the vehicle interior lighting system 1, thereby maintaining a constant color behavior of the RGB bands 4. Reference symbol list 1 Vehicle interior lighting system 2 Microcontroller 3 Driver circuit 4 RGB band 5 Manchester codec 6a Line 7a Line 7b Line 8 Logic core 9 Timer signal 10 Authentication signal 11 Analog-to-digital converter 12 External unit 13a Transceiver 13b Transceiver 14 Input signal 15 Output signal 16 Switching contact 17a Register 17b Register 17c Register 18a Driver 18b Driver 18c Driver 19a Output stage 19b Output stage 19c Output stage 20 Camera system 21 Grayscale camera 22 Color camera 23a Field of view 23b Field of view

Claims

Vehicle interior lighting system (1) with an arrangement of RGB LED units controlled by a computer unit, characterized in that a driver circuit (3) with a Manchester codec (5) is assigned to each predetermined number of RGB LED units, that the driver circuits (3) are connected to the computer units in a series circuit, that a signal sent by the computer unit is converted into a Manchester-coded signal in a first driver circuit (3) directly connected to the computer unit, and the further driver circuits (3) send and receive Manchester-coded signals, and that, depending on a calibration of the RGB LED units, control signals for the assigned RGB LED units are generated in each driver circuit (3) so that they emit light within a target color space. Vehicle interior lighting system (1) according to claim 1, characterized in that the RGB LED units are continuously calibrated during its operation. Vehicle interior lighting system (1) according to claim 2, characterized in that environmental influences acting on the RGB LED units are compensated by the calibration of these. Vehicle interior lighting system (1) according to one of claims 1 to 3, characterized in that the calibration of the RGB LED units is carried out according to customer-specific specifications. Vehicle interior lighting system (1) according to one of claims 1 to 4, characterized in that each RGB LED unit has a red light-emitting LED (light-emitting diode), a green light-emitting LED and a blue light-emitting LED. Vehicle interior lighting system (1) according to claim 5, characterized in that a strip of RGB LED units is connected to each driver circuit (3). Vehicle interior lighting system (1) according to one of claims 1 to 6, characterized in that the target color space is transformed into a CIE-1931 color coordinate system. Vehicle interior lighting system (1) according to claim 7, characterized in that the parameters of the RGB LED units present in individual coordinate systems are transformed into the CIE-1931 color coordinate system and aligned with the target color space. Vehicle interior lighting system (1) according to claim 8, characterized in that PWM (pulse width modulation) signals are generated as control signals in the driver circuits (3) for the individual RGB LED units, by means of which the parameters of the RGB LED units are optimized with regard to the target color space. Vehicle interior lighting system (1) according to claim 9, characterized in that the optimization of the parameters of RGB LED units to the target color space takes place exclusively or predominantly in the red wavelength range. Vehicle interior lighting system (1) according to claims 1 to 10, characterized in that the computing unit is a microcontroller (2) in which no Manchester codec (5) is integrated, so that it sends these uncoded signals to the driver circuits (3). Vehicle interior lighting system (1) according to one of claims 1 to 11, characterized in that the driver circuits (3) are each formed by logic circuits. Vehicle interior lighting system (1) according to one of claims 1 to 12, characterized in that the Manchester codec (5) integrated in a driver circuit (3) is designed for encoding and decoding Manchester-coded signals. Vehicle interior lighting system (1) according to one of claims 1 to 13, characterized in that the Manchester codecs (5) of the driver circuits (3) are identical. Vehicle interior lighting system (1) according to one of claims 1 to 14, characterized in that the Manchester codecs (5) are formed in the driver circuits (3) of hardware circuits. Vehicle interior lighting system (1) according to one of claims 1 to 15, characterized in that a redundant camera system (20) is used to determine parameters of bands of RGB LED units. Vehicle interior lighting system (1) according to claim 16, characterized in that the redundant camera system (20) comprises a grayscale camera (21) and a color camera (22), the fields of view 23a, 23b of which are arranged in an overlapping manner. Vehicle interior lighting system (1) according to one of claims 16 or 17, characterized in that a band of RGB LED units is completely captured by the camera system (20) arranged in a fixed predetermined position. Vehicle interior lighting system (1) according to one of claims 17 or 18, characterized in that a vignetting coefficient of an image is determined with the grayscale camera (21), and that the corresponding image of the color camera (22) is corrected by means of the vignetting coefficient, and that the chromaticity of the band of RGB LED units is determined on the basis of corrected images of the color camera (22). Vehicle interior lighting system (1) according to one of claims 16 to 19, characterized in that the parameters of bands of RGB LED units can be determined in the respective customer application.

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