What’s the Best Light Distribution and Diffuser Concentration of Multi – Function Integrated LED Automobile Signal Lamp ?

According to the installation regulations of the automobile optical signal device in the national standard, the signal lamp, as an important indication and reminder function device of the automobile, is required to be equipped. With the rise of LED technology, the shape of automobile signal lights is becoming more and more diversified. The optical design of automobile signal lights mainly adopts three kinds of structures: the first is the form of the light guide, such as Buick’s new Yinglong model; the second is the form of reflection bowl, such as GAC MOTOR’s 2013 GS4; and the third is the form of thick-walled parts, such as Xiaopeng’s G3.

The signal lamp developed in this paper is based on the third optical design, which adds an internal light distribution mirror with light diffuser in front of the thick-walled parts to achieve the effect of uniform light distribution. The uniformity of signal lights has gradually become the mainstream requirement and combined with the use of diffuser materials, the uniformity of signal lights can be greatly improved. At present, Tesla Model S / Model X and Roewe RX5 Plus are all equipped with diffuser to increase the uniformity of the front position lamp, but due to the light distribution requirements of the turn light, the Roewe RX5 Plus turn signal is still equipped with fully transparent material. In this paper, the proportional relationship between light distribution and diffuser concentration of various signal lights is analyzed and compared.

Optical Design of three-in-one signal Lamp

Hechuang 007 front combination lights, signal lights-front position.
The three functions of the light, the daytime driving light and the front turn signal are integrated, as shown in figure 1.

Combined with the application of optical diffuser, the signal lamp of the front combination lamp realizes the LED signal lamp with three functions in one, and its optical structure is shown in figure 2. The light line passes through the light port into the thick-walled part, and after passing through, the full reflection surface is reflected into the front diffuser, and the light is divergent after passing through the diffuser.
According to the input of the material company, the diffuser database does not support optical simulation for the time being. Therefore, combined with the physical test results, this paper will compare the different diffuser material ratio and the actual LED signal lamp light distribution test results, and get the diffuser material ratio and the light distribution value change trend, as well as the light distribution value in line with the critical value of laws and regulations.

2 national standard light distribution requirements

The national standard has light distribution performance requirements for front position lights, daytime driving lights and front turn signals of cars and trailers, respectively. Due to the integration of the three functions, the designed LED semaphore must consider the minimum and maximum values of the three regulations at the same time. The minimum light intensity distribution requirements and light intensity limits of the regulations are as follows.

2. 1 front position lamp.
According to GB 5920 “car and trailer front lamp, rear lamp, outline”
The light distribution performance of lamp and brake lamp requires [1] that the luminous intensity of the points on the light distribution screen in figure 3 projected from all measuring directions of the front lamp (single lamp) should not be lower than the product of the percentage value of each point shown in figure 3 and 4 cd. At the same time, the luminous intensity should not be greater than 60 cd in any direction visible from the front light.

According to figure 3, we can get the minimum light intensity distribution of each measuring direction of the front lamp as shown in Table 1.

2. 2 daytime traffic lights.
According to GB 23255 “Light distribution performance of motor vehicle driving lights during daytime” [2].
It is required that the luminous intensity of the light from all measuring directions of the daytime driving light projected to the points on the light distribution screen in figure 4 should not be lower than the product of the percentage values of the points shown in figure 4 and 400 cd. At the same time, the luminous intensity should not be greater than 1200 cd in any direction in which the driving lights are visible during the day.

According to figure 4, we can get the minimum light intensity distribution of daytime driving lights in each measuring direction as shown in Table 2.

2. 3 front turn signal

According to the requirements of GB 17509 “Light distribution of steering signal lights for automobiles and trailers” [3], the direction signal luminous area of Hechuang007 is more than 20 mm and less than 40 mm from the near luminous area, which belongs to Class 1a front steering light. The luminous intensity of the light in all measuring directions of the class 1a front steering light projected to the points on the light distribution screen in figure 5 should not be lower than the product of the percentage values of the points shown in figure 5 and 250 cd. At the same time, the luminous intensity should not be more than 800cd in any direction in which the driving lights are visible during the day.

According to figure 5, we can get the minimum light intensity distribution of class 1a front steering lights in each measuring direction as shown in Table 3.

(3) the actual test results and analysis pass the polycarbonate (PC) material in the internal light distribution mirror (internal).
The diffuser was mixed into the material, and the mass fraction was 0%, 3%, 4%, 5% and 7%, respectively. The light distribution of the three-function LED signal lamp was tested by V-H coordinate system test method [4]. Compared with the requirements of the national standard, the test results which are not satisfied with the light distribution of the laws and regulations are listed emphatically.
As shown in Table 4 and Table 5, the HV points of front position lights and daytime driving lights do not meet the requirements of regulations, and the light intensity of HV points exceeds the upper limit of regulations without adding diffuser.

ATT: Note: the italic number indicates that the light distribution result in this direction does not meet the requirements of the regulations; the “compliance” table shows that the position conforms to the light distribution regulations, but the accurate test value is not obtained.

At the same time, Table 5 also shows that the light intensity in the range of 5 °above and below and around 5 °of the HV point circle of the daytime driving light distribution screen also exceeds the upper limit required by the regulations.

When the diffuser ratio reaches 5%, the light intensity values of class 1a front turn signal HV point, H-5L point and H-5R point are lower than the lower limit required by the regulations, and the light distribution results are shown in Table 6.

Note: the italic number indicates that the light distribution result in this direction does not meet the requirements of the regulations; the “compliance” table shows that the position conforms to the light distribution regulations, but the accurate test value is not obtained.

As shown in Table 7, when the diffuser ratio reaches 7%, the light intensity values of HV, H-5R and H-10R points on the daytime light distribution screen are lower than the lower limits required by regulations, which limit the increase of diffuser concentration.

As shown in Table 8, when the diffuser ratio reaches 7%, the light intensity in the range of 5 °above and below and around 5 °of the HV points on the light distribution screen of Class 1a front turn signals is lower than the lower limit required by regulations, and the light distribution points in these areas limit the increase of diffuser concentration.

Note: italic numbers indicate that the light distribution results in this direction do not meet the requirements of laws and regulations.

According to the analysis of the above actual test results, when the diffuser concentration changes, the light intensity values of the HV points of front lights, daytime driving lights and front turn signals will change accordingly, such as Table 9, the last row of “turn signal VIS” in the table is the light intensity value of the angle of view light distribution point of turn signal D15-R45, and its changing trend is opposite to that of HV point.

It can be seen from Table 9 that the HV light distribution values of the three functions all decrease with the increase of the diffuser ratio. Among them, the light distribution value of the HV point of the daytime driving light changes most obviously, and the light intensity value when the diffuser ratio reaches 7% is about 1 / 4 of that of the non-diffuser. At the same time, the light intensity value of the viewing angle distribution point of the steering light D15-R45 increases with the increase of the diffuser ratio, and the light intensity value when the diffuser ratio reaches 7% is 2. 5 times that of the non-diffuser.

Note: the italic number indicates that the light distribution result in this direction does not meet the requirements of the regulations; the “compliance” table shows that the position conforms to the light distribution regulations, but the accurate test value is not obtained.

4 conclusion

According to the above discussion, it is found that the addition of diffuser can effectively increase the light intensity at the viewing angle and reduce the light intensity at the center of the light distribution screen. Combined with the light distribution results of the three-in-one LED automobile signal lights in this paper, the reasonable range of diffuser ratio should be less than 5%.

Furthermore, the range of diffuser ratio discussed in this paper is based on the effective luminous region and optical structure of the combined lamp in front of Hechuang 007 (figure 2). The corresponding allocation needs to be made according to the actual luminous structure.