National Institute of Metrology P.r. China

Beijing University of Technology

Guizhou Expressway Group Co., Ltd (cn)

National Institute of Metrology Peoples Republic of China

National Istitute of Metrology P.r. China

Jianping Cao

Ye Li

Zhanjun Fang

Erjun Zang

Feng Liu

Meng Wang

Yang Zhao

Xiaoyu Li

Yuanfeng Zhang

Xiaojuan Gao

Linxi Gao

Jiangbi Hu

Xiaoqin Zhang

Wenqian Ma

Weili Wang

Da Guo

Shaokai Wang

Shilong Mei

Xiaoshun Lu

The invention relates to an illumination standard calculation method for a tunnel entrance section in daytime based on safe visual recognition. The method includes: (a) setting light environment parameters of the tunnel entrance section; (b) determining a feature position in the tunnel, and measuring the average road surface brightness L of the feature position; (c) placing a target object in the feature position and then making a driver drive at different speeds from outside the tunnel towards the target object to measure visual recognition distances D required by the driver to visually discover the target object under different driving speeds, and measuring the road surface brightness Lat the position where the driver visually discovers the target object and calculating the brightness reduction factor K to be the ratio between L and L; (d) resetting the average road surface brightness L of the tunnel entrance section and repeating steps (b) and (c) to obtain a plurality of different sets of visual recognition distances D and corresponding brightness reduction factors K; (e) using Sigmoid function model to calculate and fit the data of the plurality of sets of D and K to obtain a relational model formula of D and K: (f) substituting a safe stopping sight distance Dcorresponding to a maximum speed limit of the tunnel into the formula to obtain the minimum brightness reduction factor Kof the tunnel entrance section in daytime. The invention also relates to a system for implementing the illumination standard calculation method for a tunnel entrance section in daytime based on safe visual recognition.

Illumination standard calculation method and system for a tunnel entrance section in daytime based on safe visual recognition

A method for quasi-synchronous tuning of wavelength or frequency of grating external-cavity semiconductor laser and a corresponding semiconductor laser are provided. A grating or mirror is rotated around a quasi-synchronous tuning point (Pq) as rotation center, so as to achieve the frequency selections by grating and resonance cavity in quasi-synchronous tuning, wherein the angle of the line between the quasi-synchronous tuning point (Pq) and a conventional synchronous tuning point (P) with respect to the direction of light incident on the grating is determined according to the angle difference between the incidence angle and diffraction angle of light on the grating. According to present invention, approximately synchronous tuning of laser is achieved with a simple and flexible design.

Grating external-cavity semiconductor laser and quasi-synchronous tuning method thereof

A method for quasi-synchronous tuning of wavelength or frequency of grating external-cavity semiconductor laser and a corresponding semiconductor laser are provided. A grating or mirror is rotated around a quasi-synchronous tuning point (Pq) as rotation center, so as to achieve the frequency selections by grating and resonance cavity in quasi-synchronous tuning, wherein the angle of the line between the quasi-synchronous tuning point (Pq) and a conventional synchronous tuning point (P0) with respect to the direction of light incident on the grating is determined according to the angle difference between the incidence angle and diffraction angle of light on the grating. According to present invention, approximately synchronous tuning of laser is achieved with a simple and flexible design.

Grating external-cavity semiconductor laser and quasi-synchronous method thereof

A method for quasi-synchronous tuning of laser wavelength or frequency of grating external-cavity laser and a corresponding laser are provided. A grating or mirror is rotated around a quasi-synchronous tuning point (P) to achieve the quasi-synchronous tuning of frequency selections by grating and resonance cavity, wherein, on the xOy coordinate plane, from the perspective of actual physical space of the laser, the rotation center P(x, y) satisfying the quasi-synchronous tuning condition can be considered as being extended from the rotation center P(x, y) under the conventional synchronous tuning condition to the region enclosed by two parabolas near P. According to the present disclosure, approximately-synchronous tuning of laser is achieved with simple and flexible designs.

Grating external-cavity laser and quasi-synchronous tuning method thereof

The disclosure discloses a Fabry-Perot (F-P) cavity, which is a folded confocal cavity integrally formed by a monolithic optical element, the folded confocal cavity having three reflection surfaces, wherein a first reflection surface is a plane and at the same time serves as an input/output coupling surface, a second reflection surface is a plane, and a third surface is a spherical surface, curvature radius of which is equal to half of a round trip geometric length of light in the folded confocal cavity. The invention further discloses a laser based on the F-P cavity. The solution of the disclosure solves the problems in existing folded F-P cavity, such as unsatisfactory stability, sensitive to outside inferences, bulky and complicated construction.

F-P cavity and laser using said F-P cavity

This invention relates to a monolithic folded F-P cavity used for semiconductor laser, which is composed of a monolithic optical element. The monolithic optical element is made of the material having low propagation loss for a certain spectrum range. Light entering through an input/output coupling surface of the monolithic optical element is reflected several times between the input/output coupling surface and at least two high reflection surfaces within the monolithic optical element, and then at least one part of the light exits through the input/output coupling surface along the path which is collinear with the incident light but in an opposite direction. By means of integrating reflecting and coupling parts of the folded F-P cavity within a single monolithic optical material, this invention greatly improves the reliability of the F-P cavity, and has other advantages, such as insensitive to outside interferences, smaller size, simpler structure and easy usage. A semiconductor laser using the monolithic folded F-P cavity is also provided.

Monolithic folded F-P cavity and semiconductor laser using the same

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Jianping Cao