| With the rapid development of information society,head up display technology has shown great application value in many fields.The airborne head up display system projects the information,such as flight parameters,combat alarm and so on,at infinity in front of the pilot superimposed on the scene through the collimating optical display method.The airborne head up display system directly determines the information capacity and situation awareness ability received by the pilot in unit time,which plays an irreplaceable role in improving the combat performance of the fighter and ensuring its flight safety.The traditional head up display system uses the discrete optical lens group,which has large volume and weight,and its performance is easily limited by the cockpit assembly space.The integration degree of abundant airborne equipment is deepening day by day,and the requirements of airborne cockpit assembly space are increasingly demanding.The traditional head up display system has been difficult to meet the new requirements.The new generation of light guided head up display system can effectively realize the miniaturization and lightweight of the system while ensuring the optical performance of the observation range and field of view.Light guided head up display technology has become an inevitable trend in this field.The light guided head up display technology adopts the multiple composite imaging principles,which has many application problems such as display continuity,"shutter effect" and "bright light flare effect".However,the research on the light guided head up display technology at home and abroad is rarely introduced.In order to meet the requirements of compact cockpit assembly,In this paper,the principle of light guided display is analyzed to overcome many key technologies and preparation processes,such as multiple composite continuous imaging,film array "shutter effect" suppression,and "exterior bright light flare effect" suppression.It studies flat light guided head up display system,optimizes display performance,and makes flexible layout in compact cockpit,Compatible with multiple models.The main research contents and conclusions are as follows.1)The propagation of image light in flat waveguide is analyzed by waveguide theory,which provides data for the extension of image light and the assembly.The diffraction characteristics of waveguide holographic volume grating are analyzed.Compared with conventional volume grating,waveguide reflection holographic volume grating has lower wavelength selectivity and higher diffraction efficiency,which is conducive to the application in display system.This paper analyzes the film used in the geometric light guided display.The bidirectional polarization are selected optimally,among which the bidirectional polarization can improve the natural scene under the condition of ensuring the display efficiency of the optical system.At the same time,the composition and function of the airborne light guided head up display are analyzed.The I optical configuration scheme is selected for the design of the head up display system.2)The optical system of low profile light guided head up display is designed.This paper introduces the 3.8inch polarized liquid crystal image source.A belt relay lens optical system is designed to realize the combiner of I light gudied head up display.The display image quality of the system is excellent,the distortion is less than 1%,the field of view reaches 20 °× 16 °,and the resolution is 1024 × 768.3)In view of the multiple composite imaging of the light guided head up display,the image light is divided into several times in the waveguide plate through the uniform optical channel,the light distribution area is expanded,and the imaging continuity control technology is overcome.The performance characteristics of different reflection films are compared and analyzed,and the “shutter effect” of geometric light guided combiner is solved by the bidirectional polarization splitting design.Through the theory of thin grating decomposition,the reflection holographic grating is adopted,and the gradual change of the refractive index of the surface layer of the grating film is processed,and breaks through the "bright light flare effect" suppression of the diffractive light guided head up display combiner.4)In order to avoid the introduction of stress and the damage of gluing boundary,the preparation scheme of the geometric light guided combiner is designed,and the ring polishing and grinding equipment is proposed.5)The holographic volume grating recording materials are analyzed and compared,and selected the dichromate gelatin recording materials with high transmittance and refractive index modulation to prepare the waveguide holographic volume grating.The method of controlling the exposure intensity is used to control the exposure amount.Through the application of the copper plate,the gradual diffraction efficiency distribution of the grating is realized.In order to reduce the noise and improve the quality,a double beam exposure is used to couple the light through the optical prism,and the holographic plate is soaked in the matching liquid tank.The refractive index of the optical prism,the holographic substrate and the matching liquid are the same.The fabrication process of the holographic volume grating of the diffractive light guided head up display combiner is designed.The dichromate gelatin recording plate is pretreated by 365 nm UVLED,and then the holographic volume grating of the waveguide is exposed coherently.After the chemical treatment,the diffraction peak is monitored by the spectro-photometer to match the display wavelength,and the control error is not more than ± 2nm.6)The combiner of geometric light guided head up display and diffractive light guided head up display are fabricated and assembled with the belt relay system.The geometric light guided head up display system has uniform visibility and effectively suppresses the "shutter effect".The thickness of the combiner is 18 mm,and the display efficiency is more than 10%.There is achromatic in the virtual picture of the diffractive light guided head up display system,and there is no obvious "flare effect" under the bright light in the outside scene.The thickness of the combiner is 8mm.The airborne light guided head up display system has the advantages of light-weight,low profile,modularization,frameless and so on.It can be compatible with a variety of platforms,and it is conducive to the improvement of man-machine efficiency. |
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