Design And Analysis Of Focusing Mechanism In High Resolution Space Camera

Space optical remote sensor is a important way to obtain remote sensing image,and is used in meteorology,geological exploration,agriculture,forestry,marine,environment,military,and disaster relief,which has a vast market prospect.Space camera will defocus under the condition that the influence space environment(such as temperature,pressure,etc.)change and shock vibration cause changes of positions and shapes of optical mirrors and refractive index of optical elements,which cause the deterioration of imaging quality in the process of transportation,transmission,or in-orbit operation.Therefore,in order to ensure the imaging quality of the camera,it is necessary for ensuring the imaging quality of the camera to design a focusing mechanism to compensate the optical system’s defocus.With the development of the high resolution space camera,the design of the focusing mechanism has higher requirements.On the one hand,the size of the focal plane and is the weight of the focusing mechanism is increased constantly with improvement of the resolution and the view field in the space camera.So the focusing mechanism must have higher stiffness and stability.On the other hand,the improvement of space camera resolution is mainly achieved through the increase of aperture and focal length,which makes the structure of the camera more complex,and the changes of environment will have a greater impact on the optical mirrors and mechanical parts.At the same time,the effect of defocus on image quality is more significant.So the focusing mechanism must have a greater focus range and higher precision.In conclusion,focusing mechanisms improve the adaptability of optical remote sensor to the space environment,and the development of high resolution space camera focusing mechanisms also faces more challenges.In this paper,the main factors that cause the camera to focus are analyzed,and a focusing mechanism of double cams is designed based on the characteristics of camera optical system in the background of a high resolution space camera.At the same time,Monte Carlo method was applied to calculate the precision of the mechanism and the error distribution was completed.Nonlinear finite element method is used to analyze the self-locking of the mechanism under loads of vibration and shock.the mechanism’s prototype was tested after the development of the focusing mechanism.The main contents of this paper is:(1)The structures of the focal mechanisms of space optical remote sensor is investigated.The necessity of the design of focusing mechanism is discussed by comparing the various focusing methods and combining with the actual project demand of the high resolution space camera.(2)Main factors that cause the camera defocus are expatiated,and it is analyzed that the specific requirements of precision performance of focusing mechanism for the high resolution space camera.(3)The error sources of the components in the focusing mechanism are analyzed and the error synthesis model is established.Monte Carlo method was used to calculate the precision parameters of the focusing mechanism and the error distribution was completed.(4)In order to guarantee the normal work of the focusing mechanism under in-orbit conditions,self-locking of the mechanism are analyzed in detail by nonlinear finite element method under complex dynamic environment,and the modal,the response of sinusoidal vibration and random vibration of the focusing mechanism are analyzed.(5)The positioning accuracy of the focusing mechanism and shaking amounts of the whole trip are tested.The vibration test of the prototype is completed and the precision of the mechanism is tested again.It shows that the precision of the focusing mechanism satisfies the requirement of indicators,and it is little that changes of the positioning accuracy and shaking amounts of the focal plane before and after the vibration test,and the focusing mechanism possesses good self-locking and dynamic mechanical properties.