CN103868921A - Method for determining emissivity of key surface coating of weak target detection infrared camera - Google Patents

Abstract

A method for determining the emissivity of a coating on a key surface of a weak target detection infrared camera. The stray light of the weak target detection infrared camera is divided into internal stray light and external stray light. When selecting the emissivity of key surfaces, the effects of suppression measures on internal stray light and external stray light are contradictory, and it is necessary to take comprehensive suppression measures for internal stray light and external stray light of infrared optical remote sensors. This method finds the optimal value of the surface coating emissivity by analyzing the change trend of internal stray light and external stray light when the emissivity value of the key surface coating of the weak target detection infrared camera changes, so that the emissivity satisfies the requirement of internal stray light at the same time. Combined suppression requirements with external stray light.

Description

A Method for Determining Emissivity of Key Surface Coatings of Infrared Cameras for Weak Target Detection

technical field

The invention relates to a method for determining the emissivity of a key surface coating of a weak target detection infrared camera, which is mainly used in the stray radiation analysis and suppression design of the weak target detection infrared camera in the field of aviation or spaceflight.

Background technique

For a weak target detection infrared camera in a working state, such as an infrared seeker camera or a space-based infrared early warning camera, the stray light reaching the infrared detector array of the camera can be divided into two categories: one is the camera object space vision The stray light outside the field is called external stray light, and stray light sources such as sunlight and diffuse reflection light of the earth atmosphere; the other type is the thermal radiation generated by the camera's optical-mechanical system itself, called internal stray light, stray light Light sources such as structural components, lenses, mirrors and other component surfaces, etc., this part of stray light is determined by the temperature of the system itself, the emissivity and area of the surface where thermal radiation occurs, and other factors. In weak target detection infrared cameras, regardless of internal stray light or external stray light, if the suppression effect is not ideal, it will cause misjudgment or false alarm of the target, which greatly affects the detection efficiency of the target.

At present, the suppression measures for the level of stray light in the infrared camera optical system mainly include three categories: the first part is the macroscopic structure control of stray light, and its main measures adopt methods such as hoods and light blocking rings; the second category is the control of stray light. For microstructure control, the main measures are such as surface microthreads, surface roughness rationalization, etc.; the third category mainly uses the coating characteristics of the surface.

According to Planck's law, the increase of the emissivity of the surface coating of the radiation source will increase the gray body radiation power generated by the radiation source itself, thus increasing the influence of internal stray light on the system resolution. However, when suppressing external stray light, black coating is applied to the surface to maximize the absorption of light radiation energy, reduce the reflection of light radiation energy and improve the scattering characteristics of the surface, but increasing the spectral absorption rate also increases the spectral emission Rate. Therefore, when selecting the emissivity of the surface coating, the suppression effects on internal stray light and external stray light are often contradictory.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the current situation that the emissivity design of the key surface coating of the existing weak target detection infrared camera has contradictory effects on the suppression of internal and external stray light, and provide a key surface coating of the weak target detection infrared camera The emissivity determination method is to find out the optimal value of the emissivity of the surface coating by analyzing the change trend of internal stray light and external stray light when the emissivity value of the key surface coating of the weak target detection infrared camera changes, so that the emissivity satisfies both Combined suppression requirements for internal stray light and external stray light.

The technical solution of the present invention is: a method for determining the emissivity of the key surface coating of a weak target detection infrared camera, which is characterized in that the implementation steps are as follows:

(1) Find the same key surface for internal stray light and external stray light; the internal stray light refers to the thermal radiation generated internally by the weak target detection infrared camera system itself, stray light sources, such as structural components, lenses , mirrors and other component surfaces, this part of the stray light is determined by factors such as the temperature of the camera itself, the surface emissivity and area of the heat radiation component; the external stray light refers to the object space vision of the weak target detection infrared camera Stray light outside the field, stray light sources such as sunlight and diffuse reflection light from the earth; through the analysis of internal stray light and external stray light, find out all the key surfaces related to internal and external stray light, and find out the Both stray light and external stray light have the same critical surface; the critical surface may include 1 or more than 1, if it is 1 critical surface, perform the following steps once; if it is more than 1, Repeat the following steps according to the number of key surfaces;

(2) Set different surface emissivity values for the key surfaces mentioned in step (1). The upper and lower limits of the emissivity depend on the current engineering practice. For example, set 9 emissivity values from 0.1 to 0.9 with an interval of 0.1. Re-analyze the internal stray light and external stray light of the weak target detection infrared camera, and find out the trends of internal stray light and external stray light as the emissivity changes;

(3) If the internal stray light and external stray light described in step (2) have the same changing trend with the change of emissivity, then take the maximum value of reflectance as 0.9; if the internal stray light and external stray light in step (2) The trend of stray light changing with emissivity changes is different, the weight values of internal stray light and external stray light under different emissivity are calculated respectively, and the weight values of internal stray light and external stray light under different emissivity are summed to find out The emissivity value corresponding to the minimum sum of the weight value is the emissivity value of the key surface. At this time, the comprehensive suppression of the stray light of the weak target detection infrared camera is completed.

The beneficial effect of the present invention compared with prior art is:

(1) The present invention overcomes the current situation that the emissivity design of the key surface coating of the weak target detection infrared camera has contradictory effects on the suppression of internal and external stray light. By analyzing the change of the emissivity value of the key surface coating of the weak target detection infrared camera According to the change trend of internal stray light and external stray light, the optimal value of surface coating emissivity is found, so that the emissivity can meet the comprehensive suppression requirements of internal stray light and external stray light at the same time.

(2) The surface coating emissivity design method proposed by the present invention embodies the idea of comprehensive analysis and suppression of internal stray light and external stray light of weak target detection infrared cameras, and applies this method to specific weak target detection infrared cameras In the analysis of stray radiation, it can provide the best stray radiation suppression measures for the camera, which is of great significance to improve the detection efficiency of weak target infrared cameras.

Description of drawings

Fig. 1 is a flow chart of the implementation of the key surface coating emissivity design method of the present invention.

Detailed ways

The specific embodiment of the present invention is shown in Figure 1, mainly is divided into following three steps and implements:

Step one, find out the same key surface for internal and external stray light. The internal stray light refers to the thermal radiation generated internally by the weak target detection infrared camera system itself, stray light sources such as the surface of components such as structural components, lenses, mirrors, etc., this part of stray light is caused by the temperature of the camera itself, It is determined by factors such as the surface emissivity and area of the thermal radiation element; the external stray light refers to the stray light outside the field of view of the object space of the weak target detection infrared camera, stray light sources such as sunlight, diffuse reflection light of the earth atmosphere . Through the analysis of internal stray light and external stray light, find out all key surfaces related to internal and external stray light respectively, and find out the same key surface for both. The said key surface may include 1 or more than 1, if it is 1 key surface, then perform step 2 and step 3 once; if it is more than 1, then repeat step 2 and step 3, repeat The number of times is the same as the number of key surfaces.

Step 2. Set different surface emissivity values for the key surfaces mentioned in step 1. The upper and lower limits of the emissivity depend on the current engineering practice. Set 9 emissivity values from 0.1 to 0.9 with an interval of 0.1 for weak targets The analysis and calculation of the internal and external stray light of the detection infrared camera obtains the weight values of the internal and external stray light under 9 emissivity. Figure 2 shows the calculation results of the internal and external stray light of a weak target infrared camera. This graph lists the weights of internal and external stray light as a function of surface coating emissivity.

Step 3, look for the trend of internal and external stray light changing with the change of emissivity, if the trend of internal and external stray light changing with the change of emissivity described in step 2 is the same, then take the maximum value of reflectance 0.9; if In step (2), the internal and external stray light have different changing trends with emissivity changes, which means that the uniform emissivity value has contradictory effects on the suppression of internal and external stray radiation, as shown in Table 1.

Table 1 Internal stray light and external stray light weights for critical surfaces with different emissivity

Sum the weight values of internal and external stray light under different emissivity, and find out the emissivity value corresponding to the minimum sum of weight values. This emissivity value is the emissivity value of the key surface. The key in Table 1 When the emissivity of the surface coating is 0.7, the sum of the weight values of the internal and external stray light is the minimum value. At this time, the optimal value of the emissivity of the surface coating for this weak target to detect the stray light of the infrared camera is 0.7. The process Finish.

The contents not described in detail in the present invention belong to the well-known technology of those skilled in the art.

Claims (1)

1. a little less than, target detection infrared camera critical surfaces coating emissivity is determined a method, it is characterized in that performing step is as follows:

(1) find out the critical surfaces identical with external stray light for inner parasitic light; Described inside parasitic light refers to weak target detection infrared camera system from the heat radiation, the source of stray light that produce in inside, and this part parasitic light is to be determined by the temperature of camera self, the slin emissivity that hot radiant element occurs and area factor; Described external stray light refers to the parasitic light beyond weak target detection infrared camera object space visual field; By the analysis to inner parasitic light and external stray light, find out respectively all critical surfaces relevant to inside and outside portion parasitic light, find out the critical surfaces identical with external stray light for inner parasitic light; Described critical surfaces may comprise 1 or more than 1, if 1 critical surfaces is carried out following step (2) once; If more than 1, repeat respectively following step (2) according to the number of critical surfaces;

(2) critical surfaces described in step (1) is arranged to different slin emissivity values, the upper and lower bound of emissivity all depends on current engineering reality, 9 emissivity are set by 0.1～0.9, be spaced apart 0.1, re-start the inside parasitic light of weak target detection infrared camera and the analysis of external stray light, find out respectively the trend that inner parasitic light and external stray light change with emissivity;

(3) if the inside parasitic light described in step (2) is identical with the trend that external stray light changes with emissivity, get the maximal value 0.9 of reflectivity; If the inside parasitic light in step (2) is different with the trend that external stray light changes with emissivity, calculate respectively the weighted value of inner parasitic light and external stray light under different emissivity, the weighted value of inner parasitic light and external stray light under different emissivity is added and, find out that weighted value adds and hour corresponding emissivity value, this emissivity value is the emissivity value of critical surfaces, has now completed the comprehensive inhibition of weak target detection infrared camera parasitic light.

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