CN201532254U - Automatic focusing device of thermal imaging system - Google Patents

Abstract

The utility model relates to an automatic focusing device of a thermal imaging system. The utility model adopts the technical scheme that the automatic focusing device of the thermal imaging system comprises a microprocessor, a video-frequency input circuit, a motor driving circuit and a serial-port communication circuit, wherein the microprocessor comprises an image acquisition module, an image definition judgment module, a UART communication module and a motor control module; the image acquisition module is used for receiving a processed infrared image input through the thermal imaging system and enabling the required digital signal to be read into a memory according to a focusing window set in advance, and the image definition judgment module is used for calculating the definition evaluation function value according to the digital signal read into the memory; and the motor control module is connected with the motor driving circuit, and the UART communication module is used for communication with the outside. By adopting the technical scheme, the utility model can improve the imaging quality, reduce the repeated manual work, reduce the manual intervention and enhance the convenience of use.

Description

The thermal imaging system automatic focusing system

Technical field

The utility model relates to a kind of thermal imaging system automatic focusing system, and it is long to be particularly useful for stroke, and the automatic control of the infrared lens that the direct current generator that load is big drives belongs to the infrared image processing technical field.

Background technology

Obtain distinct image and be the basic demand of various digital imaging apparatus, be provided with one group of focusing lens in the many set of contact lenses of pick-up lens specially, can reach the focusing purpose by the position that changes the focus groups eyeglass, automatic focus can replace manually finishing this process, thereby save the plenty of time, improve image quality.Automatic focus can be divided into active and passive type two classes.Active automatic focus is to utilize emission infrared ray or ultrasound wave to measure the distance of object, and uses certain calculated with mathematical model to go out best focus position, and this mode needs extra distance-measuring equipment, and the scope of application is less relatively.Passive mode refers to utilize the own information of the image that obtains to judge whether image is clear, and provide feedback signal controls lens motion, the realization of this auto-focusing algorithm based on Flame Image Process does not need extra signal source and corresponding receiving sensor, help the reduction of device volume and reduce cost, so adopted widely.

Because the used infrared lens manufactured materials of thermal imaging system is different with the general visible camera lens, so adopt the hand rotation camera lens usually or manually control direct current generator drive camera lens and obtain to focus on distinct image, this method adjustment process is long, and it is bigger that focusing accuracy is influenced by operating personnel's subjectivity; Infrared thermal imaging has reflected the Temperature Distribution of body surface, the heat picture of target is different with the visible images that human eye can be seen, the visible light camera lens adopts stepper motor to drive usually, searching algorithm is usually at step motor control, so existing application is in the passive type automatic focus technology of CCD visible images and be not suitable for thermal imaging system.

Summary of the invention

The utility model is at the existing in prior technology shortcoming, and a kind of technical scheme at the thermal imaging system automatic focusing system is provided, and adopts this scheme can improve image quality, reduces manual operation repeatedly, strengthens ease of use.

The utility model is realized by following technical measures: a kind of thermal imaging system automatic focusing system, it comprises microprocessor, video input circuit, motor-drive circuit, serial communication circuit, microprocessor comprise image capture module, image definition judge module, UART communication module, motor control module; Described image capture module is used to receive the processed infrared image of thermal imaging system output, and the digital signal of needs is read in internal memory according to predefined focus window, described image definition judge module is used for according to the digital signal of reading in internal memory, specifically can adopt pixel difference template operator to calculate the sharpness evaluation function value; Described motor control module is connected with motor-drive circuit, and described UART communication module is used for and outside communication, and wherein, video input circuit can receive the analog video signal of thermal imaging system, also can receive the digital video signal of thermal imaging system.

Above-mentioned microprocessor also is connected with SRAM.

Above-mentioned microprocessor is connected with FLASH.

Above-mentioned microprocessor is connected with level transferring chip.

The beneficial effect of this programme can learn that microprocessor can find best focus position quickly and accurately according to the narration to such scheme, reduces manual operation repeatedly, reduces manual intervention, improves image quality and strengthens ease of use.

Description of drawings

Fig. 1 is the hardware principle block diagram of the utility model embodiment.

Fig. 2 is the main program flow chart of the utility model embodiment.

Among the figure, 1, video input circuit, 2, microprocessor, 3, motor-drive circuit, 4, serial communication circuit, 5, power management module, 6, SRAM, 7, FLASH, 8, image capture module, 9, the UART communication module, 10, the image definition judge module, 11, motor control module.

Embodiment

For clearly demonstrating the technical characterstic of this programme,, this programme is set forth below by embodiment.

As shown in Figure 1, a kind of thermal imaging system automatic focusing system, it comprises microprocessor 2, video input circuit 1, motor-drive circuit 3, serial communication circuit 4, microprocessor 2 comprise image capture module 8, image definition judge module 10, UART communication module 9, motor control module 11; Described image capture module 8 is used to receive the processed infrared image of thermal imaging system output, and the digital signal of needs is read in internal memory according to predefined focus window, described image definition judge module 10 is used for according to the digital signal of reading in internal memory, calculate the sharpness evaluation function value, concrete employing is that pixel difference template detection edge grey scale change is calculated the sharpness evaluation function value in this embodiment; Described motor control module 11 is connected with motor-drive circuit 3, and described UART communication module 9 is used for and outside communication.Microprocessor 2 also is connected with SRAM 6, FLASH 7.

As shown in Figure 1, the composite video signal of thermal imaging system output converts eight digit number word image signal to through video input circuit 1, microprocessor 2 reads in internal memory according to predefined focus window with the digital signal of needs, calculate the sharpness evaluation function value and drive the rotation of focusing motor by image definition judge module 10 by motor control module 11, until finding best focus position, motor is parked in this position finishes auto-focus function.Because the control signal voltage of microprocessor output is lower, driving force a little less than, need be connected to direct current generator by motor-drive circuit 3.Power management module 5 provides operate as normal required various voltages for system's each several part circuit.UART communication module 9 is responsible for and outside communication, and the external control order comprises image pre-filtering setting (picture quality does not need smoothing processing under the situation preferably usually), the step-size in search setting, and focus window is selected, and the sharpness evaluation function threshold value is provided with etc.Level transferring chip 4 converts the Transistor-Transistor Logic level of microprocessor to the RS232 level.

SRAM 6 is a static RAM, and it is temporary to be used for working procedure and view data, and FLASH7 is a flash memory, it can keep canned data for a long time under the situation of outage, the characteristics of existing ROM have very high access speed again, are used for the storage microprocessor program code in this device.

The Digital Image Processing theory is thought, how many image focusing degree (being whether image is clear) mainly determining by light distribution medium-high frequency component, image blurring essence is the loss of high fdrequency component, the image of Ju Jiaoing comprises more details and quantity of information than the image of out of focus fully, whether piece image focuses on, be reflected on the spatial domain is whether the border and the detail section of image be clear, defocusing amount is more little, the image border is sharp more, grey scale change Shaoxing opera is strong, and its differential value is just big more, and the utility model is exactly according to these characteristics, employing pixel difference template is carried out edge texture extraction to image and is added up, thereby calculates sharpness evaluation function.The sharpness evaluation function computing method of image definition judge module 10 are as follows:

At first adopting difference template operator to carry out the edge texture to focal zone detects, this operator comprises two groups of 3x3 matrixes, be respectively and laterally reach vertically, it and image are done the plane convolution, can draw respectively and laterally reach grey scale difference approximate value longitudinally, with F (x, y) representative point (x, original image gray scale y):

Directions X: $\left[\begin{array}{ccc}+4& -1& -3\\ +1& 0& -1\\ +1& 0& -1\end{array}\right]$ The Y direction: $\left[\begin{array}{ccc}+4& +1& +1\\ -1& 0& 0\\ -3& -1& -1\end{array}\right]$

(x, convolution y) adds up to be averaged again and can obtain sharpness evaluation function E to calculate each point.

Gx＝4*F(x，y)-F(x+1，y)-3*F(x+2，y)+F(x，y+1)-F(x+2，y+1)+F(x，y+2)-F(x+2，y+2)，

Gy＝4*F(x，y)-F(x，y+1)-3*F(x，y+2)+F(x+1，y)-F(x+1，y+2)+F(x+2，y)-F(x+2，y+2)，

$E=\underset{x}{\mathrm{\Σ}}\underset{y}{\mathrm{\Σ}}G(x,y)/n$ T ₁＞G(x，y)＞T ₂，

Wherein G (x, y)=| Gx|+|Gy|, n are scale factor, are directly proportional with the total number of the pixel in the focal zone, and T1, T2 are the size threshold value of grey scale difference, after handling through thresholding, can effectively reduce noise.

Desirable sharpness evaluation function has unimodality and monotonicity, and unimodality is meant to have only an extreme value in range of adjustment, and corresponding to the optimal imaging position, monotonicity is meant in extreme value both sides monotone increasing or monotone decreasing when reaching this extreme value.And actual focusing evaluation function is owing to be subjected to interference of noise, have some local peakings, these local peakings can influence the search by hill climbing algorithm accuracy, this programme adopts the hill-climbing algorithm of optimizing, adopt earlier big step-length rough find the peak value scope, accurately locate with little step-length again, adopt thresholding to handle to the value after the rim detection simultaneously, can further reduce the interference of local peaking.

The search by hill climbing method of the optimization that the utility model adopts is as follows:

In predetermined lens driving scope, set focus direction, rotate with bigger step-length drive motor earlier, whenever make a move and just gather a two field picture, calculate the sharpness evaluation function value, if calculating the functional value of gained increases gradually, illustrate that motor-driven is in the right direction, continue to drive camera lens and move, if when functional value reduces for the first time along same direction, best focal point might be crossed in explanation, disturb in order to get rid of local peaking, this moment, drive motor moved ahead a step again, if functional value further reduces, illustrate and crossed peak value really, drive motor retreats two step-lengths, roughly gets back near the peak point, makes a long driver to move motor with small step again, find optimum lens position with same method, obtain focusing on distinct image.In motor operation course, reach camera lens qualification position if detect, then change direction and continue search.Adopt the method for big or small step-length binary search, both can guarantee focusing speed, can guarantee accurately to navigate to the peak point of sharpness evaluation function again.

The pixel that participates in calculating is many more, the operation time that focuses on evaluation function is long more, if focus window is excessive on the other hand, introduces background image and can cause erroneous judgement too much, too little then can causing of window departs from objectives, so the selection of focal zone directly affects focusing speed and focusing accuracy.Adopt three kinds of window systems of selection in this programme, the one, select middle section, this is because the user can aim at the picture center usually, but this method since target vary in size the bad control of window size; The 2nd, in order to remedy deficiency, adopt the multiwindow method to central focus, with less weights that the picture center is upper left, upper right again except the central area, the lower-left, the lower right-most portion zone counts; The 3rd, user oneself sets area-of-interest.These selection modes can send the order setting by the user by serial ports.

In order to adapt to different occasions, satisfy diversified requirement, reach optimized focusing effect, the utility model also is provided with the part additional function, as the image pre-filtering, focus window is selected, and focusing on evaluation function threshold value and step-size in search can be set by asynchronous serial communication interface by the user.

Figure 2 shows that the main program flow chart of automatic focusing system, behind the system initialization, wait for the reception order from UART communication module 9, if order is set, then according to new setting value Reparametrization, if there is not serial port command, then gather a two field picture, need to judge whether automatic focus, if desired, run search algorithm then, drive motor is to best focus position.

The utility model can pass through existing techniques in realizing without the technical characterictic of describing, and does not repeat them here.Certainly; above-mentioned explanation is not to be to restriction of the present utility model; the utility model also is not limited in above-mentioned giving an example, and variation, remodeling, interpolation or replacement that those skilled in the art are made in essential scope of the present utility model also should belong to protection domain of the present utility model.

Claims (4)

1. a thermal imaging system automatic focusing system is characterized in that it comprises microprocessor, video input circuit, motor-drive circuit, serial communication circuit, wherein, microprocessor comprises image capture module, image definition judge module, UART communication module, motor control module; Described image capture module is used to receive the processed infrared image of thermal imaging system output, and the digital signal of needs is read in internal memory according to predefined focus window, described image definition judge module is used for calculating the sharpness evaluation function value according to the digital signal of reading in internal memory; Described motor control module is connected with motor-drive circuit, and described UART communication module is used for and outside communication.

2. thermal imaging system automatic focusing system according to claim 1 is characterized in that described microprocessor is connected with SRAM.

3. thermal imaging system automatic focusing system according to claim 1 is characterized in that described microprocessor is connected with FLASH.

4. thermal imaging system automatic focusing system according to claim 1 is characterized in that described microprocessor is connected with level transferring chip.

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