CN103997610A - Night-vision camera device and focusing method thereof - Google Patents

Abstract

Disclosed are a night-vision camera device and a focusing method thereof. The night-vision camera device includes a lens, an image sensor, an infrared radiation device, a narrow-band-pass optical filtering device and a visible-light shielding device. The night-vision camera device adopts a multi-definition evaluation function union automatic focusing design method and obtains images which are high in adaptability and definition through calculation. The night-vision camera device has the characteristics of being great in elusiveness, long in service life and clear in imaging.

Description

Night vision camera device and focus adjustment method thereof

Technical field

The present invention relates to a kind of camera head, relate in particular to a kind of method of night vision camera device and focusing.

Background technology

The development of security protection industry has been related to the construction of the even national harmonious societies of huge numbers of families, and good video monitoring quality is crucial.In the daytime, be easy to obtain the video of high-quality by means of the video camera of high-quality, but The night screen has hung down, light is dimmed, monitors that screen is noise entirely, there is no effective image at all, and now, monitoring has just become ornaments.In order to play and to obtain monitoring effect clearly under the environment in dark even zero illumination, video camera manufacturer and upstream CCD/CMOS supplier thereof solve the low-light (level) problem of product painstakingly, even to this day, low-light (level), clear, hidden imaging have been the important trend of monitoring camera instrument development.

Thermal camera in the market substantially all adopts the infrared ray of 850 nanometers as supplementary lighting sources, because this wave band infrared ray approaches the visible wavelength upper limit 790 nanometers, its light source driving circuit power is unstable, the problems such as LED lamp is aging, while causing night work, infrared light is cruelly strong, has no disguise and can say.Especially imaging effect is poorer under outdoor comparatively complex environment, (such as meadow, the water surface, coal etc., infrared light to be had the place of strong absorption).

Laser night-vision device adopts laser illuminator to carry out light filling, and irradiation can reach several kilometers far away.Laser night-vision device exists that the life-span is short, screen resolution is low, the shortcomings such as flashlight effect appear in the little picture in laser visual angle, and the life-span generally, about 10000 hours, surpasses 10000 hours needs and changes laser.

The heat that thermal imaging system adopts passive infrared technology to produce by sense object is embodied as picture, and its observed range can reach several kilometers, and the life-span is about 50000 hours, expensive.Thermal imaging system carries out imaging by the heat of sense object, so can only see the hot profile of object clearly.

Traditional focus adjustment method is by comparing present image and regulating front image criterion revise focusing direction and regulate step-length, and therefore, when destination object changes (camera lens or scenery move), focusing process can make a mistake; While adjusting in addition focusing direction, if two width images are positioned at peak value both sides, because symmetry can cause erroneous judgement, impact focusing efficiency and accuracy.

Above night more or less there is the insoluble problems such as disguised low, definition is low, the life-span is short in picture pick-up device, and has the not good defect of focusing performance, and how to address the above problem is the emphasis direction of video camera research and development.

Summary of the invention

For the problems referred to above, the object of this invention is to provide the night vision camera device that strong adaptability, good concealment, definition are high, the life-span is long.

A kind of night vision camera device, comprise camera lens, imageing sensor, infrared radiation device, narrow bandpass optical lightscreening device, visible ray screening arrangement, described visible ray screening arrangement is mounted on described night vision camera device front screen inner side, described narrow bandpass optical lightscreening device is arranged on imageing sensor front end, described infrared radiation device comprises: light source driving circuit and LED radiation lamp plate, described LED radiation lamp plate is as secondary light source, LED radial burner is controlled by light source driving circuit, under light source driving circuit effect, LED light source sends to imaging object the infrared beam that some wavelength are 940 nanometers, described narrow bandpass optical lightscreening device is comprised of narrow bandpass optical filter, the working region of described optical filter is the near infrared light wave band of 940 nanometers, described visible ray screening arrangement is the saturating infrared fileter of acrylic or glass material, the ultrared penetrance of described visible ray screening arrangement 940 nanometer is more than 90%, to the visible-light absorptivity in 390 nanometer to 790 nanometer range, more than 90%, described visible ray screening arrangement outward appearance is black.

The present invention is also optimized for traditional focusing process, and in traditional focusing process, motor moves step by step, calculates the focusing evaluation function at diverse location, thereby determines best focusing point, has a strong impact on focusing efficiency, and whole system is ageing lower.For the deficiency of traditional focus adjustment method, the present invention proposes reciprocating focus adjustment method, and this focus adjustment method comprises the following steps:

The first step: select focusing motor step-length, the selection of step-length had both been guaranteed can not miss focusing Accurate Points, will meet with minimum step number and cover whole process simultaneously;

Second step: calculate the focusing function value of different focusing position, obtain focusing evaluation function and be worth region most;

The 3rd step: the step-length that the stepping motor that reduces to focus is advanced, in previous step, calculate and obtain focusing evaluation function and be worth most and in region, again calculate focusing evaluation function and be worth region most;

The 4th step: repeatedly repeat the calculating of the 3rd step, progressively dwindle focusing evaluation function and be worth region most, until obtain image clearly.

Preferably, adopt formula (1) to calculate the focusing evaluation function value that obtains camera lens diverse location in second step, concrete formula (1) is as follows:

$F\left(I\right)=\underset{x}{\mathrm{\Σ}}\underset{y}{\mathrm{\Σ}}\{{[I(x+1,y)-I(x,y)]}^2+{[I(x,y+1)-I(x,y)]}^2\}$

Wherein F (I) is focusing evaluation function functional value, and when F (I) value is larger, image is more clear.I (x, y) be the capable y row of x grey scale pixel value in present image, calculate focusing evaluation function value A, B and the C of three adjacent positions, if A<B>C, determine first and thirdly between be worth region most for focusing evaluation function.

Preferably, be worth most behind interval obtaining focusing evaluation function first, adopt formula (2) to carry out refinement calculating, until obtain best focusing point, obtain picture rich in detail, formula (2) is:

$F\left(I\right)=\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\left\{\frac{{[I(x+2,y)-I(x,y)]}^2+{[I(x+4,y)-I(x+2,y)]}^2}{2}\right\}$

In formula, the capable y row of x grey scale pixel value in the equal presentation video of I (x, y), F (I) is focusing evaluation function functional value.

Night vision camera device in the present invention, by adjusting the use of infrared light wavelength and visible ray screening arrangement, effectively raises its hidden performance, has reduced cost; And by its focus adjustment method, improved the efficiency of focusing, and then increased the definition of image.

Accompanying drawing explanation

Fig. 1 is narrow bandpass optical filter optical filtering performance schematic diagram;

Fig. 2 is infrared filtering piece performance schematic diagram;

Fig. 3 and 4 is focusing evaluation function functional value and focusing location diagram;

Embodiment

Below in conjunction with accompanying drawing, understand the present invention in depth, should understand these embodiment only for explaining that this invention does not limit the scope of application of the present invention, after reading the present invention, all decipherings of person skilled and revising all fall within the category that the present invention protects.

Night vision camera device, comprise camera lens, imageing sensor, infrared radiation device, narrow bandpass optical lightscreening device, visible ray screening arrangement, described visible ray screening arrangement is mounted on the front screen inner side of described night vision camera device, described narrow bandpass optical lightscreening device is arranged on the front end of imageing sensor, described infrared radiation device comprises: light source driving circuit and LED radiation lamp plate, described LED radiation lamp plate is as secondary light source, LED radial burner is controlled by light source driving circuit, under light source driving circuit effect, LED light source sends to imaging object the infrared beam that some wavelength are 940 nanometers, described LED radiation lamp plate is arranged on the front end of described night vision camera device, described narrow bandpass optical lightscreening device is comprised of narrow bandpass optical filter, and the working region of described optical filter is the near infrared light wave band of 940 nanometers, described visible ray screening arrangement is the saturating infrared fileter of acrylic or glass material, the ultrared penetrance of described visible ray screening arrangement 940 nanometer is more than 90%, to the visible-light absorptivity in 390 nanometer to 790 nanometer range, more than 90%, described visible ray screening arrangement outward appearance is black.

In zero illumination or low-light (level) environment, light source driving circuit drives infrared radiation LED lamp to imageable target, to send the infrared beam of 940 nanometers, light beam reflects through destination object, by camera lens and filter, act on image processor, narrow bandpass optical filter, can decay or filter out the stray light (as shown in Figure 1) except 940 nanometer infrared beams, avoid chip to receive too much noise signal, cause image to occur distortion and mess code phenomenon.Guarantee image definition and signal transmission rate.

Acrylic or the saturating infrared fileter of glass material are installed in video camera front window; do not affecting under the prerequisite of equipment performance; the protection class of increase to night vision device internal part; avoid the infringement of various light to device interior optical element; as shown in Figure 2; the saturating infrared fileter of selecting due to the present invention reaches more than 90% the visible-light absorptivity of 390 nanometer to 790 nanometers; outward appearance is aterrimus; effectively prevent extraneous front screen facilities for observation internal structure and the work at present state of seeing through, strengthen disguise and stability.

As shown in Figures 3 and 4, focus adjustment method of the present invention comprises the following steps:

The first step: selecting lens focusing motor step-length is L α, and step-length is set according to video camera lens parameters, movement performance, shooting environmental attribute etc., has both guaranteed can not miss focusing Accurate Points, will meet with minimum step number and cover omnidistance needs simultaneously.

Second step: calculate the focusing function value of different focusing position, obtain focusing evaluation function and be worth region most; Adopt formula (1) to calculate the focusing evaluation function value that obtains camera lens diverse location, concrete formula (1) is as follows:

$F\left(I\right)=\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\{{[I(x+1,y)-I(x,y)]}^2+{[I(x,y+1)-I(x,y)]}^2\}$

Wherein F (I) is focusing evaluation function functional value, and when F (I) value is larger, image is more clear.I (x, y) be the capable y row of x grey scale pixel value in present image, calculate focusing evaluation function value A, B and the C of three adjacent positions, if A<B>C, determine first and thirdly between be worth region most for focusing evaluation function.At the black-out intervals of picture field synchronizing signal, make to focus on motor and turn and move a step towards predefined fixed-direction, default step-length is L α.At the trailing edge of next field picture field synchronization, gather the focus function value compare result signal of auto-focusing algorithm module output, as functional value higher than the former signal be high level, represent that present image is than previous field clear picture, direction of motor rotation is correct, continues to rotate a step to this direction.In like manner, the field synchronization trailing edge collection focus function value compare result signal in next field picture, if be still high level, continues to rotate until become first low level to this direction.Occur that first last twice interval that focus motor step-length L α that low level shows to set first moves exists focus function peak region, focus motor is rotated two steps round about.

The 3rd step: be worth most behind interval obtaining focusing evaluation function first, adopt formula (2) to carry out refinement calculating, until obtain best focusing point, obtain picture rich in detail, formula (2) is:

$F\left(I\right)=\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\left\{\frac{{[I(x+2,y)-I(x,y)]}^2+{[I(x+4,y)-I(x+2,y)]}^2}{2}\right\}$

In formula, the capable y row of x grey scale pixel value in the equal presentation video of I (x, y), F (I) is focusing evaluation function functional value.

The 4th step: be low level first at the focus function value compare result signal that collection detected, focus motor continues to preset step-length L β and continues to rotate along inceptive direction, and L β <L α, the less focusing accuracy of L3 value is higher, if the step-length L β of take moves rear comparing result as high level, represent that present image is than previous field clear picture, direction of motor rotation is correct, continues to rotate a step to this direction.In like manner, field synchronization trailing edge in next field picture gathers focus function value compare result signal, if be still high level, continues to rotate until again become low level to this direction, focus motor turns round about after moving a step and stops electric machine rotation, and automatic focus finishes.

The focusing process that the present invention adopts is more intelligent, and system adopts ARM chip to complete the signals collecting to image, the calculating of focusing function.The signal providing according to image processor, conveniently chooses focusing window.Adopt AF (automatic focusing) engine in ARM, gather line by line grey scale pixel value, until complete single-frame images, the evaluation function of focusing immediately after system acquisition single-frame images data calculates, and after calculating finishes, starts to carry out next IMAQ work, after calculating next image focusing evaluation function, contrast with the former, repeatedly carry out data acquisition, until find focusing function to be worth most, finish automatic focusing process in given range, determine lens location, obtain picture rich in detail.

Claims (4)

1. a night vision camera device, it is characterized in that, comprise camera lens, imageing sensor, infrared radiation device, narrow bandpass optical lightscreening device, visible ray screening arrangement, described visible ray screening arrangement is mounted on described night vision camera device front screen inner side, described narrow bandpass optical lightscreening device is arranged on the front end of described imageing sensor, described infrared radiation device comprises: light source driving circuit and LED radiation lamp plate, described LED radiation lamp plate is as secondary light source, LED radiation lamp plate is controlled by light source driving circuit, under light source driving circuit effect, LED radiation lamp plate sends to imaging object the infrared beam that some wavelength are 940 nanometers, described narrow bandpass optical lightscreening device is comprised of narrow bandpass optical filter, the working region of described optical filter is the near infrared light wave band of 940 nanometers, described visible ray screening arrangement is the saturating infrared fileter of acrylic or glass material, the ultrared penetrance of described visible ray screening arrangement 940 nanometer is more than 90%, to the visible-light absorptivity in 390 nanometer to 790 nanometer range, more than 90%, described visible ray screening arrangement outward appearance is black.

2. a focus adjustment method for night vision camera device claimed in claim 1, this focus adjustment method comprises the following steps:

The first step: select lens focusing motor step-length, the selection of this step-length had both been guaranteed can not miss focusing Accurate Points, will meet with minimum step number and cover whole process simultaneously;

Second step: calculate the focusing function value of different focusing position, obtain focusing evaluation function and be worth region most;

The 3rd step: the step-length that the stepping motor that reduces to focus is advanced, in previous step, calculate and obtain focusing evaluation function and be worth most and in region, again calculate focusing evaluation function and be worth region most;

The 4th step: repeatedly repeat the calculating of the 3rd step, progressively dwindle focusing evaluation function and be worth region most, until obtain image clearly.

3. method as claimed in claim 2 wherein, adopts following formula to calculate the focusing evaluation function value that obtains diverse location in second step:

$F\left(I\right)=\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\{{[I(x+1,y)-I(x,y)]}^2+{[I(x,y+1)-I(x,y)]}^2\}$

Wherein F (I) is focusing evaluation function functional value, and when F (I) value is larger, image is more clear.I (x, y) be the capable y row of x grey scale pixel value in present image, calculate focusing evaluation function value A, B and the C of three adjacent positions, if A<B>C, determine first and thirdly between be worth region most for focusing evaluation function.

4. method as claimed in claim 3, wherein, is worth behind interval obtaining focusing evaluation function first most, adopts following formula to carry out refinement calculating, until obtain best focusing point, obtains picture rich in detail:

$F\left(I\right)=\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\left\{\frac{{[I(x+2,y)-I(x,y)]}^2+{[I(x+4,y)-I(x+2,y)]}^2}{2}\right\}$

In formula, the capable y row of x grey scale pixel value in the equal presentation video of I (x, y), F (I) is focusing evaluation function functional value.