CN102158629B - Image nonuniformity correction method for tetragonal prism scanning imaging system - Google Patents

Abstract

The invention discloses an image nonuniformity correction method for a tetragonal prism scanning imaging system, which mainly comprises the following steps of: controlling a motor to drive the rotation of a tetragonal prism by utilizing a control circuit and data acquisition and storage system, and storing information, obtained by an absolute encoder, about a rotating angle of the tetragonal prism; receiving a light field converged by the tetragonal prism scanning imaging system by utilizing a detector; acquiring and storing output signals of the detector by utilizing the control circuit and data acquisition storage system under the control of the output code synchronization signals of the absolute encoder; and obtaining required image information with high quality by utilizing the output signals of the detector and the information about the rotating angle of the tetragonal prism obtained by the control circuit and data acquisition and storage system. The method is applied in the field of imaging. Compared with similar systems, the tetragonal prism scanning imaging system adopting the method has a larger clear aperture, effectively increases a signal to noise ratio, and is favorable for obtaining the image information with high quality.

Description

A kind of image non-uniform antidote of cubic prism scanning imaging system

Technical field

The present invention relates to image processing techniques, be specifically related to a kind of image non-uniform antidote of cubic prism scanning imaging system.

Background technology

Four directions prism sweep mechanism is one of scanning mirror the most frequently used in a kind of infrared scan camera, and its major advantage is that scan efficiency is high, and dynamic balancing is also better, and picture does not revolve.

Traditional cubic prism sweep mechanism, a light tight district is left in its bottom, and this is because when supposing that ground is desirable lambert's body; And during the difference of the atmospheric transmittance that causes of the air path length difference of ignoring the different scanning angle, the instantaneous field of view of supposing camera is 2W, and the corresponding ground bin is dA; Scan angle is θ, and flying height is h, and the logical light area of camera is S; As shown in Figure 2, can derive the radiant power that camera receives and do

dP＝NπhW ²Scosθ

In the formula, P is the radiant power that camera receives, and N is a radiance.Know from following formula; The radiant power that camera receives is directly proportional with Scos θ; So introduce so light tight district; Make the logical light area of camera produce vignettings how much, the logical light area that makes camera is by the relationship change that is inversely proportional to cos θ, and promptly there is bigger logical light area at the scanning field of view edge than the center.

Light by the Square-edge mirroring is divided into left and right two-way usually, and the speculum through both sides gets into objective system simultaneously.The cubic optical path prism that light tight district is arranged is referring to Fig. 3, among the figure: a is the prism length of side, and α is the corner of cubic prism, and θ is a scan angle, has two times of angular dependences between scan angle and the prism corner; Be θ=2 α, A, B, D, E; F, G, H, M; N, the diverse location of each point when on behalf of cubic prism, P, Q, O forward different angles to.

When cubic prism is on the throne when putting 1, α=θ=0, camera is swept to the center, visual field, and the width of the light beam on both sides equates.EFGH zone among the figure is the light tight district of cubic prism, from the light of this district reflection can not be again from the plane reflection mirroring on both sides.At this moment, the clear aperature of horizontal direction is:

${\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="HSA00000477460400011.png"\; state="\{\{state\}\}">S</figure-callout>}}_1=\stackrel{\&OverBar;}{\mathrm{MN}}-\stackrel{\&OverBar;}{\mathrm{FH}}$

Rotate cubic prism, the width of the light beam on both sides is no longer equal, along with the increase of scan angle, on one side more and more, another side is fewer and feweri.When prism went to position 2, camera was scanned up to field of view edge.Light tight district is decreased to zero.At this moment, the clear aperture of horizontal direction is:

${\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HSA00000477460400011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2=\stackrel{\&OverBar;}{\mathrm{BC}}$

Introduce so light tight district for proof, can guarantee that then in the process of cubic prism rotation, the radiant power that camera receives is uniformly in whole scanning field of view, the light beam overall width that we only need proof to get into the camera light wire system is constant.Because work as under the constant situation of the light beam overall width of entering camera light wire system, the illumination of falling on the detector also is constant.So it is following just through proving that the former says something.

When cubic prism is on the throne when putting 1, the overall width that the both sides speculum is collected light beam is:

$2\mathrm{OG}=2(\frac{\sqrt{2}}{2}a-\frac{\stackrel{\&OverBar;}{\mathrm{FH}}}{2})=\sqrt{2}a-\stackrel{\&OverBar;}{\mathrm{FH}}$

When position 2, the overall width that the both sides speculum is collected light beam is:

Therefore, as long as the size in light tight district is elected as

$\stackrel{\&OverBar;}{\mathrm{FH}}=\sqrt{2}a(1-\cos \mathrm{\&alpha;})=\sqrt{2}a(1-\cos \frac{\mathrm{\&theta;}}{2})$

Then in scanning process, the light beam overall width that gets into the camera light wire system is constant, and the illumination of then falling on the detector is also constant.

Introduce so light tight district, in whole scanning field of view, the detector radiant illumination general do not change with the variation of scan angle theta, but this mode can be lost the light field energy of a part, reduces the signal to noise ratio of system.Therefore, we adopt the cubic prism scanning system that does not have light tight district.Having removed light tight district has increased the clear aperture of system, and the image inhomogeneities of introducing thus distortion, wants that through hardware and software the mode that combines carries out nonuniform line and handle.

(see figure 4) when not having light tight district in the cubic prism sweep mechanism can be known from top derivation, and when cubic prism is on the throne when putting 1 (α=θ=0), the overall width that the both sides speculum is collected light beam is:

$2\mathrm{OG}=\sqrt{2}a$

When , the overall width that the both sides speculum is collected light beam is in the position:

$\mathrm{PD}+\mathrm{QD}=\sqrt{2}a\cos \mathrm{\&alpha;}$

Promptly be directly proportional with cos α, this moment, the detector radiant illumination was uneven in whole scanning field of view, needed to use correction formula:

$P=\frac{P^{\&prime;}}{\cos \mathrm{\&alpha;}}$

Revise and just can obtain actual visual field information.

Because the radiant power that the output voltage values of detector and detector receive is proportional, so utilize the output voltage values of detector to reflect object information.Therefore, in the native system as long as the formula below the output voltage values of the detector that collects utilized:

$V=\frac{V^{\&prime;}}{\cos \mathrm{\&alpha;}}$

Correct, just can access required high-quality image information.

The cubic prism scanning imaging system of using this method can make full use of light field information, and when the prism anglec of rotation is 0 when spending, the energy of increase is:

$(1-\cos \frac{\mathrm{\&theta;}}{2})/\cos \frac{\mathrm{\&theta;}}{2}$

Wherein, θ is a scan angle.When the visual field scanning angle is 60 when spending, the energy of increase reaches 15.5%.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of image non-uniform antidote based on cubic prism scanning imaging system, utilizes the cubic prism sweep mechanism of this method not have light tight district, therefore can make full use of all information.Use the cubic prism sweep mechanism of this method to adopt absolute type encoder control to gather the output signal of detector, and note the positional information of any time, make that the positional information of noting is corresponding one by one with the signal that collects.Utilize corresponding algorithm that original image information is handled then, just can access authentic and valid high quality graphic.The cubic prism sweep mechanism of use the method can effectively improve the signal to noise ratio of system.

Method step of the present invention is following:

Step 1: utilize the rotation of control circuit and data acquisition storage system control driven by motor four directions prism 1, and the information of storing cubic prism 1 rotational angle that obtains by absolute type encoder;

Step 2: through the visual field of cubic prism 1 reflection; Reflection through first plane mirror 2, second plane mirror 3, the 3rd plane mirror 4, Siping City's face speculum 5, concave mirror 6 and converge after, received by a detector 7 that is positioned on concave mirror 6 focuses;

Step 3: control circuit and data acquisition storage system are gathered and are stored the output signal of detector 7 under the control of absolute type encoder output code synchronizing signal;

Step 4: the data to the data acquisition and memory system is preserved are corrected, and obtain real image information, correct formula and are:

$V=\frac{V^{\&prime;}}{\cos \mathrm{\&alpha;}}$

In the formula: V is through can truly reflecting the voltage signal values of object information after the correction process; V ' is the detector output voltage values without rectification that collects, and the radiant power size that this value and detector receive is proportional; The cubic prism 1 corner angle that absolute type encoder obtained when α was system acquisition V ' data.

Technique effect of the present invention:

The cubic prism scanning imaging system of using this new data processing method based on cubic prism sweep mechanism imaging system can make full use of light field information; When the prism anglec of rotation is 0 when spending; The energy that increases is:

wherein θ is scan angle; When the visual field scanning angle is 60 when spending, the energy of increase reaches 15.5%.

Description of drawings

Fig. 1 is for using a cubic prism scanning imaging system embodiment of a kind of image non-uniform antidote based on cubic prism scanning imaging system of the present invention;

1: cubic prism, 2: the first plane mirrors, 3: the second plane mirrors, 4: the three plane mirrors, 5: the Siping City's face speculums, 6: concave mirror, 7: detector, absolute type encoder, motor, control circuit and data acquisition storage system.

Fig. 2 is the sketch map that concerns of scanning camera radiant power and scan angle.

2W: the instantaneous field of view of camera, dA: the corresponding ground bin, θ: scan angle, h: flying height, S: camera leads to light area.

Fig. 3 is the cubic prism scanning system sketch map that light tight district is arranged.

A: the prism length of side, α: the corner of cubic prism, θ: scan angle, EFGH: be light tight district, A, B, D, E, F, G, H, M, N, P, Q, O: the diverse location of each point when representing cubic prism to forward different angles to, specifically see figure.

Fig. 4 is the cubic prism scanning system sketch map that does not have light tight district.

A: the prism length of side, α: the corner of cubic prism, θ: scan angle, A, B, D, E, F, G, H, M, N, P, Q, O: the diverse location of each point when representing cubic prism to forward different angles to, specifically see figure.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is described further, but should limit protection scope of the present invention with this.

See also the imaging system of Fig. 1 for a cubic prism sweep mechanism using a kind of image non-uniform antidote based on cubic prism scanning imaging system of the present invention; Also be one embodiment of the present of invention; Visible by figure; A kind of image non-uniform antidote of the present invention based on cubic prism scanning imaging system, method step of the present invention is following:

Step 1: utilize the rotation of control circuit and data acquisition storage system control driven by motor four directions prism 1, and the information of storing cubic prism 1 rotational angle that obtains by absolute type encoder;

Step 2: through the visual field of cubic prism 1 reflection; Reflection through first plane mirror 2, second plane mirror 3, the 3rd plane mirror 4, Siping City's face speculum 5, concave mirror 6 and converge after, received by a detector 7 that is positioned on concave mirror 6 focuses;

Step 3: control circuit and data acquisition storage system are gathered and are stored the output signal of detector 7 under the control of absolute type encoder output code synchronizing signal;

Step 4: the data to the data acquisition and memory system is preserved are corrected, and obtain real image information, correct formula and are:

$V=\frac{V^{\&prime;}}{\cos \mathrm{\&alpha;}}$

In the formula: V is through can truly reflecting the voltage signal values of object information after the correction process; V ' is the detector output voltage values without rectification that collects, and the radiant power size that this value and detector receive is proportional; The cubic prism 1 corner angle that absolute type encoder obtained when α was system acquisition V ' data.

Claims (1)

1. the image non-uniform antidote of a cubic prism scanning imaging system is characterized in that may further comprise the steps:

1) utilizes control circuit and data acquisition storage system to control the rotation of driven by motor four directions prism (1), and store the information of cubic prism (1) rotational angle that obtains by absolute type encoder;

2) visual field of reflecting through cubic prism (1); Reflection through first plane mirror (2), second plane mirror (3), the 3rd plane mirror (4), Siping City's face speculum (5), concave mirror (6) and converge after, received by a detector (7) that is positioned on concave mirror (6) focus;

3) control circuit and data acquisition storage system are gathered and are stored the output signal of detector (7) under the control of absolute type encoder output code synchronizing signal;

The data of 4) the data acquisition and memory system being preserved are corrected, and obtain real image information, correct formula to be:

$V=\frac{V^{\&prime;}}{\cos \mathrm{\&alpha;}}$

In the formula: V is through can truly reflecting the voltage signal values of object information after the correction process; V ' is the detector output voltage values without rectification that collects, and V ' is proportional with the radiant power size that detector receives; Cubic prism (1) the corner angle that absolute type encoder obtained when α was system acquisition V ' data.

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