CN101846752A

CN101846752A - Single wave beam scanning imaging method of passive THz wave imaging system

Info

Publication number: CN101846752A
Application number: CN201010190312A
Authority: CN
Inventors: 赵跃进; 朱维文; 董立泉; 刘小华; 张存林; 邓朝
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2010-06-03
Filing date: 2010-06-03
Publication date: 2010-09-29
Anticipated expiration: 2030-06-03
Also published as: CN101846752B

Abstract

The invention relates to a fast scanning method based on the passive imaging of a single wave beam THz wave. Aiming at the problems of longer scanning time and overhigh system construction cost in an earlier scanning imaging method of the single beam THz wave, a rocker of a crank and rocker mechanism is adopted to drive a line scanning plane mirror to sway horizontally so as to achieve fast transverse scanning motion, and a field scanning plane mirror swaying vertically in a reciprocating way is utilized to realize longitudinal scanning motion, thereby realizing the two-dimensional scanning imaging over object space. On the premise of construction cost reduction, the invention greatly improves the scanning speed per se and simultaneously amplifies the scanning viewing field. In addition, the invention is not only suitable for the passive type THz wave single wave beam scanning imaging, but also suitable for the active type single wave beam scanning imaging of the THz wave.

Description

Single wave beam scanning imaging method of passive THz wave imaging system

Technical field

The present invention is the novel optical mechaical scanning method of a kind of THz of being directed to safety check imaging (to the imaging of human body concealment article).Utilize this invention can be under the situation of only using a receiver, thereby make the inswept bigger ken scene of antenna obtain image information by mechanical motion.Because the use of this single channel scanning imagery, system greatly reduces the cost of imaging under the prerequisite that guarantees volume, very strong market outlook and competitive power are arranged.

Background technology

Because the THz ripple has penetrability and higher spatial resolution preferably, therefore can adopt THz wave radiation meter that the prohibited items (gun, cutter, explosive etc.) that are hidden under the clothing are carried out imaging, thereby reach the purpose of surveying identification.

In recent years, because the continuous development of THz technology, formed following several imaging systems: 1. mechanical scanning imaging: it is to utilize mechanical motion to obtain the target property of big ken scene, though mechanical scanning is imaged on and needs the cost certain hour in the process of obtaining signal, be difficult to realize real time imagery, but its great advantage is to utilize few receiving cable of trying one's best to be embodied as picture by scanning, so cost is relatively low, and very strong market outlook and competitive power are arranged; 2. phased array imaging: it is to utilize electron scanning to substitute mechanical scanning, phased array antenna is made up of the two-dimensional array unit, each receiving element all links to each other with a phase shifter, phase place and amplitude by the control receiving element, realize the scanning of antenna beam in the ken, but owing to be difficult to design effective radiating element, and the feed system loss is excessive, so use few at present at the THz wave band; 3. synthetic aperture imaging: mainly be to arrange according to certain rules with the miniature antenna in N true aperture, by handling to the received signal to obtain being equivalent to the effect of a synthetic wide aperture antenna, this imaging system is too complicated and expensive, and the required space of interference array is very big, thereby also is not suitable for the imaging of human body concealment article; 4. focal plane imaging: be that a plurality of receiving elements are arranged on the focal plane of focusing anteena, utilize the burnt partially different of each feed, thereby produce a plurality of different wave beams that point to and cover the ken, but because the THz wave device is still very expensive at present, so the application of this imaging system is also few.

Summary of the invention

The objective of the invention is to adopt the mode of mechanical scanning, by row, both direction are carried out point by point scanning, thereby make the inswept bigger ken scene of antenna obtain image information.

The objective of the invention is to be realized by following technical scheme: 1. the rocking bar by crank and rocker mechanism drives the horizontal scanning of the constantly reciprocal back and forth in the horizontal direction swing realization scanning system of line scanning mirror to object space.2. the continuous reciprocally swinging of the in the vertical direction by the field scan mirror is realized the vertical sweep of scanning system to object space.3. the terahertz signal of detected measured object radiation or reflection from the THz wave detector, thus realize two-dimensional scan imaging to object space.

Beneficial effect

Adopt the present invention can realize the single beam scanning imagery of THz wave band, and the THz ripple point by point scanning system than in the early time of the present invention, under the prerequisite that manufacturing cost reduces, its scanning speed degree of obtaining significantly improves, and scanning field of view also obtains enlarging simultaneously.

Description of drawings

Fig. 1 is the scanning system of passive THz ripple imaging,

Fig. 2 is the scanning synoptic diagram in the scanning system imaging process of passive THz ripple imaging,

Wherein: 1-THz wave detector, 2-concave mirror, 3-line scanning mirror, 4-field scan mirror.

Embodiment

Below in conjunction with accompanying drawing the present invention is described further:

The present invention is made up of level crossing (field scan mirror) and the concave mirror in order to converging ray of the level crossing (line scanning mirror) of a horizontal hunting, a vertical oscillation, as shown in Figure 1.In Fig. 1, detector is placed on the focal plane of concave mirror, and the line scanning mirror is positioned on the conjugate plane of detector, and be 45 ° of placements with horizontal direction, reflecting surface up, the field scan mirror be positioned at the line scanning mirror directly over, also be 45 ° of placements with horizontal direction, its reflecting surface down.Like this, the picture point of this detector just in time finally is positioned at the outside (being object space) of field scan mirror by the triple reflection of concave mirror and line scanning mirror and field scan mirror, and keeps same level height with the center of field scan mirror.

If the line scanning mirror is around its center, promptly detector carries out horizontal hunting by the conjugate points of concave mirror, and the picture point of detector then can form a kind of linear scan pattern so, and the reflex by the field scan mirror just can realize the horizontal linearity of object space is scanned again.

Because when carrying out scanning imagery, horizontal scanning requires to have than higher sweep velocity, and normal motor can't overcome the bigger moment of inertia under high speed swinging, so adopted of the driving of the rocking bar of crank and rocker mechanism in the native system as horizontal scanning, move as long as make motor high-speed driving crank just can make rocking bar produce reciprocating swing at a high speed, the horizontal scanning of system has been reached than higher speed.In the case, the motor-driven crank rotates a circle, and rocking bar is just finished from an extreme position and arrived next extreme position and return the motion of this extreme position, and promptly picture point is finished a round horizontal linearity scanning motion on object space.

In order to realize two dimensional surface scanning, can utilize the swing of field scan mirror in the vertical direction, the object point horizontal direction is changed, thereby realize the frame width of cloth scanning of vertical direction.According to actual engineering demand, for the operation of giving total system provides the guarantee of security and convenience, field scan motor employing continuous sweep pattern, and non-pulse scan pattern.So after the horizontal scanning in conjunction with the line scanning mirror, the picture point of detector can form the scanning of " an it " font at object space, as shown in Figure 2.The size of view picture scan image depends on the horizontal range of scanning object and native system, and the pendulum angle of line scanning mirror and field scan mirror, and object distance is far away more, the pendulum angle of two scanning mirrors is big more, and the image that then is scanned is just big more.

Claims

1. the method for a single beam THz ripple fast scan imaging is characterized in that: utilize the transversal scanning of the horizontal hunting realization of line scanning level crossing to object space; Utilize the longitudinal scanning of the vertical oscillation realization of field scan level crossing to object space.

2. the method for single beam THz ripple fast scan imaging according to claim 1 is characterized in that: utilize the rocking bar driving line scanning level crossing of crank and rocker mechanism to carry out horizontal hunting, in order to realize the high speed transversal scanning to object space.

3. the method for single beam THz ripple fast scan imaging according to claim 1, it is characterized in that: this scan imaging method not only goes for the imaging of passive type, also goes for active imaging.