CN104486535B - Frame transfer type CCD aerial cameras scan IMC method - Google Patents

Abstract

Frame transfer type CCD aerial cameras scan IMC method, belong to aerial camera technical field of imaging, the problem of mechanical shutter is blocked to light, this method are needed in order to solve prior art：Step 1, the sweeping angular speed in gyro to measure aerial camera relative inertness space, measurement error caused by nonorthogonality is installed in order to reduce, and the direction of gyro sensitive angular is consistent with aerial camera sweeping direction；Step 2, row shift pulse generator receives the camera sweeping angular velocity information that gyro to measure is arrived, and calculates IMC moment frame transfer CCD row transfer pulse frequency；Step 3, in the IMC stage, frame transfer CCD timing sequencers calculate the pulse signal driving frame transfer CCD produced and carry out electric charge transfer, realize IMC；Step 4, the stage is read in electric charge, frame transfer CCD timing sequencers voluntarily drive frame transfer CCD to carry out electric charge transfer, realize the photosensitive imaging to scenery picture point according to the row migration period frequency of inner setting.

Description

Frame transfer type CCD aerial cameras scan IMC method

Technical field

The invention belongs to aerial camera technical field of imaging, it is related to frame transfer type area array CCD in aerial imagery system Using, and in particular to a kind of aerial camera scanning IMC method of use frame transfer type area array CCD.

Background technology

In order to expand covered ground width, area array CCD aerial camera typically takes the working method of continuous sweeping imaging.Pendulum Scanning will be brought as moving by sweeping imaging, in order to ensure imaging resolution, it is necessary to be compensated to scanning as moving.Current Scan is as moving Compensation way is typically divided to two kinds, and one is the compensation of ray machine formula, and two be the electronic type compensation that CCD is shifted based on full frame.Ray machine formula is compensated Method makes to keep relative between time of exposure scenery picture point and photosensitive medium by the way of optical element in rotation imaging system Static, this method is limited to perform the performance of structure, compensation bandwidth and limited precision.CCD electronic type is shifted based on full frame Compensation method makes electric charge transfer linear velocity and scenery picture point movement linear velocity in the time of exposure match, when being needed after end exposure Mechanical shutter is blocked to light, so as to avoid photosensitive pixel continuation collection photon during pixel charge series read-out from causing image to drag Tail effect.But the restricted lifetime of mechanical shutter, and because the difference of shutter opening, closing control precision will cause CCD to expose It is non-homogeneous, there is considerable influence to the reliability and performance of imaging system.

The content of the invention

The present invention in order to solve prior art need mechanical shutter to block light and cause CCD expose it is non-homogeneous, it is right The problem of reliability of imaging system has considerable influence with performance, proposes a kind of frame transfer type CCD aerial cameras scanning as moving Compensation method, is compensated, this method is in IMC by driving frame transfer CCD charge movement to realize on the piece that scanning picture is moved Afterwards by the whole parallel fast transfer of frame pixel charge to dark pixel memory block, therefore light is blocked without mechanical shutter.

The technical scheme is that：

Frame transfer type CCD aerial cameras scan IMC method, comprise the following steps：

Step 1, the sweeping angular speed in gyro to measure aerial camera relative inertness space, draws to reduce installation nonorthogonality The measurement error risen, the direction of gyro sensitive angular is consistent with aerial camera sweeping direction；

Step 2, row shift pulse generator receives the camera sweeping angular velocity information that gyro to measure is arrived, and calculates IMC Moment frame transfer CCD row transfer pulse frequency；Because camera sweeping causes scenery picture point to be moved on frame transfer CCD focal planes Linear velocity V_SFor：

V_S=ω_SF (one)

Wherein ω_SFor aerial camera sweeping angular speed, unit is radian per second, and f is aerial camera focal length, and unit is rice；For Ensure that the linear velocity of scenery picture point movement is equal with electric charge transfer linear velocity, the electric charge transfer of row shift pulse generator generation Pulse period is：

(2)

Wherein b is CCD pixel dimension, and unit is rice；Then row transfer pulse frequency is：

(3)；

Step 3, in the IMC stage, frame transfer CCD timing sequencers calculate the pulse signal produced according to formula (three) Drive frame transfer CCD to carry out electric charge transfer, realize IMC；

Step 4, the stage is read in electric charge, frame transfer CCD timing sequencers are according to the row migration period frequency of inner setting Voluntarily driving frame transfer CCD carries out electric charge transfer, realizes the photosensitive imaging to scenery picture point.

The principle of the invention is：1) aerial camera is to ground Scenery Imaging by way of sweeping, and frame transfer CCD is by ground scape The photon information of thing is converted to electronic information and collected.2) be installed on gyro to measure camera in camera scanning mechanism relative to The angular scanning speed of inertial space, and scenery picture point is calculated along scanning direction by the turn meter move linear velocity.3) In order to which compensated scanning picture is moved, frame transfer CCD row transfer pulse frequency need to be calculated by digital signal processing unit, so that Time of exposure scenery picture point moves linear velocity and matched completely with the realization of electric charge transfer linear velocity.4) in a two field picture end exposure Afterwards, the whole parallel fast transfers of pixel charge of photosensitive area be will be stored in dark pixel memory block, dark pixel is finally will be stored in The electric charge series read-out in area, completes the compensation of scanning picture shifting and the reading of electric charge in a frame imaging process.

The present invention by traditional frame transfer CCD electric charge transfer by being divided into two stages：IMC stage and electric charge are read Go out the stage, not only realize scanning and light is carried out without mechanical shutter as the electronic type compensation moved, and in the electric charge reading stage Block.IMC principle be aerial camera scanning process in scenery picture point along scanning direction by occur line move, pass through Mobile photosensitive pixel is allowed to that IMC can be achieved with scenery picture point shifted matching.Without shutter during the reading of full frame pixel charge Principle of breaking to photoresistance is that all pixel charges are passed through into the dark of parallel mode fast transfer to frame transfer CCD after end exposure Pixel memory block, then series read-out.Due to dark as moving memory block not to photaesthesia, therefore the nothing in pixel charge readout Need shutter disconnected to photoresistance.

The beneficial effects of the invention are as follows this method is to scanning as the charge type compensation of shift-in row, and used is simple in construction, with biography The compensation scheme for ray machine formula of uniting, which is compared, has the high-precision aerial camera scanning IMC effect of broadband；Secondly the present invention is sharp There is the characteristics of full symmetric photosensitive imaging area is with dark pixel memory block with frame transfer CCD, without machinery when electric charge is read Shutter coordinates, therefore reliability is high and exposure heterogeneity is good.

Brief description of the drawings

Fig. 1 is frame transfer type CCD aerial cameras scanning IMC method block diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail.

As shown in figure 1, the main gyro 1, OK by measurement aerial camera relative to inertial space angular scanning speed of the present invention Shift pulse generator 2, frame transfer CCD timing sequencers 3 and frame transfer CCD 4 are constituted.

Frame transfer CCD aerial camera scanning IMC method, comprises the following steps：

Step 1, the sweeping angular speed in the measurement aerial camera relative inertness of gyro 1 space, in order to reduce installation nonorthogonality Caused measurement error, the direction of the sensitive angular of gyro 1 is consistent with aerial camera sweeping direction.

Step 2, row shift pulse generator 2 receives the camera sweeping angular velocity information that gyro 1 is measured, and calculates and is mended as moving Repay moment frame transfer CCD row transfer pulse frequency.Because camera sweeping causes scenery picture point to be moved up in frame transfer CCD focal planes Moving-wire speed V_SFor：

V_S=ω_SF (one)

Wherein ω_SFor aerial camera sweeping angular speed, unit is radian per second, and f is aerial camera focal length, and unit is rice.For Ensure that the linear velocity of scenery picture point movement is equal with electric charge transfer linear velocity, the electric charge turn that row shift pulse generator 2 is produced Move the pulse period be：

(2)

Wherein b is CCD pixel dimension, and unit is rice.Then row transfer pulse frequency is：

(3)

For example, certain aerial camera focal length is 1000mm, sweeping angular speed is 2 degrees seconds, and pixel dimension is 10 microns, according to Formula (one) can obtain scenery picture point portable cord speed V on frame transfer CCD focal planes_SFor：

(4)

And then try to achieve row shift pulse generator 2 generation electric charge transfer pulse frequency be：

(5).

Step 3, in the IMC stage, frame transfer CCD timing sequencers 3 calculate the pulse signal produced according to formula (three) Drive frame transfer CCD 4 to carry out electric charge transfer, realize IMC.

Step 4, the stage is read in electric charge, frame transfer CCD timing sequencers 3 are according to the row migration period frequency of inner setting Voluntarily driving frame transfer CCD 4 carries out electric charge transfer, realizes the photosensitive imaging to scenery picture point.In order to reduce in transfer process Streaking effect, the electric charge transfer period frequency of sets itself is does not reduce the highest line that can be reached in the case of picture quality Migration period frequency.

Claims (1)

1. frame transfer type CCD aerial cameras scan IMC method, it is characterized in that, comprise the following steps：

Step 1, the sweeping angular speed in gyro (1) measurement aerial camera relative inertness space, draws to reduce installation nonorthogonality The measurement error risen, the direction of gyro (1) sensitive angular is consistent with aerial camera sweeping direction；

Step 2, row shift pulse generator (2) receives the camera sweeping angular velocity information that gyro (1) is measured, and calculates and is mended as moving Repay moment frame transfer CCD row transfer pulse frequency；Because camera sweeping causes scenery picture point to be moved up in frame transfer CCD focal planes Moving-wire speed V_SFor：

V_S=ω_SF (one)

Wherein ω_SFor aerial camera sweeping angular speed, unit is radian per second, and f is aerial camera focal length, and unit is rice；In order to protect The linear velocity for demonstrate,proving the movement of scenery picture point is equal with electric charge transfer linear velocity, the electric charge transfer that row shift pulse generator (2) is produced Pulse period is：

$T=\frac{b}{{\mathrm{\ω}}_{S}f}$ (2)

Wherein b is CCD pixel dimension, and unit is rice；Then row transfer pulse frequency is：

$F=\frac{1}{T}\frac{{\mathrm{\ω}}_{S}f}{b}$ (3)；

Step 3, in the IMC stage, frame transfer CCD timing sequencers (3) calculate the pulse signal produced according to formula (three) and driven Dynamic frame transfer CCD (4) carries out electric charge transfer, realizes IMC；

Step 4, read the stage in electric charge, frame transfer CCD timing sequencers (3) according to the row migration period frequency of inner setting from Row driving frame transfer CCD (4) carries out electric charge transfer, realizes the photosensitive imaging to scenery picture point.