CN100375287C

CN100375287C - Method for improving face array frame transfer CCD working frame frequency

Info

Publication number: CN100375287C
Application number: CNB2005100248830A
Authority: CN
Inventors: 王跃明; 薛永祺; 王建宇; 刘银年; 黄健; 王欣
Original assignee: Shanghai Institute of Technical Physics of CAS
Current assignee: Shanghai Institute of Technical Physics of CAS
Priority date: 2005-04-05
Filing date: 2005-04-05
Publication date: 2008-03-12
Anticipated expiration: 2025-04-05
Also published as: CN1688025A

Abstract

The present invention relates to a method for increasing the working frame frequency of an area array frame transfer CCD, which comprises the following steps: dividing an M*M element image sensitizing zone of an M*M element area array CCD into an M*(M-N) element shading zone and an M*N element effective exposing zone; shielding CCD M*(M-N) image elements with a shading plate in order to decrease frame transfer time; only reading out M*N image elements in series. In this way, frame periods are decreased, and the working frame frequency is increased. The present invention can be applied to satellite-borne superspectrum imaging instruments.

Description

Improve the method for face array frame transfer CCD working frame frequency

Technical field:

The invention relates to the method that improves the area array CCD operating frequency, particularly about the high frame frequency solution of satellite-borne hyper-spectral imager with area array CCD.

Background technology:

Area array CCD is the information acquiring section part in the pull-broom type ultra-optical spectrum imager, and flying platform is finished the scanning imagery of space dimension, and the solid self-scanning mechanism of area array CCD is finished the scanning of spectrum dimension and read.The speed of service reaches on the satellite-borne hyper-spectral imager of several kilometer per seconds on relative ground, in order to obtain sufficiently high ground resolution, needs CCD with the frame frequency work up to hundreds of frames/second.The high frame frequency area array CCD device that present CCD manufacturer provides all is M * M unit as Figure 1-1 basically, and in the pull-broom type ultra-optical spectrum imager, the ranks bidimensional of area array CCD is the spectrum peacekeeping space dimension of corresponding instrument respectively.In the practical application of instrument, we require for hundreds of units (corresponding hundreds of spectrum) spectrum dimension is general, and in order to obtain the swath width of broad, wish space dimension detector pixel can reach thousands of more than.

Consult Fig. 1-1 and Fig. 2, be divided into image photosensitive area, electric charge storage region, series read-out register on the area array CCD structure of frame transfer.The work period of CCD is divided into frame transfer time and two stages of effective exposure time.In the frame transfer time, CCD finishes the transfer of electric charge from the image photosensitive area to electric charge storage region; In effective exposure time, after CCD finishes signal charge and transfers to the series read-out register line by line, read by unit by the series read-out register.Under the condition that the CCD frame frequency is fixed, short more making an appointment of frame transfer time because the frame transfer process can cause the hangover of image, cause the spectrum aliasing of hyperspectral imager, and the frame transfer time is long more, and effective exposure time can be short more, causes the signal to noise ratio of signal to descend.For the face battle array frame transfer CCD of M * M unit, reality only needs M * N unit, N＜M in hyperspectral imager.If with unnecessary M * (M-N) first total number is read, and has not only taken the time for exposure of CCD, and cause the signal bandwidth of system to increase, the difficulty of the development of signal processing circuit also increases.

Summary of the invention:

The object of the present invention is to provide the frame transfer mechanism of a kind of CCD of utilization, unnecessary Mx (M-N) unit part is adopted the method that shifts, to improve the working frame frequency of CCD, reduce the signal bandwidth of system, and satisfy the instructions for use of satellite-borne hyper-spectral imager.

Technical scheme of the present invention is as follows:

According to a kind of method that improves the area array CCD working frame frequency of the present invention, its step comprises: a. is divided into effectively exposure region of the first shading region of M * (M-N) and M * N unit to the M of the M * M CCD of unit face battle array * M unit image photosensitive area, wherein N＜M and M * (M-N) first shading region, M * N unit effectively exposure region, M * N elementary charge memory block and M unit series read-out register connect successively; B. block the first shading region of this M * (M-N) with a shadow shield; C. move the M * M CCD of unit face battle array, in effective exposure time, line by line M * N unit bearing member, image is transferred to electric charge storage region through N transfer operation successively, the next frame image begins exposure, and M * N unit bearing member, image that d. is positioned at electric charge storage region arrives the series read-out register and begins series read-out through (M-N) inferior transfer line by line again; And e. then, and each row is read by unit, repeats N time, reads the sensitization electric charge of M * N unit altogether, and CCD face battle array is finished reading of a two field picture.

Described M * M the CCD of unit face battle array is a frame transfer type area array CCD; The frame transfer time of described CCD is meant the transfer time of a M * N unit's bearing member, image from effective exposure region to charge storage.

Shadow shield according to the inventive method use, it comprises the shading surface that is made of effective shading surface and the cantilever that lays respectively at its both sides, and the installation mating surface relative with this shading surface, be that shadow shield has two working faces, working face is as the installation mating surface of shadow shield, and another working face is as shading surface.

Described shadow shield can cover the unnecessary pixel of area array CCD, makes these obsolete pixels in the satellite-borne hyper-spectral imager not be subjected to the irradiation of light.And the pixel that will use is unaffected.

The shading surface of above-mentioned shadow shield is as much as possible near the photosurface of CCD, but can not run into the CCD photosurface and cause damage.

Advantage of the present invention:

1, can effectively solve how to obtain this difficult problem of high frame rate CCD in the satellite-borne hyper-spectral imager, and simple in structure, and cost is low;

2, under the condition of identical frame frequency, the method that adopts the present invention to propose, an interior effective exposure time in frame period is longer, and the tailing problem of image is significantly alleviated;

3, under the condition of identical frame frequency, the method that adopts the present invention to propose, signal to noise ratio is higher, and the signal processing difficulty is littler.

Description of drawings:

Fig. 1-1 is the conventional full frame mode of operation schematic diagram of frame transfer area array CCD.

Fig. 1-2 is a mode of operation of the present invention, and wherein the image photosensitive area has the unit of M * (M-N) be blocked (dash area).

Fig. 2 is a frame transfer area array CCD typical frame cycle diagrammatic sketch, and Tfr is the frame period, and T1 is the frame transfer time, and T2 is effective exposure time.

Fig. 3 is for adopting the frame period diagrammatic sketch that reduces effective exposure time to M * M unit image photosensitive area, and with shown in Figure 2 to compare the T1 frame transfer time constant, T2 reduces, and Tfr reduces, and frame frequency improves.

Fig. 4 uses the frame period diagrammatic sketch of shadow shield for adopting the inventive method, and frame transfer time T 1 reduces, the length that effective exposure time is more shown in Figure 3.

Fig. 5-1 and Fig. 5-2 are the shadow shield that uses among the present invention and the scheme of installation of CCD.

Fig. 6 is the profile schematic diagram of shadow shield of the present invention.

Fig. 7-1～Fig. 9-4 is a frame sensitogram transfer operation process schematic diagram of the inventive method.

Embodiment:

Now in conjunction with the accompanying drawings invention is made a detailed description:

According to Fig. 1-2, Fig. 4～Fig. 9-4 provides better embodiment of the present invention below.

As Fig. 5-1～shown in Figure 6, shadow shield 1 is by cantilever 101, cantilever 102 and be positioned at central authorities' connection two cantilevers 101, effective shading surface 103 of 102 constitutes, its be divided into shading and and the effect that mating surface cantilever 101 and cantilever 102 be installed be: 1), in installation process, shading surface avoids causing owing to the gravity reason contact of effective shading surface 103 in the face of the photosurface 2 of CCD, causes the damage to CCD photosurface 2; 2), another effect of cantilever 101 and cantilever 102 is the contact area that increases shadow shield and CCD structure 3, improves the adhesion strength of shadow shield 1 and CCD structure 3.

Effectively the size of shading surface 103 depends on the CCD of system's needs pixel number that effectively exposes, effectively the area of shading surface 103 equal to be blocked the pixel area with.

On installation mating surface 105, be provided with mechanical

mounting fixing parts

1051,1052,1053,1054.

Be shown in the frame transfer process as Fig. 7-1～Fig. 7-4, the M * N unit effectively sensitization electric charge in the pixel of exposure operates line by line through N time and is transferred in M * M elementary charge memory block.And the M that the effective shading surface 103 of quilt covers * (M-N) unit also once shifts downwards.When M * N unit after effectively the electric charge in the pixel of exposure is transferred to electric charge storage region fully, the electric charge that effective exposure region of depositing the sensitization electric charge originally has been blocked in the pixel in district is occupied.Since by effective shading surface 103 shelter from M * (M-N) first pixel is not subjected to the irradiation of light signal all the time in the course of work of whole CCD.The charge carrier that has only the only a few thermal excitation in the pixel of shading region with respect to the sensitization electric charge, can be ignored.Therefore can think that this moment, effective exposure region was cleared.Stop the transfer of electric charge in the image photosensitive area this moment, effectively exposure region begins the exposure of next frame image.M shown in Fig. 8-1～Fig. 9-4 * N unit sensitization electric charge in electric charge storage region, shift M * (M-N) inferior after, arrive the series read-out register, revolution moves delegation's sensitization electric charge to the series read-out register, finish with regard to reading by unit, reading, shift next line sensitization electric charge and enter the series read-out register, read by unit then, repeat N time, read M * N unit sensitization electric charge altogether, CCD finishes reading of a two field picture.

With reference to Fig. 3 and shown in Figure 4, key of the present invention is: utilize shadow shield to reduce the time of frame transfer, improved effective exposure time, because the pixel of CCD has only part to be read out, therefore total frame period also is shortened, and frame frequency improves.

For example the face battle array frame transfer CCD of M * N unit adopts 1024 * 1024 yuan face battle array frame transfer CCD, under the identical situation of read output signal speed, adopts shadow shield of the present invention, effectively reads 1024 * 128 yuan, and frame frequency can improve several times.A typical example is: adopt the THX 7887A area array CCD of Thomson company, signal processing circuit need not to revise, and frame frequency can be brought up to for 400 frame/seconds from 100 frame/seconds.

Claims

1. method that improves the area array CCD working frame frequency, its step comprises:

A. the M of the M * M CCD of unit face battle array * M unit image photosensitive area is divided into effectively exposure region of the first shading region of M * (M-N) and M * N unit, wherein N＜M and M * (M-N) first shading region, the M * effective exposure region of N unit, M * M elementary charge memory block and M unit series read-out register connect successively

B. block the first shading region of this M * (M-N) with a shadow shield,

C. move the M * M CCD of unit face battle array, in effective exposure time, line by line M * N unit bearing member, image is transferred to electric charge storage region through N transfer operation successively, the next frame image begins exposure,

D. M * N unit the bearing member, image that is positioned at electric charge storage region arrives the series read-out pinning memory, the beginning series read-out through (M-N) inferior transfer line by line again; And,

E. after, each row is read by unit, repeated N time, read M * N unit sensitization electric charge altogether, CCD face battle array is finished reading of a two field picture.

2. the method for raising area array CCD working frame frequency according to claim 1 is characterized in that: the described M * M CCD of unit face battle array is frame transfer type CCD.

3. shadow shield according to claim 1, it is characterized in that: comprise by effective shading surface (103) and lay respectively at the cantilever (101 of its both sides, 102) shading surface of Gou Chenging, and the installation mating surface (105) relative with this shading surface, this effective shading surface (103) is in the face of the photosurface (2) of area array CCD.

4. shadow shield according to claim 4 is characterized in that: described effective shading surface (103) and M * M unit area array CCD unnecessary pixel M * (M-N) unit is complementary.

5. shadow shield according to claim 4 is characterized in that: the installation mating surface (105) of described shadow shield is provided with mechanical mounting fixing parts (1051,1052,1053,1054).