CN107071309B - High-speed double-pulse image exposure method based on CCD electrode direct control - Google Patents

Abstract

The invention discloses a high-speed double-pulse image exposure method based on direct control of a CCD electrode, wherein a luminous pulse image passes through an imaging lens and then is imaged on a CCD camera; aiming at the generation, the transfer and the transmission of a CCD normal signal charge packet, a transfer and transmission driving time sequence is designed in the extremely short invalid time in the middle of two exposure driving pulses, and the signal charge packet is isolated at the later stage of the invalid period of the exposure pulses by utilizing the function of isolating the signal charge packet by a transfer electrode, so that the signal charge packet generated by two exposures can be distinguished, the normal transfer and the transmission of the signal charge packet can be realized in the invalid period of the exposure pulses, and the ultrahigh time resolution imaging capability of a double-amplitude pulse image is further obtained. The invention has no compression effect of an image intensifier on the dynamic range of signals and the influence of additional extra noise, exerts the imaging performance of the CCD to the maximum extent and meets higher scientific imaging requirements.

Description

High-speed double-pulse image exposure method based on CCD electrode direct control

Technical Field

The invention relates to the field of image exposure control of framing cameras in the ultra-high speed photography technology, in particular to a high-speed double-pulse image exposure method based on direct control of a CCD electrode.

Background

In the ultra-high speed photography technique and system, a high-speed framing camera is usually used to realize the ultra-high speed photography frequency, so the high-speed framing camera is a necessary device for realizing the high-speed photography. Generally, high-speed framing cameras in the field of ultra-high speed photography mainly have two categories, one category is composed of a beam splitter prism or a beam splitter pyramid, a plurality of cameras with a high-speed fast gate control function and a time sequence control system, and the photographing frequency of the category can be very high; the other type is a high-speed digital camera, and under a certain resolving power, the working frequency of the high-speed digital camera is relatively low and is far from the object of the invention patent. In the first category, the splitting system, such as a prism or a pyramid, mainly splits the incident imaging beam to obtain multiple paths of output imaging beams, and finally obtains spatially separated image planes on which a plurality of cameras are placed, thereby forming an image framing effect. The camera with high-speed fast gate control function is usually formed by an ICCD camera, which is a high-speed photoelectric device called an image intensifier added in front of the CCD camera, mainly playing the role of shutter control and image brightness enhancement, and controlling the speed of image exposure, thereby also determining the shooting frequency: by controlling the exposure time of a plurality of ICCD cameras, the effect of sequential exposure of a plurality of images can be achieved, and a series of images can be obtained. Experiments for a long time have proved that in such a system, due to the use of an ICCD camera and also due to the image intensifier in the ICCD camera, the spatial resolution of the photography system is generally reduced by more than 2 times compared with the CCD itself with the same resolution; meanwhile, due to the enhancement effect of the image enhancer on the brightness, the dynamic range of the image signal is compressed, the noise level is increased, and the signal-to-noise ratio of the image is reduced; on the other hand, due to the limitation of the effective imaging surface of the image intensifier, a larger image surface is difficult to obtain; the beam splitting system used in the camera system further attenuates the energy of the incident imaging beam, resulting in a reduced system sensitivity. In such a system, one image corresponds to a set of imaging subsystem of the structure; the imaging branch system needs more paths for more images, so the system is generally larger and more complex. Generally, in a conventional high-speed framing camera system, due to a structural principle and performance reasons of key parts, spatial resolution and a signal-to-noise ratio of the system are affected to a certain degree, and cannot always meet certain high imaging requirements.

Disclosure of Invention

The invention aims to provide a high-speed double-pulse image exposure method based on direct control of a CCD electrode, which solves the problem that the existing high-speed camera system cannot simultaneously have high speed, high resolution, high imaging performance and large picture.

The invention is realized by the following technical scheme:

a high-speed double-pulse image exposure method based on direct control of a CCD electrode comprises the following steps:

(a) the luminous pulse image passes through the imaging lens and then is imaged on the CCD camera;

(b) aiming at the generation, the transfer and the transmission of a CCD normal signal charge packet, a transfer and transmission driving time sequence is set in the invalid time between two exposure driving pulses, and a transfer electrode is utilized to isolate the signal charge packet during the invalid period of the exposure driving pulses, so that the signal charge generated by two exposures is distinguished, the normal transfer and the transmission of the signal charge packet are realized during the invalid period of the exposure driving pulses, and the ultrahigh time resolution imaging capability of a double-amplitude pulse image is further obtained.

A typical structure of a conventional ultra-high-speed two-frame camera is shown in fig. 1, in such a frame imaging system, an imaging light beam from an imaging lens is divided into two spatially separated beams mainly by a beam splitter prism or a beam splitter pyramid in the figure, one of the two spatially separated beams continues along an original light path, an image is obtained by imaging on an ICCD camera, the other imaging light beam is imaged on the other ICCD camera through a reflector or a reflector prism to obtain another image, and if space allows, the ICCD camera can be arranged in a direction opposite to the beam splitter prism, so that the reflector prism can be omitted. Then, the shutter control system generates two control pulses synchronized with the pulse luminescence image to control the opening and closing of the image intensifier, so as to obtain the luminescence image with corresponding time, as shown in fig. 2. In such a system, the photographing speed is mainly determined by the time width and interval of the pulse for controlling the image intensifier to turn on and off, the working frequency of the CCD camera is not the main factor for limiting high-speed photographing, and the function is to preserve images, in such a system, due to the application and beam splitting of the ICCD camera, although the photographing frequency can be higher, the image quality is reduced, the spatial resolution and the signal-to-noise ratio are reduced, the image plane size is limited by the image intensifier, and cannot be larger, but the invention selects a CCD with an interlaced structure, and carries out the design of the driving timing sequence of the driving of the related electrodes: only one conventional imaging lens is adopted as an imaging optical system, and optical elements for light splitting such as a light splitting prism or a light splitting pyramid are not adopted, so that the imaging performance and efficiency of the optical system are maintained to the maximum extent, and the improvement of the image signal to noise ratio is facilitated; the simple imaging system greatly reduces the design difficulty and complexity of the conventional framing optical imaging system, and greatly reduces the development cost of the imaging optical system, and under the condition of meeting the imaging requirement of two frames of images, the simple imaging system has a simple structure which is the same as that of a common photographic optical system and is convenient to use, and because the control of image exposure is directly carried out through a CCD electrode instead of adopting an image intensifier which can be fast in speed but extremely expensive, the construction cost of the ultra-high speed photographic system is further reduced; although the control speed is slower than that of the image intensifier, the performance of the spatial resolution of the CCD is greatly kept without the link of the image intensifier; meanwhile, the compression effect of an image intensifier on the dynamic range of signals and the influence of additional extra noise are avoided, the imaging performance of the CCD is exerted to the maximum extent in the mode, and the high scientific imaging requirement can be met; the invention only adopts one imaging lens, does not need a light splitting system and a complex and expensive image intensifier, and two obtained images do not need further image alignment treatment for position registration, and the image performance can reach the same level of CCD, thereby having better application prospect in ultrahigh speed photography with small amplitude, high speed and high imaging quality requirement and meeting the scientific imaging requirement. By analyzing the working principle of the CCD, aiming at the CCDs with certain structural types, a method for directly carrying out drive control on the electrodes of the CCDs to obtain the high-speed imaging effect of two continuous images is provided, so that the imaging performance of the original CCD is achieved, and the high-speed imaging capability of the two images is obtained.

Specifically, the step (b) is carried out by:

(b1) dividing the main working time zone into 8 stages total tl-t8, when the CCD camera is not working, no effective signal is applied to each electrode, when a burst trigger pulse starts the working mode, the control circuit system generates a driving pulse on the CCD exposure electrode phi e, the high level of the driving pulse is set to correspond to the exposure is going on, and in the time zone of t1, the first exposure is going on;

(b2) in the t2 time zone, the driving pulse of the transfer electrode φ SH becomes active at the same time during the first exposure active time, resulting in the generation of photoelectrons at the exposure electrode φ e and the transfer of the photoelectrons generated by the first exposure to the electrode φ SH; ,

(b3) in the time zone t3, the drive signal on the exposure electrode φ e becomes inactive but the signal on the transfer electrode φ SH remains active, and photoelectrons can no longer be stored under the exposure electrode φ e, and are all accumulated or transferred to the transfer electrode φ SH at this time;

(b4) applying a step pulse signal through an electrode phi sl in a time zone of t4 to transfer photoelectrons stored on a transfer electrode phi SH to a position below the electrode phi sl;

(b5) in a time zone t5, after all photoelectrons under the transferring electrode phi SH are transmitted to the electrode phi sl and a certain gap is formed, a step pulse signal is applied to the electrode phi s2, and the photoelectrons under the electrode phi sl are transferred to the electrode phi s 2;

(b6) in the time zone of t6, photoelectrons kept under the electrode phi sl are transferred to the electrode phi s2 until the transfer is completed, at the moment, the transmitted photoelectron signal packet is completely isolated from the exposure electrode phi e, and meanwhile, the photoelectrons generated by re-exposure can be generated and stored under the exposure electrode phi e without being mixed with the previous photoelectrons;

(b7) in the time zone of t7, the driving pulse on the electrode phi sl becomes invalid and the driving pulse on the electrode phi s2 becomes valid, so that the photoelectrons are all transferred to the electrode phi s2 and can be independently output according to the time sequence and are not influenced by the exposure time sequence;

(b8) in the time zone t8, the signal charge packet transmitted in the light-shielding row is not affected by the exposure electrode due to the isolation of the transfer electrode, and the photoelectrons generated by the exposure are stored under the exposure electrode Φ e until the next transmission is started.

When a burst of trigger pulse is input, the timing circuit is started to work immediately: firstly, entering an exposure mode, generating an effective drive signal for the work of an exposure electrode so as to form a signal charge packet under the exposure electrode, wherein the exposure time can be set according to requirements, a transfer control pulse is generated to drive a transfer electrode in a short time before the exposure is finished, and the signal charge packet generated by the current exposure is transferred under the transfer electrode; then, the exposure mode is disabled, the transfer electrode continues to work effectively, and the related transmission electrode also starts to work effectively, at the same time, the signal charge packet generated by the previous exposure can continue to be transferred to the position below the transmission electrode; then, the exposure mode still keeps the failure state, the transfer electrode becomes the failure state, and the transmission electrode keeps the effective working state, so the signal charge packets generated by the previous exposure will be transmitted step by step under the transmission electrode until the signal charge packets are output to the CCD chip, and due to the isolation effect of the transfer electrode, the signal charge packets will not be confused with any charge packets under the exposure electrode; then, generating an effective driving pulse signal of the exposure electrode again to enter the second exposure, keeping the generated signal charge packet under the exposure electrode, and outputting the signal charge packet generated by the current exposure after the charge packet generated by the first exposure is completely output to the CCD; the output timing of the signal charge packet can be designed according to the conventional driving timing of the CCD. In the process, the strict time relation between the effective drive of the exposure electrode and the effective drive of the transfer electrode is very critical, and due to the isolation effect of the transfer electrode, signal charge packets of two successive exposures can not be mixed together, so that an effect that the two exposures can be distinguished is generated, the capability of distinguishing two pulse luminous images in time is obtained, the time distinguishing capability is mainly determined by the width of the transfer pulse, and the time distinguishing capability can easily reach the level of 1-2 microseconds on the current level, so that the time amplitude dividing effect of two ultrahigh-speed images is realized.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the invention relates to a high-speed double-pulse image exposure method based on direct control of a CCD electrode, which can complete the quick imaging function of two pulse luminous images by using a CCD chip, obtain the same excellent performance as a CCD chip and construct a high-efficiency and ultrahigh-speed two-frame camera or a photographic system with high imaging performance. Compared with the conventional high-speed photographing system, in the system, only one conventional imaging lens is adopted as an imaging optical system, and optical elements for light splitting such as a light splitting prism or a light splitting pyramid are not adopted, so that the imaging performance and efficiency of the optical system are maintained to the maximum extent, and the improvement of the image signal to noise ratio is facilitated; the simple imaging system greatly reduces the design difficulty and complexity of the conventional framing optical imaging system, greatly reduces the development cost of the imaging optical system, and has the same simple structure as a common photographic optical system and convenient use under the condition of meeting the imaging requirement of two framing images. On the other hand, because the control of the image exposure is directly carried out by the CCD electrode instead of adopting an image intensifier which can be fast but has extremely high price, the cost for constructing the ultra-high speed photographic system is further reduced; although the control speed is slower than that of the image intensifier, the performance of the spatial resolution of the CCD is greatly kept without the link of the image intensifier; meanwhile, the method has no compression effect of an image intensifier on the dynamic range of the signal and no additional influence of extra noise, and the method also gives play to the imaging performance of the CCD to the maximum extent and can meet higher scientific imaging requirements.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. l is a schematic diagram of a conventional ultra-high speed two-split camera system in the prior art;

FIG. 2 is a schematic diagram of a conventional control timing sequence of a super-high speed two-frame split camera in the prior art;

fig. 3 is a schematic diagram of an electrode arrangement of the CCD with an interlaced scanning structure according to the present embodiment;

FIG. 4 is a schematic diagram of CCD electrode driving pulse macro timing and signal charge generation according to the present invention;

FIG. 5 is a diagram illustrating the exposure, generation, and transmission of images under the electrodes in the timing sequence of FIG. 4;

FIG. 6 is a schematic diagram of a macroscopic timing control for forming an ultra-high speed binary frame camera;

FIG. 7 is a schematic block diagram of an ultra-high speed high performance two-split camera according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following examples, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not to be construed as limiting the present invention.

Examples

The invention relates to a high-speed double-amplitude pulse image exposure method based on direct control of a CCD electrode, and figure 3 is a macroscopic arrangement schematic diagram of pixels and electrodes of a CCD transferred between lines, and simplifies the specific structure and more detailed distribution schematic diagram of the electrodes, wherein phi e represents an exposed driving electrode, phi SH represents a transfer electrode, phi sl and phi s2 represent multi-stage transmission electrodes, wherein the phi SH, phi s1 and phi s2 electrodes are lightproof, and the basic principle of generation and transmission of signal charges in the CCD is as follows: when phie is active, photoelectrons generated by incident light will gather below it and form signal charge packets, and when phie is inactive, the signal charge packets gathered below it will scatter away and disappear, thereby losing the signal. When phi e changes from active to inactive and phi SH changes from inactive to active at the same time, the signal charge packet is transferred to the phi SH electrode; then under the alternate drive of phi sl and phi s2, the signal charge packet is transmitted step by step and output to CCD for digitalization, and finally a digitalized image is obtained, the invention adopts the pixel and electrode of the CCD to control as follows: (a) the luminous pulse image passes through the imaging lens and then is imaged on the CCD camera; (b) aiming at the generation, the transfer and the transmission of a CCD normal signal charge packet, a transfer and transmission driving time sequence is designed in the extremely short invalid time in the middle of two exposure driving pulses, and the signal charge packet is isolated at the later stage of the invalid period of the exposure pulses by utilizing the function of isolating the signal charge packet by a transfer electrode, so that the signal charge packet generated by two exposures can be distinguished, the normal transfer and the transmission of the signal charge packet can be realized in the invalid period of the exposure pulses, and the ultrahigh time resolution imaging capability of a double-amplitude pulse image is further obtained. The macroscopic view of the time relationship of the electrode control pulse is shown in FIG. 4, and the main operation time zones are indicated, such as tl, t2-t8 and the like in FIG. 4. No valid signal is applied to each electrode while the CCD is not in operation. When a burst of trigger pulses initiates this mode of operation, drive pulses on the CCD exposure electrode Φ e are generated by the control circuitry, assuming that the high level of the drive pulses corresponds to an exposure being performed, as represented by time zone t1 in fig. 4, at which time the first exposure is being performed, as also illustrated by tl in fig. 5; in order to transfer the photoelectron signal generated by the first exposure, it is necessary to apply an effective pulse to the transfer electrode φ SH for an exposure effective time, where the generated photoelectrons are also transferred to the electrode φ SH under the electrode φ e as shown by t2 in FIG. 5; subsequently, the drive signal on the exposure electrode Φ e becomes inactive but the signal on the transfer electrode Φ SH remains active, and photoelectrons can no longer be stored under the exposure electrode Φ e, and all of the photoelectrons are now collected or transferred under the transfer electrode Φ SH, as shown at t3 in fig. 5; in order to gradually transmit photoelectrons out to prevent the photoelectrons from flowing back to the position below the exposure electrode phi e, driving pulses meeting certain time sequence requirements are applied through electrodes phi sl and phi s2, as long as phi s2 is effective after phi s1 is effective, as shown in t4-t7 in fig. 4; when the transmitted photoelectron signal package is completely isolated from the exposure electrode, as shown in the time zone after t6 in FIG. 4, another exposure can be performed under the exposure electrode φ e; in this process, the t5 time zone in FIG. 4, in which the exposure electrode φ e drive is inactive, the transfer electrode φ SH drive is inactive, and the transfer electrode φ s1 drive is active, so that photoelectron signal charge packets are all accumulated under the transfer electrode φ s1 or simultaneously transferred under the transfer electrode φ s2, indicating that the exposure electrode φ e and the transfer electrode φ s1 are now blocked by the transfer electrode φ SH, indicating that photoelectrons generated thereafter under the exposure electrode φ e will not cross under the transfer electrode φ s1, and also indicating that the next exposure can be performed in the next time zone, as indicated by t6 in FIG. 5, where the generated exposure image is distinguishable from the former; when entering time zone t7, the signal charge packet transmitted in the light shielding row is not affected by the exposure electrode due to the isolation of the transfer electrode, and can be read out according to the output transmission timing requirement, as shown in t7 and t8 in fig. 4 and 5. The invention does not synchronize with the luminous pulse image for exposure, but skillfully utilizes the control function of the transfer pulse to transfer and isolate the signals generated by the front and the back images by setting a driving pulse time sequence, the transfer process can be fast, in the CCD, the transfer time can be as low as tens of nanoseconds, which also indicates that the time between two exposures can be very short, therefore, the synchronous relation between the interval of the two exposures and the drive of the CCD is well controlled, the control mode can realize the high-speed exposure function of the two images, as shown in figure 6, thereby realizing a high-performance two-frame camera without light splitting, as shown in figure 7, compared with the two-frame camera shown in figure 1, the components are greatly reduced, the control mode is completely the same as that of a common one-way photographic system, the structure is very simple, but the performance of the CCD and the high-efficiency performance of an optical system can be fully exerted, and high-performance imaging is met under certain use requirements.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (1)

1. A high-speed double-pulse image exposure method based on direct control of a CCD electrode is characterized by comprising the following steps:

(a) the luminous pulse image passes through the imaging lens and then is imaged on the CCD camera;

(b) aiming at the generation, transfer and transmission of CCD normal signal charge packets, a transfer and transmission driving time sequence is set in the invalid time between two times of exposure driving pulses, and a transfer electrode is utilized to isolate the signal charge packets during the invalid period of the exposure pulses, so that the signal charges generated by two times of exposure are distinguished, the normal transfer and transmission of the signal charge packets are realized during the invalid period of the exposure pulses, and the ultrahigh time resolution imaging capability of a double-amplitude pulse image is further obtained;

step (b) is achieved by:

(b1) dividing the main working time zone into 8 stages total tl-t8, when the CCD camera is not working, no effective signal is applied to each electrode, when a burst trigger pulse starts the working mode, the control circuit system firstly generates an effective driving pulse on the CCD exposure electrode phi e, the high level of the driving pulse is set to correspond to the exposure is going on, in the time zone of t1, the first exposure is going on;

(b2) in the t2 time zone, the driving pulse of the transfer electrode φ SH becomes active at the same time during the first exposure active time, causing photoelectrons generated by the first exposure to be transferred to the transfer electrode φ SH at the same time as generating photoelectrons at the exposure electrode φ e;

(b3) in the time zone t3, the drive signal on the exposure electrode φ e becomes inactive but the signal on the transfer electrode φ SH remains active, and photoelectrons can no longer be stored under the exposure electrode φ e, and are all accumulated or transferred to the transfer electrode φ SH at this time;

(b4) applying a step pulse signal through the transfer electrode phi sl to transfer photoelectrons stored on the transfer electrode phi SH to a position below the transfer electrode phi sl in a t4 time zone;

(b5) in a time zone t5, after all photoelectrons under the transfer electrode phi SH are transferred to the transmission electrode phi sl and a certain gap is left, applying a step pulse signal to the transmission electrode phi s2 to transfer the photoelectrons under the transmission electrode phi sl to the transmission electrode phi s 2;

(b6) in a time zone t6, photoelectrons kept under a transmission electrode phi sl are transferred to a position under a transmission electrode phi s2 until the transfer is completed, at the moment, a transmitted photoelectron signal packet is completely isolated from an exposure electrode phi e, and meanwhile, the position under the exposure electrode phi e can be used for generating and storing the photoelectrons generated by re-exposure, so that the photoelectrons cannot be confused with the previous photoelectrons;

(b7) in the time zone of t7, the driving pulse on the transmission electrode φ sl becomes inactive and the driving pulse on the transmission electrode φ s2 becomes active, so that photoelectrons are all transferred to the transmission electrode φ s2 and can be independently output in time sequence without being influenced by the exposure time sequence;

(b8) in the time zone t8, the signal charge packet transmitted in the light-shielding row is not affected by the exposure electrode due to the isolation of the transfer electrode, and the photoelectrons generated by the exposure are stored under the exposure electrode Φ e until the next transmission is started.

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