阅读说明：本技术 水下成像与非成像复合的激光雷达 (Underwater imaging and non-imaging composite laser radar ) 是由 张晓晖 林鸿生 韩宏伟 孙春生 白联刚 于 2020-11-26 设计创作，主要内容包括：本发明提供了一种水下成像与非成像复合的激光雷达,包括激光发射单元、光电成像单元、激光测距单元、信号/图像处理单元和监视器；其中激光发射单元根据信号/图像处理单元输出的控制信号发射激光脉冲以照明目标,激光发射单元还用于接收激光脉冲并形成相应的电脉冲信号输出至信号/图像处理单元；光电成像单元用于接收目标反射光并形成相应的电子图像,将电子图像输出至信号/图像处理单元；激光测距单元用于接收目标反射光将其放大后输入信号/图像处理单元；信号/图像处理单元根据电脉冲信号和目标反射光信号控制光电成像单元的选通切片；信号/图像处理单元优化电子图像后将其输出至监视器。本发明具备成像距离远、图像清晰的特点。(The invention provides an underwater imaging and non-imaging composite laser radar, which comprises a laser emission unit, a photoelectric imaging unit, a laser ranging unit, a signal/image processing unit and a monitor, wherein the laser emission unit is used for emitting laser beams; the laser emission unit is used for emitting laser pulses according to the control signals output by the signal/image processing unit so as to illuminate a target, and is also used for receiving the laser pulses, forming corresponding electric pulse signals and outputting the electric pulse signals to the signal/image processing unit; the photoelectric imaging unit is used for receiving the target reflected light, forming a corresponding electronic image and outputting the electronic image to the signal/image processing unit; the laser ranging unit is used for receiving the target reflected light, amplifying the target reflected light and inputting the amplified target reflected light into the signal/image processing unit; the signal/image processing unit controls the gating slice of the photoelectric imaging unit according to the electric pulse signal and the target reflected light signal; the signal/image processing unit optimizes the electronic image and outputs it to a monitor. The invention has the characteristics of long imaging distance and clear image.)

1. The underwater imaging and non-imaging composite laser radar is characterized by comprising a laser emitting unit, a photoelectric imaging unit, a laser ranging unit, a signal/image processing unit and a monitor; the laser emission unit is used for emitting laser pulses according to the control signals output by the signal/image processing unit so as to illuminate a target, and is also used for receiving the laser pulses, forming corresponding electric pulse signals and outputting the electric pulse signals to the signal/image processing unit; the photoelectric imaging unit is used for receiving the target reflected light, forming a corresponding electronic image and outputting the electronic image to the signal/image processing unit; the laser ranging unit is used for receiving the target reflected light, amplifying the target reflected light and inputting the amplified target reflected light into the signal/image processing unit; the signal/image processing unit controls the gating slice of the photoelectric imaging unit according to the electric pulse signal and the target reflected light signal; the signal/image processing unit optimizes the electronic image and outputs it to a monitor.

2. The underwater imaging and non-imaging composite lidar of claim 1, wherein the signal/image processing unit generates a reference time based on a time at which the laser emitting unit emits the laser pulse; the signal/image processing unit is used for preprocessing the target reflected light received by the laser ranging unit, removing the influence of water body back scattering noise by adopting a background difference method or a background modeling method, then extracting a target echo signal, calculating delay time according to reference time, generating a trigger signal and sending the trigger signal to the photoelectric imaging unit; the signal/image processing unit receives the image data output by the photoelectric imaging unit, denoises and enhances the input image to generate an electronic image, and transmits the electronic image to a monitor for display.

3. The undersea imaging and non-imaging composite lidar of claim 2, wherein the laser emitting unit comprises a pulsed laser, a beam expander, a beam splitter, and a PIN tube; the signal/image processing unit is connected with the pulse laser through a driving circuit and controls the output power of the pulse laser; the pulse laser emits laser pulses, and the laser pulses are expanded by the beam expander to illuminate a target; a small part of the emitted laser pulse after being split by the spectroscope is received by the PIN tube, converted into an electric pulse signal and sent to the signal/image processing unit; and the beam splitter and the PIN tube are respectively arranged on two sides of the output port of the beam expander.

4. The undersea imaging and non-imaging composite lidar of claim 3, wherein the optoelectronic imaging unit comprises a gating circuit and an enhanced charge-coupled device, the enhanced charge-coupled device is configured to receive target reflected light and form a corresponding electronic image, and output the electronic image to the signal/image processing unit; the gate control circuit is used for receiving a trigger signal from the signal/image processing unit; the gate control circuit compares the trigger signal with an internal reference clock, outputs an adjusted pulse signal, and controls the time of opening and closing the gate of the enhanced charge coupled device and the power distribution of the gating slice.

5. The undersea imaging and non-imaging compounded lidar of claim 4, wherein the laser ranging unit comprises a PMT tube and a preamplifier circuit; and the PMT tube is used for receiving the target reflected light, amplifying the target reflected light by the preamplification circuit and then sending the target reflected light to the signal/image processing unit.

6. The underwater imaging and non-imaging composite lidar according to claim 5, wherein the reference time set in the signal/image processing unit is the time of laser emission, the delay time is calculated according to the receiving time of target reflected light fed back by the laser ranging unit, and the target distance is obtained by conversion according to a formula according to the delay time; the signal/image processing unit generates a trigger signal according to the delay time to control the door opening of the enhanced charge coupled device, and then controls the door closing of the enhanced charge coupled device according to the set gating slice width; the signal/image processing unit sets the gated slice width according to the target echo width.

7. The undersea imaging and non-imaging composite lidar of claim 6, wherein when target reflected light reaches the enhanced charge coupled device, a shutter of the enhanced charge coupled device opens a receive signal and the remaining time the shutter of the enhanced charge coupled device closes to reject water backscatter noise; the opening and closing of the shutter of the enhanced charge coupled device are controlled by a control signal generated by a gate control circuit; the control signal comprises two pieces of information, namely the door opening time and the door opening duration time respectively; the door opening time is obtained by subtracting the measured front edge of the target echo signal from the reference time, and the duration time is the difference between the front edge and the rear edge of the target echo signal.

8. The undersea imaging and non-imaging composite lidar of claim 7, wherein:

after the pulse laser emits laser pulses, a small part of the pulse laser is reflected by the light splitting plate and received by the PIN tube, and after photoelectric conversion, the signals are input into a first channel of the data signal/image processing unit, the signals are flight time measurement starting signals, and a second channel of the data signal/image processing unit is triggered to carry out data acquisition; the residual laser enters water through the emission window and is emitted to a target, the residual laser is reflected after reaching the target by the distance R, a target echo signal and a water body scattering signal are received by the PMT pipe, are subjected to photoelectric conversion and amplification, and are input into a second channel of the data signal/image processing unit; the target echo pulse signal extracted by the data signal/image processing unit is used as a timing end signal; the data signal/image processing unit calculates the time interval between the start signal and the timing end signal, and calculates the target distance R according to the time interval T, and the calculation formula is expressed as:

where c is the speed of light, c_wIs the speed of light in water, n_wIs the refractive index of the water body, t₀And t_TRespectively, a timing start time and a timing stop time.

Technical Field

The invention relates to the technical field of underwater photoelectric imaging detection, in particular to an underwater imaging and non-imaging composite laser radar.

Background

With the development of laser devices and photoelectric materials, underwater imaging laser radars become an indispensable means for underwater detection. The underwater imaging laser radar is an underwater imaging system which utilizes blue-green pulse laser to irradiate a target and images by a range gating principle. The scattered light and the emitted light of the target are separated in time sequence at different distances, so that the radiation pulse reflected by the observed target reaches the camera just in the time of gating work of the camera and is imaged. If the laser pulse width and the gating pulse width are both narrow, only the reflected light near the target can reach the camera, namely only the reflected light near the target is received, most of the influence of the back scattering light can be eliminated, and the imaging distance and the imaging quality are obviously improved.

In order to achieve a good imaging effect, the underwater imaging laser radar needs to accurately set a delay time, that is, a target distance is preset, which limits the practical use of the underwater imaging laser radar. There are three main approaches to current solutions.

The first mode is manual control, and the adjustment in the mode is time-consuming, low in working efficiency and difficult to adapt to underwater working environment.

The second mode is a full gating working mode based on a high-repetition laser, namely, according to a time sequence control strategy, the accumulated pulse number in the integration time of one frame of image is distributed to continuous gating slices, and the through-vision imaging effect of a detection area is realized. However, this method distributes limited energy to the continuous gating slices, many gating slices have no target, resulting in waste of laser energy, and the contrast signal-to-noise ratio of each target in the output image is low, which affects the imaging effect.

The third way is to measure the target distance by the device and then set the delay time. At present, the sonar detection system is mainly adopted in the mode for ranging. However, due to the non-uniformity and the variability of the ocean medium, the sound velocity distribution rule is very complex, so that large positioning and direction deviation can be generated when underwater detection is carried out by using sonar. Adopt sonar detection system to measure distance and still can increase extra receiving and dispatching passageway, increase the volume and the consumption of system, be unfavorable for using to operational environment under water.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an underwater imaging and non-imaging composite laser radar which has the characteristics of long imaging distance and clear image.

The invention provides an underwater imaging and non-imaging composite laser radar which is characterized by comprising a laser emission unit, a photoelectric imaging unit, a laser ranging unit, a signal/image processing unit and a monitor, wherein the laser emission unit is connected with the photoelectric imaging unit; the laser emission unit is used for emitting laser pulses according to the control signals output by the signal/image processing unit so as to illuminate a target, and is also used for receiving the laser pulses, forming corresponding electric pulse signals and outputting the electric pulse signals to the signal/image processing unit; the photoelectric imaging unit is used for receiving the target reflected light, forming a corresponding electronic image and outputting the electronic image to the signal/image processing unit; the laser ranging unit is used for receiving the target reflected light, amplifying the target reflected light and inputting the amplified target reflected light into the signal/image processing unit; the signal/image processing unit controls the gating slice of the photoelectric imaging unit according to the electric pulse signal and the target reflected light signal; the signal/image processing unit optimizes the electronic image and outputs it to a monitor.

In the above technical solution, the signal/image processing unit generates a reference time based on a time at which the laser emission unit emits the laser pulse; the signal/image processing unit is used for preprocessing the target reflected light received by the laser ranging unit, removing the influence of water body back scattering noise by adopting a background difference method or a background modeling method, then extracting a target echo signal, calculating delay time according to reference time, generating a trigger signal and sending the trigger signal to the photoelectric imaging unit; the signal/image processing unit receives the image data output by the photoelectric imaging unit, denoises and enhances the input image to generate an electronic image, and transmits the electronic image to a monitor for display.

In the above technical solution, the laser emission unit includes a pulse laser, a beam expander, a beam splitter, and a PIN tube; the signal/image processing unit is connected with the pulse laser through a driving circuit and controls the output power of the pulse laser; the pulse laser emits laser pulses, and the laser pulses are expanded by the beam expander to illuminate a target; a small part of the emitted laser pulse after being split by the spectroscope is received by the PIN tube, converted into an electric pulse signal and sent to the signal/image processing unit; and the beam splitter and the PIN tube are respectively arranged on two sides of the output port of the beam expander.

In the above technical solution, the photoelectric imaging unit includes a gate control circuit and an enhanced charge coupled device, the enhanced charge coupled device is used for receiving the target reflected light and forming a corresponding electronic image, and outputting the electronic image to the signal/image processing unit; the gate control circuit is used for receiving a trigger signal from the signal/image processing unit; the gate control circuit compares the trigger signal with an internal reference clock, outputs an adjusted pulse signal, and controls the time of opening and closing the gate of the enhanced charge coupled device and the power distribution of the gating slice.

In the above technical solution, the laser ranging unit includes a PMT tube and a preamplifier circuit; and the PMT tube is used for receiving the target reflected light, amplifying the target reflected light by the preamplification circuit and then sending the target reflected light to the signal/image processing unit.

In the above technical solution, the reference time set in the signal/image processing unit is the time of emitting laser, the delay time is calculated according to the receiving time of the target reflected light fed back by the laser ranging unit, and the target distance is obtained by conversion according to a formula according to the delay time; the signal/image processing unit generates a trigger signal according to the delay time to control the door opening of the enhanced charge coupled device, and then controls the door closing of the enhanced charge coupled device according to the set gating slice width; the signal/image processing unit sets the gated slice width according to the target echo width.

In the technical scheme, when the target reflected light reaches the enhanced charge coupled device, the shutter of the enhanced charge coupled device is opened to receive signals, and the shutter of the enhanced charge coupled device is closed to resist the backward scattering noise of the water body in the rest time; the opening and closing of the shutter of the enhanced charge coupled device are controlled by a control signal generated by a gate control circuit; the control signal comprises two pieces of information, namely the door opening time and the door opening duration time respectively; the door opening time is obtained by subtracting the measured front edge of the target echo signal from the reference time, and the duration time is the difference between the front edge and the rear edge of the target echo signal.

In the technical scheme, after the pulse laser emits laser pulses, a small part of the pulse laser is reflected by the light splitting plate and received by the PIN tube, and after photoelectric conversion, the signals are input into a first channel of the data signal/image processing unit, wherein the signals are flight time measurement starting signals, and a second channel of the data signal/image processing unit is triggered to carry out data acquisition; the residual laser enters water through the emission window and is emitted to a target, the residual laser is reflected after reaching the target by the distance R, a target echo signal and a water body scattering signal are received by the PMT pipe, are subjected to photoelectric conversion and amplification, and are input into a second channel of the data signal/image processing unit; the target echo pulse signal extracted by the data signal/image processing unit is used as a timing end signal; the data signal/image processing unit calculates the time interval between the start signal and the timing end signal, and calculates the target distance R according to the time interval T, and the calculation formula is expressed as:

where c is the speed of light, c_wIs the speed of light in water, n_wIs the refractive index of the water body, t₀And t_TRespectively, a timing start time and a timing stop time.

The invention images by a pulse laser and a gating imaging device according to a distance gating principle, simultaneously obtains a target distance by combining laser ranging, sets delay time, and automatically adjusts the door opening time and the door closing time of the ICCD. Due to the addition of the ranging function, the laser power distribution is more optimized, so that the method has the characteristics of long imaging distance and clear image.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

FIG. 2 is a schematic diagram of a gate control circuit according to an embodiment of the present invention;

FIG. 3 is a schematic illustration of laser pulse number assignment according to the present invention;

FIG. 4 is a diagram of an embodiment of a photoelectric and analog-to-digital conversion circuit;

FIG. 5 is a waveform of a target signal in an embodiment;

FIG. 6 is a waveform of a gating signal in an embodiment;

FIG. 7 is a schematic diagram of a coarse tuning module in an embodiment;

FIG. 8 is a schematic diagram of a fine tuning module in an exemplary embodiment;

FIG. 9 is a schematic diagram of an embodiment of an application.

Detailed Description

The invention will be further described in detail with reference to the following drawings and specific examples, which are not intended to limit the invention, but are for clear understanding.

As shown in FIG. 1, the invention provides an underwater imaging and non-imaging composite laser radar, which is characterized by comprising a laser emission unit, a photoelectric imaging unit, a laser ranging unit, a signal/image processing unit and a monitor; the laser emission unit is used for emitting laser pulses according to the control signals output by the signal/image processing unit so as to illuminate a target, and is also used for receiving the laser pulses, forming corresponding electric pulse signals and outputting the electric pulse signals to the signal/image processing unit; the photoelectric imaging unit is used for receiving the target reflected light, forming a corresponding electronic image and outputting the electronic image to the signal/image processing unit; the laser ranging unit is used for receiving the target reflected light, amplifying the target reflected light and inputting the amplified target reflected light into the signal/image processing unit; the signal/image processing unit controls the gating slice of the photoelectric imaging unit according to the electric pulse signal and the target reflected light signal; the signal/image processing unit optimizes the electronic image and outputs it to a monitor.

In the above technical solution, the signal/image processing unit generates the reference time based on the electric pulse signal; the signal/image processing unit is used for preprocessing the target reflected light, removing the influence of water body back scattering noise by adopting a background difference method or a background modeling method, then extracting a target echo signal, calculating delay time according to reference time, generating a trigger signal and sending the trigger signal to the photoelectric imaging unit; the signal/image processing unit receives the image data output by the photoelectric imaging unit, denoises and enhances the input image, and then sends the input image to a monitor for display. The invention adopts a multi-gating mode for control, namely, the laser ranging is utilized to obtain the distance between a plurality of targets which are not completely shielded mutually in the longitudinal direction, and then the ICCD is controlled to open the door when the reflected light of the targets reaches the ICCD. The laser emits short laser pulses, and after light splitting, a small part of light is received by the PIN tube and converted into electric pulse signals serving as reference bases. After receiving the target signal, the PMT tube performs pre-amplification; the signal processing unit preprocesses the signal received by the PMT tube, removes the influence of water back scattering noise by adopting a background difference method or a background modeling method, then extracts a target echo signal, calculates delay time on the basis, and generates a trigger signal to be sent to the gate control circuit. The image processing unit receives the video signal output by the ICCD, processes each frame of image and sends the processed image to the monitor for display. The signal processing unit is also connected with the laser to control the transmitting power of the laser and the like.

According to the technical scheme, the laser emission unit comprises a pulse laser, a beam expander, a beam splitter and a PIN tube; the signal/image processing unit is connected with the pulse laser through a driving circuit and controls the output power of the pulse laser; the pulse laser emits laser pulses, and the laser pulses are expanded by the beam expander to illuminate a target; a small part of the emitted laser pulse after being split by the spectroscope is received by the PIN tube, converted into an electric pulse signal and sent to the signal/image processing unit; and the beam splitter and the PIN tube are respectively arranged on two sides of the output port of the beam expander. The beam expander is an electric variable beam expander; the pulse laser adopts a xenon lamp pumped neodymium-doped yttrium aluminum garnet Nd: YAG pulse laser with adjustable output power. The optical axes of the pulse laser and the electric variable beam-expanding mirror are superposed. The signal/image processing unit takes the FPGA as a control core, is connected with the laser through a driving circuit and controls the output power of the pulse laser; receiving a pre-amplification circuit signal, preprocessing, removing the influence of water body back scattering noise by adopting a background difference method or a background modeling method, then extracting a target echo signal, calculating delay time on the basis, generating a trigger signal, and controlling the opening time and the opening duration of the ICCD through a gate control circuit. A pulse laser: the pulse laser should have a high peak power and output wavelengths that conform to the optical window of the water (480nm-550 nm). Due to xenon lamp pumped Nd: YAG pulse laser technology is mature, cost is low, output laser wavelength is 1.06 μm, 532nm blue-green laser can be obtained after frequency multiplication, and laser pulse width can be compressed to ns magnitude by laser Q-switching technology, so that the peak power output by a laser with single pulse energy of hundreds of millijoules is dozens of megawatts of laser, therefore, the embodiment of the invention selects the laser as a light source of an underwater laser imaging system.

The photodiode (PIN tube) converts the pulse light intensity signal into a pulse current signal. The signal/image processing unit has an electro-optical and analog-to-digital conversion circuit to convert the electric signal into a digital signal. The photoelectric and analog-to-digital conversion circuit is shown in fig. 4. The current flows through a load resistor (R113), pulse voltage signals are formed at two ends of the load resistor, the load resistor is connected into a comparator (MAX963) through a filter of a capacitor (C150) and compared with a preset reference voltage (VINA-) to generate a 3.3V-TTL digital pulse signal, in order to avoid the situation that the signal cannot be identified due to the fact that the pulse width is too narrow, a monostable multivibrator (74HC123DB) is used for widening the digital pulse signal after the comparator to generate an identifiable digital pulse signal, and at the moment, the identifiable digital pulse signal is the reference time.

According to the technical scheme, the photoelectric imaging unit comprises a gate control circuit and an enhanced charge coupled device (ICCD), wherein the enhanced charge coupled device is used for receiving target reflected light, forming a corresponding electronic image and outputting the electronic image to the signal/image processing unit; the gate control circuit is used for receiving the trigger signal from the signal/image processing unit, comparing the trigger signal with the internal reference clock, outputting the adjusted pulse signal, and controlling the door opening and closing time of the enhanced charge coupled device and the power distribution of the gated slice. The ICCD formed by connecting the CCD camera and the micro-channel plate-type image intensifier by the optical fiber not only has nanosecond gating capacity, but also has large gain dynamic range and high sensitivity. In addition, the GaAsP cathode of the three-generation image intensifier works at the wavelength of 532nm, and the quantum efficiency is close to 50%. Based on the above advantages, the embodiment of the present invention adopts the ICCD as a receiver. The gating circuit is shown in fig. 2. It compares the input trigger signal with a reference clock and outputs the adjusted pulse signal to control the opening of the ICCD. In order to minimize the influence of the inherent delay on the shortest working distance of the system, a high-speed device is selected when the gating circuit is designed. When the target reflected laser pulse reaches the ICCD, the shutter is opened to receive the signal, and the shutter is closed to resist the backward scattering noise of the water body in the rest time. The opening and closing of the ICCD shutter is controlled by a gate control circuit generating a control signal. The control signal contains two pieces of information, the moment of opening the door follows the duration of opening the door. The door opening time is obtained by subtracting the measured leading edge of the target echo signal from the reference time, and the duration time is obtained by the difference of the leading edge and the trailing edge of the target echo signal.

As shown in fig. 6, the leading edge time of the gating signals of three different target distances is determined by the delay time, and the trailing edge time is determined by the target echo width.

The gating signal generator is a core part of the controller and is composed of a coarse tuning module and a fine tuning module, as shown in fig. 7 and 8. The coarse tuning module realizes the coarse tuning of the time domain parameters of the digital pulse signals by utilizing the counting of the high-speed clock inside the FPGA. The reference clock is the internal clock 150 MHz. The fine adjustment module outputs a gating signal.

According to the technical scheme, the laser ranging unit comprises a PMT tube and a preamplifier circuit; and the PMT tube is used for receiving the target reflected light, amplifying the target reflected light by the preamplification circuit and then sending the target reflected light to the signal/image processing unit. The delay time refers to the difference between the time at which the target echo reaches the PMT tube and a reference time. The photomultiplier tube (PMT tube) converts the pulsed light intensity signal into a pulsed current signal. The pre-amplification circuit amplifies the electrical signal. The signal/image processing unit has an electric signal processing circuit and has a background difference function. As shown in fig. 5, the non-target echo signal and the target echo signal are directly subtracted to obtain a processed target signal.

As shown in fig. 3, there are three targets (i), (iii), and (v) along the optical axis direction, and the three targets are not completely shielded from each other. L1,L2, L3, L4, L5 are gated slices with a gate width Δ. By laser ranging, it can be obtained that the echoes thereof are delayed by t from the reference time_delay-1、t_delay-3、t_delay-5. Thus setting the delay of the ICCD to t_delay-1、t_delay-3、t_delay-5And the door opening width is 2 delta/v_water(v_waterIs the speed of light in water). The laser pulses within one frame image integration time are distributed into gated slices at L1, L3, L5, respectively. Since the targets (r), (c), and (c) are located exactly in these 3 gated slices, the system can clearly image them without distributing the laser power to the L2 and L4 slices without targets.

By adopting a multi-gating imaging mode, the system can realize the detection of a plurality of gating slices every time the system outputs one frame of image, and simultaneously acquire images of a plurality of targets, and obviously, the longitudinal imaging range of the system is larger than that of a single-gating imaging mode. And the laser power is distributed according to the section where the target is located, so that the target imaging is clearer.

According to the invention, the distance value between the target and the detection system is calculated by measuring the time interval between the time when the echo pulse signal of the target is detected and the time when the pulse is transmitted, and a system block diagram is shown in FIG. 9.

After the laser emits laser pulses, a small part of the pulse laser is reflected by a beam splitter and received by a photoelectric detector 1(PIN tube), and after photoelectric conversion, a signal is input into a channel 1 of a data acquisition module, wherein the signal is a flight time measurement starting signal and triggers channel 2 to acquire data; the residual laser enters water through the emission window and is emitted to a target, the residual laser is reflected after reaching the target by a distance R, a target echo signal and a water body scattering signal are received by a photoelectric detector 2(PMT tube) and are subjected to photoelectric conversion and amplification, then the target echo signal and the water body scattering signal enter a signal processing module through a data acquisition module channel 2, the extracted target echo pulse signal is used as a timing end signal, time interval measurement is terminated, the target distance R is obtained by calculation according to the measured time interval T, and the calculation formula is expressed as follows:

wherein, c_wIs the speed of light in water, n_wIs the refractive index of the water body, t₀And t_TRespectively, a timing start time and a timing stop time.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.