DE2536133A1 - Depth of field scanning for television - is performed with low light level active illumination using varying scanning internal - Google Patents

Abstract

An automatic television distance scanning method is used to produce a picture with considerable depth of field without the picture being degraded by back scattering. The method is applied to an actively illuminated low light level television system. The picture brightness is maintained constant over the field depth, and the picture approximates as nearly as possible to a picture taken in daylight. The system uses illumination devices and a television camera. The scene is illuminated with light pulses, and the receiver scans the reflected light at discrete time points after emission. To provide depth of field, the time between illumination and scanning is varied during the picture duration.

Description

Automatic television distance scanning method with scanning The present invention relates to an actively lit low light television system ("actively illuminated low-light level television") and in particular the procedure and the arrangement for the simultaneous display of targets from different Distance. The possibility of objects at distances of several eilometers and being able to view in essentially complete darkness has in the past raised many problems. Numerous devices have been developed that Capture targets under such conditions. It can be seen that in the Night surveillance of Xampfields it sees its sinking, the possibility to avoid the discovery of the lighting device and still display an image to achieve that corresponds to what one would get in normal daylight. Correspondingly, many of these devices have a lighting device, those in the invisible Electromagnetic energy spectrum - such as IR or UV light - works. Because a laser has a very narrow spectrum Band emits infrared radiation and has considerable spectral discrimination (i.e. increases the reflectivity of many material ions), there are also Facilities in which a pulsed laser is used to illuminate the field of view of interest is used. There are distance measuring devices in which lasers are used to search for targets at a predetermined distance. With such active keys Lasersyatemen is the distance sampling interval successively after each laser pulse extended until an echo arrives, and then automatic range scanning stopped. In this way, the presence of a target object in a capture a certain distance.

While some devices objects at a certain distance visible, others only determined the distance to the target. Third wise Means to show a certain scene visually as well as simultaneously determine the distance to the objects located there. The U8-PS 3,495,906 and U.S. Patent 3,649,124 are examples. In U.S. Patent 3,495,906, a Field of view illuminated periodically and the propagation time of the reflected successive Pulses evaluated to determine the distance to the object. It becomes a special picture tube used in the ian using different deflection speeds for consecutive Lighting impulses on the field of view Image is obtained when the objects are at different distances within of the field of view are shown in their mutual assignment. the U8-PS 3,649,124 shows an active clocked television system in which successive Full images of different distance ranges are displayed as a composite image. Each distance is shown in a different color to the observed to distinguish different areas from each other. U.S. Patent 3,682,553 become successive complete image fields for successively different ones Distances generated and in a composite image to a three-dimensional representation of an object within the target area.

In the known arrangements, the examined distance range held constant for one frame period. As a periodically pulsed lighting device is operated in a row with a periodically scanned FS-Rensor, determines the distance between the pulse of the lighting device and the pulse of the scanned one Sensor the distance at which the observation is being made, lis Feldtilefe in a certain Distance is usually very short, i.e. it becomes an impulse of low spatial energy ("small spatial energy pulse") used to avoid atmospheric back scattering. As a result, a potential target object can be within the field of view and still escape detection when the search distance is too only differs slightly from the distance at which the object is located. With increasing depth of field, the atmospheric backscatter also increases up to one no longer acceptable impairment of the image quality. Furthermore, the changes recorded brightness of the scenes at different distances in a quadratic ratio to the desired object and with the atmospheric conditions under which the observation takes place.

There is a need for a low-light arrangement that allows monitoring a wide distance range, but still a uniform brightness the representation allows. In contrast to an arrangement in which a observed first distance and then a second distance or a composite image is supplemented from stored distance sub-steps, there is a need for an arrangement that continuously scans a wide range of depths and one Image generated that of a passive BS monitor with daylight illumination entapricht.

Accordingly, it is an object of the present invention to provide an assembly indicate which is an image of a considerable depth of field without impairing the image quality as a result of backscattering.

It is another object of the present invention to provide an arrangement indicate which is an illustration of a considerable depth of field delivers, in which the image brightness is constant within the depth of field.

It is another object of the present invention to provide an active keyed Indicate television system in which within each period of the FS picture a plurality scanned from distances and TO a visible mapping of the total depth of field is pictured.

It is another object of the present invention to provide an image as close as possible to one taken in daylight.

Finally, it is an aim of the present invention, an aim emphasis or suppression in selected distance ranges with simultaneous To enable representation of all other distances of interest.

The present invention provides an active keyed television system for scanning a wide depth of field during each frame period to capture an image that corresponds to a conventional passive television picture. Goals in all Distances can be observed simultaneously, with the ability to be atmospheric To suppress RLickscatter, remains and the brightness differences are eliminated between scenes.

Illumination pulses are used to illuminate a specific field of vision used. The time delay between the individual illumination pulse and a pulse that excites the optical receiving device (e.g. a bid amplifier in the optical path of the FS camera), determines the distance displayed on the FS monitor. The depth of field at this distance results from a mathematical convolution of the illumination and the sensor touch pulse, as described below his is referred to as a "spatial energy pulse". The automatic Adjustment of the time interval between the lighting pulse and the dom iuftastimpuls for the image intensifier, relative to the image and line blanking interval, the part of optical device forming camera allows a to scan the entire depth range. The time delay (distance) between the illumination pulse and the air strobe pulse for the image intensifier can be in successive Lines can be the same or different so that all distances are within a single frame time of the television camera can be illuminated. As the information given during each scan line recorded is saved and read out only once per image time and the television transmitter controls the light input signals over a full picture integrated, all distances are visible at the same time. These spatial energy impulses are distributed over the various distances in such a way that the camera absorbed reflected energy is constant for all areas. The farther away lying areas with a larger one, the closer areas acted upon with a lower number of room energy pulses, including the decrease the energy density at greater distances due to atmospheric scattering, the Attenuation along the propagation path and the broadening of the illuminating beam to balance exactly.

If the target distance is very long, it may be necessary while to illuminate one line and to key the receiver during the next line, about the finite speed of propagation of light on the way to and from Target object to be considered. Selected distances within the depth of field can be viewed more closely by increasing the number of spatial energy impulses, with which this special distance range is applied. A spatial energy impulse is essentially the depth from which a single light pulse is reflected and is picked up by an optical device.

The time interval between the pulse excitation of the lighting arrangement and the impulse keying of the image intensifier of the optical receiver as well as the The duration of the touch pulse for the image intensifier defines the "spatial energy pulse".

This procedure allows all goals between an adjustable To illuminate a minimum and a maximum distance and capture it by the television camera allow. The deterioration in image quality due to atmospheric backscattering is not due to the power distribution technology described above essential. The backscatter is more noticeable at closer distances, but from there only becomes little energy captured. Correspondingly, the backscatter at a great distance is where many spatial energy impulses are applied, no major problem. Since the decrease the energy density is balanced by a corresponding distribution of the spatial energy impulses is, the result is an FS image that is evenly illuminated as with daylight illumination.

Other objects, features, and advantages of the present invention will emerge from the following description and the accompanying drawings.

FIG. 1 is a block diagram of a preferred embodiment of FIG present invention; Fig. 2 is a timing diagram of the various Pulses in the operation of an arrangement according to FIG. 1; Fig. 3 shows an embodiment the timing circuit according to the present invention; and Fig. 4 shows a preferred one Spatial energy momentum distribution.

As shown in FIG. 1, a pulsed lighting device illuminates 10 with an optical system 12 the scene of interest. The optical system 14 has the same field of view as the optical system 12, so it is the same of interest Scene captured as the optical system 12. The captured by the optical system 14 Image (energy) runs silver through the image intensifier 16 on a television camera 18, where it is converted into a video signal, which is then used by a standard FS monitor 20 reproduces. The timing circuit 40 receives the image and line deflection signals from the camera 18 and controls the function of both the lighting device 10 as well as the scanned image verse strengthens 16. The time delay between the pulse for the lighting device and the pulse for the image intensifier determines the distance range displayed on the monitor 20 as the speed of the light on its way from the lighting device to the target and back to the camera 18 is finite. The timing circuit 40 automatically adjusts the delay between the lighting and the touch pulse in correct synchronicity with the image and line deflection signals from the FS camera 18.

FIG. 2 depicts an exemplary pulse timing diagram for the present Invention. Fig. 2 (a) shows a single field (with interlaced scanning) or a full screen. The reference numeral 30 denotes the image blanking intervals, the Numeral 32 the line blanking intervals. The strobe pulses 34 for the image intensifier are shown in Fig. 2 (b), the strobe pulses 36 for the lighting device in Fig. 2 (c). In the case of the one shown in Fig.

2, one lighting and one lighting cycle occurs per cell duration a blanking pulse, although it is not required, every line duration assign such a pair of pulses. Is e.g.

the target distance is very small, it may only be necessary in every second or third line duration a pulse pair (consisting of lighting and keying pulse) to provide for the finite speed of propagation of light to and from the target to consider.

As shown in Fig. 2, the touch pulse 36 occurs for the lighting device during an active scan line while the game amplifier 16 is blanked is. A pulse 34 scans the image intensifier 16 at a later time tl after Pulse 36 on, also within a line (or

Image-) Duration to absorb the energy that the target from a previous one Has reflected the lighting pulse. This time t1 corresponds to the delay that the timing circuit 40 operates to determine the observed distance. the Time span between the illumination pulse 36 and the gating pulse 34 for the image intensifier can be varied successfully from t1 to tn.

These delays determine the observed distances. The one you want The time delay value is generated in the timing circuit 40. These Time values can be chosen so that meager distances of interest can be scanned during a half or full image duration.

One embodiment of the timing circuit 40 is shown in Pig. 3 in their details are shown. The timing compliance is ensured by three timing signals controlled. The image and the line deflection pulses from the camera 18 are used for synchronization the Circuit 40. The frequency of the clock generator 42 is determined from the distance accuracy required for the system according to the formula f = c / 2 . # R in which f is the frequency, c is the speed of light and R is the desired distance accuracy or the desired removal sub-step.

The distance unb thus the space energy impulses are considered integer Multiples of the distance sub-step # R quantizes what the output of the lighting and blanking pulses.

The number of distance sub-steps that are illuminated Is in register 48 as a binary-coded decimal number i saved. The number of distance sub-steps that make up an active line period is stored as a binary-coded decimal number B in a register 44.

The distance that a line of the television camera 18 -comp. 2 (a) - can be calculated according to the formula R "c.t / 2, in which c is the speed of light and t is the line duration of the television camera 18. The BCD number So B is the quantity R / # R in binary form. As mentioned earlier, it may be required be a certain distance with a greater number of Spatial energy impulses to act on than other distances in order to produce either an apparent equal illumination to illuminate or to make certain distances brighter than others. The storage unit 46 stores up to 128 numbers of 8 bits each, representing the desired frequencies determine with which each distance is pulsed, starting with the number of distance sub-steps that is the minimum distance to be observed corresponds to (BCD number A), and then progressing to the maximum distance to be observed (less than or equal to the BCD number B, provided that both the lighting device and the camera are opened in each line period). With the one shown special memory can be pulsed at 128 different distances, each of these distances in turn is pulse-illuminated a maximum of 28 - 1 or 255 times can be. The memory 46 can store N programs which can be selected immediately permit. In an constructed and capable embodiment of the present invention four different programs were saved.

In operation, the BCD number A is obtained from register 48 at the beginning of the television picture entered into counter 50. The memory address register 52 is reset and enters the content of the first cell of the memory 46 into the binary up counter 54 a. Thus, the contents of the BCD up-counter 50 represent the minimum desired distance at which the observation begins and the number in the binary incremental counter is 54 the frequency with which this Illuminated and from the distance Camera is detected. At the beginning of each picture line, the BCD number B is taken from the register 44 loaded into the BCD down counter 56 and this from the clock generator 42 to zero counted down. The data in counters 56 and 50 are kept by the BCD comparator 58 continuously compared. Upon reaching the desired distance they become the same, after which the BCD comparator 58 the gating pulse 36 (Fig. 2) for the lighting device gives away. The BOD down counter 56 then continues to count to zero; is that state reached, the gating pulse 34 for the image intensifier is emitted. The camera 18 is therefore gated just within the line blanking pulse because the BCD-Cahl B and the frequency of the clock generator 42 according to the aspects described above were selected. The content in the counter 54 is counted down with the line frequency and thus continuously represents the number of times that the desired removal segment rode must still be used in counter 50. If the content of counter 54 has reached zero, an output pulse is emitted which contains the contents of the memory address register 52 increased by 1, whereby the content of the next memory cell entered into the counter 54 will. The output pulse also causes the desired partial distance to step is incremented by 1 in the counter 50. At this point the cycle continues with proceed to the new desired distance sub-step (contents of counter 50) which the desired number of times (contents of counter 54) is used. luf this way the placement of the spatial energy pulses increases during the television picture, as does it the memory 46 and the BCD number A in register 48 determine.

If a certain partial distance range is to be skipped, can into the corresponding memory cell of the memory 46 a specially coded binary number can be entered.

Is this specially coded binary number as the output variable of the memory 46 before, the single counter 54 is bypassed and the specially coded output variable causes the OR gate 60 to emit a pulse that both the counter 50 (on the next distance sub-step) and the address register 52 to the same Way it updates the binary down counter output 54 did when reaching the counting state zero. At the end of the television picture (or field in the case of the interlace method), the scanning process is ended and the entire process begins Process again with loading the BCD number A into the counter 50 and resetting of address register 52.

The down counter 56 cycles through all possible lines during each line period Distance sub-steps. The number stored in up counter 50 shows the one specific distance to be viewed during the current line. The down counter 56 starts with the highest number and counts with the clock frequency by. all distances down. Are the number stored in memory 50 and the number in the down counter 56 equals, the comparator 58 outputs a pulse which the lighting device switches on. The down counter 56 then continues to count down, until he blushed zero; at that point becomes a Impulse given, which auts the image intensifier. A corresponding process takes place in every line duration instead of. Is desired a. to observe a certain distance, for example three times the binary down counter 54 only then has an output signal via the CDER element 60 to the up counter 50 until it has counted down over three lines. in this point he gives an output pulse from the causes that the up counter 50 to the next the distance of interest. The present invention thus allows a certain distance of interest frequently, only once, or not at all to apply light pulses. The cycle repeats itself continuously to consequently every distance of interest during each field or full frame capture. The present invention works with a full line and also works perfectly with a line checking system.

Line natural lighting of all the target within the scanned Area can be reached by looking for an appropriate distance distribution of the spatial energy pulses within a single period of the FS full or field cares.

To achieve the same lighting within the entire depth of the distance to achieve, the space energy impulses are distance moderately according to the representation 4 distributed. The fig.

4 shows an exemplary spatial energy pulse distribution for a particular one Half frame time in an interlaced system. By looking at the distribution of the energy impulses and thus curve 62 is correct hiring, assign all goals the same brightness within an FS image on the FS monitor. Taking E.g., it is desired to view a scene in the distance range of 100 1000 m, and the clock frequency is set to display sub-steps of 10 m, the spatial energy impulses captured by the camera occur at distances of 100, 110, 121, ..., 1000 m and should have a width of more than 10 m, and one to ensure sufficient overlap. The number of times at each distance Rausenergleimpulse occurring is selected to approximate the curve 62 accordingly. The shape of curve 62 is generally determined by the width of the spatial energy impulses, the atmospheric conditions on the observation path and the desired energy distribution this way. Since the information recorded during each line is only recorded once is stored and read out per scan line and the FS sensor the incident Integrated light over the entire duration of the image, all targets appear with the same brightness.

By drawing a vertical line like line 64 (Fig. 4), leave determine the number of impulses with those. a certain distance within must be illuminated for an image duration. Rmax receives a stronger one during the image duration Lighting as Xi. The distribution of the spatial energy impulses at the distance R is R² proportional (around the spread of the sighting rays with increasing distance to compensate), and if nan a compensation of the energy losses due to atmospheric scattering and attenuation, you can adjust the distribution of the room energy impulses further, until the number of overlapping spatial energy impulses at the distance R this Compensates for loss on the path of propagation.

Each lighting pulse should illuminate and reflect the target will; this expansion naturally takes a certain amount of time.

In the case of large distances, it may be sufficient not to have one for each line To send out spatial energy impulses, but only for every second or third. Apparently There are many other methods to achieve the desired spatial energy distribution reach. Consequently, only an exemplary solution is given above.

Claims (21)

P a t e n t a n s p r ü c h e 1. Method of scanning a wide range of depths of range during a television image to generate a linear image in an active keyed one WEAK LIGHT ~ FS-Systen with a lighting and a receiving device, the contains an FS-Kamers by illuminating a scene with light pulses and the Receiving device at discrete times after the emission of the light pulses buttons to receive the reflected lighting, which is not possible s e i n e t that one can continue the time between the exposure of the scene and the keying of the receiving device during the image duration of the FS camera varies. 2. The method according to claim 1, characterized in that the Receiving device keys in such a way that the successively increasing distance intervals reflected lighting is detected more frequently. 3. The method according to claim 1, characterized in that one successively greater distances observed more frequently to produce an image of constant brightness and those distance intervals for which a greater brightness is desirable after observed than for an image of constant brightness from such Distances would be required. 4. The method according to claim 1, 2 or 3, characterized in that preselected distance intervals within the distance depth are suppressed, by counting the time between the lighting and the keying of the receiving device varies such that the reflected from the & u suppressing distance Lighting is not shown. 5. The method according to claim 1, 2, 3 or 4, characterized in that that the time between the lighting and the keying of the receiving device is varied by adding a number representing the number of distance intervals used corresponds to the next distance to be scanned, in an up-counter, a Number that specifies the distance intervals for a line duration of a television camera, enters into a down counter, the outputs of the down and up counter compares with each other and derives an output signal from the comparison, the one Illumination pulse causes when the output variables are the same, and the receiving device rises when the down counter reaches zero. 6. Active keyed FS arrangement for carrying out the method according to Claim 1 with an illuminating device for illuminating a scene with light energy pulses and a receiving device with a video camera with an image duration for recording the lighting of the scene, characterized by a timing circuit (40) for Control of the lighting device (10, 12) and the receiving device (16, 18) such that the camera (18) the reflected lighting energy from the observed scene at different times after lighting pulses from of the lighting device (10, 12) have been sent out, and during an image duration the camera (18) records, whereby a plurality of distance intervals during an FS image duration can be scanned. 7. active keyed FS arrangement according to claim 6, characterized getenn, that the timing circuit (40) the lighting device (10, 12) and the receiving device (16, 18) repeatedly scans, with successive pulses for the receiving device (16, 18) during the image scanning time in relation to the pulses for the lighting device (10, 12) can be shifted, whereby the camera is essentially equal amounts of energy records from different distances. 8. Active keyed FS arrangement according to claim 6, characterized in that that the timing circuit (40) the lighting device (10, 12) and the receiving device controls impulsively, with successive pulses for the receiving device during the image sampling time with respect to the pulses for the lighting device can be delayed, which means that the camera is less than a certain partial distance Detects energy and suppresses a scene at this certain partial distance. 9. Active keyed FS arrangement according to claim 6, characterized in that that the timing circuit (40) the lighting device and the receiving device controls pulsed, with successive pulses for the Ehpfangseinrichtung during the image scanning time with respect to the pulses for the lighting device be delayed, which means that the camera has more energy from a certain partial distance captures and highlights a scene at that particular part of the distance. 10. active keyed FS arrangement according to one of claims 6 to 9, characterized in that the receiving device comprises an optical device (14, 16), which is opened in pulses to transfer energy to the camera, which corresponds to the incident energy from the observed scene, and impulsively is blanked to prevent a substantial portion of the scene reflected energy continues to run to the camera. 11. Active keyed PS arrangement according to one of claims 6 to 10, characterized in that the timing circuit (40) comprises a digital device (46) that can store data corresponding to the various time intervals between the emission of the lighting by the lighting device and the recording the reflected; Corresponding lighting energy by the receiving device. 12. Active keyed FS arrangement according to claim 11, characterized in that that the digital device in a digital memory (46) for storing a plurality of numbers that indicate the frequency with which time is kept constant to which the camera applies the reflected lighting energy according to a preceding one Picks up lighting pulse, and has a digital counter (50, 54, 56), which is connected to the digital memory and the memory to a predetermined Point in time during the image scan advances to the non-following number, whereby the camera different and selected lights for each distance interval recorded. 13. Active keyed FS arrangement according to claim 11 or 12, d adurch characterized in that the digital device pulse-controls the receiving device se, that the camera absorbs lighting energy only during the camera blanking intervals. 14. Active keyed FS arrangement according to claim 13, characterized in that that the digital device causes the lighting device during each The camera's scan line sends energy out and that the camera reflects light in the interval between each scan line. 15. Active keyed FS arrangement according to one of claims 6 to 14, characterized in that the timing circuit (40) has a first counting down Device (56), an up-counting one Facility (50) and Means (58) to the output size Be of the up-counting device (50) with to compare that of the first down-counting device (56), the comparing Device emits an output pulse when the counting state of the first down counting device and that of the upcounting device are the same, and this output pulse from the comparing device to the lighting device is given. 16. Active keyed FS arrangement according to claim 15, characterized in that that the first down-counting device (56) emits an output pulse when their counting state is equal to zero, the output signal occurring at the zero state we placed at the receiving facility. 17. Active keyed FS arrangement according to claim 15 or 16, characterized characterized in that the timing device further includes an n clock generator (42) which is connected to a first input of the first down-counting device (56) is placed and its frequency is determined by the formula f = c / 2 # R, in the f is the frequency, c is the speed of light and # $ is the distance desired (Distance sub-step) are. 18. Active keyed FS arrangement according to claim 17, characterized in that through a first register (52) and a second register (46), the first register (52) contains a preset number that represents the minimum distance to be scanned (number the distance sub-steps to the minimum distance), and (ap second register (46) contains a number representing the number of distance intervals in a line duration corresponds to the television camera. 19. Aktivgeastete FS arrangement according to claim 18, characterized by Nittel to read the content of the second register (46) at the line speed of the Loading television camera into the first down-counting device (54) and means by the number in the first register (52) with the frame rate of the television camera into the up-counting device (50). 20. Active keyed FS arrangement according to claim 19, characterized in that that the device which makes the up-counting device (5) count up, a second down-counting device (54), a program storage unit (46), an address register (52) and a terminal device (60), the address register (52) is responsive to the output of the gate device (60) to progressive Information bits from the program storage unit (46) into the second down-counting Device (46) with the output to the terminal device (60) and the output of the gate device (60) is placed on the up-counting device (50) is to the counter (50) in response to an output pulse from the gate means (60) to count upwards. 21. Aktivgetsstete FS arrangement according to claim 20, characterized in that that the address register (52) responds to the image sync pulse from the FS camera, to reset the address register (52) at the frame speed of the FS camera, said second down-counting means (54) at line speed the FS camera counts down.