EP0020234A1 - Aufnahmetarget, mit einem solchen Target ausgerüstete Röhre und Aufnahmevorrichtung mit einer solchen Röhre - Google Patents

Aufnahmetarget, mit einem solchen Target ausgerüstete Röhre und Aufnahmevorrichtung mit einer solchen Röhre Download PDF

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Publication number
EP0020234A1
EP0020234A1 EP80400696A EP80400696A EP0020234A1 EP 0020234 A1 EP0020234 A1 EP 0020234A1 EP 80400696 A EP80400696 A EP 80400696A EP 80400696 A EP80400696 A EP 80400696A EP 0020234 A1 EP0020234 A1 EP 0020234A1
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EP
European Patent Office
Prior art keywords
target
signal
tube
point
elementary
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP80400696A
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English (en)
French (fr)
Inventor
Pierre Felix
Lucien Guyot
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thomson CSF SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0020234A1 publication Critical patent/EP0020234A1/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/08—Electrodes intimately associated with a screen on or from which an image or pattern is formed, picked-up, converted or stored, e.g. backing-plates for storage tubes or collecting secondary electrons

Definitions

  • the invention relates to a shooting target, as well as the shooting tube provided with such a target, and the entire device formed by the tube and its reading means.
  • the target of the invention can be of varied structure, photoconductive target in one of the usual materials, such as antimony sulfide (Sb 2 s 3 ), lead oxide (Pbo), etc., or mosaic target photodiodes-formed in a silicon substrate, or pyroelectric target ...
  • the invention applies generally to all these kinds of targets used for taking pictures, without distinction as to their nature.
  • the target has on one of its faces a conductive plate, or signal plate, from which the electrical signal corresponding to the different points of the target is sampled, during point-to-point scanning of the other face thereof, by the reading electron beam.
  • the beam deposits at each point a certain quantity of electrons to compensate for the effect produced at this point in the substrate by the incident radiation. This quantity, read in the circuit of the signal plate, constitutes the signal of the point.
  • the present invention relates to a target having a reduced signal plate capacity.
  • FIG. 1 we distinguish the target 1 and its two constituent parts, namely the target itself 10 , consisting of a plate of a photosensitive material, and, applied to one of the faces of this plate, the signal plate 11, from which, as we have said, the signals from the different points are taken in operation of the target.
  • the incident radiation arrives from the right of the figure, on the side of the signal plate, which has good transparency to this radiation, represented by the wavy arrow.
  • a cathode 21 provides , in operation, an electron beam, e (bent arrow), directed towards the target and scanning, as is known in the art, the target in question point by point; the means used to beam deflection to ensure this scanning have not been shown in this schematic view as known in the art.
  • a grid 22 placed in front of the target is connected to the voltage source U G.
  • the signal plate is polarized with respect to ground by the voltage source V C , or target voltage, by means of a bias resistor Rp of 5 MQ.
  • the preamplifier 3 with low input resistance comprises two stages, the first of which is constituted, in the example, by a field effect transistor with junction 30, at low noise level, the source and the drain of which are represented in S and D respectively, and the grid in G; the second stage consists of an operational amplifier 31, the output A of which is that of the reading device.
  • the signal plate 11 is connected to the transistor by a connection capacity C L of the order of 10 nanofarads.
  • the loop 40 includes a resistance R F of the order of a few megohms; the drain of the field effect transistor 30 is polarized with respect to ground by the voltage source V and the resistance R L.
  • FIG 2 gives the equivalent electrical diagram of the device object of Figure 1, for the AC component of the target current i (left arrow) flowing through the device.
  • C p represents the parasitic capacitance of the signal plate (reference 11 on the overview of the previous figure) and which is of the order of 8 picofarads in the example, that is to say the capacity between the signal plate in question and the mass, and that connections with respect to the same ground.
  • C L of the previous figure n t is not represented, because for the alternative, it is equivalent to a short circuit;
  • C S and C D denote in the figure the capacities of the gate of the junction transistor with respect to the source and the drain thereof, of 2.5 and 1.5 picofarads respectively;
  • the mark g represents the transconductance of the junction transistor;
  • V g represents the AC component of the voltage at the gate of the transistor.
  • the Schottky noise associated with the target current the lower the lower the target current, the thermal noise associated with the resistors R p and R F , the lower as these resistances are high, and the noise associated with the noise voltage at the junction transistor.
  • the noise associated with the target, generation and recombination noise in the case of a semiconductor target, thermal noise in the case of a pyroelectric target is generally negligible compared to the other noise sources.
  • the noise current associated with the first stage is also negligible in the case of a junction field effect transistor.
  • the noise of such a device is equivalent to a target noise current which will be designated by i a and of expression:
  • C T is equal to the sum of the stray capacitances and where denotes the noise voltage of the first stage, that is to say of the field effect transistor in The example.
  • C T Cp + C s + C D ; in this formula, B denotes the bandwidth of the device, proportional to the image frequency and to the number of points of the target, that is to say to the resolution.
  • the current i B is of the order of a few hundred picoamps.
  • the target noise i B is a direct reason, of the total capacity C T.
  • the noise is lower when the parasitic capacitance C p is lower.
  • the reduction in capacity C is obtained by splitting the signal plate into several parts, electrically isolated from each other, under the conditions which will be specified.
  • Figure 3 shows in perspective a target of the invention generally designated by the reference 1, as in Figure 1, and composed as in the case of this figure of the target itself 10 and the signal plate.
  • the latter bears the reference 110 and differs from that of FIG. 1 in that, in the invention, it is made up of several separate parts, electrically isolated from each other as shown in the drawing, and to which the references 101, 102, 103 have been given; in the figure, for clarity, the proportions of the elements, in particular their thicknesses, have not been respected.
  • the different portions of the target signal plate of the invention, or elementary plates, can have any orientation with respect to the direction of scanning of the target by the reading beam; however, in a preferred embodiment of the invention, they are arranged parallel to the direction of this scan.
  • the signal plate is thus divided into p elementary signal plates; p is equal to -, N being the number of lines of the scan, for example of television, and n the number of lines of this scan arranged opposite the elementary signal plate considered.
  • the previous capacity C is divided by p. It goes without saying that the maximum value of p is N, that is to say the number of lines of the scan; in this case there are as many elementary plates as there are scanning lines.
  • Each of the elementary signal plates is connected to a preamplifier.
  • a switching system makes it possible to switch at all times the output of the reading device to the preamplifier associated with the elementary signal plate which receives the single reading or analysis beam, according to known addressing techniques.
  • the p preamplifiers as well as the addressing register can be, depending on the case, inside or outside the camera tube, which has the corresponding number of outputs.
  • FIG. 4 The scheme of such a switching system is given in Figure 4; four elementary nameplates are represented by rectangles without markers; each covers on the target, in the example, the surface of five scanning lines (broken lines).
  • the p preamplifiers limited to four in the example, p l , P 2 , P 3 , P 4 , are connected sequentially to the output A of the output amplifier a by switching transistors t 1 , t 2 , t 3 , t 4 .
  • An address register R the scanning of which is synchronous with the scanning of the target by the reading beam, allows the sequential addressing of the gates of the transistors.
  • the targets of the invention and their reading device can be produced in various ways, which can be classified into two categories, fully integrated or hybrid; in the first, the preamplifiers are integrated on the same substrate as the target.
  • the preamplifiers are integrated on the same substrate as the target.
  • the lowest noise voltage of an integrated operational amplifier is, in nanovolts, 4. ⁇ B, B being the bandwidth measured in hertz.
  • the preamplifiers are produced in the form of separate "chips" bonded to a common substrate, which may be the window of the shooting tube, c that is to say the part of its envelope exposed to incident radiation: right-hand end face of this envelope in FIG. 1
  • Reading of the target of the invention can be done by means of several reading beams, each of these being used to read the lines located opposite a plate or a group of elementary plates.
  • analysis beams In the intermediate situation there is analysis beams.
  • Each of the P k reading beams analyzes in parallel the k elementary signal plates of the group.
  • a device for switching by analysis beam is used for reading, making it possible to connect sequentially to each of the outputs of the tube the k preamplifiers associated with each of the k plates of the group.
  • the pk electron beams required are obtained either from a single cathode and an electronic optic making it possible to divide the emitted beam into pk elementary beams, or a system of diaphragms arranged in the immediate vicinity of the cathode, or from pk elementary cathodes. Possibly the means of focusing and vertical and horizontal deflection are common to all the elementary beams.
  • a scanning speed of the elementary beams identical to the scanning speed in the case of a single beam (bandwidth unchanged).
  • This reduction is also favorable for reading a mosaic target of photovoltaic detectors, or MIS, sensitive to infrared radiation, and where the integration time is limited by the generation due to the continuous background.
  • the frame period T is kept; the scanning speed is then divided by , as well as the bandwidth.
  • the signal is also divided by .
  • the analysis time for a given point is therefore multiplied by , you can have the same reading efficiency of the target points with a beam resistance higher by a factor , so with a target current more small by a factor , the beam resistance being inversely proportional to the target current.
  • Schottky noise associated with the beam current proportional to (i c denoting the target current and B the bandwidth) is therefore globally divided by , since i and B are each separately divided by this factor.
  • the applications of the target of the invention are the same as those of the targets of the known art, in particular taking infrared shots.

Landscapes

  • Transforming Light Signals Into Electric Signals (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
EP80400696A 1979-05-29 1980-05-20 Aufnahmetarget, mit einem solchen Target ausgerüstete Röhre und Aufnahmevorrichtung mit einer solchen Röhre Withdrawn EP0020234A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7913631A FR2458141A1 (fr) 1979-05-29 1979-05-29 Cible de prise de vues, tube muni d'une telle cible, et dispositif de prise de vues comprenant un tel tube
FR7913631 1979-05-29

Publications (1)

Publication Number Publication Date
EP0020234A1 true EP0020234A1 (de) 1980-12-10

Family

ID=9225966

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80400696A Withdrawn EP0020234A1 (de) 1979-05-29 1980-05-20 Aufnahmetarget, mit einem solchen Target ausgerüstete Röhre und Aufnahmevorrichtung mit einer solchen Röhre

Country Status (3)

Country Link
US (1) US4361783A (de)
EP (1) EP0020234A1 (de)
FR (1) FR2458141A1 (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2326018B (en) * 1997-06-07 2002-01-09 Ibm Grid electrodes for a display device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2920137A (en) * 1957-03-15 1960-01-05 Garbuny Max Apparatus for reducing spurious signals in thermal image converters
GB884362A (en) * 1957-03-15 1961-12-13 Emi Ltd Improvements relating to pick-up devices for colour television
FR2341242A1 (fr) * 1976-02-11 1977-09-09 Philips Nv Camera de television et tube enregistreur convenant pour ce tube

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3889117A (en) * 1971-04-29 1975-06-10 Cincinnati Electronics Corp Tapered detector scanning array system
US4117515A (en) * 1976-12-24 1978-09-26 U.S. Philips Corporation Television camera having signal electrode strips
US4139444A (en) * 1977-12-12 1979-02-13 North American Philips Corporation Method of reticulating a pyroelectric vidicon target

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2920137A (en) * 1957-03-15 1960-01-05 Garbuny Max Apparatus for reducing spurious signals in thermal image converters
GB884362A (en) * 1957-03-15 1961-12-13 Emi Ltd Improvements relating to pick-up devices for colour television
FR2341242A1 (fr) * 1976-02-11 1977-09-09 Philips Nv Camera de television et tube enregistreur convenant pour ce tube

Also Published As

Publication number Publication date
US4361783A (en) 1982-11-30
FR2458141B1 (de) 1982-02-19
FR2458141A1 (fr) 1980-12-26

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Inventor name: FELIX, PIERRE

Inventor name: GUYOT, LUCIEN