GB1600773A

GB1600773A - Electro-optical picture signal processing system

Info

Publication number: GB1600773A
Application number: GB2360380A
Authority: GB
Original assignee: Fuji Xerox Co Ltd
Current assignee: Fujifilm Business Innovation Corp
Priority date: 1977-04-11
Filing date: 1978-04-11
Publication date: 1981-10-21

Description

(54) ELECTRO-OPTICAL PICTURE SIGNAL PROCESSING SYSTEM (71) We, Full XEROX CO. LTD., a Japanese company, of 35, 3-chome, Akasaka, Minato-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to an electrooptical picture signal processing system for converting time sequential electrical picture signals into an electrostatic latent image.

According to the present invention there is provided an electro-optical picture signal processing system comprising an electron emission plane a grid electrode to control passing of the electrons emitted from the electron emission plane, a number of secondary-electron multiplying devices, each of which has a cross section not larger than picture-element size and produces secondary-electrons in response to the incidence of photoelectrons from the electron emission plane, an electric power source providing a voltage for accelerating secondary-electrons, and an anode consisting of a number of segments as large as picture-element, for capturing multiplied secondary-electrons, wherein at least one of the electron emission plane and the grid electrode is divided into a one-dimensional array of picture-element size segments. which array is scanned from one end to the other with a gating voltage, and further a voltage between the electron emission plane and the grid electrode at selected segment portion is controlled in accordance with a time sequential picture signal, whereby to control the passage of electrons from the emission plane to the secondary-electron multiplying devices and anode segments.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a magnifically perspective view of a portion of a secondary-electron multiplier.

Fig. 2 is a schematic illustration of a secondary-electron multiplying mechanism.

Fig. 3 is a partially sectional schematic perspective view of an embodiment of the invention.

Fig. 4 is a block diagram of the driving circuit in Fig. 3.

A secondary-electron multiplier 5 is, as shown in Fig. 1 with partly expanded view composed of a bunch of secondary-electron multiplier tubes 9, each of which has a diameter of several ten pm and.DC voltage E2 is applied across the ends of the tube. Fig.

2 is a schematic view of a secondary-electron multiplying mechanism of a multiplier tube 9, wherein electrons e entered at the left side in the drawing are multiplied by means of a cascade method, so that the number of the secondary-electrons taken out of the anode 10 will be thousands times the number of the input electrons. As the secondary-electron multiplier 5 has such structure as a bunch of tubes 9, the multiplied output electrons are associated with the input electrons at their respective tubes.

Fig. 3 is a partially sectional schematic perspective view illustrating an embodiment of the invention, wherein a secondaty-electron multiplying function and a one-dimensional electrode segment array scanning function according to the present invention are applied to an electro-optical picture signal processing system or a picture signal recording system which converts time se quential picture signals into an electro-static latent image. The photocathode 27 consisting of a plurality of segments of picture element size is supplied with a voltage from the gate control circuit 23 and emits photoelectrons as it is uniformly illuminated by a luminous body 52. A flat-plate of electroluminescence material is suitable for the luminous body 52.

Although the control grid is expressed as a bar that faces the photo-cathode segment for simplicity, actually it may be a metallic mesh. The secondary-electron multiplier part is a parallel arragement of thin tubes for secondary-electron multiplication 29A, each supplied a voltage by the electrodes 42A and 43A attached to an input and output ends.

The cross section of the multiplying tube 29A is not bigger than the picture-element in size, and one or more tubes 29A are assigned to a picture-element or a photocathode segment.

Anode 31 A is also divided into segments of picture-element size, each of the segments and the corresponding pin electrode 57 connecting the inside and the outside of the evacuated housing 32 are constructed in a body or connected each other. A rear electrode 58 is placed under the insulative recording medium 59 at the pin electrodes 57, and this electrods 58 is connected with each of the anodes 31A and the pin electrodes 57 through a high voltage power source E5 and each load resistor 51. These pin electrodes are well known in the facsimile technique. The voltage of the power source E5 is chosen to be slightly lower than a firing potential of discharge between the pin electrodes 57 and the rear electrode 58.

Fig. 4 is a block diagram of a driver circuit illustrated for the purpose of explaining a scanning operation of this embodiment, wherein the same reference symbols as in Figure 3 denote corresponding parts. First, an explanation will be made about how to control the grid for the pass of photoelectrons emitted from the photocathode 27a, 27b.... excited by the light source 52. With the input (a) of the secondary electron multiplier 29A as a standard, a power source El supplies a voltage (b) of -506 volts to a constant voltage circuit 61 which in turn provides voltages (c) and (d) of -503 volts and - 497 volts to be fed to a ring-counter 33. Thus only one of the output terminals of the ring-counter 33, for example terminal g is turned to ON state and its voltage becomes -503 volts, while the other remain at OFF state, -497 volts. These voltages are applied to corresponding photocathode segments, respectively. As shown in the figure, each of the output terminals of said ring-counter 33 is connected to every photocathode segments at the same relative position in the respective groups classified with the grid electrode segments 28a, 28b Furthermor, two voltages, -506 volts (e) and -500 volts (f), produced at the constant voltage circuit 62 are fed to the ring-counter 36 and AND gates 65. Consequently, output "Q" (in OFF state) and output "1" (in ON state) of the ringcounter 36 and the AND gates 65 are -506 volts (e) and -500 volts (f), respectively. The outputs of AND gates 65 are applied to the grid segments 28a, 28b...., respectively.

When a clock signal C, is applied to the ringcounter 33 through the isolator 66, one of the output terminals of the counter is selected to be turned on and the selection is shifted by the subsequent clock signal, so that the voltage of the selected one of the photocathode segments 27a, 27b.... in each group is changed from -497 volts to -503 volts. The said clock pulses C, are fed to a frequency divider 68 which gives clock pulses C2 to the ring counter 36. Each output of the ringcounter 36 is applied to one input of each AND gate 65, on the other hand, the time sequential picture signal (j) is applied to another input of the gate 65 through the isolator 67. Therefore, under the condition that the video signal j takes its logic "1", an AND gate 65 selected by the output logic "1" of the ring-counter 36 turns on and drives the corresponding grid segment into its ON state.

Thus, the voltages at the grid segments 28a, 28b ..... are changed in turn from -506 volts to -500 volts, depending upon the clock signal C2 and the time sequential picture signal (j). When the photocathode segment is at -5Q3 volts and the grid electrode segment is at -500 volts, the voltage difference between them is +3 volts that permits the cathode segment to emit electrons. Under the other conditions, the bias voltage is - 3 volts or - 9 volts and photoelectron emission is suppressed. Accordingly, if the ratio of division at the frequency divider 68 is chosen to be equal to the number of the photocathode segments within a group of cathode segments which are placed along one of the control grid segments 28a, 28b ...., all the photocathode segments are scanned, for example, from the left end to the right end one by one in Fig. 4.

Only when the picture signal is in "1" state, the photo-electrons emitted from the segment portion or the photocathode segment are allowed to pass through the control electrode segment. The photo-electrons, after passing through the control electrode segment, are accelerated by an inter-electrode potential of about 500 volts before reaching the secondary-electron multiplying tube 29A.

The electrons multiplied therein are captured at the anode 31 A. As the result, a voltage drop occurs in the direction shown in the figure across the load resistor 51. Since a power source E5 provides a voltage slightly lower than the trigger level of the discharge between the pin electrodes 57 connected with the anodes 31A and the rear electrode 58, a voltage across the load resistor 51 will let the discharge started, yielding a certain amount of electrostatic charge on the surface of the insulative recording medium 59 according to the intensity of the picture signal.

As mentioned above, the one-dimensional scanning is performed by means of pin electrodes 57. Accordingly, when the recording system of this invention or the recorcing medium is moved perpendicularly to the scanning direction, a two-dimensional electrostatic image is produced on the recording medium. The electrostatic image produced as mentioned above, is developed with ordinary process into a visible image.

It is possible to provide a bunch of secondary electron multiplier tubes 29A for a single picture element. The cross section may be fabricated in arbitrary shape as far as they are divided to attain the desired resolving power in the direction of scanning. It is also obvious that similar effect will be obtained by using a stripe of photocathode 27 in place of cathode segments and dividing a control electrode 28 into a number of segments each having a size of obtaining the required resolving power and being independently controllable. Moreover, this embodiment can be applied to a system in which the pin electrode 57 and its cooperative electrode are positioned on the same side of the recording medium 59.

As mentioned above, the further advantage of this embodiment is as follows: Since the voltage, the level of which is slightly lower than firing potential, is previously applied between the pin electrode 57 and its cooperative electrode (58) relatively low voltage across the load resistor 51 is enough to control the firing between these two electrodes, therefore, the current through the anode 31A is also small. In addition the voltages to be controlled by the control circuit are low, and hence the device of this embodiment can be produced small in size and low in price.

WHAT WE CLAIM IS: 1. An electro-optical picture signal processing system comprising: an electron emission plane, a grid electrode to control passing of the electrons emitted from the electron emission plane, a number of secondary-electron multiplying devices, each of which has a cross section not larger than picture-element size and produces secondary-electrons in response to the incidence of photo-electrons from the electron emission plane.

an electron power source providing a voltage for accelerating secondary-electrons, and an anode consisting of a number of segments as large as picture-element, for capturing multiplied secondary-electrons, wherein at least one of the electron emission plane and the grid electrode is divided into a one-dimensional array of pictureelement size segments, which array is scanned from one end to the other with a gating voltage, and further a voltage between the electron emission plane and the grid electrode at selected segment portions is controlled in accordance with a time sequential picture signal, whereby to control the passage of electrons from the electron emission plane to the secondary-electron multiplying devices and anode segments.

2. An electro-optical picture signal processing system according to Claim 1, wherein one of the electron emission plane and the grid electrode consists of a plurality of segments as large as picture-element and grouped in such manner that each group contains the same number of said segments, the other consists of large segments which face to said each group of the pictureelement size segments, respectively, and when every picture-element size segments at the same relative position in the respective groups is selected to be turned into ON state, the remains are at OFF state, on the other hand when one of the large segments is selected to be turned into ON state, the remains are at OFF state, and consequently only when both of a picture-element size segment and a large segment corresponding to it are turned into ON state, electrons from said segment portion are allowed to pass through the grid electrode.

3. An electro-optical picture signal processing system according to Claim 1, further comprising: pin electrodes connected with the anode segments, respectively, an electrode co-operating with the pin electrodes, a high voltage power source for applying a potential slightly lower than a firing potential between said two electrodes, and an anode load resistance producing a voltage drops to be superposed upon the high potential in order to trigger discharge between said two electrodes, wherein an electrostatic latent image is produced on an insulative recording medium by secondary-electrons captured at the anode.

4. An electro-optical picture signal processing system according to Claim 2, further comprising: pin electrodes connected with the anode segments respectively, an electrode co-operating with the pin electrodes, a high voltage power source for applying a potential slightly lower than a firing potential between said two electrodes, and an anode load resistance producing a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. voltage across the load resistor 51 will let the discharge started, yielding a certain amount of electrostatic charge on the surface of the insulative recording medium 59 according to the intensity of the picture signal. As mentioned above, the one-dimensional scanning is performed by means of pin electrodes 57. Accordingly, when the recording system of this invention or the recorcing medium is moved perpendicularly to the scanning direction, a two-dimensional electrostatic image is produced on the recording medium. The electrostatic image produced as mentioned above, is developed with ordinary process into a visible image. It is possible to provide a bunch of secondary electron multiplier tubes 29A for a single picture element. The cross section may be fabricated in arbitrary shape as far as they are divided to attain the desired resolving power in the direction of scanning. It is also obvious that similar effect will be obtained by using a stripe of photocathode 27 in place of cathode segments and dividing a control electrode 28 into a number of segments each having a size of obtaining the required resolving power and being independently controllable. Moreover, this embodiment can be applied to a system in which the pin electrode 57 and its cooperative electrode are positioned on the same side of the recording medium 59. As mentioned above, the further advantage of this embodiment is as follows: Since the voltage, the level of which is slightly lower than firing potential, is previously applied between the pin electrode 57 and its cooperative electrode (58) relatively low voltage across the load resistor 51 is enough to control the firing between these two electrodes, therefore, the current through the anode 31A is also small. In addition the voltages to be controlled by the control circuit are low, and hence the device of this embodiment can be produced small in size and low in price. WHAT WE CLAIM IS:

1. An electro-optical picture signal processing system comprising: an electron emission plane, a grid electrode to control passing of the electrons emitted from the electron emission plane, a number of secondary-electron multiplying devices, each of which has a cross section not larger than picture-element size and produces secondary-electrons in response to the incidence of photo-electrons from the electron emission plane.

voltage drop to be superposed upon the high potential in order to trigger discharge between said two electrodes, wherein an electrostatic latent image is produced on an insulative recording medium by secondary-electrons captured at the anode.

5. An electro-optical picture signal processing system according to Claim I, wherein the electron emission plane comprises a photoelectron emission plane and a light source for uniformly illuminating the photoelectron emission plane.

6. An electro-optical picture signal processing system according to Claim 2, wherein the electron emission plane comprises a photoelectron emission plane and a light source for uniformly illuminating the photoelectron emission plane.

7. An electro-optical picture signal processing system according to Claim 3, wherein the electron emission plane comprises a photoelectron emission plane and a light source for uniformly illuminating the photoelectron emission plane.

8. An electro-optical picture signal processing system according to Claim 4, wherein the electron emission plane comprises a photoelectron emission plane and a light source for uniformly illuminating the photoelectron emission plane.

9. An electro-optical picture signal processing system as claimed in any preceding Claim, substantially as hereinbefore described, with reference to and as illustrated in Figure 4 and 5 of the accompanying drawings.