KR960002664B1 - An image intensifier and the manufacturing method thereof - Google Patents

Abstract

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Description

Image multiplication device and manufacturing method thereof

1 is a cross-sectional view showing a conventional image multiplication apparatus.

2 is a cross-sectional view showing an image multiplication apparatus of the present invention.

3 is a cross-sectional view showing another embodiment of the image multiplication apparatus of the present invention.

* Explanation of symbols for main parts of the drawings

10,22,50: image multiplier 14,26: photoelectron emitting wafer

12,28: Input window 16,30,58: Micro channel plate

18,34,52: Output window 20,32,64: Fluorescent screen

The present invention relates to an electro-optical device, and more particularly, to an image multiplier and an optical device for the multiplier.

The image multiplying device increases the amount of incident light received to provide an increase in light output that can be supplied to the camera or directly to the viewer's eye. Such devices are particularly useful for providing images from dark areas, and are also useful for industrial and military use. For example, such devices are used to enhance astronauts' night vision, to photograph celestial bodies, and to provide night vision to patients with retinitis pigmentosa (night blindness).

Recent image deposition apparatuses include three main elements, a photocathode, a fluorescent screen (anode), and a microchannel plat (MCP) between the photocathode and the anode. These devices are embedded in the multiplier. Photocathodes are very sensitive to the low-radiation levels of infrared light in the 580-900 nm (red) spectral region. The MCP is a thin glass plate with an array of fine pores. Each hole can act as a secondary emission electron multiplier in the form of a channel. Thousands of gains can be gained by placing the microchannel plate in the plane of the electron image in the multiplier. Because each channel of the microchannel plate operates almost independently of the others, the bright point source saturates some channels but does not extend into adjacent areas. This "local saturation" property prevents the bright area of the multiplier from expanding.

The anode of the image multiplier includes an output window and a fluorescent screen formed on one surface of the window. Known multiplication plates used a flat glass window as an output screen for an image multiplication device. Such two parallel glass surfaces of the window result in reflective and ghost images that cannot be removed even with the use of antireflective coatings. To solve this reflection problem, fiber optical output devices are used instead of flat glass output windows.

Fiber optic windows consist of a matrix of very thin core glass rods surrounded by clad glass, which is an expensive device. In addition, about 35% of the fiber optic window surface area is blocked from light reception due to the matrix structure. Thus, the performance of the image multiplying device is degraded due to the relatively low open area of the fiber optical window or the optically usable area of about 60%.

Accordingly, it is an object of the present invention to provide an image multiplication apparatus having an optical window of low reflectance.

Another object of the present invention is to provide a method for manufacturing an output window in a very economical and effective manner.

The object of the present invention described above is an input window having a light receiving surface and a light transmitting surface in planar form and formed of an optical material; An optical cathode comprising electron emitting means disposed on said light transmitting surface for emitting electrons in response to received light; Multiplication means disposed adjacent said photoelectron emitting means to multiply the number of electrons emitted from said photoelectron emitting means; Conversion means disposed adjacent said multiplication means for converting energy of said multiplied electrons into light to form an image; A lens plane 56 parallel to the planar light transmissive surface of the input window and having a single transparent spherical and aspherical surface for transmitting an image without reflection at the output of the image multiplier and for receiving an image from the conversion means; It is achieved by providing an image multiplier having means for preventing the image from being reflected between the plane light transmission plane of the input window and having output means for outputting the image from the conversion means.

The invention also has an input window (28) having parallel surfaces spaced at regular intervals, the method comprising the steps of: forming photocathodes (28, 26) for receiving input light and for emitting electrons in response to the received input; Mounting means (30) for multiplying the number of electrons emitted from the photocathode; Disposing a glass plate 42 adjacent to said multiplication means; Forming a fluorescent screen on one surface of the glass plate such that an anode for converting the multiplied electrons into an image is provided adjacent to the multiplication means; Enclosing the photocathode, the multiplication means (30) and the anode in a housing (24) having two opposing ends at one end of which the photocathodes (26, 28) are located at the other end; Made of solid glass or optical material having a single spherical or aspherical surface for transmitting the image without the reflection at the output of the image multiplier and the planar surface to prevent reflection of the image between the glass plate and the planar surface of the photocathode Provided is a method of manufacturing an image multiplier device comprising coupling a lens element 48 to the other surface of the glass plate 42.

Hereinafter, with reference to the accompanying drawings will be described in detail the object and other features of the present invention.

1 illustrates a conventional image multiplier 10 having an input window 12 of glass or optical fiber, a photoelectron emitting wafer 14 attached to the window 12, a microchannel plate 16 and an output window 18. ). The output window has a fluorescent screen 20 located on the surface of the output window located on the surface of the output window adjacent to the microchannel plate 16. The output window 18 is composed of fiber optical elements. While the image is transmitted from the input side to the output with a very low attenuation phenomenon through the fiber optical window, the performance of the window exhibits a relatively low open area ratio.

2 shows an image conduit 22 of the present invention. The multiplier 22 has the following three basic elements: the photoelectron emitting wafer 26, the microchannel plate 30 and the anode function coated on the input window or face plate 28 which functions as a cathode. It has an anode comprising a fluorescent screen 32 attached on the window 34. These elements are embedded in the housing 24. Power is supplied to the photoelectron emitting wafer 26, the MCP 30 and the fluorescent screen 32 by means integral with the housing 24 or configured outside the housing. The input window 28 is typically sealed within the housing 24 and surrounded by a peripheral flange 36. Member 38 supports input window 28 in housing 24. The retainer ring 40 seals the end of the multiplier 22 and supports the output window in the housing 24. The micro channel plate 30 is formed of a glass material having secondary emission characteristics and conductivity. The face plate 28 receives and transmits light. Light rays pass through the face plate 28 and are directed to an optoelectronic emission wafer 26 that converts photons into electrons. The converted electrons are sent to the MCP 30 which operates to multiply the number of electrons according to known principles. A typical photoelectron emitting wafer 26 is of some gallium arsenide (GaAs), but any other material may be used.

A micro channel plate 30 having an input and output surface parallel to the photoelectron emitting wafer 26 and the fluorescent screen 32 is mounted in the multiplier.

In operation, the radiant image striking on the photocathode results in electron emission directed to the micro channel plate at a higher positive potential than the photocathode. Each electron impinging on the MCP 30 results in a plurality of secondary electron emissions, which in turn results in more secondary electron emissions. The electron gain or multiplication factor in the MCP 30 is mainly controlled by the potential difference applied across the input and output surfaces of the MCP 30. Electrons emitted from the MCP and containing the input emission image information impinge on the fluorescent screen 32 to cause the screen to fluoresce and reproduce the input image.

By manufacturing the output window as a converged or diverging lens element, an improved output image with better optical resolution and higher quality images can be obtained at lower cost.

2 shows one embodiment of the invention with an output window 34 having two sections. The first section is a flat (flat) glass element 42 having an input surface 44 and an output surface 46 placed adjacent to the MCP 30. The glass of this element may be optical glass of predetermined high quality.

The second section of the output window 34 is a convex lens 48, the plane 49 of which is coupled to the output surface 46 of the glass 42. The fluorescent screen 32 is disposed on the input surface 44 of the glass element. The lens 48 may be configured in a block or concave shape having a spherical or aspherical curved surface.

3 illustrates another embodiment of the invention in which the output window is of a single optical element. The image multiplier 50 has the same structure as shown in FIG. 2 except that the output window 52 is a convex stove 52. Lens 54 is arranged such that its lens plane 56 is adjacent to MCP 58. Lens 54 is retained in gong 60 by retaining ring 62. The fluorescent screen 64 is disposed on the lens plane 56.

Lenses 48 and 54 are formed as any optical material, including glass and plastic.

The lenses 48 and 54 are configured as positive (or converging) lenses in the drawing, but negative (or diverging) lenses may be used. This lens can have a spherical or aspherical structure. A useful lens is a Gradient Index (GRIN) lens.

Two methods of making the image multiplier of the present invention are described below. The first method is carried out when the finished multiplier is assembled in the image multiplying apparatus, which will be described with reference to FIG. By using this method, no significant modifications are required to the standard multiplier forming method and the machine tool.

The second method is carried out when the heavy pipe is constructed, which will be described with reference to FIG. The method does not require any further processing steps in assembling the finished multiplier into the image multiplication device.

The image multiplier of FIG. 2 is manufactured in the following manner. An photoelectron emitting wafer 26 is formed on the face plate 28 to constitute a photocathode. A fluorescent screen 32 is attached on the input surface 44 of the glass element 42 to form an anode. This anode is fixed in the retainer ring 40. The photocathode, microchannel plate 30 and anode are mounted to the housing 24, which is filled with a potting compound. At this time, the retainer ring 40 is mounted at the end of the heavy pipe to seal the housing. This completes the manufacture of the heavy pipe. The heavy pipe manufacturing step is carried out according to a known treatment process.

Prior to insertion of the duct into the image multiplying device, the lens element 48 is bonded to the output surface 46 of the flat glass element 42. This process is accomplished by applying an optical adhesive to the surface 46, pressing the lens 48 to engage the surface 46 and allowing sufficient time for the adhesive to cure.

Other adhesives, such as UV curable adhesives, and other methods of joining glass and lenses are included in the present invention.

The aforementioned bonding step can be eliminated by using the lens 54 of FIG. According to this method, the lens 54 is secured in the retainer ring 62 so that the surface 56 will be adjacent to the MCP 58 when the ring is positioned in the tubing.

The use of lenses as output windows has been described so far, but the use of lenses as face plates or for input windows is also within the spirit of the present invention.

The invention has many applications in the field of video displays, in particular in the field of small CRT displays used for military and commercial applications, which also include thermal imaging, video cameras and similar systems.

The principles of the invention have been described above in connection with specific devices, which are described by way of example only and are not limited to the spirit of the invention as described in the appended claims.

Claims (10)

An input window 28 having a planar light receiving surface and a light transmitting surface and formed of an optical material, and photoelectron emitting means 26 disposed on the light transmitting surface for emitting electrons in response to the received light; Photocathodes 26 and 28; Multiplication means (30, 58) disposed adjacent the photoelectron emitting means (26) to multiply the number of electrons emitted from the photoelectron emitting means; Conversion means (32,64) disposed adjacent said multiplication means for converting energy of said multiplied electrons into light to form an image; The lens plane 49 for receiving the image from the conversion means and a single transparent spherical and aspherical surface for transmitting the image without reflection at the output of the image multiplier and parallel to the planar light transmitting surface of the input window; Means for preventing reflection of an image between the output means and the planar light transmitting surface of the input window 28 in the form of lens elements 48, 54 formed of solid glass or other optical material disposed adjacent to the conversion means. And an output means for outputting an image from the converting means. The image multiplier according to claim 1, wherein the multiplication means comprises microchannel plates (30,58). 3. An image multiplier according to claim 1 or 2, wherein said conversion means comprises a layer of fluorescent material (32,64). 3. An optical material element (42) according to any one of the preceding claims, further comprising an optical element (42) having two parallel surfaces (44, 46), one of which is on the image receiving surface of the lens element. Image multiplier, characterized in that arranged. Forming photocathodes (28,26) having input windows (28) having spaced parallel surfaces spaced at regular intervals, for receiving input light and emitting electrons in response to the received input; Mounting means (30) for multiplying the number of electrons emitted from said photocathode; Disposing a glass plate 42 adjacent to said multiplication means; Forming a fluorescent screen on one surface of the glass plate such that an anode for converting the multiplied electrons into an image is provided adjacent to the multiplication means; Enclosing the photocathode, the multiplication means (30) and the anode with a housing (24) having one end with the photocathode (26, 28) and two opposing ends with the glass plate at the other end; A solid glass or other optical material having a single spherical or aspherical surface for transmitting the image without the reflection at the output of the image plane and the image multiplier to prevent the image from being reflected between the glass plate and the planar surface of the photocathode Coupling the lens element (48) to the other surface of the glass plate (42). 6. The method of claim 5, wherein the step of arranging the glass plate comprises coupling a lens element to the surface of the glass plate on the side away from the fluorescent screen. 7. The method of claim 6, wherein the bonding step comprises bonding the glass plate to the lens element. 8. The method of claim 7, wherein the bonding step inserts an optical adhesive between the glass plate and the lens element. Forming photocathodes (28,26) having input windows having parallel planar surfaces spaced at regular intervals and for receiving input light and for emitting electrons in response to the received input light; Mounting means (58) for multiplying the number of electrons emitted from said photocathode; Providing a lens element 54 having a planar surface and at least one other surface; Disposing the lens element adjacent to the multiplication means; Forming a fluorescent screen (64) on the planar surface of the lens element such that an anode for converting the multiplied electrons into an image is provided adjacent to the multiplication means; Enclosing the photocathode, the multiplication means and the anode with a housing (60) having two opposing ends at one end thereof with the photocathodes (28, 26) at the other end; A single transparent spherical or aspherical surface on the lens element 54 for preventing the image from being reflected between the lens and the planar surfaces of the photocathodes 28 and 26 and for transmitting the image from the image multiplier without the reflection. Method for producing an image multiplier, characterized in that it comprises the step of providing a means comprising a. 4. An optical element (42) according to claim 3, further comprising an optical element (42) having two parallel surfaces (44, 46), one of said two parallel surfaces being disposed on said image receiving surface of said lens element. Image multiplier.

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