JPS6161353A - Light modulator - Google Patents

Abstract

PURPOSE:To increase mechanical strength and airtightness by accommodating a light modulator used for a projector by combining with a ceramic panel holding a cooling pipe for an assembly having an electro-optical crystal and a glass tube body. CONSTITUTION:A projector which projects television picture on a screen is formed by accommodating a light modulator containing an assembly 2 with a crystal having electro-optical effect with a cathode K in a tube body kept in high vacuum. The tube body 1 is formed by bonding a ceramic panel 23P comprising ceramic such a forsterite and a glass tube main part 23. The assembly 20 of the crystal, Peltier effect elements 42A, 42B, and a cooling water passage 21C are arranged within the tube body 1, and a cooling pipe 22 is drawn out from the ceramic panel 23P. Therefore, the tube body is sealed in airtightness and its mechanical strength is assured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention utilizes birefringence caused by the electric field of a crystal that has an electro-optic effect suitable for application to, for example, a projector that projects a television image onto a screen. Related to optical modulators.

[Conventional technology]

A pronoecme using an optical modulator is an assembled structure in which a crystal having an electro-optic effect is provided in a tube (1) facing an optical window (IW), as shown in FIG. 3, for example. (2) is arranged. As shown in FIG. 4, this assembled structure (2) has a dielectric mirror film (4) coated on one surface with a multilayer structure that has a high secondary electron emission ratio and reflects visible light. and a transparent conductive film (5
), for example, a crystal thin plate (3) made of KD2P04 (hereinafter referred to as DKDP) or KR2P04 (hereinafter referred to as KDP) having an electro-optical effect, on which an In2O3 film is deposited, for example, on the transparent conductive film (5) side. C
It is clamped to a transparent substrate (6) made of aF2. Moreover, this assembled structure (2) also has a transparent substrate (6).
The side is arranged so as to face the optical window (IW).

Also, inside the tube body (1) are first and second grid electrodes G facing the mirror film (4) side of the assembled structure (2).
1 and G2 are placed.

Then, as shown in FIG. 3, the electron beam b from the cathode K is focused and scanned on the mirror film (4) of this assembled structure (2). (7) and (8) indicate the electromagnetic means for focusing and scanning deflection, respectively.

Then, visible light from the light section (9) is irradiated from the front of the optical window section (IW) of the tube body (1) toward the assembled structure (2) via the polarizer 4, and the mirror film (4 ) is projected onto the screen (6) via the analyzer α stage.
A video signal, that is, a video signal to be projected onto the screen (2), is applied between the transparent conductive film (5) and the second grid G2. At this time, the electron beam from the cathode K is scanned with a constant current density Ip over the dielectric mirror film (4) with a high secondary electron emission ratio δ of the assembled structure (2), and is charged in accordance with the video signal. .

Note that the second grid G2 is placed close to the mirror film (4) at a distance of, for example, 40 μm.

In addition, the first grid G1 is given a potential of, for example, 150 V, and captures floating secondary electrons generated by the mirror film (4), and the resolution deteriorates due to the floating secondary electrons. This is to prevent this from occurring.

According to this configuration, depending on whether secondary electrons are emitted or primary electrons are accumulated from the dielectric mirror film (4) due to the impact of the electron beam b, that is, the incidence of primary electrons, a corresponding charge is generated. is generated in the dielectric mirror film (4), which gives a potential to the IT mirror film (4).When this potential becomes the same as that of the second grid G2, the emission of secondary electrons is suppressed. Therefore, the potential is balanced at this potential.In other words, at each scanning position of the electron beam b, the second grid G2
A charge field is generated in response to a voltage change due to a video signal applied to the crystal thin plate (3) between the mirror film (4) and the transparent conductive film (5). The assembly structure (2) K is arranged such that the direction of the axis of the light incident on the video signal is perpendicular to the direction of the light that is reflected by the video signal.

According to such a configuration, linearly polarized light entering the assembled structure (2) through the polarizer QO is reflected by the dielectric mirror film (4) and passes back and forth through the crystal thin plate (3), thereby producing a video signal here. It is modulated by the birefringence generated in response to the signal, which causes the original shading to pass through the analyzer α■, resulting in the projection of an optical image onto the screen (2).

In this way, a projector can be constructed by using an optical modulator, and various proposals have been made for this type of projector. An example thereof is Japanese Patent Publication No. 43-29086.

[Problem to be solved by the invention 1] The electro-optic crystal in this type of optical modulator is used in a state where it is cooled to around the Curie point, for example, about -50°C. The optical modulator is provided with cooling means. Therefore, in an optical modulator that obtains a charge pattern according to a signal by scanning an electron beam as described above, inside a vacuum tube maintained at a high degree of vacuum,
Along with the assembly structure having the electro-optic crystal, a cooling means associated therewith will also be accommodated.

Therefore, this vacuum-soil pipe has the mechanical strength to reliably hold the assembled structure of crystals having an electro-optical effect and the accompanying cooling means in place, and also In the means, it is necessary to pass a cooling water inlet pipe and an outlet arm for circulating a cooling medium, for example, cooling water, through the pipe body, and ensure airtightness of these pipes with the curved pipe body at the penetration part. hold it in
A structure that can maintain a high degree of vacuum inside the tube is required.

Usually, this type of high-vacuum tube body is composed of a glass tube body. The pipe body is divided into multiple parts and the parts are joined to form the soil pipe body. This allows the crystal assembly structure and its associated cooling means to be housed and arranged in a predetermined position.

In this case, each part of the tube is hermetically sealed and joined by a frit seal. However, this frit seal is 40
Since it requires heat treatment at about 0°C, it cannot be applied to the above-mentioned optical modulator having an electro-optic crystal with a low melting point, that is, its melting point is about 230°C. 3. When assembling and manufacturing the electro-optic crystal, consideration must be given to avoid causing thermal damage to the electro-optic crystal and, in some cases, to the Peltier effect element that is thermally coupled to it. The present invention provides an optical modulator that addresses the above-mentioned problems.

[Means for solving problems]

The optical modulator according to the present invention accommodates a crystal assembly structure having an electro-optic crystal and a cooling means for cooling this assembly structure in a vacuum-sealed tube. It consists of a tunnel section made of ceramics and provided with an optical window section, and a tube body made of glass that is joined to this panel section.

Then, each pipe for introducing and discharging the cooling medium of the cooling means is passed through the through hole bored in the AI panel made of ceramic, and the outer circumference of each knob and the hole passing through it are passed through. The inner circumferential surface of the through hole of the four-flank portion is hermetically sealed.

[Effect]

According to the above-described structure of the present invention, the tube body is constructed by joining the ceramic panel and the glass body, and the ceramic and glass can be tightly and reliably hermetically sealed; At each section, the cooling medium is introduced/input/injected. By penetrating the tube, that is, the metal arm tube, the sealing can be ensured and the mechanical strength for holding the cooling means can be maintained sufficiently. As will be clear from what will be described later, in this configuration,
By selecting the assembly procedure, it is possible to reliably seal the electro-optic crystal, Peltier effect element, etc. without any thermal influence.

〔Example〕

An example of the optical modulator according to the present invention that can be applied to the projector described in FIGS. 3 and 4 will be explained with reference to FIG. m1. In the figure, (a) shows the crystal assembly structure as a whole having a crystal thin plate (3) made of DKDP (or KDP) having an electro-optic effect, and Q]) is a cooling means attached to this. denotes each pipe for leading in and out of the cooling medium 29, and only one pipe is shown in the figure. In addition, ``(circle)'' indicates the tubular body that houses and seals these as a whole.

The crystal assembly structure (a) is constructed by attaching a thin crystal plate (3) to a transparent substrate (6) made of, for example, CaF2, in the same way as explained in FIG. The transparent substrate (6) side of the crystal thin plate (3), or the crystal thin plate (3) of the transparent substrate (6)
The transparent conductive film explained in FIG. 4 is formed on the side (not shown), and the dielectric film explained in FIG. A body mirror film is deposited. And this crystal thin plate (3
), a second grid electrode G2 and a first grid electrode G1 are sequentially arranged to face an electron beam emitting source, that is, a cathode, which is provided on the neck side (not shown) of the tube (to), and a thin crystal plate (3). are placed so that they are facing each other. A first plate (41) made of oxygen-free copper with excellent thermal conductivity is placed in contact with the front surface of the transparent substrate (6) opposite to the side where the crystal thin plate (3) is arranged. be done.

This first plate (41) has a thin crystal plate (3
), a through hole with an inner shape and size corresponding to the contour shape and size of the effective operating area is bored along the periphery of the effective operating area, and this first plate α hole is transparent. A thin crystal plate (3) arranged on the substrate (6)
contact is made in areas other than the operating area that forms a potential pattern corresponding to the projected image. Then, on the surface of this first plate (b) opposite to the side that comes into contact with the transparent substrate (6), a plurality of A first stage Peltier effect element group (42A) in which Peltier effect elements are arranged is provided. This element group (42A
) are electrically connected to each other in series, but thermally arranged in parallel; each cooling (endothermic) side is thermally closely coupled to the first plate 0. be done. Further, a second plate (43) made of oxygen-free copper is brought into contact with the heat generating side of each Peltier effect element (42A) in the first stage. (43) is also provided with a central hole facing the effective working area of the crystal thin plate (3) and having an inner shape corresponding to the outline of this working area. The contact between this second plate (43) and each Peltier effect element is also thermally tightly coupled. Furthermore, this second plate (43)
On the opposite side to the side where the first stage Peltier effect element group (42A) is arranged, a plurality of Beltier effect elements are similarly arranged around the center hole of the plate (43). A third stage Peltier effect element group (42B) is provided. In each Bertier effect element of this Peltier effect element group (42B), each Bertier effect element is electrically connected in series, and thermally arranged in parallel with each other, so that the endothermic side of each Bertier effect element is It is thermally tightly coupled to the second plate (43). Further, these first and second stage Peltier effect element groups (42A) and (42B) are, for example, connected to each other in series, and two common terminals are led out of the tube body.

A cooling means (c) is provided to be thermally coupled to the second stage Peltier effect element group (42B) of this assembled structure (7). This cooling means (goods) has a plate (21A) similarly made of good thermal conductivity, for example, oxygen-free copper, which is thermally connected to the second stage Peltier effect element group (42B) mentioned above. tightly coupled to This plate (21A) is similarly provided with a central hole at the center in the part facing the effective operating area of the thin crystal plate (3), and has a similarly thermally conductive hole with a U-shaped cross section over almost the entire circumference. A shell (21B) formed of, for example, an oxygen-free copper plate with good quality is arranged in a C-shape, and a cooling medium water channel (21C) is formed between the shell (21B) and the plate (21A). At both ends of this waterway (21C), a lead-out pipe made of, for example, Kobar/I/(Fe-Co-N1 alloy) metal pipe is placed in a liquid-tight manner through the holes drilled in the shell (21B). be welded.

The tube body (A) is a tube body (23M) consisting of a glass tube body.
The optical window (IW) is arranged on the front surface, and the cooling means (IW) is made of a ring-shaped ceramic material such as forsterite, which is lightweight and has excellent airtightness, and extends rearward from its periphery.
1) The panel part (
23P).

The arrangement of the assembly structure (a) having the electro-optic crystal and the accompanying cooling means 01) in the tube body (23) and the assembly procedure of the tube body 4 itself will be explained. First, two through holes (60) are drilled in the ceramic panel part (23P) in advance to penetrate each of the cooling means Q1), and each cooling medium welded to the cooling means ■ρ. (4) through the cooling means (2) without connecting the crystal assembly structure (2), and hermetically seal this penetration. See Figure 2. Explain about stopping. In this example, each through hole (60) of the ceramic panel (23P)
A metal layer (61), so-called metallization, is previously applied to the outer surface along the periphery of the metal layer (61). This metallizing is done by applying a paste of metal powder such as molybdenum Mo or tungsten W, and heating it in a wet hydrogen furnace at 140°C.
Heat to 0°C to 1700°C.

Furthermore, if necessary, N1 plating or Cu plating is applied thereon to ensure good thermal fusion bonding later on.

Then, a metal washer (
62) is mounted so that its center hole coincides with the through hole (60) and brazed with, for example, silver solder. Thereafter, each pipe of the cooling means 01) is passed through the through hole (60) and the center hole of the washer (62) from the inside of the panel part (23P) to the outside. A metal washer (62) made of copal, for example, is brazed with silver solder (63).In this case, 1. When the washer and the pipe (both are made of Kovar of the same composition) are constructed, the wax In this case, when joining the washer ring to the ceramic panel part (23P) and brazing the washer and arm rib, etc., the crystal assembly Since this is done without the structural frame being connected to the cooling means (21), there is no risk of it being thermally damaged, and therefore this joining is carried out by high heat treatment to obtain sufficient mechanical strength. When using the metal washer □□□ in this way, the through hole of the panel (23P) made of ceramics should be connected to the pipe (27J).
Although the pipe C is formed to a diameter that can be penetrated, it is not necessarily required to have mechanical precision that allows it to fit tightly with the pipe. can be retained.

This cooling means Cυ is used to seal the bonded ceramic panel (23P) and the tube body (23M), but prior to the bonding and sealing, the ceramic panel (23P) is sealed. The end surface to be joined to the tube main body (23M) is coated with metal to ensure good joining. That is, on the end surface of the ceramic panel (23P) which is joined to the tube body (23M), hundreds of layers of Tl are vapor-deposited in advance, and on top of this, a layer of In, for example, made of a single layer of In, is deposited to a thickness of 25 mm.
A .mu.m washer is placed thereon, and heat treatment is performed for 15 minutes at room temperature to about 650.degree. C. in a vacuum furnace at 10@-5 Torr. By doing so, an In-Ti alloy layer is generated on the end surface of the ceramic panel portion (23P) that is joined to the glass body (23M). In addition, the tube body (23M) of this ceramic panel part (23P)
) may be carried out at any step before the crystal assembly structure (a) is integrated with the cooling means (21).

On the other hand, a metal layer is also applied to the end surface of the tube main body (23M) to be joined to the ceramic panel portion (23P). In this deposition process, first, a metal, such as Cr, which is compatible with the metal layer to be formed thereon is vapor-deposited as an underlayer, and then a metal layer, such as Au, is deposited on top of this.

Either Ag, Cu, etc. is vapor-deposited.

Then, after the crystal assembly structure (4) described above is thermally tightly bonded and integrated with the plate (21A) of the cooling means Qυ attached to the panel part (23F), the tube body is attached to the panel part (23F). The metal-treated corresponding end faces of the main body (23M) are butted against each other and joined by heat treatment at 160 to 200°C. When twisting in this manner, the metal layers formed on each joint end surface of the panel (23P) and the tube main body (23M) are mutually diffused to form a strong joint. When heating this joint, a cooling medium, such as cooling water, is supplied and drawn out between each pipe (22) of the cooling means Qυ, and the water passage (21G) is
(The bonding process is carried out while circulating cooling water), thereby avoiding thermal effects on the thin crystal plate (3) or the Peltier effect element due to heating during bonding. Also, arm flannel (23P)
).) An optical window portion, that is, a glass plate (IW) is bonded to the front of the glass plate (IW). The bonding of this plastic plate to the ceramic panel (23P) can also be carried out by the same process as in the bonding part between the ceramic panel (23P) and the glass tube main body (23M), or by using ceramic solder such as Cerasolde (Asahi Glass Co., Ltd.). Product name) You can also do it with a smile.

Furthermore, the surroundings of the metal washer θ group and the ring of the through hole of the ceramic panel part (23P) in the airtight sealing of the cooling means (each pipe of 20 + 221 and the through hole of the ceramic panel part (23F) passing through it) Instead of joining with the metal layer (metallizing layer 1), the panel part (23P) and the glass tube body (23M) described above are used at the joint part of
It is also possible to apply bonding by forming an In--Ti alloy stone by interdiffusion of Ti and In, similar to that applied in the bonding with Ti and In.

〔Effect of the invention〕

According to the above-described structure of the present invention, the cooling means is attached to the panel made of ceramic, and the cooling medium is introduced into and taken out of the panel, and the arm ribs are passed through the panel, so that sufficient mechanical strength can be achieved. In addition, it is possible to achieve good air-tight sealing at this penetrating part, and it is also possible to seal the channel part made of ceramics and the glass tube body by metal treatment between them. By applying this method, the hermetic seal can be achieved reliably and firmly.Since this joining can be performed with the crystal assembly structure cooled by a cooling means, the joining process is Heating can be carried out without causing any damage to the crystal or deterioration of its properties. Therefore, since the heating can be carried out at a necessary and sufficient temperature, reliable bonding and sealing can be achieved.In addition, if a defect occurs in the crystal, etc. after assembly, the tube body can be disassembled between the ceramic panel part and the glass. Since it can be easily separated at the joint with the tube main body, each part can be reused and the cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of the main part of an example of the optical modulator according to the present invention, FIG. 2 is a further sectional view of the main part, and FIG. Diagram,
FIG. 4 is a sectional view of the main part. □□□・・・Tube body, (23M)・・・Glass tube body,
(23, P)...Ceramics panel part, (A)...
・An assembled structure having an electro-optic crystal, Cυ...cooling means, (two...for introducing the cooling medium) 4 pipes and an outlet pipe. Figure 1 Wa Q0 Figure 2

Claims (1)

[Claims] An assembled structure having an electro-optic crystal and a cooling means for cooling the assembled structure are housed in a vacuum-sealed tube, and the tube has pipes for introducing and discharging the cooling medium of the cooling means. An optical modulator that is made up of an integrated ceramic panel section that holds a glass tube body.