JPH0456292B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a charge image forming tube that forms a charge image on the surface of an electro-optic crystal placed in a vacuum container using an intensity-modulated electron beam. The present invention relates to an electronic image projection device that irradiates light onto an electro-optic crystal formed with a polarizer through a polarizer and projects the reflected light onto a screen through an analyzer.

(Prior Art) It is known that when a charge image is formed on the surface of an electro-optic crystal, a refractive index distribution corresponding to the charge image is generated inside the electro-optic crystal.

The refractive index distribution within the crystal can be read by irradiating the crystal with light through a polarizer and projecting the reflected light onto a screen through an analyzer.

Crystals such as KDP, BSO, and LiNbO ₃ are known as electro-optic crystals. A charge image forming tube is manufactured by enclosing these crystals in an electron tube having an electron image source.

(Problems to be Solved by the Invention) Among the electro-optic crystals mentioned above, KDP's properties tend to deteriorate due to heat. Therefore, there is a risk that the characteristics may deteriorate due to heat treatment such as gas release during the manufacturing process of the charge image forming tube.

In addition, BSO and BGO crystals have a photoconductive effect,
Usable wavelengths are limited.

LiNbO ₃ crystals cut at 55° to the optical axis have a lower half-wave voltage than those cut at other angles.

Furthermore, since LiNbO ₃ crystal is heat resistant and has no photoconductivity, LiNbO ₃ crystal cut in the 55° direction is considered to be suitable as the crystal for forming the charge image.

However, since the LiNbO ₃ crystal cut in the 55° direction has natural birefringence, the wavelength purity when projecting with incoherent light deteriorates, resulting in poor resolution of the projected image.

An object of the present invention is to provide an electronic image projection device that can solve the problem of natural birefringence of the electro-optic crystal.

(Means for Solving the Problem) In order to achieve the above object, a first image projection device according to the present invention projects a charge image using an intensity-modulated electron beam on the surface of an electro-optic crystal placed in a vacuum container. Charge image forming tube to form an image projection device which irradiates incoherent light through a polarizer to the electro-optic crystal on which the charge image is formed and projects the reflected light onto a screen through an analyzer, By arranging a compensating crystal having an optical path length approximately equal to the optical path length in the thickness direction of the electro-optic crystal with its axis rotated by 90 degrees from the axis of the electro-optic crystal, the natural complex of the electro-optic crystal can be reduced. It is configured to prevent the effects of refraction.

Further, in the second image projection device according to the present invention, the charge image is formed in a charge image forming tube that forms a charge image with an intensity-modulated electron beam on the surface of an electro-optic crystal disposed in a vacuum container. An image projection device for irradiating incoherent light onto an electro-optic crystal through a polarizer and projecting the reflected light onto a screen through an analyzer, the electro-optic crystal for forming a charge image being provided with the electro-optic crystal for forming a charge image. A compensating electro-optic crystal having an optical path length approximately equal to the optical path length in the thickness direction of By arranging transparent electrodes on both sides of the electro-optic crystal and applying an electric field for adjustment, the optical path lengths of the electro-optic crystal for forming the charge image and the electro-optic crystal for compensation are equalized, and the electric field for forming the electric charge image is made equal. It is configured to prevent the influence of natural birefringence of the optical crystal.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a first electronic image projection device according to the present invention, and FIG. 2 is a schematic diagram showing a first embodiment of an electro-optic crystal for forming a charge image and a first electro-optic crystal for compensation used in the projection device. It is a sectional view showing an example.

The charge image forming tube 1 includes an electron gun 3 and an assembly 2 of an electro-optic crystal for forming a charge image and a compensation crystal.

As shown in FIG. 2, this assembly 2 of electro-optic crystal for charge image formation and compensation crystal is formed from electro-optic crystal 22 for charge image formation and electro-optic crystal for compensation 24, and includes an electro-optic crystal for charge image formation. A high-resistance dielectric mirror 21 is provided on the surface of the optical crystal 22 . A transparent electrode 23 is provided on the back surface of the electro-optic crystal 22 for forming a charge image.

Image information from an image signal source 5 is connected to the electron gun 3, and the electrons whose intensity is modulated by the image information are deflected by a deflection magnetic field generated by a deflection coil 4.
Mirror 21 of the electro-optic crystal 22 for forming charge images
Directed to various parts of the world. A refractive index distribution is formed within the crystal 22 that corresponds to the distribution of the charge image formed on the surface of the electro-optic crystal 22 for forming charge images.

The light from the incoherent light source 12 is converted into parallel light beams by the collimating lens 9.

The parallel light beams pass through a polarizer 7 and a beam splitter 6.
, and enters the assembly 2 of the electro-optic crystal for charge image formation and the compensation crystal from the compensation crystal 24 side. The light that has reached the mirror 21 is reflected there and guided out of the tube 1 through the assembly 2 of electro-optic crystal for charge image formation and compensation crystal, and the light reflected by the beam splitter 6 is sent to the analyzer. 8 and is projected onto a screen 11 by a projection lens 10 as an enlarged image.

The Pockels effect exhibited by electro-optic crystals will be briefly explained with reference to FIG.

When an electric field is applied in the Z-axis direction in Figure 5, the refractive index in the x and y directions changes with respect to the linearly polarized wave propagating in the z direction, and the output light becomes elliptically polarized. .

If an analyzer is placed on the output side and the output is taken out, cooperatively modulated light is taken out.

In the crystal assembly 2 shown in FIG. 2, the y-axis of the electro-optic crystal 22 for charge image formation is perpendicular to the plane of the paper, and the y-axis of the electro-optic crystal 24 for compensation is parallel to the plane of the paper and The angle is 90° with respect to the y-axis of the electro-optic crystal 22.

Next, the reason why the influence of natural birefringence can be removed will be explained.

The output power in the case of LiNbO ₃ crystal with natural birefringence is given by the following formula:

I = I ₀ sin ² ρ where ρ = (2π/λ) (Al + BV) ... where I: Output light intensity I ₀ : Input light intensity l: Crystal thickness V: Voltage A applied to the crystal and B: Constant λ: Wavelength of incident light A simple calculation of the wavelength dependence of ρ shows that the phase changes by π in a wavelength width of 5 nm.

Therefore, it is necessary to use light with excellent wavelength purity of 5 nm or less as the incident light.

Here, (2π/λ)Al in the formula is a term of natural birefringence. In the present invention, this term can be removed. Therefore, the wavelength purity of the readout light is significantly relaxed, making it possible to use a light source composed of white light and a bandpass filter.

As shown in FIG. 2, in this embodiment, a transparent electrode 23 is attached to the side opposite to the electron beam incident side of an electro-optic crystal 22 for forming a charge image, and a transparent electrode 23 is attached to the electro-optic crystal 22 for forming a charge image with the same thickness by rotating the axis by 90 degrees. An electro-optic crystal 24 for compensation is laminated together.

The phase change when the light 18 is incident on the crystal 24 is ρ=(2π/λ)(Al) since no voltage is applied to the crystal 24.

In the crystal 22, charges formed on the mirror 21 surface by the electron beam and an electric field from the transparent electrode 23 are applied, and the crystal axis is shifted by 90 degrees, so the phase is ρ=-(2π/λ)(Al+BV ).

The total phase amount becomes ρ=−(2π/λ)(BV), and the term of natural birefringence disappears.

FIG. 3 shows a second electro-optic crystal for charge image formation and a second electro-optic crystal for compensation used in the projection device.
This embodiment uses a quartz crystal with positive natural birefringence as the compensating crystal.

The assembly of the electro-optic crystal for charge image formation and the compensation crystal in this embodiment includes a mirror 21, an electro-optic crystal for charge image formation 22, a transparent electrode 23, and a compensation crystal 25 of quartz.

In LiNbO ₃ , which has negative natural birefringence, A = -0.07, but in quartz, A = 0.0091, and the phase when using positive and negative birefringence is ρ = (2π/λ) (-0.07l ₁ +0.0091l ₂ .

l ₁ and l ₂ indicate the thickness of LiNbO ₃ and crystal, respectively.

To compensate for natural birefringence, l ₂ =7.7l ₁ .

In this way, since the thickness of the quartz crystal for compensation can be made thicker than the LiNbO ₃ for charge image formation, it becomes easy to process the thickness of the quartz crystal for compensation.

FIG. 4 is a sectional view showing an embodiment of an electro-optic crystal for forming a charge image and an electro-optic crystal for compensation used in an embodiment of the second electronic image projection apparatus according to the present invention.

The basic configuration of the second electronic image projection device is the same as the embodiment shown in FIG.

The assembly of the electro-optic crystal for forming charge images and the charge-optic crystal for compensation in this embodiment includes a mirror 21, an electro-optic crystal for forming charge images 22, a transparent electrode 23, an electro-optic crystal for compensation 26, and a transparent electrode 27. ing. A voltage is applied to the compensating electro-optic crystal 26 by a voltage source 28 for adjustment.

By applying a voltage to the compensating electro-electro-optic crystal 26 in this way, the electro-optic crystals 22, 26
It is possible to compensate for subtle differences in thickness.

(Effects of the Invention) As described above, the present invention completely solves the problem caused by the natural birefringence of the electro-optic crystal for charge image formation by making the compensation crystal correspond to the electro-optic crystal for charge image formation. Therefore, it is possible to provide an electronic image projection device with excellent statistical quality.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a first electronic image projection device according to the present invention. FIG. 2 is a sectional view showing a first embodiment of an electro-optic crystal for forming a charge image and an electro-optic crystal for compensation used in the projection apparatus. FIG. 3 is a sectional view showing a second embodiment of an electro-optic crystal for forming a charge image and a compensation crystal used in the projection apparatus. FIG. 4 is a sectional view showing an embodiment of an electro-optic crystal for forming a charge image and an electro-optic crystal for compensation used in an embodiment of the second electronic image projection apparatus according to the present invention. FIG. 5 is a perspective view for explaining the Pockels effect. DESCRIPTION OF SYMBOLS 1...Charge image forming tube, 2...Electro-optical crystal for charge image formation and compensation crystal assembly, 3...Electron gun, 4...
... Deflection coil, 5 ... Image signal source, 6 ... Beam splitter, 7 ... Polarizer, 8 ... Analyzer, 9 ...
Collimating lens, 10... Projection lens, 11...
... Screen, 12 ... Readout light source, 18 ...
Readout light, 21...Mirror, 22...Electro-optic crystal for charge image formation, 23...Transparent electrode, 24...
Compensation electro-optic crystal, 25...Compensation crystal (crystal), 26...Compensation electro-optic crystal, 28...Adjustment power supply.

Claims (1)

[Scope of Claims] 1. A charge image forming tube that forms a charge image using an intensity-modulated electron beam on the surface of an electro-optic crystal having natural birefringence that is placed in a vacuum container, and this charge image forming tube irradiating incoherent light through a polarizer to the electro-optic crystal on which the charge image is formed;
An electronic image projection device that projects the reflected light onto a screen through an analyzer, wherein the electro-optic crystal has an optical path length approximately equal to the optical path length in the thickness direction of the electro-optic crystal, and the axis of the crystal is An electronic image projection device further comprising a compensating crystal arranged to be rotated by 90 degrees from the axis of the optical crystal to prevent the influence of natural birefringence of the electro-optic crystal. 2. The electronic image projection apparatus according to claim 1, wherein the compensating crystal is a crystal made of the same material as the electro-optic crystal. 3. The electronic image projection apparatus according to claim 1, wherein the compensation crystal is a quartz crystal. 4. A charge image forming tube that forms a charge image with an intensity-modulated electron beam on the surface of an electro-optic crystal placed in a vacuum container, and a charge image forming tube that forms a charge image on the surface of the electro-optic crystal on which the charge image is formed in the charge image forming tube. An electronic image projection device that irradiates incoherent light through a polarizer and projects the reflected light onto a screen through an analyzer, the electro-optic crystal for forming a charge image having a thickness of the electro-optic crystal for forming a charge image. A compensating electro-optic crystal having an optical path length substantially equal to the optical path length in the transverse direction is arranged with the axis of the crystal rotated by 90 degrees from the axis of the electro-optic crystal for forming a charge image, and the compensating electro-optic crystal is By arranging transparent electrodes on both sides of the crystal and applying an electric field for adjustment, the optical path lengths of the electro-optic crystal for forming charge images and the electro-optic crystal for compensation are equalized, and the electro-optic crystal for forming charge images is made equal. An electronic image projection device configured to prevent the effects of natural birefringence.