JPH0234366B2 - KUKANHENCHOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spatial modulation device using an electro-optic crystal plate.

A spatial light modulator (hereinafter referred to as MSLM) using a microchannel plate as a recording medium is described in an article by Ward et al. in 1976, SPIE Vol. 177, pp. 67-70. First, we will briefly explain the principle and operation of this MSLM.

FIG. 1 is a schematic diagram showing the configuration of the MSLM.
This device includes a photocathode 22, a microchannel plate (MCP) 24, and an electro-optic crystal plate 28.
Basically, they are enclosed in a vacuum container having an entrance window 21 and an exit window 30. 23 and 25 are input and output electrodes of the MCP, respectively. A dielectric mirror surface 27 is formed on the front surface of the electro-optic crystal plate 28, and a transparent electrode 29 is provided on the rear surface. The dielectric mirror surface 27 of the electro-optic crystal plate 28 has an extremely high resistance along the surface.

When the writing light a enters the photocathode 22 and an electronic image is formed, the electronic image is amplified by the MCP 24. The amplified electron image is then transferred to the dielectric mirror surface 2.
7. The resulting surface charge distribution causes a spatial variation of the refractive index within the electro-optic crystal plate 28. The writing light projected from the lower left is reflected by the semi-transparent mirror 31 and reaches the electro-optic crystal.
It is reflected by the dielectric mirror surface 27 and returned. Since the refractive index of the electro-optic crystal plate 28 depends on the surface charge image, the reflected light d undergoes phase or intensity modulation.

Although the MSLM according to the above configuration is suitable for storing charge images for a long time, there seems to be some problems in erasing the charge images for reuse.

The main object of the present invention is to provide a spatial modulation device that can select from many usage modes, erases a written charge image, or forms a constant and uniform charge distribution state to enable rewriting. It's about doing.

In order to achieve the above main object, a spatial modulation device according to the present invention includes an electron image generating means and an electro-optic crystal plate, and forms a charge image on a mirror surface of the electro-optic crystal plate by electrons from the electron image generating source. , in a spatial modulation device using a radiation image conversion tube that changes a two-dimensional distribution of refractive index within a crystal plate by an electric field between the charge image and a transparent electrode provided on the other surface, the crystal plate and an electron image generation a secondary electron collecting electrode for collecting secondary electrons generated on the mirror surface, which is arranged between the means so as not to impede the formation of a charge image on the mirror surface; and a collecting voltage is applied to the collecting electrode. Switching the collecting electrode power supply, a first voltage to make the secondary electron emission ratio of the specular surface larger than 1, and a second voltage to make the emission ratio substantially 1 to the transparent electrode. A connectable crystal plate electrode power supply or a crystal plate electrode power supply capable of switching and connecting the second voltage and a third voltage for making the emission ratio smaller than 1 is provided.

The spatial modulation device according to the present invention will be described in more detail below with reference to the drawings and the like.

FIG. 1 is a diagram showing an embodiment of a spatial modulation device according to the present invention. In the figure, 1 is a subject, 2 is an objective lens, and 3 is an optical image of the subject formed by the objective lens 2. 4 designates the entire light image conversion tube including the glass airtight container and the components built into the container. Inside the container are a photocathode 5, a focusing electrode 6,
Microchannel plate (hereinafter referred to as MCP)
7, a secondary electron collecting electrode 8, and an electro-optic crystal plate 9 are arranged in this order. The collection electrode 8 is a copper mesh having a lattice spacing of 30 lines/mm and an aperture ratio of 60%.

The collection electrode 8 is arranged parallel to the electro-optic crystal plate 9 with a distance of 0.5 mm.

The rear end of the container serves as an information extraction window.

An input electrode 71, which is an electrode on the electron incident side of the MCP, is provided on the front surface of the MSC 7, and an output electrode 72, which is an electrode on the electron output side, is provided on the rear surface. As the electro-optic crystal plate 9, for example, LiNbO ₃ crystal or
LiTaO ₃ crystal etc. can be used.

The front surface of this crystal 9 is finished to a mirror surface and will be referred to as a mirror surface 92 hereinafter. Further, a transparent crystal plate electrode 91 is provided on the rear surface of the crystal plate 9.

In this embodiment, a photocathode is used, but in the case of an image source such as X-rays that can directly excite the MCP 7, the photocathode is no longer an essential component. It should be understood that the configuration prior to MCP is an example of an electronic image generating means.

A, B, C, D, E, F, and G are power supplies, respectively, where power supply A provides a bias voltage between the photocathode 5 and the collecting electrode 6, and power supply B provides the bias voltage between the focusing electrode 6 and the incident side electrode of the MCP. 71, and the power supply C is
Provides bias voltage for MCP7.

In this example device, these power supplies keep the photocathode 5 at -0.4 KV with respect to the reference potential (0 V) of the electrode on the emission side of the MCP.
Similarly, the focusing electrode is kept at -3.7 KV and the electrode 71 on the incident side of the MCP is kept at -1.0 KV. The power source D constitutes a power source for the secondary electron collecting electrode 8, and the secondary electron collecting electrode 8 is maintained at 4.0 KV. Power supplies E, F, and G are power supplies for determining the potential of the electrode 91 of the electro-optic crystal plate 9, and are elements of the crystal plate electrode power supply.
By switching the switch 15, it is connected to the electrode 91, and when connected to 15a, the voltage is 0.1KV, 15
A voltage of 4KV is supplied to the electrode 91 when connected to b, and a voltage of 8KV is supplied to the electrode 91 when connected to 15c.

Semi-transparent mirror 10, monochromatic filter 11, collimator lens 12, point light source 13, and photographic film 1
4 is a device for reading.

If a laser light source is used as the light source 13, an optical image using coherent light can be obtained. This optical image can be used for image calculations.

FIG. 3 is a graph showing the secondary electron emission ratio δ of the mirror surface 92 of the electro-optic crystal plate 9, with the accelerating voltage of incident electrons taken as the horizontal axis.

Here, the emission ratio δ is less than 1 when the accelerating voltage E of incident electrons peculiar to the crystal is less than ₁ , the emission ratio δ is greater than 1 between the above E ₁ and the accelerating voltage E ₂ of incident electrons peculiar to the crystal, and the above When E is larger than ₂ , the emission ratio δ becomes smaller than 1 again.

When the accelerating voltage is E ₁ or E ₂ , the secondary electron emission ratio is actually 1.

In this embodiment, the accelerating voltage is given by the potential difference between the output electrode of the MCP 7 and the mirror surface 92;
The potential of the transparent electrode 91 is approximately equal to the potential of the transparent electrode 91 when there is no charge on the surface.

In the present invention, the change in the sign of δ before and after E ₂ is utilized to form and erase a charge image or to form a uniform charge distribution state.

Therefore, by setting the secondary electron collecting electrode voltage to approximately _E2 , the difference between the output electrode voltage of the MCP 7 and the voltage of the transparent electrode 91 of the electro-optic crystal plate 9 becomes larger than _E2 shown in FIG. When a voltage is applied to the transparent electrode 91 as shown in FIG. is formed.

When the potential due to the negative charge becomes equal to the potential E ₂ of the secondary electron collecting electrode, the charge does not change even if electrons fly thereafter.

Also, the difference between the output electrode voltage of the MCP 7 and the voltage of the transparent electrode 91 of the electro-optic crystal is E ₁ shown in FIG.
When a voltage is applied to the transparent electrode ₉₁ such that the voltage is between the secondary electrons (δ
>1) is captured by the secondary electron collecting electrode 32, and as a result, a positive charge image is formed in that portion.

The operating modes of the device according to the invention are as follows:
, can be roughly divided into . FIG. 4 shows the above operation mode in comparison with the secondary electron emission ratio shown in FIG. FIG. 5 shows similar first and second operating modes. In the customer diagram, the vertical axis indicates the potential of the mirror surface 92, e(o), e(+), e(-)
indicate the absence of charge, the presence of positive charge, and the presence of negative charge, respectively. Also, Wr means write, Er means erase, and Pr means preparation.

Furthermore, each image drawn in each figure assumes a special shape, and only the one-dimensional direction of the two-dimensional image is schematically illustrated by the horizontal axis.

() First, the first operation mode will be explained (see FIG. 4).

In this mode, during writing Wr, the switch 15 is connected to the contact 15a, and the voltage of the transparent electrode 91 of the electro-optic crystal plate 9 is set to 0.1 KV. An image of the subject 1 is formed on the photocathode 5 by the writing light from the subject 1 . The photoelectrically converted electron image is multiplied by the MCP 7, and the multiplied electrons are made incident on the electro-optic crystal plate 9. As a result, the mirror surface 92 of the electro-optic crystal plate 9
A positive charge image e(+) is formed thereon.

Since there is no charge initially on the mirror surface 62 of the electro-optic crystal plate 9, it has approximately the same potential as the transparent charge image 91.
It is maintained at 0.1KV. In other words, since the potential of the mirror surface 92 is 0.1 KV higher than the output electrode 72 of the MCP 7, the secondary electron emission ratio δ is as shown on the left side of FIG.
is δ>1. Therefore, it is positively charged depending on the amount of primary electrons incident on this surface. The emitted secondary electrons have a higher potential than the mirror surface 92 E ₂ = 4KV
The secondary electron collecting electrode 8 collects the electrons. The switch 15 is also connected to the contact 15a during reading. The light from the point light source 13 passes through the collimator lens 1
2 makes it parallel light.

Then, it is converted into a monochromatic color by a filter 11. This monochromatic parallel light is modulated by an electro-optic crystal plate 9.
In other words, since the optical path length of the monochromatic parallel light in the crystal changes due to the positive charge image on the mirror surface 92 of the electro-optic crystal plate 9, there are parts where it is strengthened and parts where it is weakened due to interference, which corresponds to an optical image. Modulation is performed.

The modulated light is reflected by a semi-transparent mirror 10 and recorded on a photographic film 14.

When erasing Er, switch 15 is connected to 15b and electrode 91 is set to 4KV. Using a light source for erasing (not shown), the entire surface of the photocathode 5 is irradiated with light of uniform intensity. The uniformly distributed electrons obtained by photoelectric conversion are multiplied by the MCP 7 and incident on the electro-optic crystal plate 9, where the charge on the mirror surface 92 is reduced to 0 and erasing is completed.

As mentioned above, the mirror surface of the electro-optic crystal plate 9 is
The potential of the transparent electrode is 4KV plus a potential increase due to positive charging.
Therefore, since the potential of the mirror surface 92 is higher than E ₂ (=4KV) as shown on the left side of FIG.
becomes δ<1. Therefore, a negative charge tends to be added until _E2 is reached, and when _E2 is reached, δ=1, the charge becomes 0, and the potential of the mirror surface 92 becomes 4KV.

() Next, the second operation mode will be explained (see FIG. 4).

This mode is executed in the order of preparation, writing, and erasing, and in the preparation process, the switch 15 is
The electrode 91 of the electro-optic crystal plate connected to 5a is
Maintained at 0.1KV. Switch 15 during the writing process
is connected to 15b, and electrode 9 of the electro-optic crystal plate
1 is kept at 4.0KV. Further, in the erasing process, the switch 15 is connected to the contact 15a, and the electrode 91 is connected to the contact 15a.
is kept at 0.1KV.

During preparation Pr, the entire surface of the photocathode 5 is irradiated with light of uniform intensity. The electron image obtained by photoelectric conversion is multiplied by the MCP 7, and the multiplied electron image is made incident on the electro-optic crystal plate 9. The charge on the mirror surface 92 is made positive (e(+)).

As mentioned above, the mirror surface 92 of the electro-optic crystal plate 9
The potential of is initially 0.1KV.

At this time, the secondary electron emission ratio δ of the mirror surface 92 is δ
>1, the mirror surface 92 of the crystal plate is uniformly positively charged. As a result, the potential of the mirror surface 92 is E ₂
(=4KV), resulting in a uniform positive potential distribution.

When writing Wr, the image 3 of the subject 1 is displayed on the photocathode 5.
to project. The electronic image obtained by photoelectric conversion is multiplied by the MCP 7 and projected onto an electro-optic crystal plate.

Then, an inverted image is formed in the positive charge on the mirror surface 92. That is, writing starts from the point where the mirror surface 92 of the electro-optic crystal plate 9 is uniformly positively charged in advance in the preparation process described above. The mirror surface 92 of the electro-optic crystal plate 9 is the electrode 91 at the beginning of writing.
The potential increase (E ₂ =approximately 4 KV) due to the above-mentioned positive charge e(+) is added to the potential given by (=4KV), and the result is approximately 4KV+E ₂ =8KV. Here, as shown on the left side of FIG. 4, since δ is δ<1, negative charges tend to accumulate depending on the amount of primary electrons incident on the mirror surface 92 corresponding to the optical image. That is, since the uniform positive charge e(+) is superimposed on the negative charge of the distribution corresponding to the image, an inverted image is formed in the positive charge.

Reading is no different from the first mode of operation described above.

Erase Er is the same as preparation Pr in this mode.
The mirror surface 92 of the electro-optic crystal plate 9 has a voltage of 0.1 KV to E ₂
(=4KV) (the part where no image is formed is E ₂ ).

Since δ of the mirror surface 92 of the electro-optic crystal plate 9 is δ>1, the mirror surface 92 of the crystal plate tends to be positively charged. As a result, the positive charge increases until the potential of the mirror surface 92 reaches _E2 , and when it reaches _E2 , δ
= 1, which means that the inverted image is erased by being uniformly charged.

Upon completion of erasing, next writing becomes possible.

() Next, the third operation mode will be explained (see FIG. 5).

In this operating mode, when writing, switch 15
is connected to the contact point 15c, and the transparent electrode 91 of the electro-optic crystal plate 9 is maintained at 8.0 KV. During erasing, switch 15 is connected to contact 15b and transparent electrode 91 is maintained at 4.0 KV.

When an image of the subject 1 is projected onto the photocathode 5 during writing Wr, an electronic image corresponding to the image is formed by photoelectric conversion. This image is multiplied by MCP7.
The amplified electron image is made incident on an electro-optic crystal plate 9. As a result, a negative charge image e(-) is formed on the mirror surface 92 of the electro-optic crystal plate 9.

The principle of forming this negative charge image is as follows. The mirror surface 92 of the electro-optic crystal is initially 8.0 KV as described above. Here, as shown on the left side of FIG. 5, the secondary electron emission ratio δ is δ<1. Therefore, the mirror surface 92 is negatively charged depending on the amount of primary electrons incident on the mirror surface 92.

Reading is the same as described above for the first mode.

Erasing Er is performed by irradiating the entire photocathode with light of uniform intensity.

The uniform electron flow obtained by photoelectric conversion is
Multiplied by MCP7.

The multiplied electrons are made incident on the mirror surface 92 of the electro-optic crystal plate 9 and become e ₀ . As a result, the charge on the mirror surface 92 is erased. Before erasing, the mirror surface 92 of the electro-optic crystal plate 9 is negatively charged e(-) to 4KV.
It is in a state where the potential drop caused by Since the surface potential of the portion where the negative charge e(-) exists is lower than _E2 , the secondary electron emission ratio δ of the mirror surface 92 is δ>1. Therefore, positive charge is added until it reaches E ₂ . When E ₂ is reached, δ=1 and the charge is uniformly erased and becomes e ₀ .

() Next, the fourth operation mode will be explained (see FIG. 5).

In this mode, switch 15 is connected to 15c during preparation and electrode 91 of the crystal plate is
It is maintained at 8KV. During writing, the switch 15 is connected to 15b and the crystal electrode 91 is
Maintained at 4KV. When erasing, switch 15
is connected to 15c and the electrode 91 of the crystal plate is 8KV
is maintained.

Preparation pr is started by irradiating the entire surface of the photocathode 5 with light of uniform intensity.

Uniform electrons obtained by photoelectric conversion are NCP
The signal is multiplied by 7 and made incident on the crystal plate 9. The mirror surface 92 of the electro-optic crystal plate 9 was initially 8.0KV.
Therefore, the secondary electron emission ratio δ is δ<1, so negative charges e(-) are uniformly attached to the mirror surface.

For writing Wr, set the voltage of electrode 91 of the crystal plate to 4.0KV.
Since the secondary electron emission ratio δ of the mirror surface 92 is δ>1, an inverted image is formed in the negative charge e(-).

Reading is the same as described in the first mode.

Erasing Er sets the voltage of the electrode 91 to 8.0 KV, brings the mirror surface 92 into the region of δ<1, and uniformly attaches negative charges e(-) to the front surface.

As described above in detail, the device according to the present invention is provided with a secondary electron collecting electrode and the electrode power source of the electro-optic crystal plate can be switched in various ways, making erasing or preparation easier.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a conventional MSLM, and FIG. 2 is a diagram showing an embodiment of the MSLM according to the present invention.
FIG. 3 is a graph showing the secondary electron emission characteristics of the electro-optic crystal, FIG. 4 is a graph for explaining the first and second operation modes of the device of the embodiment, and FIG. 5 is a graph of the device of the embodiment. It is a graph for explaining the third and fourth operation modes. 1... Subject, 2... Objective lens, 3... Optical image, 4... Optical image conversion tube, 5... Photocathode, 6...
Focusing electrode, 7... Microchannel plate (=MCP), 71... Electrode on the electron incident side of MCP,
72... Electrode on the electron emission side of MCP, 8... Secondary electron collection electrode, 9... Electro-optic crystal plate, 91...
Electrode of electro-optic crystal plate, 92... Mirror surface of electro-optic crystal plate, 10... Semi-transparent mirror, 11... Monochromatic filter, 12... Collimator lens, 13... Point light source, 14... Photographic film, 15... ...Selector switch, 21...Incidence window, 22...Photocathode, 23...
MCP input electrode, 24...MCP, 25...MCP
Output electrode, 26... Gap, 27... Dielectric mirror surface, 28... Electro-optic crystal plate, 29... Transparent electrode, 30... Exit window, 31... Semi-transparent mirror, A to G
……power supply.

Claims (1)

[Scope of Claims] 1. A device comprising an electron image generating means and an electro-optic crystal plate, which forms a charge image on a mirror surface of the electro-optic crystal plate by electrons from the electron image generation source, and forms a charge image on the other surface of the electro-optic crystal plate. In a spatial modulation device using a radiation image converting tube that changes the two-dimensional distribution of refractive index within a crystal plate by an electric field between transparent electrodes, a mirror surface is formed between the crystal plate and the electron image generating means. a secondary electron collection electrode arranged so as not to impede charge image formation and for collecting two-dimensional electrons generated on the mirror surface; a collection electrode power supply supplying a collection voltage to the collection electrode; a crystal plate electrode power supply capable of switching and connecting a first voltage for making the secondary electron emission ratio of the specular surface larger than 1 and a second voltage for making the emission ratio substantially 1 to the transparent electrode; A spatial modulation device characterized by being provided with. 2 Using the crystal plate electrode power supply, the first voltage is connected to form a positive charge image to perform writing, and the second voltage is connected to irradiate the mirror surface of the crystal plate with a uniform electron flow to erase. A spatial modulation device according to claim 1, which is configured to perform the following. 3 Using the crystal plate electrode power supply, the first voltage is connected and the mirror surface of the crystal plate is irradiated with a uniform electron flow to uniformly form a positive charge to prepare, and the second voltage is connected. 2. The spatial modulation device according to claim 1, wherein writing is performed to form an inverted image in a positive charge, and erasing corresponding to said preparation is performed by connecting a first voltage. 4. includes an electron image generating means and an electro-optic crystal plate, a charge image is formed on a mirror surface of the electro-optic crystal plate by electrons from the electron image generation source, and a transparent electrode provided on the other surface of the charge image; In a spatial modulation device using a radiation image converting tube that changes the two-dimensional distribution of refractive index within a crystal plate by an electric field between the crystal plate and the electron image generating means, the formation of a charge image on a mirror surface is not hindered. a secondary electron collecting electrode for collecting secondary electrons generated on the mirror surface;
a collection electrode power source for supplying a collection voltage to the collection electrode; a second voltage for making the secondary electron emission ratio of the mirror surface substantially 1 on the transparent electrode;
A spatial modulation device characterized in that it is provided with a crystal plate electrode power supply capable of switching and connecting a third voltage to make the voltage smaller than the voltage. 5 Using the crystal plate electrode power source, a third voltage is connected to form a negative charge image to perform writing, and a second
5. The spatial modulation device according to claim 4, wherein the negative charge image is erased by connecting the voltage. 6 Prepare by connecting a third voltage using the crystal plate electrode power source to form a uniform negative charge on the crystal plate with a uniform electron flow, and then connect a second voltage to form a uniform negative charge on the crystal plate. 5. The spatial modulation device according to claim 4, wherein the spatial modulation device is configured to form an inverted image in negative charges and perform erasing by connecting a third voltage.