JPH0445811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electro-optical element used as an optical shutter.

Conventionally, electro-optical elements use PLZT as a ferroelectric material, and a polarizing plate is used as two polarizing elements arranged to sandwich the ferroelectric material, as shown in Japanese Unexamined Patent Publication No. 147611/1983. . This polarizing plate is usually composed of a polymer film, and this polarizing film is made by stretching polyvinyl alcohol so that the molecules are aligned in the stretched direction, then soaking it in an iodine-containing solution to make a long film, washing it, and drying it. Popular products include Polaroid's HN38. However, with this electro-optical element, polarizing film such as Polaroid's HN38
About 38% of the incident light can be extracted as a linearly polarized component, and even if it is placed behind the PLZT and the polarization direction matches the vibration direction of the incident light from the PLZT, about 76% of the component can be extracted as a linearly polarized component. Only light can pass through,
Approximately 29% of the light passes through the two polarizing films placed before and after the PLZT, which is extremely inefficient.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and provide an electro-optical element that improves light utilization efficiency by configuring at least one of two polarizing elements as a polarizing beam splitter. .

The present invention will be described below by way of examples with reference to the drawings.

FIG. 1 shows an example of an electro-optical element. This electro-optical element constitutes an optical shutter, and PLZT
It consists of a translucent ceramic 1 and polarizing elements 2 and 3. PLZT transparent ferroelectric ceramic
The composition of [(Pb, La) (Zr, Ti) O ₃ porcelain abbreviation] is shown by the chemical formula (Pb ₁ −xLAx)(Zr ₁ −yTiy)O ₃ . This PLZT is primary or secondary depending on its composition.
Since it has the following electro-optic effect and optical memory effect, its application to electro-optic fields such as optical shutters and displays is being studied. Especially PLZT
(x/65/35, x = 8.6 to 10.0) exhibits paraelectricity at room temperature, but when a DC voltage is applied, a ferroelectric phase is induced and a secondary electro-optic effect, the so-called Kerr effect, is exhibited. Since this type of material does not have a memory function, it is suitable for application in optical shutters and is called a slim-loop secondary electro-optic material. For example, PLZT, a slim loop secondary electro-optic material, is used as the translucent ceramic 1, and the polarizing elements 2 and 3 are
This is placed before and after PLZT1.
The polarization directions of the polarizing elements 2 and 3 are perpendicular to each other, and the voltage application direction of the PLZT 1 is inclined at 45° with respect to the vibration plane of the incident linearly polarized light. Electrode 4 of PLZT1,
When no voltage is applied between 5, the linearly polarized component of the illumination light from the light source is extracted by the polarizing element
It passes through the PLZT 1 but is blocked by the polarizing element 3. When a voltage is applied between the electrodes 4 and 5, the linearly polarized light from the polarizing element 2 is rotated by 90 degrees in the vibration direction due to the Kerr effect at the optical shutter section between the electrodes 4 and 5 in the PLZT 1, and passes through the polarizing element 3. The amount of passing light I is expressed as I=I _p sin ² (tΔn/λ)r. Here, I _p is the amount of linearly polarized light incident on PLZT1, t is the thickness of PLZT1, and λ is PLZT1
The wavelength of the transmitted light, △n is the optical axis direction component of the refractive index of PLZT1 n _e and the refractive index for ordinary light perpendicular to this n _p
n _p − n _e ). The voltage at which I is maximum is called the half-wavelength voltage. Therefore, this light shutter is turned off when no voltage is applied between the electrodes 4 and 5, and turned on when a voltage is applied between the electrodes 4 and 5.

FIG. 2 shows a conventional example of an electro-optical element constituting an optical shutter array. In this example, a plurality of signal electrodes 4 ₁ to 4 ₄ and a common electrode 5 are provided on the PLZT 1, and light between the signal electrodes 4 ₁ to 4 ₄ to which voltage is applied and the common electrode 5 is provided. Only the shutter part
Show Kerr effect and turn on.

In this conventional example, a plurality of optical shutter portions in the PLZT 1 are formed between the plurality of signal electrodes 4 ₁ , 4 ₂ . . . and the common electrode 5, and are arranged in a row in the horizontal direction. For this reason, _for example, the diagonal line is composed of a plurality of pixels 1 ₁₁ , _{1 12 .} The reproducibility of diagonal lines deteriorates.

FIG. 3 shows a first embodiment of the invention. In this embodiment, unlike the conventional example shown in FIG. 2, the rear polarizing element is composed of a polarizing beam splitter 6,
Above, two sets of electrodes 4 ₁ , 4 _{2 .} . . 5 ₁ , 5 ₂ .
It is set up so that it has an inclination of . The electro-optical element consisting of the PLZT 1 and the polarizing elements 2 and 6 is illuminated by a light source 7. As shown in FIG. 4, only the vibration component of the light from the light source 7 in the direction perpendicular to the paper is extracted by the polarizing plate 2, and the two sets of electrodes 4 in the PLZT 1
₁ , 4 _{2 .} . . , 5 _{1 ,} 5 _{2 .} . . , the vibration direction is rotated by 90° due to the Kerr effect at the optical shutter portion to which the electric field is applied, and the beam is transmitted through the polarizing beam splitter 6 .
The linearly polarized light that has passed through the part of the PLZT 1 to which no electric field is applied is polarized by about 90 degrees by the beam splitter 6. Note that in FIG. 4 and subsequent figures, black circles indicate that the direction of vibration of light is perpendicular to the plane of paper, and arrows indicating forward and reverse directions indicate that the direction of vibration of light is parallel to the plane of paper.

In this embodiment, two sets of electrodes 4 ₁ , 4 ₂ . . . , 5 ₁ ,
5 ₂ ... is placed on one side of PLZT1, and
It is arranged to have an inclination of approximately 45 degrees with respect to the vibration direction of light passing through PLZT1. For this reason,
Two sets of electrodes 4 ₁ , 4 ₂ ..., 5 ₁ , 5 in PLZT1
_2. The light shutter section formed between each of is composed of a plurality of oblique light shutter sections having an inclination of approximately 45 degrees. For example, the diagonal lines indicate that the light passing through the oblique light shutter section of PLZT1 As shown in FIG. 13, it is composed of diagonally oriented pixels 1 ₁₁ , 1 ₁₂ . . . , 1 ₂₁ , 1 ₂₂ .

FIG. 5 shows a second embodiment of the invention. In this embodiment, the arrangement of the polarizing plate 2 and the polarizing plate beam splitter 6 is reversed in the first embodiment.

FIG. 6 shows a third embodiment of the invention. In this embodiment, both of the two polarizing elements in the above embodiment are composed of polarizing beam splitters 6 and 8, and the light source 7, the optical axis, and the optical axis from which the light of the electro-optic element is emitted are approximately 90 degrees apart. Has an angle.

FIG. 7 shows a fourth embodiment of the invention. This embodiment differs from the third embodiment in that the optical axis of the light source 7 is
It has an angle of approximately 90° with the optical axis of PLZT1.

FIG. 8 shows an example of a recording apparatus using the electro-optical element 10 according to the present invention as described above. The photosensitive drum 11 is rotationally driven by a driving device, and the charging section 1
After being uniformly charged by 2, the electro-optical element 10
A latent image is formed by irradiating a light image. The electro-optical element 10 constitutes an optical shutter array, is arranged in the width direction of the photoreceptor drum 11, and is arranged between corresponding electrodes of two sets of electrodes 4 ₁ , 4 ₂ . . . , 5 ₁ , 5 ₂ . is applied to modulate the light from the light source 7. Since the optical image emitted from the electro-optical element 10 spreads after being emitted, the gap between the electro-optical element 10 and the photoreceptor drum 11 is 100.
It is necessary to keep it at around ~200μ. The latent image on the photosensitive drum 11 is developed by a developing section 13, and transferred by a transfer section 14 onto a transfer sheet from a paper feeding device.
The image is fixed on the transfer paper by a fixing section, and after the image is transferred, the photosensitive drum 11 is neutralized by a charge eliminating section 15 and cleaned by a cleaning section 16. As shown in FIG. 9, the light image emitted from the electro-optical element 10 may be formed on the photoreceptor drum 11 by a 1-magnification imaging element 17 such as a focusing light transmitter or a roof mirror lens array.

FIG. 10 shows the structure of the polarizing beam splitter used in the above embodiment. This polarizing beam splitter consists of a right-angle prism 1 made of a transparent material such as glass.
A substance 20 having a higher refractive index than a glass material and a substance 21 having a lower refractive index are alternately formed on one or both of the glass materials by vapor deposition or the like, and these are glued together with an adhesive 22.

FIG. 11 shows the operation of this polarizing beam splitter. The incident light has a P component parallel to the plane of incidence of the polarizing beam splitter, which is approximately 100
%, and the S component perpendicular to the plane of incidence of the polarizing beam splitter is approximately 100%.
% is reflected.

FIG. 12 shows an example of the wavelength distribution of the polarizing beam splitter and the light source 7. In the polarizing beam splitter, the refractive index of the glass material is 1.52, and the refractive index of the material 20 is
1.58, the refractive index of substance 21 is 1.46, and substances 20 and 21
are alternately formed in 49 layers with an optical thickness of approximately 195 μm. This polarizing beam splitter is about 550n
Separate the P component and S component of the incident light with a width of ±30 nm centered on m. If a fluorescent lamp (preferably an aperture type) that emits green light within this separable range is used as the light source 7, the light can be used very effectively.

To give an example of light utilization efficiency, in a conventional example using two polarizing films, the light is emitted from the light source (100%) → transmitted light through the polarizing film (38%) →
Light transmitted through PLZT (25%) → light transmitted through polarizing film (19%). On the other hand, in the above embodiment using two polarizing beam splitters, the light emitted from the light source (100%) → the transmitted light of the polarizing beam splitter (50%)
%) → light transmitted through the PLZT (33%) → light transmitted through the polarizing beam splitter (33%), improving light utilization efficiency by approximately 70% compared to the conventional example.

As described above, according to the present invention, at least one of the two polarizing elements in the electro-optical element is configured with a polarizing beam splitter, so that the efficiency of light utilization can be improved, and the polarizing beam splitter can also be used to divide the optical path. The degree of freedom in optical layout is improved. Moreover, since the plurality of electrodes provided on the ferroelectric material are arranged on one surface of the ferroelectric material, the light passes through the light shutter section between the electrodes in the ferroelectric light, and the light passes through the ferroelectric light. There is no loss due to the passage of the electrode as it passes through the body. Furthermore, since the plurality of electrodes provided on the ferroelectric material are arranged so as to have an inclination of about 45 degrees with respect to the vibration direction of light transmitted through the polarizing element, the reproducibility of diagonal lines is improved.

[Brief explanation of drawings]

Figure 1 is a perspective view showing an example of a light shutter;
The figure is a perspective view showing a conventional optical shutter array.
4 are a perspective view and a front view showing one embodiment of the present invention, FIGS. 5 to 7 are front views showing other embodiments of the present invention, and FIG. 8 is an example of a recording device. FIG. 9 is a schematic diagram showing a part of another example of the recording device, FIG. 10 is a configuration explanatory diagram of an example of a polarizing beam splitter, and FIG. 11 is an explanatory diagram of the operation of the polarizing beam splitter. FIG. 12 is a diagram showing an example of wavelength distribution of a polarizing beam splitter and a light source, FIG. 13 is a diagram showing an example of reproducing diagonal lines in the conventional example, and FIG. 14 is a diagram showing an example of reproducing diagonal lines in the above embodiment. 1...PLZT, 2...Polarizing element, 6, 8...Polarizing beam splitter.

Claims (1)

[Claims] 1. Comprising a ferroelectric material exhibiting a secondary electro-optic effect and two polarizing elements arranged to sandwich this ferroelectric material, at least one of these two polarizing elements is configured with a polarizing beam splitter. The plurality of electrodes provided on the ferroelectric material are arranged on one surface of the ferroelectric material and have an inclination of about 45 degrees with respect to the vibration direction of the light passing through the polarizing element. An electro-optical element characterized in that it is arranged as follows.