JP2002062491A - Imaging optical system and light amount control device using coherent modulation element - Google Patents

Abstract

(57) Abstract: A shutter element and a color separation element using an interferometric modulation (IMOD) element are provided. A light beam incident on an IMOD element via an optical system is separated at high speed into reflected light (red, green, and blue) of a specific wavelength by driving a reflector of the IMOD element.
The IMOD element 7 may be formed by one pixel,
It may be configured as a panel composed of a plurality of pixels. IM
The light intensity from the OD element 7 is taken into a storage device 13 such as a frame memory. When one set of red, green, and blue is taken in, three colors are synthesized. IMOD element 7 and storage device 1
3 is synchronized. According to this method, the same effect as the three-plate type can be obtained while the configuration is the single-plate type. Normal 3
It is smaller and lighter than a cross dichroic prism used in a plate type.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to coherent modulation (Inte
The present invention relates to an imaging optical system and a light amount control device using rferometric modulation (IMOD) elements.

[0002]

2. Description of the Related Art An image display device that modulates light by utilizing the interference of light is disclosed in JP-T-2000-500245, JP-T-Hei 10-5.
00224, USP5835255, USP6055090, USP6040937 and the like. These are MEMS (micro electric me
It modulates light by combining the technology of a mechanical system) with the resonant effect of light found in Fabry-Perot interferometers and the like.

FIG. 11 shows an outline of an interferometric modulation (IMOD) element. A reflector 100 is arranged via a spacer 102 against an inductive absorber 105 including films 104, 106 and 108. The incident medium 110 is in contact with the induction absorber 105 at one boundary.

Light enters from an incident medium 110 and is reflected by a reflector 100.
And is emitted from the incident medium 110. Reflector 100
And the interval T between the induction absorber 105 is variable. By changing this interval, the optical characteristics can be changed. film
104, 106 and 108 are, for example, zirconium dioxide, tungsten and silicon dioxide. As a structure for changing the interval T, a MEMS structure as shown in FIG. 12 is employed. With this structure, light can be modulated at very high speed by static electricity. 13 to 16,
This is a change in optical characteristics when the distance from the spacer is different. In each figure, the vertical axis represents the reflectance, and the horizontal axis represents the wavelength.

FIG. 13 shows the optical characteristics when the spacer interval is a certain value. As shown in FIG. 13, the reflectance is low over the entire visible light range. In this case, "black" is displayed.

FIG. 14 to FIG. 16 show the characteristics when the interval T has a certain value, which indicates blue, green and red, respectively. By arranging and controlling such a structure two-dimensionally, a color image can be displayed. For driving the reflector 100, for example, an electrostatic force is used. Therefore, a very high-speed operation can be performed. In expressing the gradation of an image display, it is possible to use an area gradation that changes the ratio of pixels having a high reflectance state in a certain area, or a time-division gradation expression that utilizes high-speed operation. it can.

[0007]

The above-described coherent modulation (IMOD) element is supposed to be appropriately illuminated by a certain light source to form an image on a screen. The feature of this coherent modulation (IMOD) element that can change the gradation at high speed is that it can be used as a shutter in an imaging optical system or the like to change the amount of light, or in place of a dichroic film.
It is thought that it can be used for controlling the wavelength of light emitted from the IMOD element, but such an invention has not been disclosed yet.

Accordingly, an object of the present invention is to provide a shutter element and a color separation element using an IMOD element.

[0009]

The image pickup optical system according to the present invention for solving the above-mentioned problems controls the amount of light by a coherent modulation element which performs light modulation using interference. Specifically, this imaging optical system is a coherent modulation system in which a light incident portion having an optical resonance layer in which a plurality of films made of a dielectric layer and a metal layer are laminated on a transparent substrate, and a movable reflecting mirror are opposed to each other. An image pickup optical system using an element, wherein the coherent modulation element is provided in a part of the image pickup optical system that controls the light amount, and the light amount is controlled.

Further, the light quantity control device of the present invention provides a light incident portion having an optical resonance layer in which a plurality of layers composed of a dielectric layer and a metal layer are laminated on a transparent substrate, and a coherent light for causing the movable reflecting mirror to face each other. A light quantity control device using a modulation element, wherein the light quantity control is performed by controlling the voltage to change a gradation of an optical characteristic of the coherent modulation element.

Further, the light quantity control device of the present invention comprises: a light incident portion having an optical resonance layer in which a plurality of layers composed of a dielectric layer and a metal layer are laminated on a transparent substrate; A light amount control device using an interferometric modulation element that faces each other, wherein a plurality of the interferometric modulation elements are provided, and optical characteristics of a part of the coherent modulation elements are controlled to a first state, and the remaining The optical characteristics of the number of the coherent modulation elements are controlled to the second state to perform light amount control.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a main structure near one pixel structure of the coherent modulation (IMOD) element according to the first embodiment. Actual elements have many such structures. Reference numeral 1 denotes a substrate glass, and incident light passes through the substrate glass. Numerals 2, 3, and 4 denote thin films of a dielectric layer or a metal layer, respectively, and the light resonance layer 5 is formed by appropriately selecting the thicknesses. 6
Denotes a reflector, and a resonance layer 5 is formed by a driving structure (not shown).
And the interval T between the reflector 6 changes. By changing this T 1, the characteristics of light absorption and reflection change, and an image can be displayed.

The reflected light exits from the glass substrate 1 in a direction opposite to the incident light. When the light is absorbed by controlling the interval T, the reflectance decreases and the image is displayed as “black”. Conversely, if the interval T is controlled so that red, green, and blue light are all reflected, the three colors overlap and the image displays "white". Since the reflector 6 is driven by, for example, electrostatic force, it can operate at a very high speed.

In an interferometric modulation (IMOD) element, "black" is regarded as absorbing (non-reflective) light rays, and "white" as reflecting light rays. It can be used as a reflection type light quantity control mechanism in an optical system or the like. This will be described with reference to FIGS. 2 and 3, reference numeral 7 denotes an interferometric modulation (IMOD) element. FIG. 2 shows a case where all light is reflected to display “white”, and FIG. 3 shows a case where all light is absorbed and “black” is displayed. In order to make the state of the IMOD element easy to understand, FIG. 2 shows the IMOD element 7 in white to show a reflection state, and FIG. 3 shows the IMOD element in black to show a non-reflection state. 8 shown in FIGS. 2 and 3
Denotes an image plane, which represents a film, a CCD, a CMOS sensor, or the like.

IM displaying "white" as shown in FIG.
Light incident on the OD element is reflected as it is and reaches the image forming surface. Conversely, light incident on the IMOD element displaying "black" as shown in FIG. 3 is absorbed by the IMOD element and does not reach the image forming surface. As described above, by switching the display between “white” and “black” at a high speed, the light reaching the image forming surface can be controlled, so that it can be used as a reflection type light amount control mechanism.

As described above, the IMOD element is 45 ° with respect to the incident light.
Although an example is shown in which the light source is disposed as a reflection control mechanism in an imaging optical system such as a camera, the present invention is not limited to this. The light source may be used for light obliquely incident from various angles. For example, although not shown, it is like an optical switch and has a mechanism for turning on and off each of "white" and "black" of the IMOD element. Also, as an example
If a mechanism for rotating the IMOD element is provided, light rays from various directions can be reflected in any direction. Also,
The IMOD element 7 may be formed by one pixel, or may be formed in a panel shape including a plurality of pixels.

In using the IMOD element in the present invention,
Since the IMOD element is an interference type, the wavelength of the light beam changes depending on the incident angle of the light beam. Therefore, the wavelength of the light beam perpendicularly incident to the IMOD element and the wavelength of the obliquely incident light are different,
When red, green, and blue lights are combined, the appearance of “white” is slightly different, and the reflectance may be changed. To avoid such problems, obliquely incident light rays
There are methods such as designing a dielectric layer or a metal layer film so as to obtain a desired wavelength, and arranging an optical system for making the angle of incidence on the IMOD element constant.

In the above, "black" and "white" have been described, but the present invention is not limited to this.
By providing the OD element with gradation, the amount of reflected light can be changed stepwise by the gradation.

In addition, a panel-like IM comprising a plurality of pixels
As shown in FIG. 5, the OD element can be used as an aperture in an imaging optical system by controlling the voltage applied to each IMOD element to control the intensity distribution of the reflected light. There is no limitation on the shape of the intensity distribution, and various shapes such as a circle and a polygon are possible. In addition, the combination of the case with the gradation and the effect of the aperture can be obtained at the same time.

Next, FIG. 4 shows a configuration diagram when a transmission type IMOD element is used. As shown in the figure, by interposing the reflector between the resonance layers and doubling the optical path, the IMOD element becomes a transmission type IM.
It can also be used as an OD element. Similar effects can be obtained by using such a transmission type IMOD element.

Next, a second embodiment of the present invention will be described.

FIG. 6 shows a configuration when the IMOD element 7 is used as a device for color separation. IMOD element 7
Has the same configuration as that shown in the first embodiment, and a detailed description thereof will be omitted.

A light beam incident on the IMOD element 7 via the optical system is separated into reflected light (red, green, and blue) of a specific wavelength by driving a reflector of the IMOD element 7. In addition, since the driving of the IMOD element is performed at a very high speed, if the speed is not perceived by the human eye, even if there is a time difference in the occurrence of color,
Humans cannot perceive that colors are time-shared, but at the same time feel as if they are separated. This feature
It shows that an IMOD element can be used as a substitute for a color separation element such as a dichroic film or a cross dichroic prism. Further, the IMOD element 7 may be formed by one pixel, or may be formed in a panel shape including a plurality of pixels.

The light beams temporally separated by the IMOD element 7 are stored in a storage device 13 such as a frame memory with a time difference via a time-division three-color imaging optical system. It is taken in order. Next, when one set of red, green, and blue is taken in, three colors are synthesized. Here, red, green, and blue are taken in the order, but the present invention is not limited to this, and any order may be used. Here, the IMOD element 7 and the storage device 13 operate independently.

In FIG. 7, the IMOD element 7 and the storage device 1
3, and color separation and light capture are performed.
According to this method, the same effect as the three-plate type can be obtained while the configuration is a single-plate type. In addition, compared to a cross dichroic prism normally used in a three-plate system, a compact and lightweight configuration can be achieved.

FIG. 8 shows the reflection type color separation optical system shown in FIG. 6 as an equivalent type color separation optical system using a transmission type IMOD element 7.

When a conventional cross dichroic prism is used as shown in FIG. 9, FIG.
FIG. 2 shows a configuration diagram when an element is used.

When the reflective display device is used in the present invention, since the reflective display device is of the interference type, the wavelength of the light beam changes depending on the incident angle of the light beam. Therefore, since the wavelength of the light beam vertically incident on the interference type display device and the wavelength of the obliquely incident light beam are different, when red, green, and blue light are combined,
It is conceivable that the appearance of “white” is slightly different and the reflectance changes. In order to avoid such a problem, a dielectric layer or a metal layer film is designed so that a desired wavelength can be obtained for obliquely incident light rays. There is a method such as disposing an optical system.

A panel-like IMOD comprising a plurality of pixels
In the element, by changing the area where interference occurs as shown in FIG. 5 and changing the diameter (or cross-sectional shape) of the emitted light, an effect as an aperture in an imaging optical system can also be expected. The effect can be obtained at the same time. The region in which the interference described here occurs is not limited in shape, and various shapes such as a circle and a polygon are possible.

[0030]

According to the present invention described above, a compact and lightweight optical system can be realized by arranging an IMOD element as a light amount control mechanism and a wavelength control mechanism at appropriate positions in an imaging optical system. .

[Brief description of the drawings]

FIG. 1 is a perspective view of an IMOD element.

FIG. 2 is a configuration diagram of the first embodiment when the display of the IMOD element is white.

FIG. 3 is a configuration diagram of the first embodiment when the display of the IMOD element is black.

FIG. 4 is a configuration diagram of a first embodiment when a transmission type IMOD element is used.

FIG. 5: Change of interference area of IMOD element

FIG. 6 is a configuration diagram of a second embodiment according to the present invention.

FIG. 7 shows a second example in which the IMOD element and the color signal storage device are synchronized.
Configuration diagram of the embodiment

FIG. 8 is a configuration diagram of a second embodiment when a transmission type IMOD element is used.

FIG. 9 shows color separation by a conventional dichroic prism.

FIG. 10 shows color separation by an IMOD device according to the present invention.

FIG. 11 is a configuration diagram of an IMOD element.

FIG. 12 is a configuration diagram of a reflector of an IMOD element.

FIG. 13 shows characteristics of an IMOD element (black).

FIG. 14 shows characteristics of an IMOD element (blue).

FIG. 15 shows characteristics of an IMOD element (green).

FIG. 16 shows characteristics of an IMOD element (red).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate glass 2 Thin film 3 Thin film 4 Thin film 5 Optical resonator 6 Reflector 7 IMOD element 8 Imaging surface 9 Projected object 10 Time-division three-color imaging optical system 11 Color separation means 12 Light modulation element 13 Storage device

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Claims (9)

[Claims] 1. An imaging optical system wherein light quantity control is performed by a coherent modulation element that performs light modulation using interference. 2. An imaging optics using an interferometric modulation element in which a light incident portion having an optical resonance layer in which a plurality of films composed of a dielectric layer and a metal layer are laminated on a transparent substrate, and a movable reflecting mirror are opposed to each other. An imaging optical system, wherein the coherent modulation element is provided in a part of the imaging optical system that controls the amount of light, and the amount of light is controlled. 3. The light incident portion and the movable reflecting mirror,
3. The image pickup optical system according to claim 2, wherein the image pickup optical system is opposed via an air layer. 4. A light-quantity control device using an interferometric modulation element in which a light incident portion having an optical resonance layer in which a plurality of layers composed of a dielectric layer and a metal layer are laminated on a transparent substrate, and a movable reflecting mirror are opposed to each other. A light quantity control device, wherein the light quantity control is performed by controlling the voltage to change a gradation of an optical characteristic of the coherent modulation element. 5. The light incident part and the movable reflecting mirror,
5. The light amount control device according to claim 4, wherein the light amount control device faces each other via an air layer. 6. A coherent modulation system in which a light incident portion having an optical resonance layer in which a plurality of layers composed of a dielectric layer and a metal layer are laminated on a transparent substrate, and a movable reflecting mirror face each other via an air layer. A light amount control device using an element, wherein a plurality of the coherent modulation elements are provided, optical characteristics of a part of the coherent modulation elements are controlled to a first state, and the remaining number of the coherent modulation elements are controlled. A light quantity control device for controlling the light quantity by controlling the optical characteristics of the element to a second state. 7. A color separation optical system, comprising: the coherent modulation element provided at a portion where color separation is performed; and a storage device for storing output light intensity from the coherent modulation element. The imaging optical system according to claim 1, wherein the color separation is performed by controlling a voltage to be applied, and a result of the color separation is stored in a storage device. 8. The coherent modulation element causes light to enter from the light incident part, reflects the light by the movable reflecting mirror,
The imaging optical system according to claim 2, wherein the imaging optical system is a reflective coherent modulation element that emits the light from the light incident unit. 9. The coherent modulation element causes light to enter from the light incident part, reflects the light by the movable reflecting mirror,
7. The light amount control device according to claim 4, wherein the light amount control device is a reflective coherent modulation element that emits the light from the light incident portion.