JPH08201755A - Projection optical system and image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide a projection optical system having high brightness and high contrast, and suppressing the occurrence of unnecessary aberrations. [Structure] The light emitted from the illumination system 1 enters the optical system 2 to be substantially parallel light forming an angle 2θ with the optical axis 6, and reaches the reflection panel 3. The reflection panel 3 is arranged so that the normal direction and the optical axis of the optical system 2 coincide with each other. The light specularly reflected by the reflection panel 3 passes through the optical system 2, and most of it is It is blocked by the light shielding member 4 and forms a dark portion on the projection surface 7. The light beam reflected in the normal direction of the reflection panel 3 and emitted parallel to the optical axis 6 is again condensed by the optical system 2 and passes through the opening 41 of the light shielding member 4 to form a bright portion on the projection surface 7. To form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical system, and more particularly to a projection optical system using a Schlieren optical system.

[0002]

2. Description of the Related Art An example of a conventional projection type optical system using a reflection type spatial modulation optical element and a Schlieren optical system is shown in FIGS. In FIG. 9, the light emitted from the light source 11 is directly reflected by the reflecting mirror 12 or the condensing lens 13
Incident on. Next, the light reflected by the reflecting mirror 14 passes through the optical system 2 to become substantially parallel light, and enters the liquid crystal panel 30 at the incident angle 2θ as shown in FIG. Therefore, in the liquid crystal panel 30, the light reflected without being scattered passes through the optical system 2 again as a substantially parallel light, inclined by 2θ with respect to the optical axis of the optical system 2. The light flux is condensed by the optical system 2, passes through the opening of the light shielding member 4, and is projected on the projection surface 7. Further, most of the light scattered and reflected at the voltage applying portion of the liquid crystal panel 30 passes through the optical system 2 and is blocked by the light shielding member 4 and does not reach the projection surface 7.

[0003]

However, in the projection optical system as described above, since the reflected light from the liquid crystal panel 30 passes through a portion distant from the optical axis, high-order aberrations are likely to occur and It was not preferable in terms of correction.

The present invention provides high brightness and high contrast,
An object of the present invention is to provide a projection optical system in which unnecessary aberrations are suppressed.

[0005]

In order to achieve the above object, the first invention of the present application is such that the illumination light is set to the first
Optical element that switches between a first state in which the illumination light is regularly reflected and a second state in which at least a part of the illumination light is not regularly reflected in the first direction; A projection optical system having an optical system for forming incident substantially parallel light and projecting by receiving reflected light specularly reflected in the first direction by the pixels of the optical element,
The reflective surface of the pixel in the first state is inclined with respect to the optical axis of the optical system so that the first direction is substantially parallel to the optical axis of the optical system. This makes it possible to provide a projection optical system that suppresses the generation of unnecessary aberrations.

A second invention of the present application is an image forming apparatus having the projection optical system of the first invention of the present application.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 shows the configuration of the projection optical system in this embodiment.
Shown in 1 is an illumination system, 11 is a light source, 12 is a reflecting mirror, 1
3 is a condensing optical system, and 14 is a reflecting mirror. 2 is an optical system, 3
Is a reflective panel. In this embodiment, a reflection type spatial modulation element is used which can reflect incident light in the normal direction of the reflection panel, that is, in the direction substantially parallel to the optical axis of the optical system 2. This will be described later in detail. Reference numeral 4 is a light blocking member having an opening 41, 6 is an optical axis of the optical system 2, and 7 is a projection surface.

The light emitted from the light source 11 enters the optical system 13 directly or after being reflected by the reflecting mirror 12. The light condensed by the optical system 13 reaches the reflecting mirror 14 and is reflected thereby to form an illumination light flux. In this way, the light emitted from the illumination system 1 enters the optical system 2 to be substantially parallel light that forms an angle 2θ with the optical axis 6, and reaches the reflection panel 3. Here, it is arranged so that the normal direction of the reflection panel and the direction of the optical axis of the optical system 2 coincide with each other. The light specularly reflected by the reflection panel 3 passes through the optical system 2, and most of the light is blocked by the light blocking member 4 to form a dark portion on the projection surface 7. The light is reflected in the direction normal to the reflection panel 3 and the optical axis 6
The light flux emitted substantially in parallel with is condensed again by the optical system 2 and passes through the opening 41 of the light shielding member 4 to form a bright portion on the projection surface 7.

When color display is performed in this embodiment, a color filter may be placed on the surface of the reflection panel, for example.

Next, the reflection panel 3 used in this embodiment will be described in detail.

As a reflection type spatial modulation optical element used in the reflection panel 3, a P type which is generally used as a polymer dispersion type liquid crystal.
By using DLC (Polymer Dispersed Liquid Crystal), a projection optical system with good light efficiency can be constructed.

The structure of the reflective PDLC panel used in this embodiment is shown in FIG. 201 is a glass plate serving as a counter substrate,
202 and 206 are transparent electrodes, 203 and 205 are alignment films,
Reference numeral 204 is a PDLC layer, 207 is a reflection electrode having an inclination of θ ′ with respect to the reflection panel 3, 208 is a signal line wiring,
Reference numeral 209 is a gate polysilicon of the pixel portion TFT, 210 is a polysilicon layer forming the pixel portion TFT, 211 is an insulating layer, 212 is a silicon substrate, and 213 and 214 are interlayer films.

The inclination θ'of the reflection electrode 207 with respect to the reflection panel 3 is such that the reflection light is emitted in the normal direction of the reflection panel 3 with respect to the illumination light incident on the reflection panel 3 at the incident angle 2θ. The angle is set.

The operating principle of the light / dark state of light in the PDLC panel will be described below.

The PDLC layer 204 is a transparent electrode 202, 20.
As the voltage is applied by 6, the light diffusion state changes.
When a voltage is applied, the liquid crystal alignment in the polymer spheres becomes uniform and the incident light becomes transmitted light as it is. Therefore, the illumination light incident on the liquid crystal panel 3 at the incident angle 2θ is emitted in the normal direction of the liquid crystal panel. When no voltage is applied, the liquid crystal is disordered and not aligned, so that scattered light is generated. By controlling the applied voltage for each pixel in this way, image display can be performed.

In the configuration of FIG. 2, the incident light from the illumination system is PD
Since the light travels back and forth through the LC layer 204, the degree of scattering becomes stronger, and the contrast of the PDLC layer becomes about twice that of a transmissive PDLC panel.

Further, since the traveling directions of the reflected light on the front surface and the back surface of the counter substrate 201 are different from the traveling directions of the reflected light on the reflection electrode 207, ghost and flare are reduced and the contrast is improved. There is also. In addition,
When the inclined electrode is formed, if the polysilicon layer 210, the gate polysilicon 209, and the signal line wiring 208 are sequentially arranged as shown in FIG. 2, a step is formed obliquely. When this local step is smoothed by resist etch back or the like, the interlayer film 214 has a shape as shown in FIG. After the electrode 207 is formed here, it may be flattened by the interlayer film 213 and contacted with the reflective electrode 207 and the transparent electrode 206. In this case, an electric field is uniformly applied between the flattened transparent substrate 206 and the counter electrode, so that uneven distribution does not occur.

As another reflection-type spatial modulation optical element, a large number of micromirrors described in JP-A-62-125772 are arranged in a grid pattern, and a reflection-type space whose angle can be controlled in units of these micromirrors. Modulation optics (Deformable M
There is a device using an irror device element, which will be referred to as a DMD element hereinafter. This DMD element will be described with reference to FIGS.

In FIG. 3, 301 is a mirror, which is made of Al, A
It is made of a material such as g and plays a role of reflecting incident light.
A substrate 302 supports the mirror 301 and is made of Au or the like. Reference numerals 303 and 304 denote a mirror 301 and a support substrate 302.
The supporting member 303 is called a mirror contact, and particularly receives a hinge portion that performs electromechanical operation.
Reference numeral 04 is an insulating material made of polyoxide Si or the like.
Reference numeral 305 denotes a polysilicon gate, which serves as a gate of a MOS FET transistor. 306 is an air gap,
It is a cavity of 0.6 μm to several μm. A floating field plate 307 applies a voltage from the N + floating source 308 to the floating field plate 307 according to ON / OFF information of the transistor. Reference numeral 309 represents an N + drain. This is also a MOS type FE
Plays the role of the T-transistor. Reference numeral 310 is a gate oxide, and 311 is a P-type silicon substrate.

FIG. 4 is a front view from the direction A in FIG.
Reference numeral 2 is an air gap, 413 is a mirror swing portion that swings electromechanically, and 414 is a hinge portion. Reference numeral 415 denotes a mirror surface other than the mirror oscillating portion 413 on the surface of the light deflection element.
The light deflection element is manufactured by a process similar to the IC or LSI process.

FIG. 5 shows an electrical equivalent diagram of the light deflection element.
516 is a voltage V applied to the mirror 301 and the supporting substrate 302
Indicates _M. Reference numeral 517 denotes the voltage V _F applied to the N + floating source 308. Reference numeral 518 denotes a transistor configuration, which is a D (drain) signal of the N + drain 309,
ON of G (gate) signal of polysilicon gate 305,
When turned off, the voltage of V _F is N + floating source 3
It is turned on and off at 08. At this time, the voltage V _M is applied to the mirror 301 and the support substrate 302, and the mirror 30
1. Support substrate 302 and N + floating source 308
The potential difference between them is increased or decreased by the ON and OFF signals. Then, a force F according to the following equation is generated between the air gap 306 and the floating field plate 307 according to the potential difference.

F∽KVα (K: constant V: potential difference
α: constant F: bending force) This force F causes the mirror swing unit 413 to move to the hinge portion 41.
It is swung around 4.

The left view of FIG. 3 shows the mirror 301 and the support substrate 30.
2 and the N + floating source 308 have a large potential difference, the mirror oscillating portion 413 causes the hinge portion 414 to move.
The incident light is reflected by changing the double angle of the deflection angle of the mirror due to this action. On the other hand, when the potential difference is small, as shown in the right diagram of FIG. 3, the mirror oscillating portion 413 composed of the mirror 301 and the support substrate 302 has a small pulling force by the floating field plate 307 and is not curved. Therefore, the incident light is reflected while the mirror is not shaken. That is, the light deflection element is to convert electrical ON / OFF to ON / OFF of the swing of the mirror swing unit 413, and further to change the deflection angle of light.

By using this DMD element for the reflection panel 3, it is possible to perform projection with extremely high contrast without the light rays in the dark part reaching the projection surface.

Further, the projection optical system may be constructed as shown in FIG. What is characteristic in FIG. 6 is that, as shown in FIG. 7, in addition to the opening 41, the opening 42 for allowing the illumination light to pass is provided in the light shielding member 4. When a color display is performed by configuring the projection optical system as described above, in addition to the method of placing the color filter on the surface of the reflection panel 3, as shown in FIG. Place it in front of or behind
A method such as rotating in synchronization with the driving of the reflection panel can be adopted. The latter method has an advantage that the color filter can be miniaturized because the color filter is arranged near the condensing portion of the illumination light flux.

In the projection optical system of this embodiment, the normal line direction of the reflection panel 3 and the optical axis of the optical system 2 are aligned, and the specular reflection light of each pixel is tilted by tilting the reflection surface of each pixel. The light is emitted substantially parallel to the optical axis. However, the reflective surface of each pixel is parallel to the reflective panel (for example, a conventionally known TN (Twisted Nematic) panel).
Type reflective liquid crystal panel, etc.), the same effect as this embodiment can be obtained by inclining the reflective panel itself with respect to the optical axis. In this case, the image is deformed, but it can be corrected by the optical system.

[0028]

As described above, according to the present invention,
It is possible to provide a system that has higher brightness and higher contrast than the conventional projection optical system and that suppresses the generation of unnecessary aberrations.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical system according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a PDLC element.

FIG. 3 is a sectional view of a DMD element.

FIG. 4 is a front view of a DMD element.

FIG. 5 is an electrical equivalent diagram of a modulator having a micro mirror of the present invention.

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

FIG. 7 is a diagram showing a light shielding member according to a second embodiment of the present invention.

FIG. 8 is a view showing a case where a color filter is arranged in front of or behind the light shielding member of FIG.

FIG. 9 is a diagram showing an example of a conventional projection optical system.

FIG. 10 is an enlarged view of a main part of a conventional projection optical system.

[Explanation of symbols]

 1 Illumination system 2 Optical system 3 Reflection panel 4 Light-shielding member 5 Projection lens 6 Optical axis of projection optical system 7 Projection surface

Claims (8)

[Claims] 1. For each pixel, a first state in which illumination light is specularly reflected in a first direction and a second state in which at least a part of the illumination light is not specularly reflected in the first direction are separated. And an optical system that forms substantially parallel light that is obliquely incident on the optical element as the illumination light and that receives and reflects the reflected light that is specularly reflected in the first direction by the pixels of the optical element. In the projection optical system having, the reflection surface of the pixel in the first state is inclined with respect to the optical axis of the optical system so that the first direction is substantially parallel to the optical axis of the optical system. Projection optical system. 2. A light-shielding member having a first opening,
The reflected light that is specularly reflected in the first direction by the pixels of the optical element is condensed and projected by the optical system in the first opening of the light shielding member. The projection optical system described. 3. The projection optical system according to claim 2, wherein the light shielding member has a second opening for collecting the illumination light. 4. The projection optical system according to claim 3, wherein a distance from a point where the illumination light is condensed to a main plane of the optical system is substantially equal to a focal length of the optical system. 5. The polymer dispersion type optical element, wherein in the first and second states, the reflection surface of the pixel has an inclination with respect to a surface perpendicular to the optical axis of the optical system for each pixel. The projection optical system according to claim 1, wherein the projection optical system is a liquid crystal and scatters the illumination light in the second state. 6. The optical element is an optical element in which a large number of minute mirrors are arranged in a grid pattern and the angle of each minute mirror can be controlled. In the second state, the illumination light is directed in the first direction. 5. The projection optical system according to claim 1, wherein the projection optical system specularly reflects in a second direction different from. 7. The optical element is a twisted nematic type liquid crystal sandwiched between two polarizing plates in front of the reflective surface of the pixel, and the reflective surface of the pixel is in the first and second states. The projection optical system according to claim 1, wherein the projection optical system is inclined with respect to the optical axis and absorbs the illumination light in the second state. 8. An image forming apparatus comprising the projection optical system according to claim 1.