JPS61232411A - Photoscanning optical system - Google Patents

Abstract

PURPOSE:To eliminate the influence of an error in the arrangement of an optical system by turning an optical modulator around an axis coincident with or near the array direction of a mirror rocking part in a main scanning direction. CONSTITUTION:An electromechanic optical modulator 27 like a DMD element is equipped with a position correcting mechanism 38 which rotate the modulator 27 around the axis coincident with or nearby direction of line printing. Namely, even if luminous flux A incident on the optical modulator 27 shifts into luminous flux A', the optical modulator 27 is so rotated as to correct it, and consequently signal light B' can be made incident on the entrance pupil of an image forming lens 29 as well as a signal B having no shift. The axis around which the optical modulator 27 is rotated is not relative to the tilt direction of the mirror rocking part 13 for the optical modulator so much and set in the array direction of the main scanning direction of the mirror rocking part 13. Consequently, corrections are easily made and an image output device which has a little influence of an error in the position of the optical system is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light scanning optical system of an image output scanner using an electromechanical light modulator.

[Prior art]

Image output scanners are used in copying machines, facsimile machines, etc.
This is a device that scans an original image of a document or the like and outputs it as image information using light or electrical signals. Various types of such image output scanners are known.

For example, the image output scanner used in general PPC copying machines scans the original with light from a halogen lamp, etc., and images the reflected light directly onto an electrophotographic photoreceptor. . Another method is to convert an original image into an electrical signal, such as a laser beam glare/tar, and then use an optical modulator to form a laser beam onto a photoreceptor.

Furthermore, in recent years, with the development of integrated circuit technology, an image output scanner using an electromechanical optical modulator having a large number of minute deflection elements on a substrate has been proposed.

Examples of the above electromechanical optical modulator include DMD.
(Deformable Mirror Device
e) is known.

Regarding DMD elements, IEE Transaction
onElectron Dsvics Vol,
It is described in FD-30 No. 5544 (1983),
The optical system is also disclosed in Japanese Patent Laid-Open No. 59-17525.

The general mechanism of the DMD will be explained below based on the drawings.

FIG. 4(,) shows an enlarged sectional view of the DMD. 1 is a mirror structure made of a material such as AI-a Ag, and serves to reflect incident light. 2 is a substrate that supports the mirror structure of 1 and is made of Au or the like. 3 and 4 are the support members of 1.2, 3 is called a mirror contact, and is especially for receiving the palm part that performs electromechanical operation, and 4 is ? It is an insulating material of lyoxide St.

5 is a polysilicon gate and shows the role of dart in FETMO8) run sister. 6 is air gear, pu.

It is 0.6μ to several μ in the sky. 7 is floating,
At the field plate, voltage is applied to the shift floating and field plate based on the ON/OFF information of the transistor from the 8ON+floating source.

9 indicates an N+ drain. This also serves as a configuration of a run sister (MO8 type FET).

10 is dirt oxide, and 11 is a P silicon substrate.

FIG. 4(b) is an enlarged front view from the direction A of FIG. 4(,), in which 12 is an air gap, 13 is an electromechanically oscillating mirror swinging portion, and 14 is a base portion.

Reference numeral 15 indicates a mirror surface other than the mirror portion 13 on the DMD surface. A DMD is manufactured using a process similar to that of an IC or LSI.

FIG. 4(c) shows an electrical equivalent diagram of the DMD. 16 is 1
．． The voltage vM applied to the filter and support member of No. 2 is shown.

17 indicates the voltage V applied to 8. 18 shows the transistor configuration [Oshi, 9 D (drain) signal, 50G
When the (dirt) signal is turned ON and OFF, the voltage of V is turned ON and OFF' at 8. At this time, the voltage v at 1°2
M is turned on), the potential difference is ON between 1, 2 and 8,
It will be increased or decreased by the OFF signal.

At this time, a force F according to the following formula is generated between 6 and 7 depending on the potential difference, and FC/3KV" (K: constant i V: potential difference α: constant F: bending force) Mirrors 1 and 2 are hinged. It is swung by the section 14.
) shows the case where there is a large voltage difference between 1, 2 and 8, the mirror swinging part 13 is bent from the hinge part 14, and due to this action, the incident light is 2 times the deflection angle of the mirror. It is reflected at twice the angle.

On the other hand, when the voltage difference is small, as shown in the right diagram of FIG. 4(a), the mirror swinging parts 1 and 2 are not bent due to the small force exerted by the mirror 7. Therefore, the incident light is reflected without touching the mirror. The DMD element is electrically turned on and off when the rocking of the mirror rocking unit 13 is turned on.
, OFF, and further converts it into the deflection angle of light.

Generally, the DMD elements shown in FIGS. 4(-) to 4(C) are used in a light scanning optical system 19 as shown in FIG. 5, and are used together with an electrophotographic process 20, and are applied, for example, as a printer. In Figure 2, 21 is a lamp, 22.24 is D
An optical system 23 for illuminating the MD element is the ninth slit plate of the optical system, and is configured to illuminate only the mirror array portion of the mirror array element of the DMD element. 25
．． 26 is a folding mirror, and 27 is a DMD element. This element operates mechanically in accordance with the principle shown in Figs. The elements are arranged. (several tens to thousands) 28 is a circuit that drives the DMD element 27, 29 is a lens that focuses the reflected light from the DMD element 27 onto the photoreceptor 30, which normally forms an image only when the signal to the DMD element 27 is turned ON. Light enters the pupil of the image lens 29. 31 to 35 are those normally used in the electrophotographic process; 31 is a developing device; 32 is a charger for transferring the toner on the photoreceptor 30 onto copy paper 33; 34 is a cleaner; and 35 is a charger for charging the photoreceptor 30. It is a charger that gives Further, 36 is a light shielding plate that should cut off the OFF signal light of the DMD element.

The function as a printer is performed by applying a command input to the DMD element 27 from a signal input to the DMD element drive circuit 28. The DMD element 27
One of the array mirrors 37 reacts electromechanically according to the operating principle shown in Figures (,) to (c), and responds to the signal in a large number of arrays as shown in Figure 6. move. The light A of the illumination system emitted from the lamp 21 is transmitted to the illumination optical system 2.
2, 23.

24, 25, and 26 are illuminated onto the DMD element 27 in a slit shape. When the mirror of the mirror array 37 on the DMD element 27 is OFF, the irradiated light A is reflected in the direction C and is blocked by the light shielding plate 36, so that the light does not reach the photoreceptor 30. In the case of ON, the light is reflected in the B direction and enters the imaging lens 29, and a dot pattern corresponding to one array mirror is formed on the photoreceptor 30. Therefore, a line of ON.

When an OFF signal is input to the drive circuit 28, the toner image is developed through an electrophotographic process and then acts as a solinter, in which the toner image is transferred onto copy paper.

[Problem that the invention seeks to solve]

Now, as described above, when the MD element 27 is used in the scanning optical system 19 as shown in FIG.
Errors in the arrangement (particularly errors occurring when handling the lamp 21 and changes in the position of the optical system over time) become a problem.

FIGS. 7 and 8 are diagrams for explaining the influence of such a change in the position of the optical system 19.

FIG. 7 shows the placement error of the DMD element 27, when the DMD element 27 is placed at a 00 degree deviation from the normal angle (indicated by the dotted line) and the other optical elements are placed at the normal positions. This is what is shown.

In the same figure, in the DMD element 27 which is normally arranged, A
When the signal is ON, the light is directed to the imaging lens 29 by the dotted line B.
Enter Noyo 5. Also, when the signal is OFF, the DMD element 27
The light polarized by is reflected in the direction of dotted line C.

FIG. 8 illustrates the relationship between the pupil of the imaging lens 29 and the reflected light flux from the DMD hexagon 27. In FIG. 8(-), A indicates the size of the pupil of the imaging lens 29 when viewed from the X direction in FIG. The reflected light B of the signal ON from the DMD element 27 which is now properly placed shows a wide circle on the pupil A of the imaging lens 29, and the reflected light B from the DMD element 27 is reflected inside the imaging lens 29. Everything is included in this. On the other hand, when the signal is OFF, the reflected light C moves to a circle C at a position away from the pupil A of the imaging lens 29 as the mirror swinging section 13 of the DMD element 27 is deflected by the signal, and the light enters the pupil A of the lens. does not come at all, and the light intensity at signal 08 and OFF (DMD element 2
However, if the DMD element 27 is shifted by θ0, the signal will not be detected even if the light from A is incident in the same way as shown in FIG. 7. O
The reflected light B' of N is shifted by 20 from the normal reflected light B, and similarly, the reflected light C' of the signal OFF is shifted by 20 from the normal reflected light C.
It shifts. Here, in FIG. 8(,), the spread of reflected light B' with respect to the pupil A of the lens is cut off by the pupil A of the lens as shown by circle b'. The reflected light C' will completely escape from the pupil A of the lens, but the amount of signal light (reflected light B/) will be small on the photoreceptor, and S will be degraded. Furthermore, considering the case where the DMD element 27 is shifted by θO in the opposite direction, both the reflected light B' of the signal ON and the reflected light σ of the signal 0 FIY are present in the pupil A as shown in FIG. 8(b). However, the deterioration of the S/N ratio becomes even greater.

Next, in FIG. 9, let us consider the deviation of the luminous flux A when the lamp 21 is in a state where the filament position is deviated due to lamp replacement or durability. In Fig. 9, when the filament is in the normal position, the illumination optical system 22, 23, 24, 25, 2
The light passing through 6 becomes the principal ray of regular light. At this time, if the lamp '21 is displaced by a distance t, the principal ray of the luminous flux will be shifted from A', or the angle of incidence on the DMD element 27 will be shifted, resulting in the same situation as shown in FIG. Similarly, the angle of incidence on the DMD element 27 also shifts due to the positional error of the illumination optical system 22.degree. 24.25, 26.

As mentioned above, when using a DMD element for an image output scanner, the mirror device uses the angle of the incident light of the illumination system or the reflected light of the mirror of the imaging system. It requires twice as much accuracy as compared to the conventional method, and has the drawback that alignment is time-consuming.If the accuracy is poor, the required performance cannot be obtained. Additionally, when a lamp is used in the illumination system, the position of the lamp filament may shift over time, the filament may not be properly aligned when the lamp is replaced, etc. There is also a problem that the S/N, which is the ratio of the amount of light when the imaging light is ON and the amount of light when it is OFF, changes greatly. These two problems greatly affect the print quality that is the output of the thermal recording device, and become a serious problem if the above alignment cannot be precisely achieved.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides an electric machine in which a large number of mirror swinging parts are arranged in the main scanning direction and can deflect a light beam from a radiation source in at least two directions according to an input signal. An optical scanning optical system of an image output scanner that illuminates a target light modulator, divides the reflected light by switching the deflection direction of each element, and images only the signal light on a photosensitive member using an imaging optical system. There is provided an optical scanning optical system, characterized in that the optical modulator can be rotated around the alignment direction of the mirror swinging section in the main scanning direction or around the axis.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the optical scanning optical system of the present invention. In the figure, an electromechanical optical modulator 27 such as a DMD element is a position corrector that rotates the modulator 27 around the line printing direction or its vicinity. fIt
It has 38. Even if a shift occurs in the light beam A entering the optical modulator 27 and the light beam A' becomes the light beam A', by rotating the light modulator 27 in a direction that corrects the deviation, the signal light B' is transferred to the imaging lens 29. It is made to enter the entrance pupil in the same way as the signal light B when there is no shift. It is effective to set the direction of the axis for rotating the optical modulator 27 in the direction in which the mirror oscillating parts 13 of the optical modulator 27 are arranged in the main scanning direction, regardless of the direction in which the mirror oscillating parts 13 of the optical modulator 27 fall. is large.

The direction of the rotation axis mentioned above will be explained in more detail.

Figures 2 (a) and (b) show the DM when the hinge part 14 is located at the lower left corner of the mirror part 13 and directly below it, respectively.
This shows a D element. The incident light flux A is (a).

In both (b), when the mirror part 13 is not fallen as in (1), it becomes reflected light C, and when it is fallen as in (ii), it becomes reflected light B (signal light).

Figures 3(a) and (b) are similar to Figures 2(a) and (b).
FIG. 4 is a diagram schematically showing the distribution of reflected light on a plane including the entrance pupil of the imaging lens 29 that is a finite distance away from the DMI (DMI) element in the reflection direction. In the same figures (a) and (b), C is the distribution of reflected light C in the signal OFF state, that is, the diffraction of unnecessary light? It is a turn (actually it is close to a cross-shaped diffraction turn), and 39 is an image of a filament. Also, a is the entrance pupil of the imaging lens 29, and b is the signal O.
The distribution of reflected light B in the N state is shown. If so, D
If the MD element deviates in angle, the light distribution of the reflected light B when the signal is ON will shift to the position b', and the unnecessary diffraction pattern C will become C'.
It will shift to the position of

Here, as shown in FIG. 2, by rotating the optical modulator 27 about the axis t in the arrangement direction (line printing direction) in the main scanning direction of the mirror swinging section 13, as shown in FIG. a)
, (b), it becomes possible to correct b' to the position of b. Of course, it is desirable to have the rotation axis in this direction for the correction effect, but even if the rotation axis is provided at a position slightly deviated from this direction, the deviation of the optical system can be corrected to a certain extent.

Furthermore, as described in Fig. 9, the filament position shift due to rung replacement, etc., and the illumination optical system shift,
Although the position of the light hitting the DMD element will be shifted, it is possible to set the illumination system to widen the irradiation width for the DMD element, or
A sufficient countermeasure can be achieved by combining settings such as adjusting the height of the Di element itself with the measure of attaching a rotating shaft to the DMD element of the present invention.

Furthermore, by moving the optical wave modulator substantially in the line direction, it can be moved substantially parallel to the direction of the generatrix of the drum-shaped photoreceptor, which has the advantage of preventing oblique scanning, which is advantageous in terms of image quality.

〔Effect of the invention〕

As explained above, according to the light scanning optical system of the present invention, the positional error or alignment error of the optical system can be easily corrected by rotating the optical modulator around the line direction, thereby eliminating the influence of the positional error of the optical system. It is possible to provide an image output device that is not easily affected.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the area around the optical modulator of the optical scanning optical system of the present invention. Figure 2 is a diagram showing two examples of optical modulators in which the mirror portions are tilted in different ways, and Figure 3 is a diagram showing signals on a plane containing the entrance pupil of the imaging lens of the two optical modulators. FIG. 3 is a schematic diagram showing the shift of light. FIG. 4 is an explanatory diagram of a DMD element, FIG. 5 is a schematic diagram of a printer using the element, and FIG. 6 is a front view of the DMD element. FIG. 7, FIG. 8, and FIG. 9 are diagrams each illustrating the influence of the deviation of the optical system. 21: Lang, 22. 23, 24, 25, 26: Illumination optical system, 27: Electromechanical light modulator, 29: Imaging lens,
38: Position correction mechanism. Agent Patent Attorney Minoru Yamashita Child 1 Figure 1. ---B Ichiku Ward Figure 5, 719 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] (1) The light flux from the synchrotron radiation source is irradiated onto an electromechanical optical modulator consisting of a large number of mirror oscillating units arranged in the main scanning direction that can deflect the beam in at least two directions according to an input signal, and An optical scanning optical system of an image output scanner that splits reflected light by switching the deflection direction and images only the signal light on a photosensitive member by an imaging optical system, the optical scanning system comprising: 1. A light scanning optical system, characterized in that the moving parts are rotatable about the arrangement direction in the main scanning direction or around the axis.