JPH04196869A - Optical scanner - Google Patents

Abstract

PURPOSE:To use a liquid crystal lens in a form effective for the optical correction of optical scanning by executing the optical correcting with a liquid crystal device. CONSTITUTION:A ferroelectric liquid crystal cell 6 is arranged between a scanning mirror 3 and a photosensitive body 5. Then, it is necessary to seal ferroelectric liquid crystal into the cell 6 for the utilization in a state possessing a liquid crystal property and large correcting effect can be obtained by putting a bend liquid crystal cell 14 and a curvature cell 16 into the one side of the cell. Thus since the liquid crystal lens 6 is allowed to have the distribution of refractive index and the distribution can be made variable as necessary, the distortion aberration, the curvature of an image surface and a surface tilt are corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of an optical correction section in an optical scanning device.

[Prior art] Conventional technology uses nematic liquid crystals for eyeglasses, etc. as described in document ED79-30... Susumu Sahara "Variable focal length nematic liquid crystal lens cell", and as liquid crystals, displays, shutters, etc. It was applied to light polarizing elements, etc.

[Problems to be Solved by the Invention] In the prior art described above, the refractive index of a liquid crystal lens changes uniformly, and the refractive index does not become non-uniform. Furthermore, conventionally, there has been no example of using a liquid crystal lens for optical correction of optical scanning.

An object of the present invention is to utilize a liquid crystal lens in an effective manner for optical correction of optical scanning. Another advantage is to use a liquid crystal lens with a non-uniform refractive index.

[Means for Solving the Problem] In order to achieve the above object, a liquid crystal lens is provided with a refractive index distribution, and the refractive index distribution is made variable as necessary. It is something that has the means.

[Effect]

By providing a liquid crystal lens with a refractive index distribution and making the distribution variable as necessary, distortion aberration and curvature of field can be corrected.

【Example〕

In conventional optical scanning devices, optical correction is usually performed using an optical lens. At this time, optical glass is generally used as the optical lens, and recently, plastic has come to be used because of its low cost and ease of manufacture. In the case of this type of lens, due to the uniformity of the refractive index distribution within the lens, even if only geometric correction is considered, in order to correct field curvature and distortion aberration, in the main scanning direction, In addition to three curved surfaces between the scanning mirror 3 and the photosensitive member 5, one curved surface is provided between the laser emitting unit 1 and the scanning mirror 3 in the sub-scanning direction, and one curved surface is provided between the scanning mirror 3 and the scanning mirror 3 in the sub-scanning direction. Two to four curved surfaces were required between the photosensitive members 5. This is shown in FIG. 2 as a cylinder lens 9. f-
The above curved surface is arranged on the 110°f-Q lens 211 of the Q lens.

The present invention is characterized by using an optical correction lens having liquid crystal properties for optical scanning, thereby reducing the number of required curvature surfaces as described above, and adding new load value by utilizing low cost, compactness, and liquid crystal properties. It is. In the following detailed examples, ferroelectric liquid crystals and polymer liquid crystals will be particularly described, but other liquid crystals may also be used.

First, in the case of using ferroelectric liquid crystal, in order to use it in a liquid crystal state, it is necessary to seal the ferroelectric liquid crystal into the cell. Figure 3 is an example of this, (a)
is the case when two parallel liquid crystal cells 13 are used,
(b) is the case where the liquid crystal cell is bent and used. The liquid crystal side cell 15 does not need a normal liquid crystal thickness of about 5 μm, but in order to improve the optical correction characteristics, it is necessary to increase the liquid crystal thickness, and in this case, it is necessary.
This is no longer the case due to improvements in liquid crystal materials. Here, the third
With the configuration shown in the figure, it is difficult to significantly improve the characteristics;
As shown in the figure, bend liquid crystal cell 14 on only one side of the cell.
or insert a curvature cell 16 on one side as shown in Figure 5.
A large correction effect can be obtained by adding .

In actual use for correction, as shown in FIG. 6, a transparent electrode 17 is attached inside the liquid crystal cell, and a voltage is applied to it from the voltage generating section 7. The idea is to change the refractive index of the liquid crystal cell by changing the applied voltage.

In FIG. 7, a ferroelectric liquid crystal cell 6 was used. - An example of the configuration of an optical scanning device. This has a ferroelectric liquid crystal cell 6 arranged between a scanning mirror 3 and a laser control section 1. It attempts to correct part or all of the curvature of field by changing the focal length depending on the scanning position, and attempts to compensate for the rest with another optical system.

FIG. 8 shows an example of the configuration of the voltage generating section 7. Synchronous sensor 4
In response to a signal from the control section 19, the control section 19 reads necessary output information from the storage section 20, and outputs a necessary voltage from the output section 18.

FIG. 1 is an example of an optical installation configuration in which a ferroelectric liquid crystal cell is disposed between a scanning mirror and a photoreceptor.

This liquid crystal cell 6 can be used for various purposes. A detailed example will be explained below.

First of all, this is an example of correcting field curvature or distortion aberration. For example, by using the configuration shown in FIG. 6 and varying the applied voltage according to the scanning position, Part or all can be corrected. Also, the 9th
As shown in the figure, by using the curvature cell, part or all of the field curvature or distortion can be corrected without changing the applied voltage. At this time, the thermal applied voltage may be varied.

Next, as an example of performing surface tilt correction, for example, as shown in FIG. 10, the transparent electrodes 17 on one side of the opposing liquid crystal cells 13 are grounded, and the opposing electrodes are connected to the ground as shown in the figure.
It has a configuration in which an ND electrode 22 is placed inside and applied voltage electrodes 21 are placed at both ends, to which a voltage is applied. Thereby, as shown in FIG. 11, it becomes possible to change the refractive index n with respect to the applied voltage Vcc with respect to the y-axis. In this configuration, it is also possible to change the electrodes on both sides to the three electrode configuration described above.

FIG. 12 shows an example of a configuration for correcting part or all of field curvature and distortion in addition to the above-mentioned surface tilt correction. In FIG. 10, a voltage is also applied to the GND electrode 22. By making this voltage variable, the refractive index distribution is changed even within the zx plane, and part or all of field curvature and distortion can be corrected.

Further, in the above embodiment, a method may be considered in which the liquid crystal cell 13 is replaced by a bend liquid crystal cell 141 and a curvature cell 16 to correct part or all of the field curvature and distortion using a constant voltage.

Another method is to consider the resistivity distribution of the applied voltage electrode 21 in FIG. 10.

By changing the low resistivity, the refractive index distribution does not change even at constant voltage.

Figure 13 shows the general form of a ferroelectric liquid crystal. In actual use, a material whose refractive index changes greatly depending on the electric potential is used. The above objective can also be achieved by substituting a CN group or the like in the structure shown in FIG. For example, the configuration shown in FIG. 14 can be considered as an example.

The above explanation is based on the case where a ferroelectric liquid crystal is used, but the case where a polymer liquid crystal is used will be described below. A feature of polymer liquid crystals is that they do not have the same high-speed response as ferroelectric liquid crystals, so they are not suitable for real-time control. , in that the state can be fixed. In this state, a thermal cell or the like is unnecessary. In other words,
If it can have an ideal curvature and refractive index distribution in that state, it can be handled in the same way as a general lens, and moreover, it can have the effects of multiple lenses.

FIG. 15 shows an example of the arrangement of the polymer liquid crystal lens 24. Generally, it is placed between the scanning mirror 3 and the photosensitive member 5 and used in the aforementioned polymer state.

FIG. 16 shows an example of the shape. Like a general lens, it has a curved shape and has a three-dimensional refractive index distribution inside. The thermal shape does not need to have a curved surface, and the refractive index distribution may be arbitrary.

The unpaid arrangement may be between the laser 1 and the scanning mirror 3, or even on the surface of the scanning mirror 3, and the position does not matter. This is common to all types of lenses.

It is also conceivable to use the polymer liquid crystal not in a polymer state but in a fluid monomer state. In this case, you need to put it in a cell. FIG. 17 shows an example. The aim is to obtain a refractive index distribution by applying a fixed voltage to a 100% polymer liquid crystal. At this time, the thermal voltage may be made variable. For optical correction, cell 16or13
Since various shapes can be considered, an optical correction effect on the cell side can also be expected. In Figure 18, 1000 polymer liquid crystal 2
In order to improve the orientation of the liquid crystal 9, it is conceivable to provide an alignment film between the transparent electrode 7 and the monomer polymer liquid crystal 7. This also applies to cases where other liquid crystals are used.

FIG. 24 is an example of the applied voltage method. Similar to the explanation in FIG. 12, a three-dimensional refractive index distribution is provided.

It is also conceivable to devise various cell shapes or to distribute the low resistivity of the transparent electrode 17. Any means may be added as long as it contributes to the refractive index distribution. This is common to all other cases.

In addition to the above-mentioned electric field, polymer liquid crystals have the property of being oriented in response to a magnetic field. FIG. 18 is an example of this, and in this configuration, the transparent electrode 17 is unnecessary. The monomer polymer liquid crystal is three-dimensionally aligned by the magnetic field generating means 30.

As for the magnetic field generating means in this case, as an example, it is possible to generate a magnetic field in the y-axis direction simply by using the configuration shown in FIG. 26. This causes the current to flow from the output control 42 to the coil 4.
3 to create a magnetic field. FIG. 27 shows an example of an attempt to control the above to a higher degree. (1) is y
It provides a magnetic field not only in the direction but also in the X direction.

In addition, (2) is used to scan the small coil 43 as necessary to partially control the magnetic field more precisely.

FIG. 28 is also an example of a magnetic field generator. A magnetic field is generated by an electromagnet. In the illustrated example, magnetic fields are generated in the X direction and the X direction. At this time, the magnetic field is controlled by controlling the current flowing through each coil 43. Also, at this time,
As an example of more finely controlling the magnetic field, as shown in FIG. 29, a position displacement section 46 is provided to control the magnetic field by moving the position back and forth or by changing the angle.

Furthermore, it is conceivable to change the shape of the tip of the magnetic field generating section 4s as necessary. That is, as shown in Figure 29, (2
) In the state (1), the magnetic field at the center can be made stronger, and in the state (3), the magnetic field can be made weaker. At this time, you may consider adjusting the tip of the tip if necessary.
It is also possible to provide a means for controlling the shape of the tip.

The methods described above generate magnetic fields in the X direction and the

A possible method is to generate magnetic fields in both the X and Z directions.

Next is a method for adjusting the refractive index distribution, and an example thereof is shown in FIG. First, as an example of adjusting the liquid crystal 29 in the monomer polymer liquid crystal lens 1200, for example, a sensor is placed at a portion corresponding to the photosensitive member 5 and a laser beam is actually irradiated. This light is received by the sensor section 36. The light reception information includes position information, spot diameter, etc. The information processing unit 35 is the part that receives this information and adjusts the values so that they are optimal for the scanning line. The information processing section 35 sends the processed information to the electric field/magnetic field generation section.

In the electric field/magnetic field generation section, the control section 33 stores information obtained from the information processing section 35 in the storage section 34 and controls the output of the output section 32 . The sensor in this case needs to be able to obtain information such as position, spot diameter, spot shape, etc., and a small COD or the like may be used. FIG. 25 shows a spot image. Ideally, it is necessary to scan the scanning line 39 in an ideal shape (a circle is shown as an example in FIG. 25) and at an ideal position. In reality, for example, the position, size, and shape of the received light spot image 41 are deformed with respect to the ideal spot image 40.

Next is a method of adjusting the input values to make them optimal. As an example, as shown in FIG. 19, the information processing section 35 is provided with ideal scan information and allowable range information.

By providing refractive index change information due to magnetic field changes and simulation functions for gradient index lenses, for example, scanning line information can be taken in and adjusted to keep it within an acceptable range and to optimize it. The adjusted high force information is stored in the storage unit 34.

In the above case, manufacturing errors are also taken into consideration, and the polymer liquid crystal lens 24
has been adjusted, but the scanning mirror is not taken into account. In general, a multifaceted scanning mirror has errors from the center to each scanning surface and tilt errors for each scanning surface. In other words, the scanning mirror 3 and polymer liquid crystal lens 2 that are actually used
There is no problem when adjusting with the combination of 4, but if you want to fix the scanning mirror and replace only the polymer liquid crystal lens to speed up the adjustment, consider the manufacturing error tolerance of the scanning mirror. It is necessary to make adjustments. FIG. 30 is an example of a scanning mirror configuration used in that case. A position/orientation adjustment section 49 made of, for example, a piezoelectric element is provided between the scanning mirror member 48 and the optical scanning section 50, and a data group of the worst value of the manufacturing error of the scanning mirror 3 is taken in, and an adjustment value that satisfies all of them is determined. It is meant to guide you. Although the above description has been made regarding the scanning mirror 3, the same applies to the laser 1 and other members, and it is possible to apply the above-mentioned concept.

The above is a case where a monomer polymer liquid crystal is used. Next is a method for preparing a polymer liquid crystal, and FIG. 20 shows an example thereof. The method for adjusting the polymer polymer liquid crystal lens 25 is that, as a first step, after adjusting the monomer polymer liquid crystal 29 shown in FIG.
7, and then the cells are removed and used simply as a lens. At this time, you may use it with the unpaid cell attached. If the cell is used after being removed from the cell, the optical effect of the cell must be taken into consideration during the adjustment. In addition, when photopolymerized, whiskers occur like general plastic lenses, so this must be taken into consideration in advance. As an example of achieving the above objective, it is conceivable to provide the information processing section 35 with a simulation capability or to have an optimal line output example obtained in advance by simulation.

Furthermore, the most important feature of the adjustment of the polymer liquid crystal is that adjustment can be performed for each optical path. If you try to adjust the entire system, it will be difficult to do so even if it is within the tolerance, but if you adjust each optical path, you can achieve extremely high precision adjustment. FIG. 31 shows an example. As for the adjustment procedure, firstly, for each optical path, the issuance information control unit 5
2 emits a laser l, which is received by a sensor 36, and an information processing unit 35 adjusts the obtained information so that it is optimal. Thereafter, the issuance information control section causes the polymerization means generation section 35 to emit a light beam for photopolymerization, and photopolymerizes the portion set to the correct value. Repeat this process below. After adjusting the portion affected by surface tilt, the entire remaining portion is photopolymerized. With the above, extremely accurate adjustment is possible for each optical path.

Alternatively, a method of adjusting the polymer liquid crystal lens 25 as it is may be considered. In order to change the refractive index distribution, the monomer polymer liquid crystal must be in the 26 state, but as shown in FIG. 21, a large amount of energy is required to change from the polymer state to the monomer state. FIG. 22 shows an example of the configuration. The energy supply section changes the required portion from the polymer state to the momer state, and after the adjustment is completed, the polymerization means generation section photopolymerizes it again. At this time, a method of adjusting each optical path may be considered as described above.

Further, as a polymer liquid crystal material, a larger length of 6 m is advantageous. Typical materials are shown in Figure 23. Furthermore, instead of CN=N, it is also possible to use CH=CH, N=N, COO, etc.

When constructing an optical scanning device using the method described above, assembly and adjustment can be made extremely simple.

A case where a ferroelectric liquid crystal cell 6 is used as an example will be explained using FIG. 32. First, the storage section 20 of the voltage generating section 7 of the ferroelectric liquid crystal cell 6 is adjusted independently by the method described above. Subsequently, as shown in FIG. 32, an optical scanning device is assembled, but at this time, installation errors inevitably occur. At this time, a method of adjusting the mounting position may be considered, but it may be possible to deal with this by adjusting the refractive index control method of the ferroelectric liquid crystal cell 6 by providing one or more adjustment sensors 53. Specifically, information on the position and spot diameter obtained from the adjustment sensor 53 is input to the information processing section 35, and the information obtained here is fed back to the control method of the voltage generation section 7 based on the base material.

By adopting such a configuration, all electrical adjustments can be made automatically without having to adjust the mounting position.

Further, FIG. 33 shows an example of a configuration in which the mounting position can be adjusted without changing the refractive index distribution.

Based on the information obtained from the adjustment sensor 53, the information processing section 35
transmits the adjustment amount to the position adjustment control section 53, and the position adjustment control section 53 uses each position adjustment section 55 to perform final position adjustment. As the position adjustment section, for example, a piezoelectric element or the like can be considered. Automatic adjustment is also possible with this adjustment method. Further, this adjustment method does not require any type of lens, and any element forming the optical system may be adjusted. Further, it may be used in combination with the above-mentioned refractive index control method adjustment.

As described above, by using this method, the automation of manufacturing will be significantly improved, and it will be extremely effective in reducing labor costs, which is currently a major problem.

As an example of an application of the present invention, a laser beam printer can be considered as an optical scanning device. It can also be applied directly to scanners. It is also possible to apply liquid crystal lenses to CDs, cameras, optical measurement devices, and the like. Also, regarding motor control, it can be applied to electric motors, etc.

[Effects of the Invention] According to the present invention, since the liquid crystal lens can have a refractive index distribution and can be made variable as necessary, distortion aberration and curvature of field 9 can be corrected.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of an optical system, Figure 2 is a diagram showing an example of a conventional optical system, Figures 3, 4, and 5 are diagrams showing a liquid crystal cell, and Figure 6 is a diagram showing a liquid crystal drive. 7 is a block diagram of an optical scanning device using a liquid crystal lens, FIG. 8 is a block diagram of a voltage generating section, FIG. 9 is a diagram showing a liquid crystal drive, and FIG. 10 is a diagram showing a liquid crystal drive. , Fig. 11 is a diagram showing refractive index changes with respect to applied voltage, Fig. 12 is a diagram showing liquid crystal driving, Fig. 13, Fig. 1
Figure 4 shows the composition of ferroelectric liquid crystal, Figure 15 shows the configuration of an optical scanning device using a polymer liquid crystal lens, Figure 16 shows a polymer liquid crystal lens, and Figure 17 shows the monomer height. Figure 18 is a diagram showing the molecular liquid crystal drive, Figure 18 is a block diagram of magnetic field alignment control, Figures 19 and 20 are diagrams showing polymer liquid crystal lens adjustment, Figure 21 is a diagram showing energy transition of polymer liquid crystal, Figure 21 is a diagram showing the energy transition of polymer liquid crystal, Figure 22 is a diagram showing polymer liquid crystal molecular liquid crystal lens adjustment;
FIG. 23 is a polymer configuration diagram, FIG. 24 is a diagram showing voltage application to a liquid crystal lens cell, and FIG. 25 is a diagram showing a spot image.
Figures 26 and 27 are diagrams showing the application of a magnetic field to the liquid crystal lens; Figures 28, 29, and 30 are configuration diagrams of the scanning mirror for adjustment; Figure 31 is a diagram of the configuration of the adjustment optical system; Figure 32 is a configuration diagram of automatic adjustment, Figure 33 is a configuration diagram of automatic adjustment, and Figure 34 is a configuration diagram of automatic adjustment.
The figure shows a magnetic field generator. 6... Ferroelectric liquid crystal cell, 7... Voltage generating section, 17
・Magnetic field generating means, 24...Polymer liquid crystal lens, 2S・
...Polymer polymer liquid crystal lens, 27... Monomer polymer liquid crystal, 31... Magnetic field/electric field generating section, 37... Polymerization means generating section, 53... Adjustment sensor, 54... Position adjustment control section.
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Claims (1)

[Claims] 1. An optical scanning device characterized by performing optical correction using a liquid crystal device. 2. An optical scanning device according to claim 1, characterized in that a cell encapsulation device is used. 3. The optical scanning device according to claim 1, wherein optical correction is performed by a polymer liquid crystal device. 4. The optical scanning device according to claim 3, wherein the refractive index is optimally set for each scanning optical path. 5. The optical scanning device according to claim 1, wherein optical correction setting or installation error correction is automatically performed.