JPH0789129A - Optical system using microlens - Google Patents

Abstract

PURPOSE:To prevent the positional shift of the condensing points on a photosensitive drum and to enhance resolving power by parallelly arranging a microlens array in the vicinity of the photosensitive drum so that the arranging direction of microlenses is made to coincide with a luminous flux arranging direction and refracting incident luminous flux in the optical axis direction of the microlenses. CONSTITUTION:Linearly continued condensing points are formed on an image forming surface by many luminous fluxes radially incident on the image forming surface from light sources 4, 7 through condensing lenses 1,8. In this optical system, a microlens array 10 wherein many microlenses 9 are linearly and continuously formed is parallelly arranged in the vicinity of the image forming surface so that the arranging direction of the microlenses 9 is allowed to coincide with the arranging direction of luminous fluxes 2 and the respective luminous fluxes 2 incident through the condensing lenses 1,8 are refracted in the optical axis direction of the microlenses 9. As a result, the positional shift of the condensing points on the photosensitive drum can be prevented and resolving power can be enhanced and a dimensional common difference is taken wide to achieve mass production.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system using a microlens array.

[0002]

2. Description of the Related Art A photosensitive optical system incorporated in a laser printer, an LED printer, a liquid crystal printer or the like forms a linearly continuous condensing point on an image forming plane. For example, in FIG.
As shown in FIG. 1 and FIG. 12, a large number of light fluxes 2 are radially incident on the photosensitive drum 3 by the condenser lenses 1 and 8, and one scanning line is exposed by the concatenation of the condensing points. This exposure is performed for each rotation of the photosensitive drum 3 by one pitch, and
When the exposure of the sheet is completed, the toner is adsorbed to the latent image formed on the photosensitive drum, the toner is further transferred to the paper, and the toner is melted and fixed by heat to perform printing.

FIG. 11 shows a photo-sensing optical system of a laser printer. A laser light 2 emitted from a laser light source 4 such as a laser diode is focused by a collimator lens 5 into parallel light of a few mmφ, and a polygon mirror. And enters the optical deflector 6. The light deflector 6 radially deflects the laser light by rotation, and the deflected laser light is
The linearity is corrected by the condenser lens 1, and the light is condensed and imaged on the photosensitive drum 3.

FIG. 12 shows a photosensitive optical system of an LED printer or a liquid crystal printer. In the case of an LED printer, an LED array 7 is used as a light source, and a condenser lens 8 is provided for each LED array. The LED array 7 is formed by arranging and forming a plurality of LED elements (light emitting diodes) on a substrate in a straight line at a fine pitch, and aligns the LED elements in the scanning direction (axial direction of the photosensitive drum 3). Then, they are linearly arranged with a predetermined interval. The condenser lens 8 forms an inverted variable magnification real image of each LED array 7 on the photosensitive drum in a connected state. Since each image formation is inverted, the print data is divided for each part of each LED array 7 and inverted to cause the LED array 7 to emit light. As a result, the inverted variable-magnification real image on the image plane is oriented normally.

In the liquid crystal printer, a liquid crystal plate in which liquid crystal cells are linearly formed is arranged in front of a light source to form an arrayed light source, which is arranged in place of the LED array 7, and the other parts are arranged. It is similar to the LED printer.

While the optical system of the laser printer shown in FIG. 11 radiates the laser light focused into a beam by reflection at the optical deflector 6, the optical system of the LED printer or liquid crystal printer shown in FIG. Is different in that an inverted variable magnification real image of the array light source 7 is formed on the photosensitive drum 3 by the condenser lens 8. However, in any of the printers, the incident shape of the light flux 2 on the photosensitive drum 3 is common in that the light fluxes are individually converged by the condenser lenses 1 and 8 and are individually incident radially.

[0007]

In the printer to which the above-mentioned photosensitive optical system is assembled, the pitch of the condensing points formed on the photosensitive drum 3 is as small as 63.5 μm in a 400 DPI printer. Therefore, in order to maintain the positional accuracy and resolution of the condensing point imaged on the photosensitive drum 3 at required values, a very small tolerance is required for each component and assembly dimension.

A particular problem with the above-mentioned allowable tolerance is that the image forming surface of the photosensitive drum 3 and the position of the focal point formed by the optical system are displaced in the optical axis direction. This displacement is
This occurs due to expansion and contraction of the condenser lenses 1 and 8 with respect to ambient temperature changes, or variations in mounting dimensions when assembling the optical system to the printer housing equipped with the photosensitive drum 3. However, in mass production, variations in mounting dimensions have an effect. Is the largest.

When the position shift occurs in the optical axis direction as described above, the manner in which the focal point shifts in the scanning direction (the direction orthogonal to the optical axis) and the resolution deteriorates will be specifically described.

FIG. 13 is an enlarged view of the image forming surface portion of the photosensitive drum 3 in the optical system of the laser printer of FIG. 11, in which the laser light source 4, the condenser lens 1 and the photosensitive drum 3 are as designed. When the arrangement is maintained, as shown by the solid line, the respective light fluxes 2 are individually focused on the regular position on the photosensitive drum. However, as indicated by the chain double-dashed line, when the photosensitive drum 3 moves away from the condensing lens, each condensing point deviates from the position where the degree of convergence is maximum, the resolution is degraded, and the formation of each luminous flux having a different incident angle is formed. The arrangement pitch of the condensing points becomes uneven and the linearity is impaired. The deviation of the condensing point in the scanning direction and the deterioration of the resolution are greater due to the peripheral luminous flux having a large incident angle with respect to the normal direction.

The deviation of the condensing point in the scanning direction and the deterioration of the resolution similarly occur in the optical system of the optical system of the LED (liquid crystal) printer shown in FIG. However, in the optical system of the LED (liquid crystal) printer shown in FIG. 12, a linearly arranged LED array 7 (liquid crystal type light emitter) is used as a light source, and a light collecting unit provided for each LED array (liquid crystal light emitter). The lens 8 forms a constant-magnification variable-magnification image of each LED array (liquid crystal light-emitting device) on the photosensitive drum so that adjacent ones are continuous, so that there is no positional deviation in the scanning direction of the condensing point. As shown in FIG. 14, it also appears as an overlap (a) between the ends of the constant-magnification real image or an opening (b) between the ends.

As described above, the positional deviation of the condensing point of the incident light beam focused in the form of a beam and the deterioration of the resolution have been described. However, in the above conventional optical systems, the focal lengths of the condensing lenses 1 and 8 are long, There is also a problem that it is difficult to make the optical system compact because it is necessary to secure an optical path length corresponding to this.

Therefore, the present invention provides an optical system capable of reducing the positional deviation of the condensing point in the scanning direction and the deterioration of the resolution with respect to the positional deviation of the photosensitive drum 3 and the condensing point in the optical axis direction, thereby improving the component accuracy. It is also an object of the present invention to provide a structure that relaxes the tolerance condition for the assembly size and to provide an optical system that can be made compact.

[0014]

The present invention utilizes the light converging action of a microlens array. The inventions of claims 1 to 5 solve the first object of the problem of the positional deviation of the condensing point of the incident light beam focused into a beam and the deterioration of the resolution. Specifically, the inventions of claims 1 to 5 are used as a photosensitive optical system for a laser printer, an LED printer, a liquid crystal printer, or the like. The inventions of claims 6 to 8 are the second
The purpose of this is to make the optical system compact, and it is used in photo-sensing optical systems, photo couplers, document reading devices, and the like.

A first aspect of the present invention is a basic configuration of means for achieving the first object. This is because, as shown in FIG. 1, a plurality of light fluxes 2 radially incident from the light sources 4 and 7 through the condenser lenses 1 and 8 on the image forming surface form a condensing point linearly connected on the image forming surface. In the optical system to be formed, a microlens array 10 in which a plurality of microlenses 9 are linearly formed continuously
By arranging the microlenses 9 in parallel in the vicinity of the image plane with the direction of arrangement of the microlenses 9 aligned with the direction of arrangement of the light fluxes, and directing each light flux incident through the condenser lens in the direction of the optical axis of each microlens 9 It has a function of refracting, and each microlens 9 may have any type of power from − to 0 to +.

According to a second aspect of the present invention, the condition of improving the resolution is added to the first aspect. That is, as shown in FIG. 4, each lens 9 of the microlens array 10 is a convex lens of + power, and the lens pitch of the microlens array 10 is set to the microlens array 10.
The microlens array 10 is positioned in the scanning direction so as to match the pitch of the light beam 2 incident on the light beam 2 with each microlens 9 in a one-to-one correspondence.
Each incident light beam is refracted in the optical axis direction and, at the same time, converges on the image plane.

Since the structure of claim 3 improves the resolution in a pseudo manner, in the structure of claim 1, the lens pitch of the microlens array 10 is set to the incident surface of the microlens array 10 as shown in FIG. It is smaller than the pitch of the incident light beam.

In the structure of claim 4, since the converging action of the microlens 9 in the structure of claim 2 is utilized for eliminating the chromatic aberration, as shown in FIG. 7, a set of light emitting elements of RGB three colors is linearly formed as a light source. Use the ones lined up in
The light flux for one dot formed by the set of light emitting elements of three colors corresponds to one microlens 9.

According to a fifth aspect of the present invention, an LE is used in which the optical system according to the first to fourth aspects is used by arranging a plurality of arrayed light sources.
It is used in a D printer or a liquid crystal printer, and is used to eliminate the overlap and separation of the end portions of each variable-magnification real image. That is, as the light source, a plurality of array light sources 7 in which a large number of light emitting elements are linearly formed are arranged linearly at predetermined intervals, and a condenser lens 8 is provided for each array light source. Each condensing lens is configured so that the inverted variable-magnification real images of the array-shaped light sources are linearly connected in a connected state on the image forming plane.

According to a sixth aspect of the present invention, a photosensitive optical system for a printer is provided in a compact form. As shown in FIG. 8, a plurality of light emitting elements 11 such as LEDs are linearly arranged at a predetermined pitch. A light source 12 is arranged in parallel so as to face an image forming surface which is a photoconductor, and a plurality of microlenses 9 are linearly connected between the light source and the image forming surface at the same pitch as the light emitting element 11 of the light source. The microlens array 10
The optical axis of each microlens 9 is aligned in parallel with the optical axis of the corresponding light emitting element 11, and by the light of each light emitting element 11 converged by the microlens 9, a condensing point linearly connected on the imaging plane. To form.

As shown in FIG. 9, the structure of claim 7 provides a photocoupler having a plurality of light emitting and receiving element pairs, wherein a light source 12 having a plurality of light emitting elements 11 arranged therein and a plurality of microlenses 9 are provided. A microlens array 12 in which the light emitting elements 11 are connected and formed in the same arrangement, and a light receiver 14 in which a plurality of light receiving elements 13 are arranged in the same arrangement as the light emitting elements,
The light-emitting element 11, the microlens 9 and the light-receiving element 13 at the corresponding positions are arranged in parallel so that the optical axes thereof coincide with each other.
By converging the light of No. 1 by the microlens 9 and incident on the light receiving element 13, an independent light emitting / receiving system is formed for each of the light receiving element 11, the microlens 9 and the light receiving element 13 whose optical axes match.

The structure of claim 8 is as shown in FIG.
A compact original reading apparatus is provided, in which a plurality of light receiving elements 13 arranged linearly at a predetermined pitch are arranged in parallel so as to face an object surface to be read, and the light receiving elements 13 are arranged in parallel. And the object plane, a microlens array 10 in which a plurality of microlenses 9 are linearly connected at the same pitch as the light-receiving elements 13 of the light-receiving device 14 is formed, and a light-receiving element 13 corresponding to the optical axis of each microlens 9 is formed. Are arranged in parallel with each other to match the optical axis of
Light emitted from the object surface at a position where the optical axis is extended is condensed and made incident by the microlens 9.

[0023]

According to the first aspect of the present invention, each microlens 9 of the microlens array 10 makes the incident light beam 2
Refract in the respective optical axis directions. Since the microlenses 9 are arranged at an equal pitch, the position of the condensing point in the scanning direction is displaced due to the displacement of the photosensitive drum 3 in the optical axis direction with respect to the incident light beam that is inclined. To correct.

According to the second aspect of the invention, each of the microlenses 9 using a convex lens corresponds to one incident light beam and converges in an independent state. Therefore, the converging point can be reduced to improve the resolution. This convergence action is
Since one light beam is moved in the optical axis direction, the action of correcting the positional deviation of the condensing point in the scanning direction can be made higher than that of the first aspect.

According to the third aspect of the invention, when one light beam having one dot of information is incident on the plurality of microlenses 9, each microlens 9 forms a plurality of condensing points, and the pseudolenses are formed in a pseudo manner. Will improve the resolution. Eg 4
In an optical system designed with 00 DPI, if the pitch of the microlenses 9 is ½, a converging point twice as large as the incident light beam is formed, which is a pseudo 800 DPI.

The invention of claim 4 improves the chromatic aberration by utilizing the converging action of the microlens 9 of the invention of claim 2. That is, in a color printer in which light of light emitting elements of three colors RGB is input for each dot of printing, the position of the condensing point of each color is shifted in the condensing lens due to the difference in wavelength of each color. This is converged to one point by the microlens 9 to prevent color shift.

According to a fifth aspect of the present invention, the invention described in the first to fourth aspects is applied to an LED printer or a liquid crystal printer using the array light source 7, and each operation of the first to fourth aspects is basically Naturally as an action. The feature of the invention of claim 5 is that the function of correcting the positional deviation of the condensing points in the scanning direction by the microlens array 10 prevents the overlapping of the inverted variable magnification real images by the pair of the arrayed light source 7 and the condensing lens 8. Is also demonstrated.

In the sixth to eighth aspects of the present invention, while the condensing lenses 1 and 8 and the microlens array 10 are used in combination with the first to fifth aspects of the invention, the optical system is composed of only the microlens array 10. However, by making the optical path length extremely short,
Enables compactness.

According to the sixth aspect of the invention, as shown in FIG. 8, the light of the light emitting element 11 is directly converged on the image plane by the microlens 9. The light emitting element 11 and the microlens 9 have a one-to-one relationship
In this case, one light emitting element 11 forms one condensing point on the image plane. Light emitting element 11 and microlens 9
Since the pair is arranged linearly in parallel with the image forming plane, the condensing points are linearly connected, whereby one scanning line of light is sensed in the photosensing optical system for the printer. Since a microlens array in which a plurality of microlenses 9 are integrally formed is used, high assembly accuracy can be easily obtained.

The invention of claim 7 relates to the relationship between the light emitting element 11 and the microlens 9 as shown in FIG.
The present invention differs from the invention of claim 6 in that it has the same structure as the above, and instead of using an image-forming surface as a photoconductor, a light-receiving device 14 including a plurality of light-receiving elements 13 whose optical axes coincide with each other is arranged. The present invention provides a photocoupler having a plurality of light emitting / receiving element pairs as a single component. The light converging action of the microlens 9 allows a plurality of light emitting elements 11 and a plurality of light receiving elements 13 arranged to face each other to be adjacent to each other. They are optically coupled so that they do not interfere with each other.

The invention of claim 8 has a structure in which an image of an opposite point on the document surface is directly formed by the microlens array 10 on the light receiving elements 13 linearly arranged as shown in FIG. Is provided in a compact structure.

[0032]

1 to 7 show an optical system in which a plurality of light beams radially incident on an image forming surface form a light collecting point linearly continuous on the image forming surface in a scanning direction of the light collecting point. An example of the structure that can reduce the positional deviation and the deterioration of the resolution is shown, and each example will be described below in order.

FIG. 1 is a diagram showing the basic structure in which the light fluxes incident from the condenser lenses 1 and 8 are microlens array 10.
Through, the state of forming an image on the photosensitive drum 3 is shown.

The microlens array 10 is formed by continuously forming the microlenses 9 in a straight line by resin molding or the like, and is integrally formed on a cover glass facing the photosensitive drum 3, for example. The type of microlens 9 is not specified. For example, in addition to the plano-convex lens shown in FIG.
Meniscus lens (a) as shown in FIG. 2, biconvex lens
(b), can be used, and the lens power is --0 to +
All up to are included. The planar shape of the microlens 9 is generally circular as shown in FIG. 2 (c), but if the microlenses 9 are brought close to each other without changing the lens diameter R and the overlapping portions are aligned to the higher side, It becomes an oval shape as shown in (d). The arrangement pitch P of the microlenses 9 basically corresponds to the pitch of the light flux incident on the microlens array 10 in a one-to-one correspondence. For example, when the resolution of the printer is 400 DPI, the pitch of the microlenses 9 is 63.5 μm.

Condensing lens 1 and L for laser printer
The condensing lens 8 for an ED (liquid crystal) printer can be composed of a combination lens, but if these are made into a single lens using an aspherical lens and manufactured by resin molding, optical performance such as aberration is secured. However, the cost can be reduced.

The basic configuration shown in FIG. 1 has the basic effect that the deviation of the focal point in the scanning direction can be corrected by incorporating the microlens array 10 (corresponding to claim 1).
However, other effects (corresponding to claims 2 to 5) can be obtained by changing the combination of the selection and arrangement of the microlens array 10 and the type of light source.

FIG. 3 shows the effect of correcting the deviation of the focal point in the scanning direction.
Will be described. FIG. 3 is an enlarged view showing a state of image formation at an end portion of adjacent inverted variable magnification real images in an LED (liquid crystal) printer using an LED array (liquid crystal type light emitter) as the array light source shown in FIG. Then, this optical system is displaced in the direction in which the photosensitive drum 3 is separated from the optical system due to the displacement when incorporated in the printer housing.

The two light beams A and B forming the condensing points at the adjacent ends of the inverted variable-magnification real image are incident with an inclination with respect to the optical axis while being converged by the two adjoining condensing lenses. If the microlens array 10 is not provided, as shown by the chain double-dashed line, the condensing points overlap. However, when the microlens array 10 is provided, the incident light beams A and B are refracted in the optical axis direction and the inclination is reduced. Therefore, as shown by the solid line, the positional deviation of the two converging points in the scanning direction is corrected. Separate and image as independent points.

The effect of correcting the positional deviation will be further described. Consider a case where the incident light flux A is further incident as the shifted incident light flux C so as to increase the overlapping amount of the two condensing points. In this case, even if the shift amount before entering the microlens array 10 is α, the shift amount of the image plane is as small as β.

The effect of correcting the positional deviation of the focal point by incorporating the microlens array 10 is LED (liquid crystal).
In addition to the printer, it can be similarly applied to a laser printer. This correction effect is achieved by refracting the light beams that are obliquely incident in the optical axis direction by the microlenses 9 and suppressing the deviation when each light beam travels from the microlenses 9 to the photosensitive drum 3. Therefore, when a plurality of light fluxes are successively incident on the microlens array 10, it is preferable that the light fluxes be linearly maintained as linearly as possible. The main problem to be solved by the present invention is the variation in the assembling dimensions when the optical system is incorporated into the printer housing. Therefore, by incorporating the microlens array 10 into the optical system, the microlens array 10 is integrated. A practical manufacturing method is to maintain the linearity of the incident light flux so that the variation in the assembling dimension appears as the variation in the distance L between the microlens 9 and the photosensitive drum. This is because the effect of preventing the displacement of the microlens array 10 is high with respect to this change in the distance L. As far as the function of correcting the positional deviation of the condensing point is concerned, the lens power of the microlens 9 may be any of + to 0 to-, as long as it has a refracting function in the optical axis direction.

Next, a configuration for improving the resolution at the same time as the correction of the positional deviation which is the content of claim 2 will be described. The above-described optical system of FIG. 3 receives one light flux by the two microlenses half by half, so that the focal point for one light flux is a combination of the light fluxes converged by each lens. Even though a convex lens having a peak and a lens power of + is used as the microlens 9, the converging action of the light flux is not clearly shown.

Therefore, as shown in FIG. 4 or 5, a convex lens having a lens power of + is used as the microlens 9, and at the same time, one incident light beam is incident on only one microlens 9. The optical system is assembled by matching the pitch of the light beams incident on the lens array 10 with the formation pitch of the microlenses 9 and positioning the microlens array 10 in the scanning direction.

FIG. 4 shows a normal case, and FIG. 5 shows a case where a diffused light flux is incident. In this way, the converging action of the microlens 9 is clearly shown, and the resolution can be improved. This improvement in resolution means reducing the focal point and eliminating so-called blurring. Further, when the light flux is converged in this way, the refracting power of the incident light flux in the optical axis direction becomes stronger, so that the effect of suppressing the positional deviation of the focal point described with reference to FIG. 3 is further enhanced.

This converging action becomes greater as the lens power of the microlens 9 increases to +, for example, as shown in FIG. 2B showing a biconvex lens. However, since the size of the required condensing point is naturally determined by the printer, the lens power is determined so as to obtain an appropriate degree of convergence.

Next, a structure for improving the resolution in a pseudo manner, which is the content of claim 3, will be described. This is to make the pitch of the microlenses 9 smaller than the pitch of the light beams 2 incident on the microlens array 10, as shown in FIG. FIG. 6 shows a case where the pitch of the microlenses 9 is set to ½ of the pitch of the light flux incident on the microlens array 10 in the optical system designed at 200 DPI. In this case, for one incident light flux, 2
Since the two microlenses 9 individually form a condensing point, the pseudo resolution is 400 DPI.

The ratio of each pitch is not limited to an integer, but is 1
In order to form a light-converging point of a fixed integer multiple with one light beam having dot information, it is necessary to set the ratio of each pitch to an integer and at the same time position the microlens array 10 in the scanning direction with respect to the incident light beam 2. There is.

Next, a structure for obtaining the effect of correcting chromatic aberration, which is the content of claim 4, will be described. As shown in FIG. 7, this is the structure of the invention of claim 2, that is, a convex lens is used for the microlens 9, and at the same time, the pitch of the light flux for one dot incident on the microlens array 10 and the microlens 9 In the configuration in which the formation pitches are matched, the microlens array 10 is positioned in the scanning direction so that the RGB three-color light flux forming one dot enters only one microlens 9. This is a structure implemented in a liquid crystal printer or an LED printer, and an array light source (liquid crystal type light emitter,
In the LED array), three light emitting points corresponding to RGB three colors are formed in a light emitting area corresponding to a one-dot condensing point on the photosensitive drum.

According to this structure, the light fluxes of the three colors emitted from the three light emitting points cause chromatic aberration in the condenser lens 8 and enter the microlens 9 from different directions.
Due to the converging action of the microlenses 9, they overlap each other,
One dot forms an image on the photosensitive drum. This prevents color misregistration.

Next, a structure for preventing overlapping and separation of inverted magnified real images, which is the feature of claim 5, will be described. As described with reference to FIG. 3, this action overlaps when the microlens array 10 is incorporated into an LED printer or a liquid crystal printer that uses a plurality of arrayed light sources 7 side by side and the microlens array 10 is not provided. When the microlens array 10 is incorporated, the two condensing points are functions of forming an image apart from each other, and are obtained as an extension of the function of correcting the deviation of the condensing points of the microlens array 10 in the scanning direction. Therefore, the configuration of claim 5 is the same as that of claim 1.
When the configurations of 4 to 4 are carried out in the LED printer or the liquid crystal printer, they are obtained with the respective actions of claims 1 to 4.

This action works only in the direction of eliminating the overlap. Therefore, by increasing the dimensional tolerance of the optical system in the direction in which the overlapping occurs and decreasing it in the direction in which the opening occurs, the overlapping and the opening shown in FIGS. 13A and 13B are consequently prevented.

8 to 10 show the microlens array 1
0 is used to make the optical system compact, and FIG. 8 shows an embodiment as a photosensitive optical system, FIG. 9 shows an embodiment as a photocoupler, and FIG. 10 and will be described below.

FIG. 8 shows a photosensitive optical system for a printer in which a light source 12 in which a plurality of light emitting elements 11 are linearly arranged is arranged to face a photosensitive drum 3 which is a photosensitive body with a microlens array 12 interposed therebetween. . The light source 12 may be any one capable of arranging the light emitting elements 11 linearly at a predetermined pitch and having a required length (for example, B4 or A4 paper size), and LEDs arranged at this pitch, or a liquid crystal light emitter. Etc. can be used. The microlens array 10 is formed by linearly connecting microlenses 9 (including all of the types illustrated in FIGS. 2 (a) (b) (c) (d)) having a positive lens power by resin molding or the like. For example, it is integrally formed on a cover glass facing the photosensitive drum 3. During assembly, the microlenses 9 are positioned and fixed so that the optical axes of the microlenses 9 coincide with the optical axes of the light emitting elements 11.

For example, if the resolution of the printer is 200 DPI
(0.125 mm pitch) and the pitch of the light emitting element 11 and the microlens 9 is adjusted to this, the distance between the light source 12 and the photoconductor 3 can be T _C of 1 to 5 mm.
It becomes an extremely compact optical system.

Further, in this optical system, the light emitting element is set to RGB3.
If a primary color light emitting element is used, the color printer having the color shift prevention effect described with reference to FIG. 7 can be provided.

FIG. 9 shows a structure in which a plurality of light emitting elements 11 and a plurality of light receiving elements 13 are opposed to each other with the microlens array 10 interposed therebetween, and is used as a photocoupler having a plurality of light emitting and receiving element pairs.

In this structure, the light emitting element 11, the light receiving element 13 and the microlens 9 are arranged in the same array, and the optical axes of the elements at corresponding positions are made coincident with each other to form independent light emitting and receiving systems. This array is not limited to a linear array as long as a pitch is ensured so that optical interference does not occur between adjacent light emitting / receiving systems. The light emitting element 11 may be a controllable light emitting body such as an LED, and the light receiving element 13 may be an arbitrary photoelectric conversion element such as a photodiode. The microlens array 10 is manufactured in the same manner as in FIG. 8 except that the microlenses 9 are arranged as described above.

The feature of this optical system is that a large number of pairs of light emitting / receiving elements can be arranged in parallel without causing optical interference between adjacent optical systems due to the light converging action of the microlenses 9. It is possible to provide an optical connector with a plurality of lines insulated in a space-saving structure.

FIG. 10 shows an optical system for a document reading device in which a light receiver 14 in which a plurality of light receiving elements 13 are linearly arranged is arranged to face the document reading surface with the microlens array 10 interposed therebetween.

Comparing this optical system with the structure of FIG.
A light receiving element (photoelectric conversion element such as a photodiode) 13 is arranged in place of the light emitting element 11, and the photoconductor is changed to the original surface (the paper surface facing through the cover glass or the like).
The dimensional relationship between the microlens array and each part is the same as that described in FIG. 8. For example, when the document reading resolution is 200 DPI (0.125 mm pitch),
Similar to the optical system in FIG. 8, the distance T _C between the light receiver 14 and the document surface can be set to 1 to 5 mm, and an extremely compact document reading device can be provided. Even in this optical system, if the light receiver 14 is capable of color recognition, it can be used as a color image scanner.

[0060]

According to the present invention, by incorporating the microlens array 10 into an optical system used in a printer having a photosensitive drum, it is possible to obtain the effects of preventing positional deviation of the focal point on the photosensitive drum and improving the resolution. Therefore, it is possible to achieve mass production with a large dimensional tolerance.

Further, by constructing the optical system with only the microlens array 10, it is possible to provide an extremely compact photosensitive optical system, a document reading device, and a high-density mounted photocoupler.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of an optical system using a microlens array 10 of the present invention.

FIG. 2 is a diagram showing an example of the shape of a microlens array 10 used in the optical system of FIG. 1, where (a) and (b) are sectional views,
(c) and (d) are plan views.

FIG. 3 is a diagram showing a refraction state of a light beam when the optical system of FIG. 1 is configured as an LED (liquid crystal) printer, and a function of correcting a positional deviation of a condensing point and an effect of preventing an inverted magnification real image from overlapping. is doing.

FIG. 4 is a diagram showing a converged state of a light beam for explaining the resolution improving action of the microlens 9.

FIG. 5 is a diagram showing a converging action of a microlens 9 on a diffused light flux.

FIG. 6 is a diagram showing an example of the shape of a microlens array that improves resolution in a pseudo manner.

FIG. 7 is a diagram illustrating a color misregistration prevention effect of the microlens array 10.

FIG. 8 is a diagram showing the structure of a compact optical system for photosensitization in which the optical system is composed of only the microlens array 10.

FIG. 9 is a diagram showing a structure of a photocoupler that enables high-density mounting by the microlens array 10.

FIG. 10 is a diagram showing a compact document reading device in which the optical system is configured only by the microlens array 10.

FIG. 11 is a diagram showing an optical system of a laser printer.

FIG. 12 is a diagram showing an optical system of an LED (liquid crystal) printer.

FIG. 13 is a diagram showing a state in which the condensing point is displaced due to a dimensional error in the laser printer, and the resolution is reduced.

FIG. 14 is a diagram showing a manner in which the inverted variable-magnification real images on the photosensitive drum overlap (a) or separate (b) due to a dimensional error of an optical system in the LED (liquid crystal) printer shown in FIG.

[Explanation of symbols]

 1,8 Condensing lens 2 Luminous flux 3 Photosensitive drum 4 Laser light source 6 Optical polarizer 7 Array light source (LED array, liquid crystal light emitter) 9 Microlens 10 Microlens array 11 Light emitting element (LED) 12 Light source 13 Light receiving element 14 Receiver

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Claims (8)

[Claims] 1. A light source to an image plane through a condenser lens,
In an optical system that forms a linear condensing point on the image plane by a plurality of radially incident light beams, a microlens array in which a plurality of microlenses are continuously formed in a straight line is used. A microlens characterized by being arranged in parallel in the vicinity of an image plane in line with the direction of arrangement of the light fluxes and refracting each light flux incident through the condenser lens in the optical axis direction of each microlens for each light flux. Optical system using. 2. Each lens of the microlens array is a convex lens, and the lens pitch of the microlens array is made to match the pitch of the light beams incident on the microlens array so that each light beam and each microlens have a one-to-one correspondence. An optical system using a microlens according to claim 1, wherein the microlens array is positioned in the scanning direction, and each incident light beam is refracted in the optical axis direction and at the same time converges on the image plane. 3. The optical system using a microlens according to claim 1, wherein the lens pitch of the microlens array is smaller than the pitch of the incident light beam on the incident surface of the microlens array. 4. A light source in which a group of light emitting elements of three colors RGB is arranged in a line is used, and a light flux for one dot formed by the group of light emitting elements of three colors RGB is associated with one microlens. An optical system using the microlens according to claim 2. 5. A light source is a plurality of arrayed light sources in which a large number of light emitting elements are linearly arranged and arranged in a straight line at predetermined intervals, and a condenser lens is provided for each arrayed light source. The inverted variable-magnification real image of each array light source is formed so as to be linearly connected in a connected state on the image forming surface by each condensing lens. Optical system using microlenses. 6. A light source, in which a plurality of light emitting elements are linearly arranged at a predetermined pitch, is arranged in parallel so as to face an image forming surface which is a photoconductor, and a plurality of microlenses are provided between the light source and the image forming surface. A microlens array linearly connected at the same pitch as the light emitting element of the light source, and arranged in parallel with the optical axis of each microlens aligned with the optical axis of the corresponding light emitting element,
An optical system using a microlens, characterized in that light converging points which are linearly connected are formed on the image forming plane by the light of each light emitting element converged by the microlens. 7. A light source in which a plurality of light emitting elements are arranged, a microlens array in which a plurality of microlenses are connected and formed in the same arrangement as the light emitting element, and a plurality of light receiving elements are arranged in the same arrangement as the light emitting element to receive light. The optical axes of the light emitting element, the microlens, and the light receiving element at the corresponding positions are aligned in parallel so that the light of the light emitting element is converged by the microlens and is incident on the light receiving element. An optical system using a microlens, characterized in that a light emitting element, a microlens array, and an independent light emitting / receiving system are formed for each light receiving element. 8. A light receiver in which a plurality of light receiving elements are linearly arranged at a predetermined pitch is arranged in parallel so as to face an object surface to be read, and a plurality of microlenses are provided between the light receiver and the object surface. , A microlens array linearly formed at the same pitch as the light-emitting element of the above-mentioned light receiver, arranged in parallel with the optical axis of each microlens aligned with the optical axis of the corresponding light-receiving element, for each light-receiving element, An optical system using a microlens, characterized in that light emitted from the object surface at a position where the optical axis is extended is condensed and made incident by the microlens.