JPH06250118A - Line image forming element - Google Patents

Abstract

PURPOSE:To provide a line image forming element where a subject and an image are corresponded to one to mass or mass to one. CONSTITUTION:This element is constituted of two Dove prisms 3, 3 which are placed symmetrically with reflection surfaces 3' facing outside, a convex lens 1 placed on one side of an incident plane/a light-emitting surface and the convex lenses 2 of two sheet or above arranged in a direction perpendicular to the arrangement direction of the Dove prisms and whose focal distance are equal to the convex lens 1, and is constituted so that plural pieces of the constitution units are arranged in line so that the reflection surfaces of the Dove prisms 3 are faced each other. Further, another image forming element is constituted so that the functions of the convex lenses 1, 2 are realized by the combination of two pieces of cylindrical convex lenses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line image forming element used in facsimiles, digital copying machines, LED printers, liquid crystal printers and the like.

[0002]

2. Description of the Related Art In facsimiles and digital copying machines, a contact image sensor of a type in which an image of the original size is projected on a line image sensor having a reading width and is read is used. Further, in LED printers, liquid crystal printers, and the like, line array elements that project linearly arranged LED arrays or liquid crystal shutters on a photosensitive drum at equal magnification are used.

As an image forming element used for such an application, a so-called rod lens array or an array of spherical lenses is formed by forming an array of cylindrical transparent bodies whose refractive index continuously changes in the radial direction from the center. Laminated plates (in many cases, three layers) are stacked (see, for example, Japanese Patent Publication No. 49-8893, Japanese Patent Publication No. 57-104923, Japanese Patent Publication No. 57-66414, etc.), Dach prism An erecting equal-magnification optical system arranged in an array by a combination of a lens and a lens (for example, JP-A-61-2103).
19, JP-A-56-117201, JP-A-56-126801, and JP-A-56-140301.
JP, JP-A-56-149002, JP-A-60
-254018, JP-A-60-254019, JP-A-60-254020, and JP-A-61-2.
33714, JP-A-62-91902, JP-A-62-201417).

[0004]

In the contact image sensor using the above-mentioned image forming element, a single line image sensor using a large-area semiconductor film or a plurality of short line image sensors are used side by side. Especially when the reading width is long, it is difficult to cover the entire reading length with a single line image sensor as in the former case, and a plurality of line image sensors must be used. When using a plurality of line image sensors connected in this way, it is difficult to arrange adjacent line image sensors so that the light-receiving surfaces are in contact with each other without a gap. This causes a shift in the reading line, and it is necessary to correct this in a circuit manner.

Also in an LED printer or a liquid crystal printer, it is not technically easy to make an LED array or a liquid crystal shutter having a length equal to the print width. This is an unavoidable problem as long as a conventional imaging optical system in which a subject and an image correspond one-to-one is used. Therefore, it is an object of the present invention to provide a line imaging element in which the subject and the image correspond to one-to-many or many-to-one, which can avoid the above-mentioned problems.

[0006]

A line imaging element according to the first invention of the present application has two Dove prisms symmetrically placed with their reflecting surfaces facing outward and one of these input / output surfaces. The convex lens and the convex lens having the same focal length as that of the convex lens having two or more convex lenses arranged in the direction perpendicular to the arrangement direction of the Dove prism on the other input / output surface are used as constituent units, and the reflecting surface of the Dove prism is a surface. As described above, a plurality of the structural units are arranged on a straight line.

In the line imaging element according to the second aspect of the present invention, two dove prisms symmetrically placed so that the reflecting surfaces are on the outside, and a bus bar on the input / output surfaces of these dove prisms are arranged. A cylindrical convex lens having two equal focal lengths arranged so as to be perpendicular to the direction is used as a structural unit, and a plurality of the structural units are arranged in a straight line so that the reflecting surface of the Dove prism faces. , A cylindrical convex lens having a generatrix facing one of the cylindrical convex lens rows and parallel to the arrangement direction of the constituent unit, and a cylindrical convex lens having a generatrix parallel to the arrangement direction of the constituent unit facing the other cylindrical convex lens row, It is constructed by arranging more than one in line.

[0008]

In a line image forming element using a lens array, it is necessary for each constituent unit to form an erect image so as to obtain a continuous line image. However, since the condition of this erect image is sufficient to be satisfied only in the longitudinal direction, in the present invention, the burden on the lens is reduced by using the image inverting action of the Dove prism in the longitudinal direction, and the burden of chromatic aberration and optical axis alignment is reduced. Made it possible.

According to the above-mentioned specific configuration, in the contact image sensor, the images on one line are connected to two or more lines, and the line image sensors arranged in a zigzag pattern on these lines form the same line. Since line images can be read, line correction is not necessary. In addition, in LED printers and liquid crystal printers, images of short LED arrays and liquid crystal shutters arranged in a zigzag pattern on a plurality of lines are displayed on the same line. Since a complete line image can be created by tying it together, the LE is easy to manufacture.
It becomes possible to use a D array and a liquid crystal shutter.

[0010]

1 is a perspective view showing structural units in an embodiment of a line imaging element according to the first invention of the present application.
FIG. 2A is a plan view of the yz plane, and FIG. 2B is a plan view of the xz plane.
In the figure, reference numerals 1 and 2 denote a convex lens composed of one convex lens and two convex lenses having the same focal length as that of the convex lens, and 3, 3 each have a reflecting surface 3'so that it is on the outside. Dove prisms or trapezoidal prisms that are symmetrically joined, and 6 and 7 are an object plane and an image plane located at a focal distance from the convex lenses 1 and 2, respectively. In addition, 4 is a light-shielding member, and 5 is an adhesive layer described later. According to this structural unit, two inverted images are obtained in the y direction as shown in FIG. 2A, and an erect image is obtained in the x direction by the action of the Dove prism.

FIG. 3 illustrates the operation of a Dove prism, that is, a trapezoidal prism. Light incident on an incident surface at an angle α, which is the optical axis, is reflected by a reflecting surface 3'and goes backward from the emitting surface. Emit at the same angle α. This is a characteristic of the dove prism, that is, the trapezoidal prism, and since the entrance / exit surface forms an acute angle θ with the reflecting surface, it efficiently acts on the light along the optical axis due to refraction.

The operation of the structural units of this embodiment will be described within the xz plane in FIG. Convex lens 1 from the point x _{1 on the} object plane 6
The incident light is first converted into parallel light which forms an angle −tan ⁻¹ (x ₁ / f) with the optical axis (z axis) by the action of the lens 1 (where f is the focal length of the lenses 1 and 2). Represents). Next, by the action of the Dove prism described above, this light is converted into parallel light that makes an angle tan ⁻¹ (x ₁ / f) with the optical axis, and by the action of the lens 2, it becomes a point of coordinate x ₁ on the image plane 7. Focus.

That is, (1) position-angle conversion by the lens 1, (2) angle reversal by the Dove prism, (3)
By the angle-position conversion by the lens 2, an erecting equal-magnification image in the x direction can be obtained. This means that the position information between the lens 1 and the lens 2 is meaningless, which leads to the optical stability of the present imaging element. That is, in FIG. 2 (b),
Even if the position of the lens 1 or the lens 2 slightly shifts in the x direction, it appears only in the movement of the image in the x direction, and the quality of the image itself hardly changes. The most important problem in assembling a lens array is that the variation in the pitch between the lenses is integrated in the array direction and causes a non-negligible optical axis shift. It is characterized by being less susceptible to.

FIG. 4 shows an example of use of the line imaging element according to the first invention of the present application in which the above-mentioned structural units are arranged. Since images on the same line are projected on the line image sensors 12 arranged in two rows, the line image sensors 12 arranged in a staggered manner can obtain information on one line without loss. If 12 is replaced with LED array or liquid crystal shutter, LE on two lines will be reversed.
The image of D or the liquid crystal shutter is synthesized and projected on one line.

In the above-mentioned constitutional unit, it is preferable that the surfaces of the two Dove prisms 3 facing each other, that is, the surface opposite to the reflecting surface 3 ', be a rough surface and be bonded with a black adhesive 5.
As a result, as shown by the dotted line in FIG. 5, light rays that have not reached the emission surface after being reflected by the reflection surface 3'are absorbed, and the effect of preventing the generation of stray light is obtained. However, this is not essential. For example, if this surface is a smooth surface equivalent to the reflecting surface 3 ', the light reflected on the smooth surface as shown in FIG. , Becomes the effective light undergoing the angle reversal. As shown in FIG. 8, stray light is the component reflected by the incident / reflection surface, but the angle θ is θ ≧ 90 ° -sin ⁻¹ (1 / n) (where n is the refraction of the Dove prism). Ratio), this component becomes as shown in FIG.
As shown in FIG. 5, the light is transmitted through the reflecting surface 3 ′ and absorbed by the light shielding member 4, which does not pose a problem.

However, it is preferable to use the black adhesive 5 in practice because it is easier to actually use the black adhesive 5 because increasing the number of one smooth surface parallel to the reflecting surface with the required accuracy increases the manufacturing cost of the Dove prism. Even when the black adhesive 5 is used, stray light as shown in FIGS. 6 and 7 may be generated, but the stray light as shown in FIG. 6 is θ ≦ 90 ° -sin ⁻¹ (1 /
It does not exist if n) is satisfied, and the conditional expression θ ≧
Since 90 ° -sin ^-1 (1 / n) is also a sufficient condition that stray light does not occur as shown in FIG. 7, θ = 90 ° -sin ^-1 (1
If / n), there will be no problem.

As is clear from the above, the reflecting surface 3'of the dove prism 3 must utilize total reflection, and must not be subjected to a reflection enhancing coating such as metal plating. 10 to 12 show the relationship between the length of the Dove prism and its action. FIG. 10 shows the optical axis (z axis)
Is a condition that a ray along the line propagates without loss, and a / b = tan {θ + sin ⁻¹ (cos θ / n)} + tan {(π
/ 2) -θ} .... In this case, the image around the central axis of the lens is the brightest in each structural unit, and it is advantageous in that the portion with the smallest aberration can be effectively used.

FIG. 11 shows a view in which a is made smaller than this, and although the brightness of the image around the central axis is reduced, the effect of expanding the field of view in the y direction (depth direction in the paper) and slightly reducing the size is achieved. Can be expected. Further, FIG. 12 shows a case where a is large, and since the image of the center axis of the lens is slightly darker than that of FIG. 10, there is also an effect of increasing the uniformity of brightness. It is effective when using the lens. In any case, if the relationship is greatly deviated from the above expression, brightness or aberration becomes large, which is not preferable.

As a concrete example of the structural unit of the line imaging element according to the first aspect of the present invention, a =
Made of polymethylmethacrylate with 11.8 mm, b = 2.8 mm, θ = 45 °, 20 Dove prisms of material BK7 with prism height 6 mm, and 10 square convex lenses 6 mm × 6 mm with radius of curvature 8 mm. One lens array, one polymethylmethacrylate lens array in which 10 rectangular convex lenses of 6 mm × 3 mm with the same radius of curvature are arranged in two rows, and the light shielding means 4 is cut into a rectangle of 11.8 mm × 6 mm. Using 11 sheets of black paper, a line imaging element as shown in FIG. 4 was assembled. It was confirmed that two lines of bright inverted equal-magnification images with a conjugate length of 47 mm were obtained using this line imaging element. In the present embodiment, the same clear image was obtained even when the black paper of the light shielding means 4 was omitted, and the contrast at this time was slightly lowered.

FIG. 13 is a perspective view showing a structural unit in an embodiment of the line imaging element according to the second invention of the present application,
14A is a plan view of the yz plane, and FIG. 14B is a plan view of the xz plane. This structural unit is obtained by replacing the functions of the lenses 1 and 2 in the imaging element shown in FIGS. 1 and 2 with a combination of two cylindrical convex lenses 8, 10 and 9, 11, respectively. Although the number of parts is increased by using a cylindrical convex lens like this,
(1) Cylindrical convex lens 10 when arrayed,
11 can be a single common cylindrical convex lens, and as a result, it is difficult to cause image shift in the y direction of each structural unit. (2) If necessary, change the focal lengths and positions of the cylindrical convex lenses 10 and 11. There is an advantage that the viewing angle (aperture angle) in the y direction can be changed, and enlargement / reduction can be performed.

FIG. 15 is a perspective view showing an example of use of the line imaging element according to the second invention of the present application in which the constituent units shown in FIGS. 13 and 14 are arranged. As a concrete example of the structural unit of the line imaging element according to the second invention of the present application, the same Dove prism 2 as the concrete example described above is used.
0, two polymethylmethacrylate lens arrays with 10 square 6 mm × 6 mm cylindrical convex lenses with a radius of curvature of 9 mm, and a cylindrical convex lens with a radius of curvature of 8 mm and a width of 6 mm, and a width of 3 mm with the same radius of curvature The cylindrical image forming element shown in FIG. 15 was assembled using two cylindrical convex lenses (1) and 11 black papers similar to those described above. It was confirmed that this line imaging element can obtain bright two-row inverted equal-magnification images with a conjugate length of 50 mm.

FIG. 16 is a perspective view showing a structural unit of another embodiment of the line imaging element according to the second invention of the present application, in which three cylindrical convex lenses 13 on one side are arranged in parallel. This is a line imaging element effective when the contact color image sensor is composed of three long line image sensors in total of RGB. To configure this with a short line image sensor, as shown in FIG. 17, a line image sensor of each color arranged in four rows and a line connection according to the present invention configured to obtain four line images. The image elements may be combined.

[0023]

As described above, in the line imaging element according to the present invention, unlike the rod lens array and the three-layer lens array, image inversion is performed by utilizing reflection to reduce the burden on the lens, and therefore, it is caused by refraction. Chromatic aberration is small compared to other lens arrays.

Further, by using the line imaging element according to the present invention, even when a contact image sensor is formed by using a plurality of short line image sensors, it is necessary to correct the read line deviation between the line image sensors in a circuit manner. In addition, the printer head can be configured using a plurality of short LED arrays and liquid crystal shutters.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a configuration unit in an embodiment of a line imaging element according to the first invention of the present application.

FIG. 2 is a plan view of structural units in the line imaging element of FIG.

FIG. 3 is an explanatory diagram for explaining the action of the Dove prism.

FIG. 4 is a perspective view showing a usage example of the line imaging element according to the first invention of the present application.

FIG. 5 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 6 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 7 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 8 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 9 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 10 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 11 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 12 is an explanatory diagram for explaining the operation of the structural units in the line imaging element according to the present invention.

FIG. 13 is a perspective view showing a configuration of a configuration unit in an embodiment of the line imaging element according to the second invention of the present application.

14 is a plan view of constituent units in the line imaging element of FIG.

FIG. 15 is a perspective view showing a usage example of the line imaging element according to the second invention of the present application.

FIG. 16 is a perspective view showing a configuration of a configuration unit in another embodiment of the line imaging element according to the second invention of the present application.

FIG. 17 is an explanatory diagram showing an example of a method of arranging line image sensors of respective colors when a contact color image sensor is formed using the line image forming element according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Convex lens 2 ... Convex lens 3 ... Dove prism 3 '... Reflective surface 4 ... Light-shielding member 5 ... Black adhesive 6 ... Object surface 7 ... Image surface 8 ... Cylindrical convex lens 9 ... Cylindrical convex lens 10 ... Cylindrical convex lens 11 ... Cylindrical convex lens 12 ... Line image sensor 13 ... Cylindrical convex lens

Claims (2)

[Claims] 1. A pair of Dove prisms symmetrically placed with their reflecting surfaces facing outward, a convex lens placed on one of these entrance / exit surfaces, and a Dove prism on the other entrance / exit surface. A line in which two or more convex lenses arranged in a direction perpendicular to the arrangement direction and a convex lens having the same focal length are used as a constituent unit, and a plurality of the constituent units are arranged on a straight line so that the reflection reflection of the Dove prism faces. Imaging element. 2. Two dove prisms placed symmetrically so that the reflecting surface is on the outside, and two dove prisms placed on these input / output surfaces so that the generatrix is perpendicular to the direction in which the dove prisms are arranged. A cylindrical convex lens having the same focal length is used as a constituent unit, and a plurality of such constituent units are arranged in a straight line so that the reflecting surface of the Dove prism faces, and one of these cylindrical convex lens rows is installed. And a cylindrical convex lens having a generatrix parallel to the arrangement direction of the constituent unit, and a cylindrical convex lens having a generatrix parallel to the arrangement direction of the constituent unit, which is installed side by side to the other cylindrical convex lens array. Line imaging device with.