JP2000309118A - Optical printer head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an optical image forming means highly efficient in an optical printer head that makes light from a light source form an image on a recording medium by an image forming means. SOLUTION: Between a fluorescent arc tube 15 and an SLA 10, and between the SLA 10 and a recording medium 20, four light reflecting members 25, 26, 27 and 28 are provided mutually parallelly in four positions symmetrical relative to the central face 12 of the SLA or the optical axis face 13 of an optical path. In relation to an upper row and lower row of luminous dots 1 and 2, the lower side of the optical axis has a light quantity transmission rate opposite to the upper side of the optical axis. When ghosts 1c and 2c are superposed on real images 1a and 1b from above and below, an equal light quantity improvement is realized. In the SLA 10, the loss in the quantity of light due to a lens itself is very small, so the light quantity transmission rate is determined by the quantity of incident light on the lens. If the reflectance of the reflective members is 95%, and 90% in two reflections in relation to an improvement of 50%+30%=80% in the quantity of light for the real images, about 70% improvement in the total quantity of light can be expected. It is equivalent to an efficiency improvement equal to the arrangement in four rows of SLA 10 in two row specification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical print head which forms an image by forming an image of a dot-like light from a light emitting element on a recording medium by a lens.

[0002]

2. Description of the Related Art FIG. 8 is a perspective view of an optical imaging means used in an optical print head. This optical imaging means is an assembly of selfoc lenses, which are erect equal-magnification imaging lenses (Selfoc lens array, abbreviated as SLA).
It is. The SLA 10 in FIG. 8 has a structure in which a number of Selfoc lenses 11 are arranged in two rows in a staggered manner, sandwiched between plates from above and below, and fixed.

[0003] In FIG. 8, the axial direction of each of the cylindrical SELFOC lenses 11 constituting the SLA 10 corresponds to the SLA 10.
In the direction of the optical axis. The direction in which the SELFOC lenses 11 are arranged perpendicular to this is the longitudinal direction of the SLA. This longitudinal direction coincides with the scanning direction during optical writing. The direction in which the SELFOC lenses 11 arranged in the longitudinal direction are staggered, which is a short direction orthogonal to the longitudinal direction, is S
This is the width direction of LA. Then, as shown in FIG.
A plane orthogonal to the optical axis of A10 and bisecting the optical axis of SLA 10 is referred to as a lens center plane 12. Further, a plane orthogonal to the lens center plane 12 and thus parallel to the optical axis of the SLA 10 and located between the two lines of SELFOC lenses 11 is called an optical axis plane 13 of the optical path. The optical axis plane 13 of this optical path is also called a lens focal plane.

FIG. 9 shows a fluorescent arc tube printhead module (VFP) using this SLA 10 as an optical imaging means.
FIG. 2 is a side view and a cross-sectional view of an H module).
The fluorescent light emitting tube 15 (VFPH) is a light emitting device in which light emitting dots 1 and 2 that repeat blinking according to image data are arranged in a staggered manner in the main scanning direction. While the VFPH module and the recording medium 20 move relative to the sub-scanning direction,
The light emitting dots 1 and 2 of the FPH module emit light. VF
The dot light from the light-emitting dots 1 and 2 of PH15 is S
Erect real-size real images (1a, 1a,
An image is formed as 2a).

[0005] In the optical print head having such a configuration, the brighter the image (the higher the energy), the more useful the light sensitivity characteristic of the recording medium 20 and the more advanced multi-tone control. However, less than 1% of the light is actually used. Therefore, two methods shown in FIGS. 10 and 11 have been proposed to increase the efficiency of the optical system.

In the method shown in FIG. 10, while the optical specifications of the lens elements (Selfoc lens 11) constituting the SLA 10a are the same as those in FIG. 9, the arrangement of the lens elements is changed from two rows in FIG. Has been changed to. This improves the efficiency by 70% or more.

In the method shown in FIG. 11, the focal length and the incident angle are changed in the optical specifications of the lens element (Selfoc lens 11) constituting the SLA 10b. As a result, the efficiency can be improved by 600% or more depending on the specification.

[0008]

In the method of arranging lens elements in four rows as shown in FIG. 10, the number of lens elements is increased, so that the cost is increased and the dimensions and mass of parts are increased. To give a specific example, the cost is about doubled,
The component size is about 1.4 times the lens width from 4.8 mm to 6.8 mm, and the mass is about 1.5 times from 22 g to 32 g.

In the optical print head, R (red),
A full-color image is obtained by preparing three types of VFPH modules having light-emitting dots that emit light of each color of G (green) and B (blue) and superposing and exposing the dot light of each color on a recording medium. There are types that form. However, if the number of exposures for each color is the same, generally R
(Red) light is usually insufficient.
Only the module No. adopts the above-described four-row lens structure, and the G and B modules have two-row lenses. For this reason, there is a portion where the module components, the assembly jig, the light amount measurement jig, and the like cannot be shared, and the production efficiency is reduced.

There are the following problems in shortening the focal length of the lens shown in FIG. First, there is a problem of insufficient dimensions in mechanical design. The VFPH module and the recording medium are used by being relatively moved. For this reason, the size of the mechanical gap between the VPPH module and the recording medium is specified by the user, and a physically short-focus lens cannot be used. Further, shortening the focal length of the lens also has the following problem. That is, chromatic aberration is generated by shortening the focal length, and the chromatic aberration requires adjustment of the focal length in an optical print head having a module for each of R, G, and B colors. Also, switchable RG to a single module
In an optical print head of the type having a B filter, a color defocus occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to increase the efficiency of an optical image forming means in an optical print head for forming an image of light from a light source on a recording medium by an optical image forming means.

[0012]

An optical print head according to claim 1, wherein a light source (fluorescent light emitting tube 15) and light image forming means for forming light from said light source on a recording medium (20). (SLA10).
A light reflecting surface (25, 26, 27, 28, 30, 31) is arranged near an optical path between the light source and the recording medium.

An optical print head according to a second aspect is the optical print head according to the first aspect, wherein the light source (fluorescent light emitting tube 15) and the light imaging means (SLA10).
And between the optical imaging means (SLA10) and the recording medium (20).
2) or four light reflecting surfaces (25, 26, 2) at four positions symmetrical with respect to the optical axis surface (13) of the optical path.
7, 28) are provided so as to be parallel to each other.

An optical print head according to a third aspect of the present invention is the optical print head according to the second aspect, wherein the light source (fluorescent light emitting tube 15) and the optical imaging means (SLA10).
Between the two light reflecting surfaces (25, 26) provided between the light source and the light source, for guiding light having a different direction from the optical axis of the light imaging means between the two light reflecting surfaces. (35) is provided.

According to a fourth aspect of the present invention, in the optical print head according to the second aspect, the two light beams provided between the optical imaging means (SLA10) and the recording medium (20). A guide reflection surface is provided between the reflection surfaces (27, 28) and the recording medium (20) for reflecting light emitted from the two light reflection surfaces and guiding the light to the recording medium. I have.

According to a fifth aspect of the present invention, in the optical print head according to the second aspect, the light source (fluorescent luminous tube 15) is arranged so that the light imaging means (SLA10) is in the main scanning direction at the time of optical writing. ) Has a plurality of light emitting dots (1, 2) along the longitudinal direction, and the light reflecting surface (25, 26) is in the width direction of the light imaging means, which is a sub-scanning direction at the time of optical writing. Are arranged on both sides of the optical path so as to be parallel to each other.

According to a sixth aspect of the present invention, in the optical print head of the second aspect, the optical imaging means (SLA10) is an erecting equal-magnification imaging lens;
The distance between the reflecting surfaces (25 and 26, 27 and 28) symmetrically arranged with respect to the optical axis surface (13) is equal to the width of the erecting equal-magnification imaging lens in the sub-scanning direction. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a fluorescent light emitting tube 15 as a light source of the present example includes an envelope 18 in which a box-shaped container portion 17 is sealed on an anode substrate 16 made of a material such as translucent glass. I have. On the anode substrate 16 in the envelope 18, a translucent anode conductor and an anode made of a phosphor coated on the anode conductor are formed. The anode of this example is formed by a large number of light emitting dots 1 and 2 arranged in a staggered manner at a predetermined interval in FIG. The fluorescent light emitting tube 15 has the main scanning direction as the direction in which the light emitting dots 1 and 2 are arranged, and the direction perpendicular to the direction in the plane of the anode substrate 16 is the sub-scanning direction. For convenience, one upper side (1) of the two rows of light emitting dots arranged in a zigzag pattern is referred to as an upper row, and the other lower side (2) is referred to as a lower row.

The fluorescent luminous tube 15 of the present embodiment uses a ZnO: Zn phosphor which is a zinc oxide-based phosphor which has a wide emission spectrum and emits light in the blue to red region. If a color filter is used for this, a desired emission color can be obtained.

As shown in FIG. 1 and FIG.
The SLA 10 is provided in the vicinity of the fluorescent light emitting tube 15 as a light image forming means for forming the light of No. 5 on the recording medium 20. The basic structure of the SLA 10 and the arrangement with respect to the fluorescent tube 15 are substantially the same as those described in the related art.

The SLA 10 has a structure in which a large number of Selfoc lenses 11 are arranged in a staggered pattern in two rows, stacked, and fixed by sandwiching them from above and below. In FIG. 1, SLA1
The direction perpendicular to the optical axis of each of the SELFOC lenses 11 and the direction in which the SELFOC lenses 11 are arranged is referred to as the longitudinal direction of the SLA 10. The direction perpendicular to the longitudinal direction and the optical axis of the SLA 10, that is, the short direction in which the SELFOC lenses 11 arranged in the longitudinal direction overlap each other, is SL
This is the width direction of A10. The definitions of the lens center plane 12 and the optical axis plane 13 (lens focal plane) of the optical path are the same as those described in the related art.

The SLA 10 is arranged as follows with respect to the fluorescent tube 15. That is, the optical axis plane 13 (lens focal plane) of the optical path of the SLA 10 is parallel to the main scanning direction (the direction in which the light emitting dots are arranged) of the fluorescent light emitting tube 15, and It coincides with the center line between the two rows parallel to the light emitting dots (1) and the lower row of light emitting dots (2).

In the optical print head of this embodiment having the fluorescent light emitting tube 15 and the SLA 10, a total of four light reflecting surfaces 25, 26, 27, with respect to the lens center plane 12 of the SLA 10 and the optical axis plane 13 of the optical path of the SLA 10. 28 are symmetrically arranged.

First, two light reflecting surfaces 25, 26 and 27, 28 are arranged at a position between the fluorescent tube 15 and the SLA 10 and at a position between the SLA 10 and the recording medium 20, respectively. The light reflection surfaces 25 to 28 are total reflection surfaces. Further, the two light reflecting surfaces 25, 26 and 27, 28 at each position are arranged symmetrically with respect to the optical axis plane 13 (lens focal plane) of the optical path of the SLA 10, and are parallel to the longitudinal direction of the SLA 10. ing. At each position,
The two reflection surfaces 25, 26 and 27, 28 face inward and face each other. The interval is SLA10
(For example, about 2 mm).
The length of the light reflecting surfaces 25 to 28 in the main scanning direction is SLA10
Is equal to or longer than the length in the longitudinal direction. SL
The length of the light reflecting surfaces 25 to 28 in the optical axis direction of A10 is the distance between the fluorescent arc tube 15 and the SLA 10, or the length of the SLA1.
The distance between 0 and the recording medium 20 is maximized, and is determined in consideration of the effective light reflecting surface from the optical path obtained from the incident angle of the SLA 10.

As described above, at the two positions on the incident side and the exit side of the SLA 10, two light reflecting surfaces 25, 26 and 27, 28 are respectively provided on the optical axis surface 13 of the optical path of the SLA 10.
However, the pair of light reflecting surfaces at both positions are also symmetrically arranged with respect to the center plane 12 of the SLA 10.

In order to explain the effect of this embodiment, the operation of the light reflecting surface in the optical print head will be described sequentially with reference to FIGS. 4 and 5 show a case where one light reflecting surface 25 is added to the conventional optical print head shown in FIG. The added position is the SLA 10 and the fluorescent arc tube 15
1 mm above the optical axis surface 13, and is disposed parallel to the optical axis surface 13. Observing the light reflection surface 25 from the incident point of the SLA 10, the inverted images 1b and 2 of the light emitting dots 1 and 2
b is observed. That is, a virtual image is formed at a position as shown in FIG. Next, the real images 1a,
The ghosts 1c and 2c due to the virtual image together with the recording medium 2a
It is observed that the image is formed above the 0 real images 1a and 2a.

FIG. 6 shows a case where one more light reflecting surface 27 is added to the optical print head of FIG. The added position is between the SLA 10 and the recording medium 20, and is a position symmetrical with respect to the light reflection surface 25 in FIG. The light reflecting surface 27 provided between the SLA 10 and the recording medium 20 is used to convert the ghosts 1c and 2c appearing in FIG.
a, 2a. The ghosts of the light emitting dots 1 and 2 in the upper and lower rows have different distances from the optical axis of the lens, so that the efficiency of incidence on the lens differs. Specifically, the light amount transmissivity is 30% at a position outside the optical axis and 50% at a position inside the optical axis. Therefore, when a ghost is superimposed on the real image, a light amount difference occurs between the light emitting dots of the upper row and the lower row.

Therefore, the light reflecting surfaces 25 and 27 shown in FIG.
Are also arranged at opposite positions symmetrical with respect to the optical axis surface 13 of the SLA 10 to make a total of four sheets. This is the above-described optical print head of the present example. For each of the light emitting dots 1 and 2 in the upper row and the lower row, the lower side of the optical axis has a light amount transmission rate opposite to that of the upper side of the optical axis described above. Light quantity improvement is realized. SLA
In No. 10, since the loss of light amount by the lens itself is extremely small, the light amount transmission rate is determined by the lens incident light amount. For a 50% + 30% = 80% improvement in light quantity with respect to the real image,
The reflectivity of the light reflecting surface is set to 95%, and the light is reflected twice to obtain 9%.
Considering that the reflection is 0%, it can be expected that the total light amount is improved by about 70%. This is a two-row SLA10
Is equivalent to an improvement in efficiency equivalent to four rows.

Next, a second embodiment of the present invention will be described with reference to FIG. In this example, in order to reduce the size of the optical print head of the first example, the optical axis is placed between the two light reflecting surfaces 30, 31 arranged on the fluorescent light emitting tube 15 side and the fluorescent light emitting tube 15. A guide reflection surface 35 for bending is provided. In this example, the two light reflecting surfaces 30, 31 and the guiding reflecting surface 35 are integrally formed. The guide reflection surface 35 is
It is inclined by 45 ° with respect to the optical axis plane 13 of the SLA 10.
Such a guide reflection surface 35 can be disposed between the recording medium 20 and the two light reflection surfaces 27 and 28 disposed on the recording medium side. Of course, they can be provided at both positions as needed. As described above, even when the guide reflection surface 35 for bending the optical axis of the SLA 10 is provided for downsizing the head, the effect of improving the light amount can be obtained by providing the pair of reflection surfaces on the incident side and the emission side of the SLA 10. Can be

In each of the examples described above, a plane mirror is shown as a light reflecting surface. However, a similar optical element is used by using an optical element in which the outer surface of a solid body made of a light transmitting material such as glass is mirror-finished. A configuration can be obtained and a similar effect can be achieved.

[0031]

According to the present invention, in an optical print head using an SLA having the same lens element specifications, four positions are symmetrical with respect to the center plane or the optical axis plane of the SLA having two rows of lenses. Since two light reflecting surfaces are provided parallel to each other, the performance regarding chromatic aberration and focal length remains the same,
The improvement of the light amount equivalent to the four-row specification was realized, and the brightness could be greatly improved.

Further, in a full-color optical print head provided with three types of VFPH modules provided with light-emitting dots that emit light of R (red), G (green), and B (blue),
Normally, the amount of light of R (red) is insufficient. Therefore, only the R module has the above-described four-row lens structure, and the G and B modules have two-row lenses. However, according to the present invention, even in such a case, an R head using a four-row lens can be designed with a two-row lens due to insufficient light quantity, so that the dimensions are the same as those of G and B. Some parts and assembly jigs can be shared.

Further, since the G and B heads have about 1.7 times the amount of light as compared with the conventional heads, it is possible to drive the light emission with a reduced luminance as the fluorescent light emitting tube, which has an effect on the reproducibility of light emission and the life. is there.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first example of an embodiment of the present invention.

FIG. 2 is a sectional view showing a first example of an embodiment of the present invention.

FIG. 3 shows a first example of an embodiment of the present invention;
FIG. 2 is a front view of the device observed with a line of sight parallel to the optical axis.

FIG. 4 is a cross-sectional view of an optical print head having one light reflecting surface.

FIG. 5 is a partially enlarged view of FIG. 4;

FIG. 6 is a cross-sectional view showing a state where one more light reflection surface is added to the optical print head of FIG. 4;

FIG. 7 is a sectional view showing a second example of the embodiment of the present invention.

FIG. 8 is a perspective view schematically showing an example of the structure of a conventional optical print head.

FIG. 9 is a side view and a sectional view schematically showing an example of the structure of a conventional optical print head.

FIG. 10 is a side view and a sectional view schematically showing an example of the structure of a conventional optical print head.

[Explanation of symbols]

1, 2, light-emitting dots 10 Selfoc lens array (S
LA) 12 lens center plane 13 optical axis plane 15 fluorescent tube as light source 20 recording medium 25, 26, 27, 28, 30, 31 light reflecting surface 35 guiding reflecting surface

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshikazu Iidaka 629 Oshiba, Mobara-shi, Chiba Futaba Electronics Co., Ltd. F-term (reference) 2C162 FA19 FA34 FA44 FA70 5C051 AA02 CA10 DA03 DB22 DB24 DB28 DB31 DC04 DC07 EA01

Claims (6)

[Claims] 1. An optical print head comprising: a light source; and optical imaging means for imaging light from the light source on a recording medium, wherein light is reflected near an optical path between the light source and the recording medium. An optical print head having a surface arranged. 2. The optical system according to claim 1, wherein the light source and the optical imaging means and the optical imaging means and the recording medium are symmetrical with respect to a center plane of the optical imaging means or an optical axis plane of the optical path.
2. The optical print head according to claim 1, wherein four light reflecting surfaces are provided at two positions so as to be parallel to each other. 3. A light beam having a different direction from an optical axis of the light imaging means is provided between the two light reflecting surfaces provided between the light source and the light imaging means and the light source. 3. The optical print head according to claim 2, further comprising a guide reflection surface for guiding the light between the light reflection surfaces. 4. A method according to claim 1, further comprising: a step between the two light reflecting surfaces provided between the optical imaging means and the recording medium and the recording medium.
3. The optical print head according to claim 2, further comprising a guide reflection surface for reflecting light emitted from the two light reflection surfaces and guiding the light to the recording medium. 5. The light source has a plurality of light emitting dots along a longitudinal direction of the optical imaging means which is a main scanning direction at the time of optical writing, and the light reflecting surface is a sub-scan at the time of optical writing. 3. The optical print head according to claim 2, wherein the optical print heads are arranged so as to be parallel to each other on both sides of the optical path at an interval in a width direction of the optical imaging means. 6. The optical imaging means is an erecting equal-magnification imaging lens, and the distance between the reflecting surfaces symmetrically arranged with respect to the optical axis plane is equal to the sub-scanning of the erecting equal-magnification imaging lens. 3. The optical printhead according to claim 2, wherein the width is equal to the width in the direction.