JP3077228B2 - Optical signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal generator, and more particularly to an optical signal generator used for an image writing head of an image forming apparatus such as a printer or a facsimile.

[0002]

2. Description of the Related Art Conventionally, an optical signal generator used as a head for writing an image on a photosensitive member converts light from a light source such as a halogen lamp into a linear shape (main scanning direction) through an optical fiber array. An optical shutter array made of PLZT turns on and off light emitted from an optical fiber array based on an image signal, and forms an image on a photosensitive member via a lens array.

In such an optical signal generator, in order to reduce unevenness in the amount of light in a light-receiving portion of an optical fiber array, a light-collecting reflecting mirror provided on the back of a light source is precisely polished or a light source (halogen) is used. The inner surface of the tube of the lamp is frosted to increase the light diffusion, and a light diffusion plate is provided between the two. However, even if the above measures are taken, the uniformity of the light amount (particularly the uniformity in the main scanning direction) is insufficient or the light amount itself is reduced, and the required performance is not satisfied.

[0004]

Object, structure and operation of the present invention
It is an object of the present invention to provide an optical signal generator capable of efficiently guiding light emitted from a light source to an optical fiber array and having a uniform light amount distribution. In order to achieve the above object, an optical signal generating device according to the present invention includes a cylindrical reflecting member having an inner peripheral surface that is a mirror surface or a light diffusing surface, and the following expression between a light source and an optical fiber array. It was provided in a satisfactory position.

0 <L ₁ ≦ (R ₂ −R ₁ ) / tan θ ₁ L ₁ : distance between cylindrical reflection member and optical fiber array R ₁ : radius of aperture of optical fiber array R ₂ : diameter of cylindrical reflection member Aperture radius θ ₁ : light receiving angle of optical fiber array Light emitted from the light source is repeatedly reflected on the inner peripheral surface of the cylindrical reflecting member, and the light amount distribution is made uniform at the exit of the reflecting member. When the distance L ₁ exceeds the upper limit of the above formula, variation occurs in the amount of light in the optical fiber array lighting unit.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical signal generator according to the present invention will be described below with reference to the accompanying drawings. [First embodiment, see FIGS. 1 to 4] As shown in FIG. 1, a light signal generating apparatus includes a light source 10, a heat ray absorbing filter 13, a cylindrical reflecting member 15, and an optical fiber array 2.
0, optical shutter array 30, lens array 40 for imaging
It is composed of

The light source 10 is composed of a halogen lamp and has a reflecting mirror 11 composed of a dichroic mirror. The cylindrical reflecting member 15 has a mirror surface or a light diffusing surface on the inner peripheral surface, and its arrangement will be described later. The optical fiber array 20 is composed of a number of optical fibers, one end of which is bundled to form a lighting unit 21, and the other end of which is arranged in the main scanning direction (indicated by an arrow X) to form an emission unit 22. The light guided to the lighting unit 21 is emitted from the emission unit 22 in a straight line along the main scanning direction X. The optical shutter array 30 has an optical shutter element 32 made of PLZT and a driving circuit 33 thereof linearly arranged on a glass substrate 31, and polarizers 35 and 36 (polarizer 35, analyzer 36) are installed before and after the optical shutter element 32. Have been. The lens array 40 is composed of a number of converging rod lenses and forms an image of light on the photosensitive drum 50.

In the above arrangement, the light emitted from the light source 10 is condensed by the reflecting mirror 11 and
And the optical fiber array 20 via the cylindrical reflecting member 15
And the light is emitted linearly from the emission unit 22. This light is transmitted through the polarizer 35 to the optical shutter array 3.
Irradiate 0. The voltage of each optical shutter element 32 is turned on and off based on the image signal, and only light transmitted through the element 32 to which the voltage (half-wavelength voltage) is applied passes through the polarizer 36. The light passing through the polarizer 36 forms an image on the photosensitive drum 50 via the lens array 40. Photoconductor drum 5
0 is driven to rotate at a constant speed in the direction of arrow a, and a predetermined image is formed as an electrostatic latent image on its surface.

In the cylindrical reflecting member 15, incident light is repeatedly reflected on the inner peripheral surface thereof.
At the exit, the light quantity distribution is averaged. Therefore, it is preferable that the cylindrical reflecting member 15 has a length enough to sufficiently exhibit the multiple reflection effect. In this embodiment,
The radius of the aperture of the spheroidal reflecting mirror 11 is R ₃ , the radius of the aperture of the cylindrical reflecting member 15 is R ₂ , and the optical fiber array 20
The radius of the aperture of the daylighting unit 21 is R ₁ , and the optical fiber array 2
Assuming that the light receiving angle of 0 is θ ₁ , the distance L ₂ from the light source 10 to the entrance of the cylindrical reflecting member 15 and the cylindrical reflecting member 1
It is preferable that the distance L ₁ from the exit port of _No. 5 to the lighting surface of the optical fiber array 20 satisfies the following expressions (1) and (2) (see FIG. 2).

L ₂ ≦ (R ₃ −R ₂ ) / tan θ ₁ (1) L ₁ ≦ (R ₂ −R ₁ ) / tan θ ₁ (2) where R ₁ <R ₂ ≦ R ₃ or less The reason will be described. Figure 3 shows the result of the light amount unevenness delta ₂ in the opening angle of the optical fiber array 20 simulates <br/> at the exit surface of the cylindrical reflector member 15 with respect to the distance L _2. The solid line in FIG. 3 indicates that the light source 10 is a perfect diffusion spherical light source, that the light source 10 is located at the focal point of a cylindrical elliptical reflecting mirror 11, and that the reflecting mirror 11 has a single curved surface, and has a diameter of 2R _3. Is 40mm, focal length is 30mm
This is the result of simulation based on the assumption that Also,
The circles plotted in FIG. 3 are actual measurement data. In this case, R ₂ is 17 mm, θ ₁ is 30 °, R ₃ is 20 mm as described above, and the length of the cylindrical reflecting member 15 is 100 mm.

As shown in the graph of FIG. 3, when the expression (1) is satisfied, the light quantity distribution on the exit surface of the cylindrical reflecting member 15 is extremely uniform. However, the distance L ₂ is above the upper limit, the light amount unevenness delta ₂ are generated. If the distance L ₂ is more than the upper limit, when viewed incident side from the exit surface of the cylindrical reflector member 15 at the opening angle of the optical fiber array 20, the light source 1
There are places where there is no real image and no virtual image of the 0 and spheroidal reflecting mirrors 11, which causes uneven light amount Δ ₂ .

On the other hand, FIG. 4 shows the result of simulating the light amount unevenness Δ ₁ within the opening angle of the optical fiber array 20 on the incident surface of the optical fiber array 20 with respect to the distance L ₁ . Diameter 2R ₁ of the cylindrical reflector member 15 is 15 mm, the opening angle theta ₁ is 30 degrees. The solid line in FIG. 4 is a simulation result on the assumption that light is emitted with a uniform light amount distribution within the opening angle of the optical fiber array 20 on the emission surface of the cylindrical reflecting member 15. Also, circles plotted in FIG. 4 is a measurement data when the distance L ₂ satisfies the formula (1). Referring to FIG distance L ₂
As described above, when Expression (2) is satisfied, the light amount distribution on the exit surface of the cylindrical reflecting member 15 is extremely uniform. However, the distance L ₁ is exceeds the upper limit, the light amount unevenness delta ₁ are generated. As with because of the distance L _2, the distance L ₁ exceeds the upper limit, when viewed incident side from the exit surface of the cylindrical reflector member 15 at the opening angle of the optical fiber array 20, the light source 10 and reflector This is because there are places where there are no 11 real images and no virtual images.

As is apparent from the above considerations, in order to prevent the light amount unevenness in the optical fiber array 20, the distance L
It is preferable that ₁ and L ₂ satisfy the above formulas (1) and (2). [Comparative Example, See FIG. 5] FIG. 5 shows a comparative example with respect to the present invention, in which a light-receiving portion 21 of an optical fiber array 20 is coupled to an emission end of a cylindrical reflecting member 15 via a heat insulating material 16. Here, the distance L ₁ is 0. Also L ₁ is 0, as described with reference to FIG. 4, the amount of light incident on the optical fiber array 20 is uniform, the optical performance is not a problem.

However, the radiation heat from the light source 10 and the reflecting mirror 11 causes the temperature of the cylindrical reflecting member 15 and the lighting part 21 of the optical fiber array 20 to rise sharply. For example,
A 100 W halogen lamp is used as a light source 10 with a reflecting mirror 11 made of a dichroic mirror, and a heat prevention (heat ray absorbing) filter 13 is used as a Sigma Koki HAF-50.
Using S-30H, the cylindrical reflecting member 15 has a length of 90
In the case of using an aluminum tube having a diameter of 2 mm, as shown in FIG. 5, the lighting unit 21 of the optical fiber array 20 is fixed to the cylindrical reflecting member 15 via the heat insulating material 16 or is completely non-contact. the distance L ₁ was experimented in a state of 0, unless a cooling device, a cylindrical reflecting member 15 in about 30 minutes the surface temperature of 180 ° C., the internal space temperature is 105
° C, the incidence surface of the optical fiber array 20 rose to 110 ° C. Quartz and plastic optical fibers are provided as optical fibers, and it is preferable to use plastic fibers from the viewpoint of cost and handling. However, if the distance L ₁ is set to 0, as described above, the surface of the optical fiber array 20 at a temperature rise due to radiation heat strongly thermal effects, exceeds the melting point of the plastic. Therefore, air cooling and water cooling devices for cooling the optical fiber array 20 from the outside are required. Distance L ₁ can not be directly cooling the lighting part 21 of the optical fiber array 20 since it is 0, the cooling apparatus is enlarged.

In the first embodiment shown in FIG. 2, L ₁ =
When the temperature was measured as (R ₂ −R ₁ ) / tan θ _{1 under} the same conditions as described above, the cylindrical reflective member 15 had a surface temperature of 175 ° C., an internal space temperature of 95 ° C., and an optical fiber array 2.
The 0 incidence plane rose only up to 80 ° C. The heat-resistant temperature of a plastic optical fiber is generally about 80 ° C. Therefore, it can be used without requiring external cooling.

In consideration of the above points, it is preferable that the distance L ₁ satisfies the following equation (2 ′) based on the above equation (2). 0 <L ₁ ≦ (R ₂ −R ₁ ) / tan θ ₁ (2 ′) [Second embodiment, see FIG. 6] In the second embodiment, between the light source 10 and the cylindrical reflecting member 15 A heat ray absorbing filter 14 having one or both surfaces frosted was provided. In the second embodiment, since the filter 14 has a light diffusing function, unlike the first embodiment, the distance L constraint eliminates represented by ₂ in the formula (1), likewise reflector 11
There is no special restriction on the aperture of the cylindrical reflecting member 15 and the aperture of the cylindrical reflecting member 15.

However, the radius R _{4 of} the diameter of the light transmitting portion of the heat ray absorbing filter 14 subjected to the light diffusion processing, and the distance L ₃ between the filter 14 and the incident surface of the cylindrical reflecting member 15 are represented by the following equation (3).
Is preferably satisfied. L ₃ ≦ (R ₄ −R ₂ ) / tan θ ₁ (3) [Other Embodiments] The light-generating signal device according to the present invention is not limited to the above-described embodiment, but falls within the scope of the gist. Can be changed in various ways.

For example, in the first embodiment, a light diffusing plate may be provided between the cylindrical reflecting member 15 and the optical fiber array 20, which is effective in achieving a uniform light amount distribution. Further, this light diffusing plate allows the cylindrical reflecting member 15 to be used.
Of the optical fiber array 20
Temperature rise can be reduced. If the inner surface of the cylindrical reflecting member 15 is a light diffusing surface, it is possible to make the light amount distribution more uniform.

The same performance can be obtained by using a parabolic mirror or a spherical mirror as the reflecting mirror 11 for covering the light source 10 in addition to the spheroidal mirror. There may be. Furthermore, 0 <but can be prevented as much as possible an increase in temperature of the optical fiber array 20 under the conditions of L _1, to further enhance this effect, it is effective to cool the incident surface of the optical fiber array 20 directly by the cooling fan .

[0020]

As is apparent from the above description, according to the present invention, since the cylindrical reflecting member is disposed at a position satisfying the expression (2 '), the light emitted from the light source can be efficiently transmitted to the optical fiber. The light can be guided to the array, the light amount distribution becomes uniform, and the density unevenness of the image can be prevented. Further, the temperature rise of the optical fiber array due to the heat generated by the light source can be prevented as much as possible, and a large cooling device is not required.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of an optical signal generator according to the present invention.

FIG. 2 is a sectional view showing an arrangement of a cylindrical reflecting member in the device shown in FIG.

3 is a graph showing a light amount unevenness delta ₂ on the emission surface of the cylindrical reflective member with respect to the distance L ₂ between the light source and the cylindrical reflecting member.

FIG. 4 shows a distance L between a cylindrical reflecting member and an optical fiber array.
₄ is a graph showing light amount unevenness Δ1 on the incident surface of the optical fiber array with respect to ₁ .

FIG. 5 is a sectional view showing a main part of a comparative example for the present invention.

FIG. 6 is a sectional view showing an arrangement of a cylindrical reflecting member in a second embodiment of the optical signal generator according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 15 ... Cylindrical reflecting member 20 ... Optical fiber array 30 ... Optical shutter array 40 ... Lens array for imaging

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Atsushi Fujita 2-3-13-1 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside the Osaka International Building Minolta Camera Co., Ltd. (56) References JP 1-273069 (JP, A) JP-A-60-254116 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/445 G02F 1/13 505 G02F 1/1335 G03G 15/04 111

Claims (1)

(57) [Claims] 1. A light source, an optical fiber array for converting light from the light source into a straight line, an optical shutter array for turning on and off light emitted from the optical fiber array, and an imaging lens array. A cylindrical reflecting member having a mirror surface or a light diffusing surface on its inner surface is provided between the light source and the optical fiber array at a position satisfying the following expression: 0 <L ₁ ≦ ( R ₂ -R ₁ ) / tan θ ₁ L ₁ : distance between the cylindrical reflection member and the optical fiber array R ₁ : radius of the aperture of the optical fiber array R ₂ : radius of the aperture of the cylindrical reflection member θ ₁ : optical fiber array An optical signal generator characterized by the following light receiving angles.