JPH058440A - Optical signal generator - Google Patents

Abstract

PURPOSE:To obtain an optical signal generator in which fluctuation of the amount of light is suppressed by suppressing the periodical fluctuation of the amount of light. CONSTITUTION:First and second focusing light transmitter arrays 30, 31 comprise a plurality of focusing light transmitters 30a, 31a arranged in zigzag in the longitudinal direction at a pitch of D/2. Each of the focusing light transmitters 30a, 31a has diameter of D. Focusing light transmitters having parabolic refractive index distribution from the center toward the periphery, for example, are employed as the focusing light transmitters 30a, 31a. The focusing light transmitter 31a in the first focusing light transmitter array 30 is shifted by half of the arranging pitch of the focusing light transmitter, i.e., a distance of D/4, in the arranging direction from the focusing light transmitter 31a in the second focusing light transmitter array 31. Consequently, fluctuations of the amount of light on the reflecting faces of the first and second focusing light transmitter arrays 30, 31 are offset each other resulting in suppression of periodical fluctuation.

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 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. It is known that the light emitted from this optical fiber array is turned on and off based on an image signal by an optical shutter array made of PLZT and an image is formed on a photoconductor through a converging optical transmission body array. ..

In such an optical signal generator, in order to reduce the variation in the amount of light in the light collecting portion of the optical fiber array, the converging reflecting mirror provided at the back of the light source is precisely polished or the light source ( Halogen lamp) is frosted on the inner surface of the tube to set a large diffusion of light, and a light diffusion plate is provided between the two. However, even if the above measures are taken, the arrangement pitch of the converging light transmitters is set to 1 because the optical signal generator uses the converging light transmitter array.
There has been a problem that a periodical variation in the amount of light as a period occurs.

Therefore, an object of the present invention is to provide an optical signal generator having a small variation in the amount of light by reducing the periodic variation in the amount of light.

[0005]

In order to solve the above-mentioned problems, the optical signal generator according to the present invention has first and second optical signal generators.
The converging light transmitting bodies of the converging light transmitting body array are arranged at the same pitch, and the first converging light transmitting body array and the second converging light transmitting body array are arranged in the arrangement direction of the converging light transmitting bodies. It is characterized in that it is displaced by a half of the array pitch.

The light emitted from the light source enters the first converging optical transmission medium array through the optical fiber array and is emitted from the emission surface of the first converging optical transmission medium array. The emitted light has a periodic variation in the amount of light, with the arrangement pitch of the converging light transmitters of the first converging light transmitter array as one cycle. The emitted light is incident on the second converging light transmitting body array through the optical shutter array and is emitted from the emitting surface of the second converging light transmitting body array. At this time, even in the second converging optical transmission medium array, there is a periodical variation in the amount of light with the converging optical transmission medium array pitch of the second converging optical transmission medium array as one cycle. Since the array and the second converging optical transmission medium array are deviated from each other in the arrangement direction of the converging optical transmission mediums by a dimension of 1/2 of the arrangement pitch, the periodical light quantity variation generated in the first converging optical transmission medium array. And the variation in the amount of light that occurs in the second converging light transmitting element array cancel each other out. Therefore,
Light having a small variation in the amount of light will be emitted from the emission surface of the second converging optical transmission body array.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical signal generator according to the present invention will be described below with reference to the accompanying drawings. The optical signal generator is
As shown in the schematic configuration of FIG. 1, it is composed of a light source 1, an optical fiber array 10, an optical shutter array 20, and first and second converging optical transmission body arrays 30 and 31.

The light source 1 comprises a halogen lamp, a xenon lamp, a metal halide lamp or the like. Light source 1
A reflecting mirror 5 having a focal point at the position of the light source 1 is arranged behind the. The reflection mirror 5 has a high near-infrared transmittance,
Moreover, a spherical cold mirror or the like in which a reflecting surface is coated with a dielectric multilayer film having a characteristic of high reflectance of visible light is adopted. The optical fiber array 10 is composed of a large number of optical fibers. One end of the optical fiber array 10 is bundled to form a light collecting section 11, and the other end is arranged in the main scanning direction (shown by an arrow A) to form an emitting section 22. As the optical fiber, for example, a step index type fiber including a core material of high-purity methacrylic resin and a coating material of special transparent fluororesin is used. The light guided to the daylighting section 11 is linearly emitted from the emission section 12 along the main scanning direction A. Light source 1 and optical fiber array 10
A heat ray absorbing filter (not shown) is arranged between the light collecting section 11 and the light collecting section 11 to protect the optical fiber array 10 from the radiant heat of the light source 1.

The optical shutter array 20 is provided so that its longitudinal direction is parallel to the main scanning direction A. The optical shutter array 20 has a structure in which an optical shutter element made of PLZT and its drive circuit are arranged on a glass substrate. The first converging optical transmission medium array 30 condenses the light emitted from the optical fiber array 10 on the optical shutter array 30, and the second converging optical transmission medium array 31 is emitted from the optical shutter array 20. The light is focused on the photosensitive drum 40. The same type of converging optical transmitter array is used for both, and the arrangement thereof will be described later.

In the above structure, the light emitted from the light source 1 is condensed by the reflecting mirror 5 or is directly guided to the daylighting section 11 of the optical fiber array 10 and is linearly emitted from the emission section 12. This light is condensed on the optical shutter array 20 via the first converging light transmitting body array 30. Each optical shutter element is turned on and off based on the image signal,
Only the light transmitted through the optical shutter element to which the voltage (half-wavelength voltage) is applied passes through the optical shutter array 20. The light passing through the optical shutter array 20 forms an image on the photosensitive drum 40 via the second converging light transmitting body array 31. The photosensitive drum 40 is rotationally driven in the direction of arrow a at a constant speed, and a predetermined image is formed on its surface as an electrostatic latent image.

A more detailed description will be given with reference to FIG. When the light receiving angle of the reflecting mirror 5 is θ (0) and the light receiving angle of the optical fiber array 10 is θ (1), the light source 1 is designed to satisfy the condition of θ (0) ≧ θ (1). The emitted light is efficiently condensed by the reflecting mirror 5 and is incident on the incident portion 11 of the optical fiber array 10. here,
Of the many optical fibers forming the optical fiber array 10, attention is paid to the three optical fibers A, B, and C arranged at the left and right ends and the central portion. Assuming that the light emitted from the light source 1 is incident on the optical fibers A and B at an incident angle θ (1) and is incident on the optical fiber C at an incident angle of 0 (that is, vertical), the optical fibers A, B, and C are The light that has passed through the optical fibers A, B, and 0 at the exit angles θ (1), θ (1), 0, respectively.
Emit from C. Aperture angle θ of each optical fiber A, B, C
(F) satisfies the relational expression of θ (F) ≧ θ (1). The light emitted from the optical fibers A, B, and C is incident on the optical shutter array 20 via the first converging optical transmission body array 30 at incident angles θ (1) and θ, respectively.
(1), 0 is incident. First converging optical transmitter array 30
The opening angle θ (S) of satisfies the relational expression of θ (S) ≧ θ (1). The light that has passed through the optical shutter array 20 forms an image on the photoconductor 40 via the second converging light transmission body array 31. The aperture angle θ (K) of the second converging optical transmission body array 31 satisfies the relational expression of θ (K) ≧ θ (1).

By the way, the first and second converging optical transmission body arrays 30 and 31 are arranged in the relationship shown in FIG. 3 in order to reduce the periodic variation of the light amount. As shown in FIG. 3, the first and second converging optical transmission body arrays 30 and 31 are sandwiched between two frame plates 50 and 51 so that their longitudinal directions are parallel to the main scanning direction A. Has been done. The converging optical transmission medium arrays 30 and 31 are composed of a plurality of converging optical transmission mediums 30a and 31a arranged in a zigzag pattern at a D / 2 pitch in the longitudinal direction.
Is equipped with. Here, D is the converging optical transmission body 30a, 3
The diameter is 1a. As the converging light transmission bodies 30a and 31a, for example, a converging light transmission body having a parabolic refractive index distribution from the center to the periphery is adopted. The field of view radius at the exit surface of each converging optical transmission body 30a, 31a is X ₀ ,
Assuming that the peak light quantity is E ₀ , each converging optical transmission body 30a,
The amount of light E (X) on the emission surface at a distance X from the optical axis of 31a in the main scanning direction is

[0013]

[Equation 1]

It is represented by The light amount distributions on the emission surfaces of the first and second converging optical transmission medium arrays 30 and 31 are expressed by the formula (1), and the light amounts E (X) on the emission surfaces of the converging optical transmission mediums 30a and 31a are expressed by It is obtained by adding them together. The curve 36 shown in FIG. 4 is the first converging optical transmission medium array 30 or the second converging optical transmission medium array 3 based on the equation (1).
1 shows the light amount distribution on the exit surface of No. 1. The vertical axis represents the relative light amount at the exit surface when the light amount of the light incident on the first converging light transmitting array 30 or the second converging light transmitting array 31 is used as a reference, and the horizontal axis indicates the main light amount. The distance in the scanning direction is taken. The curve 36 indicates the first and second converging light transmission bodies 30a and 31a of the first and second converging light transmission body arrays 30 and 31 because the converging light transmission bodies 30a and 31a are arranged in a staggered pattern at the arrangement pitch D / 2.
It is shown that the light emitted from the converging light transmitting element array causes periodic light amount unevenness of D / 2 pitch.

The first and second converging optical transmission medium arrays 30 and 31 having the above characteristics are converging optical transmission mediums 30a and 31a.
Are arranged with a displacement of 1/2 of the arrangement pitch D / 2. That is, both arrays 30 and 31 are displaced by a distance of D / 4 in the arrangement direction of the converging optical transmitters 30a and 31a. The light emitted from the first converging optical transmission medium array 30 arranged in this manner has a periodic variation in the amount of light with the arrangement pitch D / 2 of the converging optical transmission medium 30a as one cycle as shown by the curve 36. Have The emitted light enters the second converging light transmitting body array 31 via the optical shutter array 20, and is emitted from the emitting surface of the second converging light transmitting body array 31. At this time, even in the second converging optical transmission medium array 31, there is a periodical variation in the amount of light with the arrangement pitch D / 2 of the converging optical transmission mediums 31a as one cycle. Focusing optical transmitters 30a, 31a
Since they are arranged so as to be shifted by D / 4 in the arrangement direction, the periodical unevenness of the light amounts cancel each other out, and the emitted light having a uniform relative light amount shown by the straight line 38 is obtained. Here array 3
Although 0 and 31 are displaced in the arrangement direction of the converging optical transmission bodies 30a and 31a, it is preferable to arrange them so as to be accurately aligned in the direction orthogonal to this.

The optical signal generator according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the gist thereof. An elliptical mirror or the like may be used as the reflecting mirror of the light source. In addition, the light source and the optical fiber array 10
A condenser lens, an integrating cylinder, or a diffusion filter may be arranged between the light receiving surface and the incident surface. By arranging these, the amount of light emitted from the optical fiber array can be made uniform and the brightness can be increased.

Further, the exit surface of the optical fiber array and the first
A diffusion filter is provided between the converging optical transmission medium arrays 30 or between the first converging optical transmission medium array 30 and the optical shutter array 20 to diffuse the light condensed on the optical shutter array 20. You may make it uniform.

[0018]

As is apparent from the above description, according to the present invention, the converging light transmitting members of the first and second converging light transmitting member arrays are arranged at the same pitch, and Since the converging optical transmission medium array and the second converging optical transmission medium array are displaced from each other in the arrangement direction of the converging optical transmission medium by a dimension of 1/2 of the arrangement pitch, each of the first and second optical transmission medium arrays. Since the variations in the amount of light on the output surfaces of the two cancel each other out and the periodic variations are reduced, it is possible to obtain an optical signal generator having a small variation in the amount of light.

Further, unnecessary light to the photoconductor is reduced, and even if light having different directivity is incident on each optical fiber, the first and second arrangements are shifted by a half of the arrangement pitch of the converging optical transmission members. Since the directivity of the light is made substantially uniform by passing through the second converging light transmitting body array, unevenness of the light amount does not occur in the image formation on the photoconductor. Further, the length of the emitting portion of the optical fiber array in the main scanning direction may be substantially the same as that of the optical shutter array, and a compact optical signal generator can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an optical signal generator according to the present invention.

FIG. 2 is an operation explanatory view of the optical signal generator shown in FIG.

FIG. 3 is a partial front view showing a positional relationship between first and second converging optical transmission body arrays of the optical signal generator shown in FIG.

FIG. 4 is a graph showing a relative light amount distribution on the emission surface of the first or second converging optical transmission medium array and a relative light amount distribution after passing through the first and second converging optical transmission medium arrays.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 10 ... Optical fiber array 20 ... Optical shutter array 30 ... 1st converging optical transmission body array 31 ... 2nd converging optical transmission body array 30a, 31a ... Converging optical transmission body

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H04N 1/04 101 7251-5C (72) Inventor Matsubara and 2-chome Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 3-13 No. 13 Osaka International Building Minolta Camera Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A light source, an optical fiber array for linearly converting the light from the light source, and a first converging optical transmission array for converging the light emitted from the optical fiber array. And an optical shutter array for turning on / off the light emitted from the first converging light transmitting array, and a second converging light transmitting array for forming an image of the light emitted from the optical shutter array. The first and second converging optical transmission element arrays are arranged at the same pitch, and the first converging optical transmission element array and the second converging optical transmission element array are converged. An optical signal generator characterized in that it is displaced by a dimension of 1/2 of the arrangement pitch in the arrangement direction of the optical waveguides.