JPH02198877A - Image forming device - Google Patents

Abstract

PURPOSE:To shorten a distance between body images, and to form image data onto the surface of a photosensitive body with high accuracy by setting each element so that an incident angle at a time when luminous flux emitted from the emission-picture end section of a fine light source is projected to the midpoint of a fine light source on a surface on the side reverse to the surface emission section of a transparent optical member and an adjacent fine light source is made larger than a critical angle. CONSTITUTION:Each element of the array pitches P of fine light sources, the refractive index (n) and thickness (d) of a transparent optical member 3, etc. is set so that an incident angle thetaat a time when luminous flux 1a1 emitted from the end section la of the effective emission region (l) of the fine light source 1a of a surface emission section 1 is projected to the midpoint 3a1 of a fine light source 1a on a surface (an outgoing surface) 3a on the side reverse to the surface emission section 1 of the transparent optical member 3 and a fine light source 1b adjacent to the light source 1a is made larger than an angle, where total reflection is generated, a critical angle thetaC. Luminous flux intended to be projected to regions except a region 6a on a recording surface 6 corresponding to the fine light source 1a in luminous flux emitted from the fine light source 1a is totally reflected by the outgoing surface 3a, guided to the side section of the transparent optical member 3 and is not projected to other regions of the recording section 6, thus preventing a crosstalk.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus, and in particular, uses a surface emitting section such as an LED array in which a plurality of minute light sources are arranged at a predetermined pitch. The present invention relates to an image forming apparatus suitable for data communication, facsimile communication, word processing, etc., in which image information is written and recorded on a recording surface such as a photosensitive drum, which is a light-receiving surface, by controlling the state.

(Prior art) Conventionally, high-density light emitting diode (LED) arrays and the like are used, each of these elements is driven and controlled by electrical signals, and light is selectively guided from each light emitting part onto the surface of a photoconductor via an optical system. An image recording apparatus such as a so-called LED printer that forms and records image information using the above-mentioned methods has been proposed, for example, in Japanese Patent Laid-Open No. 62-250468 and Japanese Patent Laid-Open No. 63-44777.

FIGS. 7 and 8 are schematic diagrams of main parts of a conventional image recording apparatus.

In FIG. 7, a surface light emitting unit 71 such as an LED array is imaged onto the surface of a photoreceptor 73 by a monocular imaging system 72.

The light emitting state of the surface emitting section 71 is controlled by an electric signal (not shown), and image information based on the light emitting state of the surface emitting section 71 at this time is formed on the surface of the photoreceptor 73.

Further, in FIG. 8, a surface light emitting unit 81 is formed into an erect, equal-magnification image on the surface of a photoreceptor 83 by a SELFOC lens array (SLA) 82 consisting of a plurality of SELFOC lenses (trade name). Similar to the image recording apparatus shown in FIG. 7, image information based on the light emitting state of the surface light emitting section 81 is written and recorded on the surface of the photoreceptor 83.

(Problems to be Solved by the Invention) In the image recording device using the monocular imaging system shown in FIG. However, there is a problem in that the distance between the object and image becomes as long as several 100 mm, which increases the size of the entire device and increases the cost.

In addition, in the image recording device using the SELFOC lens array shown in Fig. 8, the distance between the object and image is as short as several tens of millimeters, making the entire device more compact. In order to remove talk, a special light-shielding member must be placed in the optical path from the surface light-emitting section 81 to the lens exit surface 82a, which makes the entire device complicated and difficult to manufacture. Another problem is that lens arrays made in this way are expensive.

The present invention takes these problems into consideration, and allows the object-to-image distance to be easily shortened, making it easy to downsize the entire device, and eliminating the need for any special light-shielding member. An object of the present invention is to provide an image recording device that can form information on a photoreceptor surface with high accuracy.

(Means for Solving the Problems) The image forming apparatus according to the present invention controls the light emitting state of each of the small light sources of the surface emitting section in which a plurality of small light sources are arranged at a pitch P, and displays the plurality of small light sources on the light receiving surface. When forming image information based on the light emission state of a minute light source, a transparent optical member is closely integrated with the surface emitting section, and the light beam emitted from the end of the light emitting surface of the minute light source is transmitted to the surface of the transparent optical member. Each element is characterized in that each element is set so that the angle of incidence at the midpoint between the minute light source and the adjacent minute light source on the surface opposite to the light emitting section is larger than the critical angle.

In particular, in the present invention, the length of the effective light emitting area of the minute light source is 1, the refractive index of the transparent optical member is n, and θc=s i
When n −' (1/n), the thickness d of the transparent optical member including the adhesive layer is subtracted by 10 d (P-2)·co70.

It is characterized by being set to satisfy the following conditions.

(Embodiment) FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention. 11 in the figure is an image processing unit, such as a document reader, a TV
A scanning system 15 scans an image plane 14 of a document such as a camera,
A reflected light image based on the image information is received by a light receiving means, and the image information is converted into an electrical signal. In addition, it may be recorded on a recording medium, called from the recording medium, and controlled. 1
Reference numeral 2 denotes a control section, which drives and controls the surface light emitting section 1 such as an LED array in the recording section 13, which will be described later, based on electric signals sent from the image processing section 11. The recording section 13 forms and records image information on a recording surface 6 such as a photoreceptor drum, which is a light receiving surface, using electrical signals based on the image information controlled by the control section 12 .

The recording unit 13 in this embodiment is composed of the following elements as shown in the figure. 1 is a surface emitting part, which has an effective light emitting area (length) I that can control ON/OFF of an LED array, etc.
It is constructed by arranging a plurality of L minute light sources at a pitch of P in a seven-dimensional pattern on the second surface of the substrate. Reference numeral 3 denotes a transparent optical member, which is made of a member having a parallel plane plate or a lens array to be described later, and is disposed in close contact with the light emitting surface side of the surface light emitting section 1 via an adhesive layer or the like so that no air layer exists. ing.

In this embodiment, a case is shown in which it is made of a parallel plane plate. Reference numeral 5 denotes an air layer, and 6 a recording medium, which includes a photosensitive drum and the like.

In this embodiment, the luminous flux lal emitted from the end fLa of the effective light emitting area 1 of the small light source 1a of the surface emitting section 1, for example, is transmitted onto the surface (exit surface) 3a of the transparent optical member 3 on the opposite side from the surface emitting section 1. The arrangement pitch P of the minute light sources is adjusted so that the incident angle θ when it enters the intermediate point 3al between the minute light 1!1a and the adjacent minute light source 1b is larger than the so-called critical angle θc, which is the angle at which total reflection occurs. Each element such as the refractive index n and thickness d of the optical member 3 is set.

For example, the thickness d of the transparent optical member 3 including the adhesive layer is set as θc=sin-'('). Further, from the viewpoint of optical properties, it is desirable that the refractive index of the adhesive layer is approximately the same as the refractive index of the transparent optical member.

As a result, among the light beams emitted from one of the plurality of minute light sources 1a, the light beams that are about to enter an area other than the area 6a on the recording surface 6 corresponding to the minute light source 1a are removed from the exit surface of the transparent optical member 3. The light is totally reflected by the light beam 3a and guided to the side portions of the transparent optical member 3 to prevent it from entering other areas of the recording section 6, thereby preventing crosstalk. Further, it is desirable that the refractive index of the adhesive layer is approximately the same as that of the transparent optical member.

In this embodiment, such a configuration effectively prevents crosstalk between minute light sources, and forms image information sent from the image processing section 11 with high precision on the surface of the photoreceptor.

If the thickness of the transparent optical member becomes too thin exceeding the lower limit of conditional expression (1), it will be difficult to protect the light emitter and effectively obtain the desired total internal reflection, and if the thickness of the transparent optical member exceeds the upper limit If it becomes too much, the light flux that is not totally reflected will enter other areas of the photoreceptor 6, causing crosstalk, which is not good.

FIGS. 2 to 6 are schematic diagrams of main parts of the recording sections of second to sixth embodiments of the present invention, respectively.

In the second embodiment shown in FIG. 2, the transparent optical member 21 is formed of a plurality of optical elements 22a each having a refractive index distribution corresponding to a plurality of minute light sources 1a, lb, -.

22b, 22c, - (hereinafter referred to as "lens array")
It is made up of more. That is, a plurality of graded refractive index optical elements 22 a , 22 b , with the same pitch P as the arrangement pitch of the minute light sources so as to correspond one-to-one with each minute light source.
22 c , --- is constructed by monolithically arranging a lens array.

In this embodiment, when each optical element has a positive refractive power, the light flux in the marginal region of the light flux emitted from the minute light source is at the aforementioned intermediate point 2 of the exit surface 21a of the transparent optical member 21.
By configuring the beam to be totally reflected at 1a1, the light beam incident on the adjacent optical element area will also be totally reflected, and crosstalk can be effectively prevented.

In addition, in this embodiment, even without providing a special light shielding member, the light flux emitted from the exit surface 21a of the transparent optical member 21 is only the light flux that enters the optical element that corresponds one-to-one with the minute light source. Therefore, if the optical element at this time has a positive refractive power, the photosensitive surface can be set apart from the transparent optical member 21 so as to sandwich the air layer 5 therebetween. Even if the image formation by the lens array is not an erect image formation system but an inverted image formation system, the transparent optical member 21
Image information based on the light emitting state of the surface light emitting section 1 can be formed with high accuracy on the photoreceptor surface 6 on the exit surface 21a side.

In the third embodiment shown in FIG. 3, a transparent optical member 31 similar to the transparent optical member 21 in the second embodiment shown in FIG. Light sources 1a, lb.

A light shielding layer 31a is applied at the same pitch P as the pitch P of 1c, for example, by vapor deposition. Light shielding layer 31 in this example
Since a is the exit surface of the transparent optical element, it can be easily applied.

In this example, the incident angle θ1 corresponding to the incident angle θ shown in FIG. 1 of the luminous flux emitted from the light emitting end of the minute light source is θ1
It becomes 4θc.

In this embodiment, the light-shielding layer 31a can completely cut out the sudden spread of the emitted light into the air layer 5 near the critical angle, so it is possible to effectively reduce flare light on the photoreceptor surface. Further, it has the advantage that the alignment accuracy between the lens array and the plurality of minute light sources of the surface emitting section 1 can be relaxed by the width of the light shielding layer 31a.

In the fourth embodiment shown in FIG. 4, the transparent optical member 41 is made of a parallel plane plate similar to that of the first embodiment shown in FIG.
and minute light sources 1a and lb.

A light shielding layer 41a similar to that shown in FIG. 3 is provided at the same pitch P as the pitch P of 1c.... In this embodiment, since the light-shielding layer 41a can block the rapid spread of the emitted light near the critical angle, the distance of the air layer 5 can be made longer than in the first embodiment.

Other effects of the light shielding layer 41a are similar to those in the third embodiment.

Fifth. 5. shown in FIG. In the sixth embodiment, a plurality of optical elements of refractive index distribution type are provided on the entrance surface side and the exit surface side of the transparent optical member, respectively. In the fifth embodiment shown in FIG. 5, a plurality of optical elements 51a and 51b are arranged at a pitch P to face the entrance surface and the exit surface of the transparent optical member 51.

This embodiment has the advantage that the thickness of the air layer 5 can be made longer than in the embodiment shown in FIG. 2, and the depth during image formation can be increased.

In the sixth embodiment shown in FIG. 6, a plurality of optical elements 61a of a refractive index distribution type provided on the entrance surface side and the exit side of the transparent optical member 61,
The arrangement pitch P of the arrays 61b is shifted by 1/2 pitch. As a result, the thickness d of the transparent optical member 61 is made longer than, for example, the embodiment shown in FIG. 2, and the surface emitting section 1 is effectively protected.

In addition, 5th. In the sixth embodiment, if a light shielding layer similar to the light shielding layer shown in FIG. 3 is provided on the exit surface side of the transparent optical member, flare light can be effectively removed as in the third embodiment, and the lens The alignment accuracy between the array and the surface light emitting section can be further relaxed.

(Effects of the Invention) According to the present invention, by integrating a transparent optical member having the above-mentioned structure with an adhesive or the like into a surface emitting unit made up of a plurality of minute light sources such as an LED array, light can be emitted from one minute light source. The light flux is guided only to the corresponding area on the photoreceptor surface, which is the light-receiving surface, and the light flux incident on other areas is totally reflected on the exit surface of the transparent optical member, effectively preventing crosstalk. It is possible to achieve an image forming apparatus that can form image information on the surface of a photoreceptor with high accuracy according to the light emitting state of the part.

In addition, if the transparent optical member is provided with a lens array consisting of a plurality of optical elements of a refractive index distribution type having a light-condensing property, it becomes possible to set an air layer between the exit surface and the photoreceptor surface. Crosstalk can be effectively prevented without the need for a special light-shielding member, and it is also possible to use an inverted imaging system, making it possible to create a simple and compact image forming device with a shorter optical path length. can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main part of the first embodiment of the present invention, FIGS. 2 to 6 are schematic diagrams of the main part near the recording section of the second to sixth embodiments of the invention, and FIG. FIG. 8 is a schematic diagram of the main parts of a conventional image recording apparatus. In the figure, 11 is an image processing section, 12 is a control section, 13 is a recording section, 15 is a scanning system, 14 is an image, 1°71.81 is a surface emitting section, 2 is a substrate, 3 is a transparent optical member, 22a, 22b, 2
2c is an optical element, 5 is an air layer, 6, 73, 83 is a recording medium, and 31a is a light shielding layer.

Claims (4)

[Claims] (1) When controlling the light emitting state of each small light source of a surface emitting unit in which a plurality of small light sources are arranged at a pitch P and forming image information based on the light emitting state of the plurality of small light sources on the light receiving surface, the surface A transparent optical member is closely integrated with the light emitting part, and the light beam emitted from the end of the light emitting surface of the micro light source is adjacent to the micro light source on the surface of the transparent optical member on the opposite side to the surface light emitting part. An image forming apparatus characterized in that each element is set so that an incident angle at an intermediate point with a minute light source is larger than a critical angle. (2) The image forming apparatus according to claim 1, wherein each of the elements is an arrangement pitch P of effective light emitting parts of the plurality of minute light sources, and a refractive index and thickness of the transparent optical member. (3) When the length of the effective light emitting area of the minute light source is l, the refractive index of the transparent optical member is n, and θ_c=sin^-^1 (1/n), the transparent optical system including the adhesive layer The thickness d of the member is (P/10)<d<・{(P-l)/2}・cotθ_
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to satisfy condition c. (4) The image forming apparatus according to claim 1 or 2, wherein the transparent optical member includes a plurality of optical elements each having a refractive index distribution corresponding to the plurality of minute light sources.