JPH11218701A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical device using an LED array as a light source and having a high speed processing property, a wide optical scanning area and the high degree of freedom in optical arrangement. SOLUTION: A circuit board 2A loading an LED array 1A and its driving circuit, a coupling lens 3A for coupling beams emitted from respective LED emitting parts, a linear image forming optical system 4A for forming each outgoing beam from the lens 3A as a linear image oblong in a main scanning corresponding direction, a light deflecting means 5A having a deflecting reflection face 6A in the vicinity of each linear image and capable of simultaneously deflecting respective beams at an equal angular speed, and a scanning formed- image optical system 7A for converging respective deflected beams on a surface 8 to be scanned as mutually separated optical spots and arranging the position of the reflection face 6A of the means 5A and the position of the surface 8 as approximately conjugate relation in geometrical optics about a sub-scanning corresponding direction are united as an optical scanning unit, plural optical scanning units A, B are arranged in the main scanning corresponding direction of the common surface 8 to be scanned and the main scanning areas of respective units A, B are mutually continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scanning optical device.

[0002]

2. Description of the Related Art Optical scanning devices are widely known in relation to digital copiers, optical printers and the like. In such an optical scanning device, a multi-beam type scanning optical device that optically scans a plurality of lines at a time is intended for the purpose of speeding up image writing by optical scanning. Also,
As a measure for enlarging an area in which an image can be written by optical scanning, a "wide-area optical scanning device" is known which optically scans a surface to be scanned simultaneously with two systems of light beams separated from each other in the main scanning direction (Japanese Patent Application Laid-Open No. Sho 60/1985). -35712). By the way, in a conventional scanning optical device, a semiconductor laser having a high emission intensity is used as a light source. Although it is intended to use a semiconductor laser array as a light source in the above-described multi-beam scanning optical device, the number of semiconductor laser light emitting units that can be arrayed by the semiconductor laser array is only a few at most, and the number of lines that can be simultaneously scanned is also limited. At most a few lines. Further, in the above-described wide area optical scanning device, a common rotary polygon mirror is used to deflect a light beam from each light source, and therefore, there is a problem that the layout of each light source and the imaging optical system is greatly restricted. On the other hand, as an optical writing device, a device using an LED array (light emitting diode array) is conventionally known. Since an LED array usually has several tens to several hundreds of LED light emitting units, such an LED
Array chips are densely arranged in the light emitting unit arrangement direction, and each L chip is used using a “1 × image forming system” such as a SELFOC lens array.
A 1: 1 image of the ED light emitting unit is formed on the surface to be scanned. LED
The problem with the optical writing device using an array is that a large number of LED array chips must be densely arranged in a straight line, and thus a large number of chips are required as light sources. For example, as a typical example of an LED array, one chip has 128 LED light emitting portions and a density of 400 dpi. Since the length of this chip is approximately 8 mm, for example, writing is performed in a region of 210 mm width. In order to perform the above, 26 chips must be arranged, and the linearity of the chip arrangement must be ensured.

In the case of the above-described scanning optical device, the scanning speed of the surface to be scanned by the deflected light beam is high, so that unless a semiconductor laser having a high emission intensity is used as a light source, the photoconductive photoreceptor forming the substance of the surface to be scanned is exposed to light. Therefore, there is a problem that it is difficult to write an electrostatic latent image, and therefore, a scanning optical device using an LED as a light source has not been put to practical use. However, recently, the sensitivity of the photoconductive photoconductor has been improved, and it has become possible to form an electrostatic latent image with a smaller amount of light.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a scanning optical device which uses an LED array as a light source, has a high speed, has a wide optical scanning area, and has a high degree of freedom in optical system arrangement. .

[0005]

The scanning optical device of the present invention has a plurality of "optical scanning units". Each of the optical scanning units has a circuit board, a coupling lens, a line image forming optical system, a light deflecting unit, and a scanning image forming optical system. The “circuit board” is a board on which the LED array and its driving circuit are mounted. "Coupling lens" is LE
The luminous flux from each LED light emitting unit of the D array is coupled. This coupling lens is connected to each of the LEs serving as a light source.
This lens is common to the D light emitting unit. The action of the coupling lens may be a “collimating action” for converting the light flux from each LED light emitting section into a parallel light flux, or may be an action for converting each of the light fluxes into a weakly divergent or weakly converging light flux. The “line image forming optical system” converts each emitted light beam from the coupling lens into a main scanning corresponding direction (in each optical scanning unit, a direction corresponding to the main scanning direction on an optical path from a light source to a surface to be scanned). This is an optical system that forms an image as a long linear image, and is common to the above-mentioned respective emitted light beams. As the line image forming optical system, a “sub-scanning corresponding direction (in each optical scanning unit,
A cylindrical lens or a concave cylinder mirror having a positive power only in the direction corresponding to the sub-scanning direction on the optical path from the light source to the surface to be scanned). The “light deflecting unit” has a deflecting reflection surface near each line image formed by the line image forming optical system, and deflects each light beam simultaneously and at a constant angular velocity. As the light deflecting means, a well-known rotating polygon mirror, rotating single mirror, or rotating two-face mirror can be used. The “scanning optical system” is provided in common for each light beam deflected at a constant angular velocity by the light deflecting unit, and condenses each light beam as a light spot separated from each other on the surface to be scanned. The scanning imaging optical system makes the position of the deflecting reflection surface of the light deflecting means and the position of the surface to be scanned substantially geometrically conjugate with respect to the sub-scanning corresponding direction. The scanning image forming optical system can be constituted by only a lens or a concave mirror having an image forming function, and can also be constituted as a mixed system of a reflecting mirror having an image forming function and a lens. It is preferable to have a function (fθ characteristic or linearity) for making the main scanning of the scanned surface uniform by the light spot, as well as the scanning image forming optical system.

That is, the optical scanning unit couples the light beams from the individual LED light emitting units of the LED array to the subsequent optical system by the coupling lens, and converts each light beam emitted from the coupling lens to a line image forming optical system. As a result, a long line image is formed in the main scanning corresponding direction. Then, the light is deflected at a constant angular velocity by the light deflecting means, and each deflected light beam is condensed as a light spot separated from each other on the surface to be scanned by the scanning image forming optical system, and the surface to be scanned is optically scanned. The plurality of optical scanning units are arranged in a direction corresponding to the main scanning with respect to a common surface to be scanned, so that the main scanning regions of the respective optical scanning units can be connected to each other.

That is, for example, in each optical scanning unit, when the first LED light emitting portion emits light to perform optical scanning, a line written by scanning by each optical scanning unit on the same surface to be scanned is one line. Can be written as a continuous line. That is, the scanning optical device of the present invention is capable of “wide-area light scanning”.

In the optical scanning unit, "the direction in which the light spot moves when performing the main scanning" is referred to as "main scanning direction". "Same direction".
In this case, synchronous light detecting means for detecting synchronous light at the start of writing is provided for each optical scanning unit so that the write start positions in the optical units are aligned.
Since the writing length of each optical scanning unit (the distance between the optical scanning start position and the optical scanning end position) is determined for each optical scanning unit, if the writing start position in an arbitrary optical scanning unit is determined, the optical scanning in that unit ends. Since the position is uniquely determined, by making the writing start position in one of the adjacent optical scanning units and the optical scanning end position in the other one continuous, as described above, the “main scanning areas of the respective optical scanning units are connected to each other. It can be done. The writing lengths of the respective optical scanning units may be set to be equal to each other, or may be set to be different from each other. In at least one pair of optical scanning units adjacent to each other of the plurality of optical scanning units, the direction of the main scanning is reversed, and the optical scanning units in the (paired) optical scanning units are disposed in the middle of the paired optical scanning units. In common, a synchronous light detecting means for detecting the synchronous light at the start of each write may be provided (claim 3). In this case, the write start positions of the adjacent optical scanning units are made continuous with each other in accordance with the synchronous light detected by the synchronous light detecting means.

L of LED array in optical scanning unit
The arrangement direction of the ED light emitting units is substantially the same in all the optical scanning units. In this case, the arrangement direction of the LED array light emitting units of the LED array in each optical scanning unit may be "aligned in the main scanning corresponding direction",
It may be "substantially parallel to the sub-scanning corresponding direction" (claim 4). The arrangement pitch of the LED light emitting units in the LED array chip is standardized and determined, for example, at 400 dpi, but the arrangement pitch has "variation" due to an error for each individual chip. In such a case, when there is variation in the arrangement pitch of the LED light emitting units for each optical scanning unit, in all the optical scanning units,
If the LED light emitting unit array direction of the LED array is aligned with the sub-scanning corresponding direction, the scanning line pitch becomes uneven due to the variation of the light emitting unit array pitch for each LED array chip. In such a case, the LEDs in the LED array
By slightly tilting the light emitting unit arrangement direction with respect to the sub-scanning corresponding direction, it is possible to adjust the interval of the light spot on the surface to be scanned in the sub-scanning direction. In the above description, "the arrangement direction of the LED array light emitting units is substantially parallel to the sub-scanning corresponding direction" means that the arrangement direction is slightly inclined to the sub-scanning corresponding direction to correct the irregularity of the scanning line pitch. Contains. Alternatively, the scanning line pitch can be switched by switching the angle of the arrangement direction with respect to the sub-scanning corresponding direction.

In the scanning optical device according to the present invention, each optical scanning unit can have an "beam shaping aperture" between the coupling lens and the line image forming optical system. In the invention described in claim 4, when the function of the coupling lens is a "substantial collimating function", it is preferable to dispose the aperture near the focal plane of the coupling lens (claim 5). In the LED array of each optical scanning unit, it is preferable that the center of the LED light emitting unit array is positioned near the optical axis of the coupling lens in the optical scanning unit. Claim 5
In the case of the invention described in (6), the substantial arrangement position of the beam shaping aperture is set as the object-side focal plane position of the line image forming optical system, and the focal length of the coupling lens is:
f _col and the focal length f _cy of the line image forming optical system in the sub-scanning corresponding direction can be made equal to each other (claim 7).

As described above, the actual surface of the surface to be scanned is the photosensitive surface of the photoconductive photosensitive member. As the photoconductive photoreceptor in the scanning optical device of the present invention, a "photosensitive photoreceptor having a high sensitivity such that an electrostatic latent image can be formed by light from an LED light emitting unit as a light source" is used. A conventionally known cylindrical shape or an endless / endless belt shape can be appropriately used. By the way, in the scanning optical device of the present invention, the light source used for each optical scanning unit is an LED array, and the LED light emitting units are 64 to 256.
In the case where the arrangement direction of the LED light emitting units is oriented in the sub-scanning corresponding direction as in the case of the invention according to claim 4, the scanning surface is optically scanned 64 to 256 lines at a time. become. For simplicity, 1m on the scanned surface
Considering the case where scanning is performed with 10 lines per m, for example, if there are 128 LED light emitting units, the width of light scanning at a time is 12.8 mm. When the photoconductive photoreceptor has a cylindrical shape, if the diameter is small, the diameter of the light spot may not be constant due to the curvature of the cylindrical surface within the width of 12.8 mm scanned simultaneously. Can be In order to avoid such a problem, the photoconductive photoconductor, which is the substance of the surface to be scanned common to the respective optical scanning units, is formed in an endless or endless belt shape, and the photoconductor is stretched in a plane. In this case, optical scanning may be performed (claim 8). Of course, when the arrangement direction of the LED light emitting units is oriented in the main scanning direction, the above problem does not occur even if a cylindrical photoconductor is used. However, even when the arrangement direction of the LED light emitting units is oriented in the main scanning direction, the photoconductor may be in the form of an endless or endless belt, and optical scanning may be performed in a portion where the photoconductor is stretched in a plane. Needless to say. Although the number of optical scanning units is appropriate, setting the number of units to 2 (claim 9) is practical in terms of compactness and cost of the apparatus.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numerals A and B denote an "optical scanning unit", and reference numeral 8 denotes a "photosensitive member which is a substance of a scanned surface common to the optical scanning of the optical scanning units A and B". ing.

The optical scanning unit A includes a circuit board 2A on which the LED array 1A and its driving circuit are mounted, a coupling lens 3A, a cylindrical lens 4A, a rotary polygon mirror 5A, a scanning image forming optical system 7A, and a synchronous light. It has a photosensor 9A for detection.

The optical scanning unit B includes a circuit board 2B on which the LED array 1B and its driving circuit are mounted, a coupling lens 3B, a cylindrical lens 4B, a rotary polygon mirror 5B, a scanning image forming optical system 7B, and a synchronous light. It has a photo sensor 9B for detection.

Since the functions of the optical scanning units A and B are the same, they will be described together. LED array 1
A (1B) is a circuit board 2A (2
B). The LED array has an LED light emitting unit of 64 to 2 with an array density of 300 dpi to 1200 dpi.
Those having 56 are known, and these known ones can be appropriately used. In this embodiment,
The arrangement direction of the LED light emitting units of the LED array 1A (1B) is set in a sub-scanning corresponding direction (a direction orthogonal to the drawing). The drive circuit mounted on the circuit board 2A (2B) together with the LED array includes each LE in the LED array.
The light emission output of the D light emitting unit can be controlled independently, and pulse width modulation or the like can be performed during optical scanning. The coupling lens 3A (3B) is provided in common to each LED light emitting unit in the LED array 1A (1B), and at least one coupling lens 3A (3B) is provided.
LED array 1A (1B) composed of two lenses
The light flux emitted from each LED light emitting unit is coupled to an optical system thereafter. Coupling lens 3A (3B)
May be a function of converting the light beam from each of the LED light emitting units into a “parallel light beam” or a function of converting the light beam into a “weakly divergent or weakly converging light beam”. Here, for the specificity of the description, the coupling lens 3A (3B)
Is a collimating action, and each L
The luminous flux from the ED light emitting unit is coupled to the coupling lens 3A (3
By B), a substantially parallel light beam is assumed.

A plurality of light beams coupled by the coupling lens 3A (3B) pass through the beam shaping aperture 10A (10B), and are condensed by the cylindrical lens 4A (4B) in the sub-scanning corresponding direction. An image is formed as a “long line image in the main scanning corresponding direction” separated from each other in the scanning corresponding direction. The rotary polygon mirror 5A (5B) has a deflecting / reflecting surface 6A (6B) near the image forming position of the line image, and rotates at a constant speed in the direction of the arrow (clockwise), respectively.
A plurality of light beams reflected by the deflecting reflection surface are simultaneously and uniformly deflected. The plurality of light beams deflected by the rotary polygon mirror 5A (5B) are condensed as light spots on the surface of the photosensitive member 8 which is the actual surface to be scanned, by the imaging operation of the scanning imaging optical system 7A (7B). I do. These light spots are coupled to a coupling lens 3A (3B), a cylindrical lens 4A (4B), and a scanning image forming optical system 7A (7
6B is an image of each LED light emitting unit according to B). In this embodiment, the scanning image forming optical system 7A (7B) is composed of one lens, and is an “anamorphic fθ lens” having positive power different in the main scanning corresponding direction and the sub-scanning corresponding direction. Regarding the sub-scanning corresponding direction, refer to “Deflection / reflection surface 6A (6
The position B) and the position of the surface to be scanned have a function of making them substantially geometrically optically conjugate. For this function, the "surface tilt" in the rotary polygon mirror 5A (5B) is corrected. Has functions. The photo sensor 9A (9B) is a "synchronous light detecting means", and receives at least one of a plurality of deflected light beams by the rotating polygon mirror 5A (5B) to generate a synchronization signal for starting optical writing. Each light beam emitted from each LED light emitting unit of the LED array 1A starts writing from a write start position: e, optically scans an area LA up to the position: f, and emits light from each LED light emitting unit of the LED array 1B. Each of the light fluxes starts writing from a position: f, and optically scans an area: LB up to a writing end position: g. Therefore, optical scanning can be performed continuously from the writing start position: e to the writing end position: f on the scanned surface at the position: f.

FIG. 2 is an explanatory diagram showing an optical arrangement in a state where an optical path from the LED array 1A (1B) to the surface to be scanned is linearly developed. The vertical direction in the figure is the sub-scanning corresponding direction. Multiple L of LED array 1A (1B)
The ED light-emitting portions (the LED arrays 1A and 1B are of the same type, and the number of LEDA light-emitting portions and the array density are the same) are arranged at regular intervals in the sub-scanning corresponding direction between the regions a and b in the figure. I have. Although the actual number of LED light emitting portions is as large as 64 to 256, five light emitting portions (marked by x) are shown for convenience of illustration. The LED array 1A (1B) is provided with its LED light emitting unit array surface substantially coincident with the object-side focal plane of the coupling lens 3A (3B). For this reason, when the light flux from each LED light emitting unit passes through the coupling lens 3A (3B), each light flux becomes a parallel light flux. In FIG. 2, a distance: f _col is a focal length of the coupling lens 3A (3B). Coupling lens 3
Each light beam (parallel light beam) transmitted through A (3B) passes through an aperture 10A (10B), is beam-shaped, and then passes through a cylindrical lens 4A (4B) to form a deflecting / reflecting surface of a rotary polygon mirror. A long line image is formed at the position 6A (6B) in the main scanning corresponding direction (the direction orthogonal to the drawing). The image formed at this time is shown in the area:
This is performed between a ′ and b ′. Aperture 10A (10
B) is provided substantially coincident with the image-side focal plane position of the coupling lens 3A (3B). Further, the approximate center of the LED light emitting unit array in the LED array 1A (1B)
It is located at the optical axis position of the coupling lens 3A (3B). The aperture 10A (10B) is also provided substantially coincident with the object-side focal plane of the cylindrical lens 4A (4B). The distance: f _cy shown in FIG. 2 is the focal length of the cylindrical lens 4A (4B). At this time, each line image formed by the cylindrical lens 4A (4B) forms an image on the image-side focal plane of the cylindrical lens 4A (4B) (which substantially matches the deflecting / reflecting surface 6A (6B)). . Each deflecting light beam by the deflecting reflection surface 6A (6B) is divided into a region a ″-
The light is focused as a light spot during b ''. LED array 1
Suppose the number of LED light emitting units in A (1B) is “128”
In this embodiment, the area between the write start position: e and the write end position: g in FIG. I can do it. The distance between the plurality of light spots on the surface 8 to be scanned in the sub-scanning direction is determined by the combination of the coupling lens 3A (3B), the cylindrical lens 4A (4B), and the scanning imaging optical system 7A (7B). The image forming magnification in the direction is determined by m, and the arrangement interval of the LED light emitting units in the sub-scanning corresponding direction is ξ with respect to 間隔. If the focal lengths f _col and f _cy shown in FIG. 2 are set to be equal to each other, the area: ab and the area: a′-b ′ in FIG. 2 become equal. Is the magnification in the sub-scanning direction of the scanning imaging optical system 7A (7B).

That is, the scanning optical device described in the above embodiment is composed of a circuit board 2A on which the LED array 1A and its driving circuit are mounted, and an LED for coupling a light beam from each LED light emitting portion of the LED array. A coupling lens 3A common to the light emitting unit, a line image forming optical system 4A for forming each of the emitted light beams from the coupling lens as a long line image in the main scanning corresponding direction, and the line image forming optical system Deflecting means 5A having a deflecting / reflecting surface 6A in the vicinity of each line image formed by the above and deflecting each light beam simultaneously and at a uniform angular velocity.
A light spot deflected by the light deflecting means, provided in common to each light flux, and condensed as light spots separated from each other on the surface to be scanned; And a scanning image forming optical system 7A having a substantially optically conjugate relationship with respect to the sub-scanning corresponding direction as an optical scanning unit, and a plurality of optical scanning units A and B A scanning optical device (Claim 1) is arranged in a scanning corresponding direction so that main scanning areas: LA and LB by respective optical scanning units can be made continuous with each other.
The "main scanning direction" in each of the optical scanning units A and B is the same direction, and each of the optical scanning units has synchronous light detecting means 9 and 9 'for detecting synchronous light at the start of writing. ).

In each of the optical scanning units A and B, L
The ED arrays 1A and 1B are arranged such that the arrangement direction of the LED light emitting units is substantially parallel to the sub-scanning corresponding direction (claim 4). Each of the optical scanning units A and B has apertures 10A and 10B for beam shaping between the coupling lenses 3A and 3B and the line image forming optical systems 4A and 4B. The action of the coupling lenses 3A, 3B is a substantial "collimating action", and the substantial arrangement position of the apertures 10A, 10B is the image-side focal plane position of the coupling lenses 3A, 3B. . As described above, the action of the coupling lenses 3A and 3B is substantially a collimating action, and the positions of the apertures 10A and 10B are the image-side focal plane positions of the corresponding coupling lenses 3A and 3B. , 1B pass through the coupling lenses 3A, 3B and become parallel luminous fluxes, and the principal rays of the luminous fluxes are transmitted through the apertures 10A, 10B.
B is a telecentric arrangement passing through the central portion (in the direction corresponding to the sub-scanning), and the beam shaping action of the apertures 10A and 10B can be made uniform for each light beam. Further, in the LED arrays 1A and 1B in each of the optical scanning units A and B, the center of the LED light emitting unit array is set near the optical axis of the corresponding coupling lens 3A or 3B (claim 6). For this reason, the effective diameter of the coupling lenses 3A and 3B can be efficiently used for the arrangement of the LED light emitting units. Also, an aperture 10A for beam shaping,
Since the substantial arrangement position of 10B is the object-side focal plane position of the cylindrical lenses 4A and 4B, which are linear image forming optical systems, the principal ray of each light beam transmitted through the cylindrical lenses 4A and 4B is a rotating polygon mirror. It becomes orthogonal to the rotation axes of 5A and 5B. Then, the coupling lenses 3A, 3
Since the focal length of B: f _col and the focal length in the sub-scanning corresponding direction of the cylindrical lenses 4A and 4B, which are linear image forming optical systems, f _cy are equal to each other, an image is formed in the vicinity of the deflecting and reflecting surface of the rotary polygon mirror. The distance in the sub-scanning corresponding direction of the line image
It becomes substantially equal to the interval between the D light emitting units. Since the array density of the LED light emitting units is standardized, such as 300, 400, 600, and 1200 dpi, in a commercially available LED array, the distance between the light spots on the surface to be scanned in the sub-scanning direction can be reduced. It can be easily set only by the relationship between the magnification of the scanning imaging optical systems 7A and 7B in the sub-scanning corresponding direction and the array density of the LED light emitting units. For example, if a 1200 dpi LED array is used to realize a scanning line pitch of 600 dpi in the sub-scanning direction on the surface to be scanned, the lateral magnification of the scanning imaging optical system in the sub-scanning corresponding direction is set to twice. good. Further, in the above-described embodiment, the optical scanning units are the two optical scanning units A and B (claim 9).

In the embodiment shown in FIG. 1, the photoreceptor 8 which is a substance of the surface to be scanned has a cylindrical shape. Of course, a belt-like photoreceptor is used, and the photoreceptor is stretched in a plane. Needless to say, it is possible to perform multi-beam optical scanning in the specified portion (claim 8). In the case of using a belt-shaped photoconductor, the shaft for driving the belt is shown in FIG.
In this case, the photoconductor surface may be parallel to the main scanning direction, which is the vertical direction, so that the surface of the photoconductor is optically scanned and becomes a plane orthogonal to the drawing of FIG. FIG. 3 is an explanatory diagram showing a scanned state of the photoconductor 8 in the above-described embodiment. The area indicated by the code DA is the area optically scanned by the optical scanning unit A, and the area indicated by the code DB is the area optically scanned by the optical scanning unit B.
As described above, the continuity of the boundary between the two is ensured by the proper setting of the write start position by the photosensors 9A and 9B as the synchronous light detecting means. In the above embodiment, the arrangement direction of the LED light emitting portions of the LED arrays 1A and 1B is aligned with the sub-scanning corresponding direction.
The synchronization signal for the light writing start position is shared by all the LED light emitting units in the LED array,
With a single synchronization signal for each array, the write start positions for multiple beams can be aligned. 5. The LED according to claim 4, wherein each of the light scanning units A and B has an LED.
The arrangement direction of the LED light emitting units of the arrays 1A and 1B is set to be "substantially parallel" to the sub-scanning corresponding direction, and the angle between the arrangement direction and the sub-scanning corresponding direction is adjusted so that the scanning line pitch by the writing areas LA and LB is adjusted. If you want to adjust the same, LED
When the array is controlled by the same synchronization signal, according to the inclination of the arrangement direction of the LED light emitting units with respect to the sub-scanning corresponding direction,
Since the write start position of the light spot is shifted for each light spot, in this case, the write start timing for each light spot is individually set according to the inclination angle and executed by the drive circuit. I do. In the above embodiment,
In the multi-beam optical scanning by one optical scanning unit, the number of deflecting and reflecting surfaces of the rotary polygon mirror is “N”, the moving speed of the photoconductor in the sub-scanning direction is v (mm / sec), and the number of LED light emitting units in the LED array is Assuming that “n” and the light emitting unit array density is “ρ (dpi)”, the number of rotations per unit minute in the rotary polygon mirror: R _M (rpm) is “R _M = ｛60 · ρ
(V / n)｝ / (25.4N) ”, and as n increases, the rotation speed of the rotating polygon mirror may be reduced. As in the scanning optical device of the present invention, n
= LED with "large n" such as 54-256
By using an array, the number of revolutions of the rotating polygon mirror can be effectively reduced, and the number of revolutions is relatively small. Therefore, the rotating polygon mirror can be rotated by an inexpensive motor. Also,
Since the wide area optical scanning is performed by two optical scanning units, the scanning area for each optical scanning unit may be the same as that of the conventional optical scanning. Therefore, the time required for writing one line is the same as that of the conventional optical scanning. Optical scanning of a main scanning area twice as large as that described above, and a large-area recorded image can be written at a high speed. In the above-described embodiment, the photo sensors 9A and 9B are provided as synchronous light detecting means for each of the optical scanning units A and B in order to determine the writing start position. However, it is possible to omit the synchronous light detecting means 9A in FIG. 1 by performing the following. That is, in the optical scanning units A and B, the rotation directions of the rotary polygon mirrors 5A and 5B are reversed, and the writing of the optical scanning areas LA and LB starts at the same position:
Start from f. In relation to FIG. 1, the optical scanning unit A performs optical scanning from the position: f to the position: e, and the optical scanning unit B performs optical scanning from the position: e to the position: g. To do. In this way, by disposing the “common synchronous light detecting means” for the optical scanning units A and B at the position of the photosensor 9B in FIG. 1, the synchronous light in each optical scanning unit can be detected. (Claim 3). However, when the synchronous light detecting means is shared by the two optical scanning units, it is necessary to identify which unit the detected synchronous light belongs to. Various measures are possible for this, but the following can be considered as an example. That is, in the above-described embodiment, since each LED array directs the LED light emitting unit in the sub-scanning corresponding direction, the LED scanning unit A, B provided at the position of the photo sensor 9B in FIG. As the synchronous light detecting means, a means having two light receiving sections separated in a direction orthogonal to the drawing is used. Then, when detecting the synchronization light, one LED array emits only the LED light emitting unit that emits a light beam that can be incident on only one of the two light receiving units, and the other LED array emits light. Only the LED light-emitting unit that emits a light beam that can enter only the other light-receiving unit emits light. With this configuration, it is possible to identify which of the optical scanning units the detected deflection light flux is based on which of the two light receiving units receives the light receiving signal.

It should be noted that the optical scanning units A and B can be used in common with the synchronous light detecting means, or the photo sensors 9A and 9B can be used as in the above-described embodiment. The light scanning units A and B are shielded by an appropriate light-shielding means so that the respective deflected light beams do not enter the scanning areas of the other units. So that it can be incident.

In the above embodiment, the optical arrangement of the optical path portion in the rotary polygon mirror from the LED array is reversed with respect to the optical scanning units A and B, but they are all arranged on the same side with respect to the rotary polygon mirror. May be. Although the case where the arrangement direction of the LED light emitting units of the LED array in each optical scanning unit is set to the sub-scanning corresponding direction has been described above, the arrangement direction of the LED light emitting units of the LED array of each optical scanning unit is aligned with the main scanning direction. It is also possible. In this case,
It is no longer multi-beam scanning. Further, the case where the number of optical scanning units is two has been described above. However, three or more optical scanning units may be used, and it is obvious what the embodiment in that case is. There will be.

[0023]

As described above, according to the present invention, a novel scanning optical device can be realized. The scanning optical device of the present invention uses an LED array as a light source, has a wide optical scanning area, and is capable of optical writing of a light beam. Also, the optical system for optical scanning is unitized as an optical scanning unit,
Since a plurality of optical scanning units are used, the degree of freedom in optical arrangement is high. According to the third aspect of the present invention, the number of synchronous light detecting means can be reduced as compared with the number of optical scanning units. According to the fourth aspect of the present invention, it is possible to perform wide-area optical scanning by multi-beam optical scanning at a time on 64 to 256 lines according to the number of LED light emitting units in the LED array.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one embodiment of a scanning optical device of the present invention.

FIG. 2 is a diagram for describing imaging in a sub-scanning corresponding direction in each optical scanning unit in the embodiment.

FIG. 3 is a diagram for explaining a scanned state of a photoconductor in the embodiment.

[Explanation of symbols]

 1A LED array 2A Circuit board 3A Coupling lens 4A Cylindrical lens 5A Rotating polygon mirror 7A Scanning imaging optical system 8 Photoreceptor 9A Synchronous light detecting means

Claims (9)

[Claims] A circuit board on which an LED array and a driving circuit for the LED array are mounted; a coupling lens common to the LED light emitting units for coupling a light beam from each LED light emitting unit of the LED array; It has a line image forming optical system for forming each light beam emitted from the lens as a long line image in the main scanning direction, and a deflecting reflecting surface near each line image formed by the line image forming optical system. A light deflecting means for simultaneously deflecting each light beam at an equal angular velocity; and a light deflecting means commonly provided for each light beam deflected by the light deflecting means, and condensing each light beam as a light spot separated from each other on the surface to be scanned. A scanning imaging optical system in which the position of the deflecting reflection surface of the light deflecting means and the position of the surface to be scanned are geometrically optically substantially conjugated with respect to the sub-scanning corresponding direction, as a unit as an optical scanning unit; Units, common arranged in the main scanning corresponding direction relative to the surface to be scanned, the scanning optical apparatus characterized by being adapted to be mutually made continuous in the main scanning region by the optical scanning unit. 2. The scanning optical device according to claim 1, wherein the main scanning direction in each optical scanning unit is the same, and each optical scanning unit has a synchronous light detecting means for detecting synchronous light at the start of writing. A scanning optical device, characterized in that: 3. The scanning optical device according to claim 1, wherein at least one pair of optical scanning units adjacent to each other has a main scanning direction opposite to that of the optical scanning unit, and an intermediate portion between the paired optical scanning units. A scanning optical device, comprising: a synchronous light detecting unit that is provided in common to these optical scanning units and detects synchronous light at the start of each writing. 4. The scanning optical device according to claim 1, wherein the LED array in each optical scanning unit is provided with the arrangement direction of the LED light emitting units substantially parallel to the sub-scanning corresponding direction. Scanning optical device. 5. The scanning optical device according to claim 4, wherein the action of the coupling lens is a collimating action, and each optical scanning unit is provided between the coupling lens and the line image forming optical system for beam shaping. A scanning optical device having an aperture, wherein a substantial arrangement position of the aperture is an image-side focal plane position of the coupling lens. 6. The scanning optical device according to claim 5, wherein the LED array in each optical scanning unit includes an LED array.
A scanning optical device, wherein a center of a light emitting unit array is set at a position near an optical axis of a coupling lens in the optical scanning unit. 7. The scanning optical apparatus according to claim 5, wherein the substantial arrangement position of the beam shaping aperture is the object-side focal plane position of the line image forming optical system, and the focal point of the coupling lens. A scanning optical device, wherein a distance: f _col is equal to a focal length: f _cy of a line image forming optical system in a sub-scanning corresponding direction. 8. A scanning optical device according to claim 1, wherein the photoconductive photoconductor, which is the substance of the surface to be scanned common to each optical scanning unit, has a belt shape. A scanning optical device wherein optical scanning is performed in a portion where a photoconductor is stretched in a plane. 9. The scanning optical device according to claim 1, wherein the number of optical scanning units is two.