JP3197804B2 - Multi-beam scanner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an image forming apparatus such as a laser printer and a digital copying machine.
The present invention relates to a multi-beam scanning apparatus that collectively scans a surface to be scanned (photoconductor) with a plurality of semiconductor lasers or a semiconductor laser array as a light source.

[0002]

2. Description of the Related Art There has been known a so-called multi-beam scanning apparatus for simultaneously scanning a plurality of light beams on a surface to be scanned (photoconductor). This multi-beam scanning device includes a beam combining system that combines a plurality of light beams using a plurality of semiconductor lasers (LDs) as light sources using a prism or the like, and a semiconductor laser array (L) that also includes a plurality of light emitting units as light sources.
D array) is most commonly used.

The above beam combining method is disclosed in, for example,
JP-A-1-245174, JP-A-3-225314, and Japan Hardcopy '93 p.
222.

These devices take out a light beam from a direction which does not contribute to optical writing of a beam combining means (prism), guide the light beam to a detecting means such as a split sensor, detect a beam interval, and automatically control means (servo control mechanism). Thus, it is intended to control the beam interval on the surface to be scanned during the non-writing time.

[0005] In these beam synthesizing methods, any attempt has been made to eliminate or reduce the beam interval fluctuation caused by the light source section, that is, the portion from the light source to the beam synthesizing means.

FIG. 7 is an explanatory view showing an optical arrangement of a conventional general multi-beam scanning device. FIG. 7 shows a state in which an optical path is linearly developed from an LD to a beam combining prism with respect to a sub-scanning section. Is shown.

In the figure, light emitting units 701a, 701 of each LD are shown.
The light beam emitted from the light source 01b is converted into a substantially parallel light beam by each of the collimating lenses 701c and 701d, and then combined by a prism (not shown).
After a linear image is formed in the vicinity of the deflection reflection surface 704a of the deflector 704 via the cylinder lens 703, the deflection reflection surface 704a and the surface to be scanned 706 are set to be substantially conjugate in the sub-scan section. The second imaging optical system (fθ optical system) 705 causes a minute spot 7
The images are formed as a and 7b.

[0008] The spot interval Ps on the scanned surface 706 is
Ps = | βs | · f _1s · tan θs is represented by the angle θs between beams before the incidence of the cylinder lens 703, the focal length f _1s of the cylinder lens 703, and the imaging magnification βs of the second imaging optical system 705. You. Further, the angle θs is set so as to obtain a predetermined spot interval Ps.

Here, since the distance between the aperture 702 and the cylinder lens 703 is arbitrary, they are usually arranged close to each other. At this time, the angle θ's between the beams emitted from the cylinder lens 703 is: The beam is incident on the second imaging optical system 705 with almost the same as before the incidence, each beam is inverted in angle by the second imaging optical system 705, and each beam is crossed at the intersection 708 in front of the surface to be scanned 706. Crosses once to arrive at the scanned surface 706.

On the other hand, the LD array system is disclosed in, for example, Japanese Patent Application Laid-Open No. 54-158251. Here, a predetermined scanning line interval is obtained on the surface to be scanned by installing the LD array with the light emitting unit array direction of the LD array inclined at a predetermined angle with respect to the main scanning direction.

By the way, even in the beam synthesizing method, when each beam is close to the main scanning direction at the time of detecting the synchronizing signal, an accurate synchronizing signal cannot be obtained due to crosstalk or the like.
Since it is necessary to set the distance apart by about 1 to 2 mm or more in the main scanning direction, similarly, the beam interval in the main scanning direction on the deflecting / reflecting surface increases.

For this reason, in Japanese Patent Publication No. Sho 64-10804, the image-side focal length of the collimator lens is set in the vicinity of the deflecting reflection surface so as to eliminate the beam spread in the main scanning direction on the deflecting reflection surface. .

[0013]

However, in the conventional multi-beam scanning apparatus as described above, in the beam combining method, the crossing point is the image-side focal point F ' _2S of the second imaging optical system. And the surface to be scanned is located very close to the surface to be scanned, so that pitch fluctuation due to defocus is likely to occur near the surface to be scanned.

That is, if the surface to be scanned relatively fluctuates due to environmental fluctuations or assembling errors, and shifts to the position indicated by 707, the spot interval changes from Ps to P's, so-called pitch unevenness occurs. I will.

This phenomenon is not limited to the beam combining method,
The same applies to the array system, which is a problem caused by the multi-beam scanning optical system. In particular, this phenomenon becomes more remarkable when the magnification of the second imaging optical system is small.

In Japanese Patent Publication No. Sho 64-10804, the focal length of the collimating lens is usually as small as about 30 mm or less, and the collimating lens and the deflecting reflector are usually used to correct the tilting of the deflecting reflecting surface. It is necessary to dispose an optical system (usually a cylinder lens) having a refractive power in the sub-scan section between the surface and the surface, but such a configuration is physically extremely difficult. Further, when the focal length of the collimating lens is increased, the light use efficiency is reduced, so that there is a problem that a sufficient light amount cannot be obtained.

Further, in the LD array system, when trying to obtain a predetermined scanning line interval, the beam interval in the main scanning direction is widened on the deflecting and reflecting surface of the deflector (such as a rotary polygon mirror). However, there has been a problem that the rotation angle becomes narrow and the size of the deflector needs to be increased.

Further, in the LD array system, as described above, the LD array is installed at a predetermined angle with respect to the main scanning direction. At this time, the direction of the pn junction surface of the LD array is substantially perpendicular to the sub-scanning direction. The far-field pattern (far-field pattern) of the light intensity distribution has an elliptical shape long in the sub-scanning direction.

This is inferior in compatibility with the optical system of an ordinary optical scanning device, and the focal length of the collimator lens must be increased in order to obtain a required beam diameter after exiting the collimator lens in the main scanning direction. . At this time, since the beam diameter in the sub-scanning direction becomes unnecessarily large, there is a problem that large vignetting occurs due to the aperture, and the light use efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and suppresses occurrence of spot intervals in the sub-scanning direction due to defocus, and realizes high-quality multi-beam scanning with a simple configuration. It is another object of the present invention to suppress the spread of a beam in the vicinity of the deflector, thereby avoiding an increase in the size of the deflector and realizing multi-beam scanning with high light use efficiency.

[0021]

According to a first aspect of the present invention, there is provided a multi-beam scanning apparatus, comprising: a light source for emitting a plurality of light beams; and a light source for emitting a plurality of light beams. A deflector that deflects a plurality of light beams and exposes and scans the surface to be scanned, an aperture that is disposed between the light source unit and the deflector, and performs beam shaping, and between the aperture and the deflector. A first imaging optical system for linearly imaging each of the arranged and incident light beams near the deflector, and a first imaging optical system arranged between the deflector and the surface to be scanned, and And a second imaging optical system for forming an image as a minute spot on the surface to be scanned.
One lens of which is a cylindrical lens, the second lens including an optical axis of an optical system and being parallel to a main scanning direction in which a light beam is scanned on the surface to be scanned by the deflector. In the first section, the first imaging optical system is an afocal optical system for expanding the diameter of a light beam, and the first imaging optical system is optically conjugate with the aperture and a point near the deflector. In the second section including the optical axis of the optical system in the first imaging optical system and parallel to a sub-scanning direction perpendicular to the direction in which the light beam is scanned on the surface to be scanned by the deflector, Disposing the aperture on the light source side with respect to the object side focal point of the first imaging optical system, and optically conjugate the aperture and the object side focal point of the second imaging optical system. What is configured to become A.

That is, by arranging the aperture on the light source section side of the object-side focal point on the sub-scanning surface of the first imaging optical system, the light beam emitted from the first imaging optical system is The distance between the intersection point where the light beams intersect and the surface to be scanned is increased, and the angle between the beams near the surface to be scanned is also reduced. This makes it difficult for spot intervals to fluctuate in the sub-scanning direction due to defocus.

Further, the first imaging optical system is configured such that the aperture and the object-side focal point of the second imaging optical system are optically conjugate in the sub-scanning section, so that the second imaging Since the optical system is a telecentric optical system in the sub-scanning cross section, the light beams near the surface to be scanned are parallel to each other, and substantially no fluctuation of the spot interval in the sub-scanning direction due to defocusing occurs.

The first imaging optical system is an afocal optical system for expanding the diameter of the light beam in the main scanning section, and the aperture and a point near the deflector are optically conjugate in the main scanning section. With this configuration, the spread of the beam near the deflector can be suppressed, and multi-beam scanning with higher light use efficiency can be realized without increasing the size of the deflector.

[0025]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

(Basic Configuration of Multi-beam Scanning Apparatus) FIG. 1 is an explanatory diagram showing a basic configuration of a multi-beam scanning apparatus according to the present invention. In the figure, 101 is a light source unit that emits a light beam, 102 is an aperture for shaping the light beam, and 103 is a first light source using a cylinder lens described later.
104 is a deflector that has a mirror surface on each surface of a regular polygon and rotates at a high speed. 105 is a second imaging optical system using an anamorphic fθ optical system. 106 is a folding mirror. is there. Reference numeral 110 denotes a photosensitive drum on which an electrostatic latent image is formed, and 107 denotes a surface of the photosensitive drum 110 to be scanned.

FIG. 2 is an explanatory diagram showing the configuration of the light source unit 101 in FIG. In FIG. 2B, 201a to 201a
Reference numeral 201b denotes a laser diode (LD);
202b is a collimating lens, 203 is a prism for performing beam synthesis. Also, as shown in FIG.
The light source unit 101 of the LD array type has an L having a plurality of light emitting units.
It comprises a D array 201 and a collimating lens 202.

(Operation of Multi-beam Scanning Apparatus) In the above configuration, each light beam emitted from the light source unit 101 is transmitted to the aperture 102 and the first imaging optical system 103.
Are incident on the deflecting and reflecting surface 104a of the deflector 104 so as to form a linear image, and are repeatedly deflected in the main scanning direction by the deflecting and reflecting surface 104a of the deflector 104.

Each of the deflected light beams passes through a folding mirror 106 provided as necessary by a second imaging optical system 105, and the photosensitive drum 1 on the surface to be scanned 107 is turned on.
Exposure scanning is performed while forming an image at a predetermined spot interval Ps in the sub-scanning direction.

The second imaging optical system 105 is an anamorphic fθ optical system. In the main scanning section, the incident light beam is scanned on the scanning surface 107 while almost satisfying the fθ characteristic.
In addition to forming an image on the upper side, the deflecting reflection surface 104a and the surface to be scanned 107 are set to be substantially conjugate in the sub-scan section, and have a so-called surface tilt correction function.

Next, an embodiment according to the present invention will be described based on the above basic configuration [Embodiment 1], [Embodiment 2], [Embodiment 3].
Will be described in this order.

First Embodiment FIG. 3 is an explanatory view showing an optical arrangement of a multi-beam scanning device according to a first embodiment.
The optical path from 01 to the scanned surface 107 is shown in a linearly developed state.

Each light beam emitted from the light emitting units 201a and 201b of each LD (or the light emitting units 201a and 201b of the LD array) is applied to each of the collimating lenses 202a and 202b.
2b (or a collimating lens 202), each of them is converted into a substantially parallel light beam, then synthesized by a prism (not shown), and deflected by a deflector 10 via an aperture 102 and a first imaging optical system (cylinder lens) 103, respectively.
An image is formed linearly in the vicinity of the deflecting reflection surface of No. 4.

Thereafter, the light beam is applied to a second imaging optical system (anamorphic f) set so that the deflection reflecting surface 104a and the surface to be scanned 107 are substantially conjugate in the sub-scanning section.
The optical system 105 forms an image as a minute spot on the surface to be scanned 107.

In this case, the spot interval on the surface to be scanned 107 is set to a predetermined pitch Ps. That is, the angle θs between the beams emitted from the light source unit 101, the focal length f _{1S of} the cylinder lens (first imaging optical system 103), and the imaging magnification βs of the second imaging optical system 105 are as follows: Ps = | Βs | · f _1S · tan θs is set.

Here, since the aperture 102 is disposed closer to the light source 101 than the object-side focal point F _1S of the cylinder lens (the first imaging optical system 103), the aperture 10
The conjugate point A of the second cylinder lens (the first imaging optical system 103) is
It is formed closer to the surface 107 to be scanned than 3).

Accordingly, each light beam incident on the cylinder lens (first imaging optical system 103) while being collectively shaped by the aperture 102 and expanding each other at the relative angle θs is applied to the cylinder lens (first imaging optical system 10).
The direction is changed by 3), and the light is incident on the second imaging optical system 105 while the beam interval is narrowed.

Here, the second imaging optical system 10 at the conjugate point A
5, the conjugate point B is at least the second imaging optical system 10
5 are formed closer to the light source unit 101 than the image-side focal point F ′ _2S , the respective light beams once intersect at the position of the conjugate point B and then form at the interval Ps on the surface to be scanned 107 as described above. Imaged.

Therefore, as compared with the case where the aperture 102 is arranged close to the cylinder lens (the first imaging optical system 103) (see FIG. 1), the distance between the intersection point B of the light beam and the surface 107 to be scanned is larger. Becomes larger, the scanned surface 107
The angle between adjacent beams becomes small, and the fluctuation of the spot interval due to defocus hardly occurs.

The second imaging optical system 105 is a normal anamorphic fθ optical system, and FIG.
Although shown as a single lens, it is actually composed of at least two or more lens (or mirror) systems as generally used.

(Effects of the First Embodiment) According to the first embodiment, the aperture 102 is disposed closer to the light source than the object-side focal point on the sub-scanning surface of the cylinder lens (first imaging optical system 103). The light beam emitted from the first imaging optical system 103 is incident on the second imaging optical system 105 such that the distance between the light beams is reduced on the sub-scanning surface, and the light beam crosses the intersection point where the light beams intersect. The distance from the scanning surface 107 increases, and the angle between the beams in the vicinity of the scanning surface 107 also decreases, so that the spot spacing in the sub-scanning direction due to defocus does not easily change. Therefore, high-quality multi-beam scanning is realized with a simple configuration.

[Embodiment 2] FIG. 4 is an explanatory view showing an optical arrangement of a multi-beam scanning apparatus according to Embodiment 2;
The optical path from 01 to the scanned surface 107 is shown in a linearly developed state.

The light beams emitted from the light emitting units 201a and 201b of each LD (or the light emitting units 201a and 201b of the LD array) are respectively transmitted to the collimating lenses 202a and 202b.
2b (or a collimating lens 202), each of them is converted into a substantially parallel light beam, then synthesized by a prism (not shown), and deflected by a deflector 10 via an aperture 102 and a first imaging optical system (cylinder lens) 103, respectively.
An image is formed linearly in the vicinity of the deflecting reflection surface of No. 4.

Thereafter, the light beam is applied to a second imaging optical system (anamorphic f) set so that the deflecting reflection surface 104a and the surface to be scanned 107 become substantially conjugate in the sub-scanning section.
The optical system 105 forms an image as a minute spot on the surface to be scanned 107.

In this case, the spot interval on the surface to be scanned 107 is set to a predetermined pitch Ps. That is, the angle θs between the beams emitted from the light source unit 101, the focal length f _{1S of} the cylinder lens (first imaging optical system 103), and the imaging magnification βs of the second imaging optical system 105 are as follows: Ps = | Βs | · f _1S · tan θs is set.

Here, the aperture 102 is set to be optically conjugate with the object side focal point F _{2S of} the second imaging optical system 105 by the cylinder lens (the first imaging optical system 103).

That is, the focal length of the cylinder lens (first imaging optical system 103) is f _2S , the distance between the aperture 102 and the cylinder lens (first imaging optical system 103) is s,
Assuming that the distance between the cylinder lens (first imaging optical system 103) and the object-side focal point _F2S of the second imaging optical system 105 is s ', 1 / s = 1 / _f1S- 1 / s' is satisfied. Is set to

Accordingly, the light beams incident on the cylinder lens (the first imaging optical system 103) while being collectively shaped by the aperture 102 and expanding each other at the relative angle θs are converted to the cylinder lens (the first imaging optical system 10).
The direction can be changed by 3), and the second imaging optical system 10
After crossing around the object side focal point F _{2S of} No. 5, the light enters the second imaging optical system 105.

That is, each light beam emitted from the second imaging optical system 105 is made parallel to the optical axis, and
07 is imaged at an interval Ps. Therefore, the fluctuation of the spot interval due to the defocus does not substantially occur.

The second imaging optical system 105 is a normal anamorphic fθ optical system, and FIG.
Although shown as a single lens, it is actually composed of at least two or more lens (or mirror) systems as generally used.

(Effects of Second Embodiment) According to the second embodiment, the cylinder lens (the first imaging optical system 103) has the object-side focal point of the aperture 102 and the second imaging optical system 105 in the sub-scan section. Are optically conjugated to each other, so that the second imaging optical system 105 becomes a telecentric optical system in the sub-scan section,
The light beams in the vicinity of the surface to be scanned 107 are parallel to each other, and do not substantially change the spot interval in the sub-scanning direction due to defocus, thereby realizing simple and high-quality multi-beam scanning.

Third Embodiment FIGS. 5 and 6 are explanatory views showing an optical arrangement of a multi-beam scanning device according to a third embodiment. FIG. 5 shows a main scanning section, and FIG. 6 shows a sub-scanning section. The optical paths from the light source 101 to the surface to be scanned 107 are linearly developed.

The light beams emitted from the light emitting units 201a and 201b of each LD (or the light emitting units 201a and 201b of the LD array) are respectively transmitted to the collimating lenses 202a and 202b.
2b (or a collimating lens 202), each of them is converted into a substantially parallel light beam, then synthesized by a prism (not shown), and deflected by a deflector 10 via an aperture 102 and a first imaging optical system (cylinder lens) 103, respectively.
An image is formed linearly in the vicinity of the deflecting reflection surface of No. 4.

Thereafter, the light beam is applied to a second imaging optical system (anamorphic f) set so that the deflecting reflection surface 104a and the surface to be scanned 107 are substantially conjugate in the sub-scanning section.
The optical system 105 forms an image as a minute spot on the surface to be scanned 107.

In this embodiment, the first image forming optical system (cylinder lens) 103 comprises a cylinder lens 103a and a spherical lens 103b having a refractive power in the main scanning section.
Assuming that the focal length of the cylinder lens 103a is f _3M and the focal length of the spherical lens 103b is f ₄ (> f _3M ), as shown in FIG. 5, the lens is arranged between the aperture 102 and the deflecting / reflecting surface 104a. In the cross section, the aperture 102 and the deflecting / reflecting surface 104 are conjugated to each other, and each of the incident light beams is a beam expander that expands the beam by m (= f ₄ / f _3M ) times.

Therefore, in the main scanning section, each light beam spreading from the aperture 102 at an angle θ _M is expanded by m times on the deflecting / reflecting surface 104a, and furthermore, becomes an overlapped light beam. Thus, it is not necessary to increase the size of the deflector 104, and a multi-beam system with high light use efficiency is possible in the LD array system. Further, the collimating lenses 202a,
Since the focal length of 02b can be reduced, the size of the apparatus can be reduced.

In the sub-scanning section, the first imaging optical system 103, that is, the spherical lens 103b is set so that the aperture 102 and the object-side issue F _{2S of} the second imaging optical system 105 are conjugate. Have been.

That is, the distance between the aperture 102 and the first imaging optical system (cylinder lens) 103 is set to s (= 2 · f
_3M + f ₄ ), first imaging optical system (cylinder lens) 10
3 'When, 1 / s = 1 / f 4 -1 / s' distance s of the object-side focal point F _2S of the second imaging optical system 105 is set so as to satisfy.

Accordingly, in the sub-scan section, the light beams after passing through the second imaging optical system 105 are made parallel, and the spot interval in the sub-scan direction on the surface to be scanned 107 does not change due to defocus.

Here, the spot interval on the surface to be scanned 107 is set to a predetermined pitch Ps. That is, the angle θs between the beams emitted from the light source unit 101, the focal length f _{1S of} the cylinder lens (first imaging optical system 103), and the imaging magnification βs of the second imaging optical system 105 are as follows: Ps = | Βs | · f _1S · tan θs is set.

The relationship between the spot interval P _M on the surface to be scanned 107 in the main scanning direction and the angle θ _M between the beams in the main scanning section after the light is emitted from the light source unit is determined by the second imaging optical system 105. When the focal length in the main scanning cross section and f _2M, denoted as _{P M = f 2M · θ M} [ rad] / m, θ _M is set to a predetermined P _M based on the above equation by the beam combining scheme Is done.

The second imaging optical system 105 is a normal anamorphic fθ optical system, and FIG.
Although shown as a single lens, it is actually composed of at least two or more lens (or mirror) systems as generally used.

(Effect of Third Embodiment) According to the third embodiment, in addition to the effects of the first and second embodiments, the cylinder lens (the first imaging optical system 103) emits a light beam in the main scanning section. Since the diameter of the afocal optical system is increased, and the point near the aperture 102 and the deflector 104 is optically conjugate in the main scanning section, the spread of the beam near the deflector 104 can be suppressed. Thus, multi-beam scanning with higher light use efficiency can be realized without increasing the size of the deflector 104.

[0064]

As described above, according to the multi-beam scanning apparatus of the present invention, the aperture is arranged closer to the light source than the object side focal point on the sub-scanning surface of the first imaging optical system. The light beam emitted from the first imaging optical system is reduced in the sub-scanning surface so that the distance between the light beam
In this case, the distance between the intersection point where the light beams intersect and the surface to be scanned increases, the angle between beams near the surface to be scanned decreases, and the spot spacing in the sub-scanning direction due to defocusing Is less likely to occur. Therefore, multi-beam scanning with high quality and a simple configuration is realized.

According to the multi-beam scanning device of the present invention, the first imaging optical system optically conjugates the aperture and the object-side focal point of the second imaging optical system in the sub-scanning section. With such a configuration, the second imaging optical system becomes a telecentric optical system in the sub-scanning cross section, so that the light beams near the surface to be scanned become parallel to each other and are substantially defocused in the sub-scanning direction. Interval fluctuations do not occur. Therefore, high quality and
Multi-beam scanning with a simple configuration is realized.

Further, according to the multi-beam scanning apparatus of the present invention, the first imaging optical system is an afocal optical system for expanding the diameter of the light beam in the main scanning section, and the point near the aperture and the deflector is provided. Is configured to be optically conjugate in the main scanning section, so that the beam spread near the deflector can be suppressed, and multi-beam scanning with higher light use efficiency is realized without increasing the size of the deflector. I do.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a basic configuration of a multi-beam scanning device according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a light source unit in FIG.

FIG. 3 is an explanatory diagram illustrating an optical arrangement of the multi-beam scanning device according to the first embodiment.

FIG. 4 is an explanatory diagram illustrating an optical arrangement of a multi-beam scanning device according to a second embodiment.

FIG. 5 is an explanatory diagram illustrating an optical arrangement (main scanning section) of the multi-beam scanning device according to the third embodiment.

FIG. 6 is an explanatory diagram illustrating an optical arrangement (sub-scan section) of the multi-beam scanning device according to the third embodiment.

FIG. 7 is an explanatory diagram showing an optical arrangement of a conventional multi-beam scanning device.

[Explanation of symbols]

Reference Signs List 101 Light source unit 102 Aperture 103 First imaging optical system 104 Deflector 105 Second imaging optical system 107 Scanned surface 201 LD array 202 Collimating lens 201a, b LD 202a, b Collimating lens

Claims (1)

(57) [Claims] A light source for emitting a plurality of light beams; a deflector for deflecting the plurality of light beams emitted from the light source to expose and scan a surface to be scanned; and a light source and the deflector. An aperture arranged between the apertures for beam shaping; and a first imaging optics arranged between the aperture and the deflector to linearly image each of the incident light beams near the deflector. A second system disposed between the deflector and the surface to be scanned and configured to form each light beam as a minute spot on the surface to be scanned.
In the multi-beam scanning apparatus provided with the imaging optical system, the first imaging optical system is at least two lenses, one of which is a cylindrical lens, In a first section including an optical axis and parallel to a main scanning direction in which the light beam is scanned on the surface to be scanned by the deflector, the first imaging optical system is used to expand the light beam. A focal optical system, and the aperture and a point near the deflector are configured to be optically conjugate to each other, and the optical axis of the optical system in the first imaging optical system is included by the deflector. In the second section parallel to the sub-scanning direction perpendicular to the direction in which the light beam is scanned on the surface to be scanned, the aperture is provided on the light source side with respect to the object-side focal point of the first imaging optical system. Place, and Multibeam scanning apparatus characterized by being configured the object side focal point of the said aperture second imaging optical system so as to be optically conjugate.