JPH1184287A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately obtain a synchronizing signal by independently and respectively detecting a synchronizing position in the sub-scanning direction of plural light beams with a simple constitution. SOLUTION: A collimator lens 2 makes the plural light beams emitted from a light source 1 into parallel light beams. The plural light beams are image- formed in the vicinity of the deflecting and reflecting surface of a light deflector 4 by a cylindrical lens 3, and reflected and deflected by the deflecting and reflecting surface. The deflected light beams are image-formed on the surface of a photoreceptor 7 to be scanned by an fθ lens 5 and a long toroidal lens 6, and scan the surface to be scanned by the rotation of the deflector 4. A synchronizing signal detector 8 diffracts the plural light beams in the sub- scanning direction orthogonally crossing a main scanning direction, the respective beams are independently and respectively detected by utilizing the diffracted light beams of the respective light beams, so that timing for starting writing that the plural light beams start writing the required scanning area of the surface to be scanned is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device for scanning a surface to be scanned with a light beam in an image forming apparatus such as a laser printer, and more particularly to a method for simultaneously scanning with a plurality of light beams on the surface to be scanned. In the multi-beam optical scanning device for simultaneously forming a plurality of scanning lines, the present invention relates to a technique for detecting a synchronization position in the sub-scanning direction of the plurality of light beams to obtain a synchronization signal.

[0002]

2. Description of the Related Art In an image forming apparatus such as a laser printer, a surface to be scanned is scanned with the light beam while modulating a light beam such as a laser beam with an information signal to form an image on the surface to be scanned. When scanning the light beam, the light beam spot on the surface to be scanned starts the scanning of a predetermined scanning area to be scanned. A light beam detecting element for detecting a beam spot is provided. That is, the detection signal of such a light beam detection element is used as a synchronization signal of the modulation timing. By the way, in such an image forming apparatus, a multi-beam optical scanning device using a method of simultaneously scanning a surface to be scanned with a plurality of light beams has been proposed in order to achieve high speed or high resolution.

An example of a technique for detecting a synchronization signal in such a multi-beam scanning apparatus is disclosed in Japanese Patent Application Laid-Open No. 57-10260.
No. 9 (Title of Invention: "Scanning Method and Apparatus Using Multiple Beams"). JP-A-57-102
The configuration disclosed in Japanese Patent Application Laid-Open No. 609-609 uses a cylindrical lens optical element to condense a light beam spot that draws a plurality of scanning lines on one scanning line, and uses a single light beam spot detection element to detect a plurality of light beams. Each light beam spot is received, and a synchronization signal is detected. That is, when the light beam spot of the plurality of light beams passes through the light beam detecting element, the interval and the position of each light beam spot are not changed in the main scanning direction in which the light beam spot is scanned. In the sub-scanning direction, the positions where the light beam spots pass are made substantially equal.

As another example of a technique for detecting a synchronization signal in a multi-beam scanning apparatus, see Japanese Patent Application Laid-Open No. H8-7603.
No. 9 (name of invention: "Multi-beam laser recording apparatus"). This Japanese Patent Application Laid-Open No. 8-7603
The configuration disclosed in Japanese Patent Application Laid-Open No. 9-29139 uses a one-dimensional CCD (charge-coupled device) as a light beam detecting element and uses the one-dimensional CCD along a sub-scanning direction orthogonal to the main scanning direction in which the light beam scans.
A scanning line interval detecting means provided with a D sensor and making the scanning of the CCD sensor correspond to the sub-scanning, or a photo sensor having an opening oblique to the main scanning direction as a light beam detecting element, The synchronizing signal detecting means is also used.

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 57-10 / 57
In the configuration disclosed in Japanese Patent No. 2609, when the light beam spots of the respective light beams are close to each other in the main scanning direction, each light beam spot passes through the light beam detection element at a short time interval, There is a possibility that two or more light beam spots are simultaneously incident on one light beam detection element. That is, in this configuration, each light beam must be separated to some extent in the main scanning direction. However, considering the formation of an output image, it is desirable that the light beams overlap in the main scanning direction as much as possible.

In this sense, in the configuration of Japanese Patent Application Laid-Open No. 8-76039, it is possible to detect a synchronization signal of each light beam even if the light beam spots overlap in the main scanning direction. However, as the resolution of the image forming apparatus increases, the interval between adjacent scanning lines becomes narrower, and accordingly, the pixel pitch of the CCD sensor needs to be made smaller. This may not only involve technical difficulties, but also lead to increased costs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has a simple configuration, independently detects the synchronization positions of a plurality of light beams in the sub-scanning direction, and obtains a synchronization signal accurately. It is an object of the present invention to provide an optical scanning device capable of performing the above. A first object of the present invention is, in particular, to provide an optical scanning device capable of effectively separating a plurality of light beams, detecting each of the light beams independently, and obtaining a synchronization signal. A second object of the present invention is to provide an optical scanning device capable of more accurately detecting a plurality of light beams for obtaining a synchronization signal.

A third object of the present invention is to provide an optical scanning apparatus which can easily manufacture a configuration for detecting a light beam in order to obtain a synchronization signal. A fourth object of the present invention is, in particular, to provide an optical scanning device capable of independently detecting a plurality of light beams and obtaining an independent synchronization signal. A fifth object of the present invention is to provide an optical scanning device capable of easily manufacturing a configuration for detecting a light beam and obtaining a synchronization signal.

[0009]

According to a first aspect of the present invention, there is provided an optical scanning apparatus comprising: a plurality of light beams; In a multi-beam optical scanning device for simultaneously scanning the scanned surface with a plurality of scanning lines parallel to the main scanning direction and arranged in the sub-scanning direction on the scanned surface, the plurality of light beams are scanned. A synchronization signal detection device for detecting a writing start timing for starting writing of a required scanning area of a surface,
A diffractive optical element for diffracting each light beam in the sub-scanning direction; and a light beam detecting element for individually detecting each light beam diffracted by the diffractive optical element for each beam using diffracted light. It is characterized by doing.

According to a second aspect of the present invention, in order to achieve the second object, the diffractive optical element includes a blazed grating having a grating parallel to the main scanning direction. It is characterized by. According to a third aspect of the present invention, there is provided an optical scanning device according to the third aspect, wherein the blazed grating has a blazed inclined surface forming a blazed angle of a grating groove in a stepped shape. It is characterized by including a lattice.

According to a fourth aspect of the present invention, in order to attain the fourth object, the light beam detecting elements are monolithically integrated and arranged on a single semiconductor chip. And a plurality of semiconductor light receiving units. In order to achieve the fifth object, in the optical scanning device according to the present invention as set forth in claim 5, the light beam detecting elements are individually formed on different semiconductor pieces and integrated into a hybrid. It is characterized by including a plurality of semiconductor light receiving units arranged.

[0012]

In the optical scanning device according to the first aspect of the present invention, a plurality of light beams are used to scan a plurality of scanning lines parallel to the main scanning direction on the surface to be scanned and arranged in the sub-scanning direction on the surface to be scanned. A multi-beam optical scanning device that simultaneously scans the surface to be scanned with a line, diffracts each of the plurality of light beams in the sub-scanning direction using a diffractive optical element, and uses the diffracted light to apply each of the beams. Are individually detected by the light beam detecting elements to constitute a synchronization signal detecting device, and the timing at which each of the light beams starts writing in the essential scanning area on the surface to be scanned is detected. With such a configuration, despite the simple configuration, each light beam can be effectively separated and received and detected at a pitch wider than the light beam interval of the plurality of light beams. Synchronous positions in the sub-scanning direction are separately detected, and a synchronous signal can be accurately obtained.

In the optical scanning device according to a second aspect of the present invention, the diffractive optical element is constituted by a blazed grating having a grating parallel to the main scanning direction. With such a configuration, in particular, a specific diffracted light of each light beam can be emphasized, and a plurality of light beams for obtaining a synchronization signal can be detected more accurately. According to a third aspect of the present invention, in the optical scanning device, the blazed grating is constituted by a binary blazed grating in which a blazed inclined surface forming a blazed angle of a grating groove is formed in a stepwise manner. With such a configuration, in particular, a blazed grating for detecting a light beam to obtain a synchronization signal can be easily manufactured.

According to a fourth aspect of the present invention, in the optical scanning device, the light beam detecting element is constituted by a plurality of semiconductor light receiving sections which are monolithically integrated and arranged on a single semiconductor piece. With such a configuration, in particular, a plurality of light beams can be independently detected, and an appropriate synchronization signal independent of each light beam can be obtained. In an optical scanning device according to a fifth aspect of the present invention, the light beam detecting element is constituted by a plurality of semiconductor light receiving sections individually formed on each of the separate semiconductor pieces and arranged in a hybrid integrated manner. With such a configuration, in particular, a light beam detecting element that detects a light beam and obtains a synchronization signal can be easily manufactured using a semiconductor.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical scanning device according to the present invention will be described in detail based on embodiments with reference to the drawings. [First Embodiment] (corresponding to claim 1) FIGS. 1 and 2 show a configuration of a main part of a multi-beam optical scanning device according to a first embodiment of the present invention. FIG.
1 schematically shows the entire configuration of the multi-beam optical scanning device, and FIG. 2 schematically shows the detailed configuration of the synchronization signal detecting device in FIG. The multi-beam optical scanning device shown in FIG. 1 includes a light source 1, a collimating lens 2, a cylindrical lens 3, an optical deflector 4, an fθ lens 5, a long toroidal lens 6, a photoconductor 7, and a synchronization signal detecting device 8.
Is provided.

The light source 1 emits a plurality of light beams. The collimating lens 2 collimates the plurality of light beams emitted from the light source 1 into parallel light. The cylindrical lens 3 forms the plurality of light beams, which have been converted into parallel light by the collimator lens 2, near the deflection reflection surface of the optical deflector 4 as a long line image in the main scanning direction. The light deflector 4 includes a polygonal polygon mirror having a plurality of deflecting and reflecting surfaces, and is driven to rotate to reflect and deflect the plurality of light beams by the deflecting and reflecting surface. The fθ lens 5 and the long toroidal lens 6 form an image of the light beam deflected by the light deflector 4 on the surface to be scanned of the photoconductor 7, and rotate the light deflector 4 so that the light beam Scan. The synchronization signal detecting device 8 diffracts the plurality of light beams in a sub-scanning direction orthogonal to the main scanning direction, and detects each light beam individually for each beam using the diffracted light of each light beam. Thus, the writing start timing at which the plurality of light beams start writing in the essential scanning area of the scanned surface is detected.

FIG. 2 shows a detailed configuration of the synchronization signal detection device 8 shown in FIG. 1. The synchronization signal detection device 8 has a transmission type phase grating 81 and a light receiving element 82. In this example, as the diffractive optical element constituting the synchronization signal detecting device 8, for example, a transmission-type phase grating 81 having a plurality of diffraction grooves parallel to the main scanning direction is used. That is, the transmission type phase grating 81 is formed by periodically forming diffraction grooves parallel to the main scanning direction on a transparent parallel flat plate.
Synchronous detection method of, for example, four parallel light beams (for example, the pitch of each beam is set to 42.33 μm and used for a printer corresponding to 600 dpi) using a transmission type phase grating 81 as a diffractive optical element. Will be specifically described.

As shown in FIG. 3, light beams B11 and B1
When light beams B2, B13 and B14 are incident on a transmission type phase grating 81 as a diffractive optical element, each light beam B11, B12, B
Diffracted light beams such as 0th-order diffracted light (undiffracted light), ± 1st-order diffracted light, ± 2nd-order diffracted light,... Of 13 and B14 are emitted from the transmission phase grating 81. That is, the transmission-type phase grating 81 converts the light beams B11, B12, B13, and B14 into the 0th-order diffracted light (transmitted light), ± 1st-order diffracted light, and ± 2d of the light beams B11, B12, B13, and B14.
Next, it is split into diffracted light beams such as diffracted light.

Of these diffracted lights, the second-order diffracted light beam as the synchronous light beam corresponding to the light beam B11 and the synchronous light beam corresponding to the light beam B12 are:
As a synchronous light beam corresponding to the first-order diffracted light beam and the light beam B13, the zero-order diffracted light beam and a synchronous light beam corresponding to the light beam B14 are -1.
As shown in FIG. 4, a light receiving element 82 is arranged at a position where these diffracted light beams are sufficiently separated from each other, and the synchronization timing of each light beam B11, B12, B13 and B14 is individually determined. Can be detected. At this time, it goes without saying that the light receiving element 82 is arranged at a position where other diffracted light is not detected.

Thus, a plurality of light beams B11,
The synchronization signals of B12, B13 and B14 can be independently detected. The order of the diffracted light beam selected from the diffracted light beams and used as the synchronization light beam is not particularly limited here. Further, in this embodiment, the light beams B11, B12, B
Although 13 and B14 are assumed to be parallel to each other, this is not a special condition.

Further, in this embodiment, the case where the transmission type phase grating 81 is used as the diffractive optical element has been described, but instead of the transmission type phase grating 81, for example, a transmission type amplitude grating, a reflection type phase grating, A reflection type amplitude grating or the like may be used as the diffractive optical element. As described above, it is possible to selectively use a large number of alternatives instead of the transmission type phase grating, or to perform the modification with appropriate modifications and changes.

[Second Embodiment] (corresponding to claim 2) FIG. 5 shows a configuration of a synchronization signal detecting device which is a main part of a multi-beam optical scanning device according to a second embodiment of the present invention. Is shown. The synchronous signal detection device shown in FIG. 5 uses, as a diffractive optical element, a transmission type blazed grating 83 in which a plurality of diffraction grooves parallel to the main scanning direction are formed, instead of the transmission type phase grating 81 shown in FIG. It is composed. The transmission type blazed grating 83 is formed by periodically forming diffraction grooves formed parallel to the main scanning direction as V-shaped grooves whose groove surfaces are inclined at a blazed angle θ, and having a substantially sawtooth cross section. I have.
Such a transmission-type blazed grating 83 is configured to incline a groove surface at a predetermined blazed angle θ, so that diffracted light of a specific order is compared with diffracted light of another order with respect to light of a specific wavelength. Can be stronger.

A method of synchronously detecting, for example, four parallel light beams using a transmission type blazed grating 83 as a diffractive optical element will be specifically described. Similarly to the case of the transmission type phase grating 81 shown in FIG.
When light beams B1, B13 and B14 enter the transmission type blazed grating 83 as a diffractive optical element, each light beam B1 is diffracted by passing through the transmission type blazed grating 83.
Diffracted light beams such as 0th-order diffracted light (undiffracted light), ± 1st-order diffracted light, ± 2nd-order diffracted light,... Of 1, B12, B13 and B14 are emitted from the transmission-type blazed grating 83.
That is, each light beam B11, B12, B13, and B14 is converted by the transmission type blazed grating 83 into the 0th-order diffracted light (transmitted light), ± 1st-order diffracted light, ± 2nd-order diffracted light of each light beam B11, B12, B13, and B14. .. Are split into diffracted light beams like.

As is well known, in a blazed grating, a diffractive light beam of a specific order is particularly generated with respect to a light beam of a specific wavelength by giving a groove surface of the grating groove an inclination angle according to the blazed angle θ. Can be stronger. Therefore, among these diffracted lights, the second-order diffracted light beam as a synchronous light beam corresponding to the light beam B11, the first-order diffracted light beam as the synchronous light beam corresponding to the light beam B12,
Since the 0th-order diffracted light beam is used as the synchronous light beam corresponding to the light beam B13 and the -1st-order diffracted light beam is used as the synchronous light beam corresponding to the light beam B14, the blazed angle of the transmission-type blazed grating 83 is used. is set so that the diffracted light of the order corresponding to these synchronous light beams of the light beams B11 to B14 becomes strong.

In this manner, the synchronization timing of each of the light beams B11, B12, B13 and B14 is individually detected by the light receiving element 82 arranged at a position where these diffracted light beams are sufficiently separated. That is, as shown in FIG.
In the transmission type blazed grating 83, the blazed angle θ11 is set so that the second-order diffracted light is particularly strong in the area where the light beam B11 is incident, and the blazed angle is such that the first-order diffracted light is particularly strong in the area where the light beam B12 is incident. θ12
Is set, and the blazed angle θ13 is set so that the 0th-order diffracted light is particularly strong in the region where the light beam B13 is incident, and the blazed angle is such that the −1st-order diffracted light is particularly strong in the region where the light beam B14 is incident. θ14 is set. At this time, it goes without saying that the light receiving element 82 is arranged at a position where other diffracted light is not detected.

Therefore, a plurality of light beams B11, B1
2. The synchronization signals of B13 and B14 can be detected independently and more accurately. It should be noted that the order of the diffracted light beam selected from the diffracted light beams by the diffraction, the blazed angle θ is set accordingly, and the blazed angle θ is used as the synchronous light beam is not particularly limited here. is not. Also, in this embodiment,
Light beams B11, B12, B13 and B14 incident on the transmission-type blazed grating 83 of the synchronization signal detector (8).
Are parallel to each other, but this is not a particularly limiting condition.

Further, in this embodiment, the case where the transmission type blazed grating 83 is used as the diffractive optical element has been described. However, for example, a reflection type blazed grating or the like may be used as the diffractive optical element. In this way, various alternatives can be selectively used instead of the transmissive blazed grating, or can be implemented with appropriate modifications and changes.

[Third Embodiment] (corresponding to claim 3) FIG. 7 shows a diffraction pattern used in a synchronization signal detecting device which is a main part of a multi-beam optical scanning device according to a third embodiment of the present invention. 2 shows a configuration of an optical element. The transmission type blazed grating 83 described in FIGS. 5 and 6 is an inclined surface having a desired blazed angle θ on the groove surface of the grating groove, but the diffractive optical element is changed to a binary blazed grating as shown in FIG. If it is 84, processing is easy.

Here, the "binary type" means that, as shown in FIG. 7, instead of the inclined surface forming the groove surface of the diffraction groove, processing is performed stepwise according to the blazed angle θ. It is processed so that the angle formed by the step surface becomes a required blazed angle θ. Even when such a binary blazed grating 84 is used, a synchronization signal can be individually detected as in the case of FIGS. 5 and 6 described above. Therefore, a plurality of light beams B11, B12, B13 and B
The fourteen synchronization signals can be more accurately detected independently of each other, and the diffractive optical element of the synchronization signal detector can be easily manufactured.

[Fourth Embodiment] (corresponding to claim 4) FIG. 8 shows a light receiving device used in a synchronization signal detecting device which is a main part of a multi-beam optical scanning device according to a fourth embodiment of the present invention. 1 shows the configuration of an element. FIG. 8 shows the first to third embodiments described above.
13 shows a configuration of a photodiode used as a light receiving element for receiving a synchronous light beam split by a diffractive optical element in the configuration of the synchronous signal detecting device shown in the embodiment. The photodiode 85 shown in FIG. 8 has a so-called monolithic configuration in which a plurality of light receiving portions 851, 852, 853, and 854 are formed on a single semiconductor piece 850.

The distance between the light receiving surfaces of the light receiving portions 851 to 854 is determined by the arrangement distance between the diffractive optical element and the light receiving element, and the order of the diffracted light beam with respect to each of the light beams B11, B12, B13 and B14. It is uniquely determined based on whether the beam is selected. Each light receiving section 851 to 854
The gaps are substantially insulated, so that individual synchronization light beams can be detected independently of each other. Therefore, the plurality of light beams B11, B12, B13 and B1
4 can be detected independently and accurately.

A phototransistor may be used in place of the photodiode.

[Fifth Embodiment] (corresponding to claim 5) FIG. 9 shows a light receiving device used in a synchronization signal detecting device which is a main part of a multi-beam optical scanning device according to a fifth embodiment of the present invention. 1 shows the configuration of an element. FIG. 9 shows the above-described first to third embodiments.
13 shows a configuration of a photodiode used as a light receiving element for receiving a synchronous light beam split by a diffractive optical element in the configuration of the synchronous signal detecting device shown in the embodiment. In the photodiode 86 shown in FIG. 9, a plurality of light receiving portions 861, 862, 863 and 864 are formed by individual semiconductor pieces ST1, ST2, ST3 and S, respectively.
It has a so-called hybrid configuration in which components formed on T4 are combined.

The distance between the light receiving surfaces of the light receiving portions 861 to 864 is determined by the arrangement distance between the diffractive optical element and the light receiving element and the order of the diffracted light beam with respect to each of the light beams B11, B12, B13 and B14. It is uniquely determined based on whether the beam is selected. Each light receiving section 861 to 864
Since each is an individual semiconductor, it is easy to process, and it is possible to independently detect individual synchronous light beams.
Therefore, the synchronization signals of the plurality of light beams B11, B12, B13, and B14 can be independently and accurately detected, and the light receiving element of the synchronization signal detection device can be easily manufactured. Also in this case, a phototransistor may be used instead of the photodiode. Further, a CCD image sensor may be used as the light receiving element.

[0035]

As described above, according to the present invention, a plurality of scanning beams parallel to the main scanning direction on the surface to be scanned and arranged in the sub scanning direction on the surface to be scanned by the plurality of light beams. A multi-beam optical scanning device that simultaneously scans the surface to be scanned with a line, diffracts each of the plurality of light beams in the sub-scanning direction using a diffractive optical element, and uses the diffracted light to apply each of the beams. By individually detecting by the light beam detection element, by configuring a synchronization signal detection device, by detecting the timing of the write start when each light beam starts writing in the essential scanning area of the scanned surface, Despite the simple structure, each light beam can be effectively separated and received and detected at a pitch wider than the light beam interval of the plurality of light beams, and synchronization of the plurality of light beams in the sub-scanning direction can be achieved. Check the position separately And, it is possible to provide an optical scanning device capable of obtaining an accurate synchronization signals.

According to the optical scanning device of the second aspect of the present invention, the diffractive optical element is constituted by a blazed grating having a grating parallel to the main scanning direction. Can emphasize the diffracted light of
A plurality of light beams for obtaining a synchronization signal can be detected more accurately. According to the optical scanning device of the third aspect of the present invention, the blazed grating is constituted by a binary blazed grating in which a blazed inclined surface forming a blazed angle of a grating groove is formed in a stepwise manner, and in particular, a synchronization signal is formed. A blazed grating for detecting the light beam to obtain it can be easily manufactured.

According to the optical scanning device of the fourth aspect of the present invention,
By configuring the light beam detecting element with a plurality of semiconductor light receiving sections monolithically integrated and arranged on a single semiconductor piece, in particular, detecting a plurality of light beams independently of each other, And an appropriate synchronization signal independent of the above can be obtained. According to the optical scanning device of claim 5 of the present invention,
By configuring the light beam detecting element with a plurality of semiconductor light receiving sections individually formed on each different semiconductor piece and arranged in a hybrid integrated manner, in particular, a light beam is detected and a synchronization signal is generated. The obtained light beam detecting element can be easily manufactured using a semiconductor.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a configuration of a main part of a multi-beam optical scanning device according to a first embodiment of the present invention.

FIG. 2 is a side view schematically showing a detailed configuration of a synchronization signal detection device of the multi-beam optical scanning device of FIG.

FIG. 3 is a schematic side view for explaining the operation of a transmission-type phase grating as a diffractive optical element of the synchronization signal detection device of FIG. 2;

FIG. 4 is a schematic side view for explaining the operation of the synchronization signal detection device of FIG. 2;

FIG. 5 is a side view schematically showing a configuration of a main part of a synchronization signal detecting device using a transmission type blazed grating as a diffractive optical element of a multi-beam optical scanning device according to a second embodiment of the present invention. .

FIG. 6 is a schematic side view for explaining the operation of the synchronization signal detection device of FIG. 5;

FIG. 7 is a side view schematically showing a detailed configuration of a main part of a binary blazed grating used as a diffractive optical element in a synchronization signal detecting device of a multi-beam optical scanning device according to a third embodiment of the present invention. is there.

FIG. 8 is a perspective view schematically showing a detailed configuration of a main part of a monolithic photodiode used as a light receiving element in a synchronization signal detecting device of a multi-beam optical scanning device according to a fourth embodiment of the present invention. .

FIG. 9 is a perspective view schematically showing a detailed configuration of a main part of a hybrid photodiode used as a light receiving element in a synchronization signal detecting device of a multi-beam optical scanning device according to a fifth embodiment of the present invention. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Collimating lens 3 Cylindrical lens 4 Optical deflector 5 fθ lens 6 Long toroidal lens 7 Photoconductor 8 Synchronous signal detector 81 Transmission type phase grating 82 Light receiving element 83 Transmission type blazed grating 84 Binary type blazed grating 85 Monolithic photo Diode 86 Hybrid photodiode 850, ST1 to ST4 Semiconductor piece 851 to 854, 861 to 864 Light receiving section

Claims (5)

[Claims] 1. A surface to be scanned is simultaneously scanned by a plurality of light beams by a plurality of scanning lines parallel to a main scanning direction on the surface to be scanned and arranged in a sub-scanning direction on the surface to be scanned. In the multi-beam optical scanning device, a synchronization signal detecting device for detecting a writing start timing at which each of the plurality of light beams starts writing in an indispensable scanning region of the surface to be scanned, wherein the synchronization signal detecting device detects the light beams in the sub-scanning direction. An optical scanning device, comprising: a diffractive optical element that diffracts the light beam into a plurality of light beams; and a light beam detecting element that individually detects each light beam diffracted by the diffractive optical element by using the diffracted light. . 2. The optical scanning device according to claim 1, wherein the diffractive optical element includes a blazed grating having a grating parallel to the main scanning direction. 3. The blazed grating includes a binary blazed grating in which a blazed inclined surface forming a blazed angle of a grating groove is formed in a stepped manner.
3. The optical scanning device according to claim 1. 4. The optical scanning device according to claim 1, wherein the light beam detecting element includes a plurality of semiconductor light receiving units monolithically integrated and arranged on a single semiconductor piece. 5. The light beam detecting element according to claim 1, wherein the light beam detecting element includes a plurality of semiconductor light receiving portions individually formed on each different semiconductor piece and arranged in a hybrid integrated manner. Optical scanning device.