JPS6292573A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To correctly control the starting point of scanning in the main scanning direction and to miniaturize the titled device in the sub-scanning direction by detecting the reflecting light and generating a main scanning synchronizing signal in the scanning area of a light beam. CONSTITUTION:A light beam 2 from a light source 1, after the beam is modulated at the picture signal by a modulator 6, is deflected by a rotating polygon mirror 3, reflected through an image forming lens 4 by a long-sized sub-scanning mirror 10 and image-formed to an image forming position P1 of the lens 4 and a conjugate position P2. The mirror 10 is linearly shifted over a scanning range S of the beam 2 in the C direction, the main scanning line, which the beam 2 forms on a scanning sheet 5, is shifted in the D direction and the sub- scanning is executed. In such a case, a long-sized light detecting device 22 is provided along a reflecting belt 21 provided in parallel to the side end of the sheet 5 in the scanning area of the light beam of a sheet holding surface 11a, and the detecting device 22, based upon the reflecting light to occur each time the light beam passes through the reflecting belt 21, generates the main scanning synchronizing signal corresponding to the timing of the start of the recording for respective scanning lines.

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a light beam scanning device that scans a light beam using an optical deflector, and more particularly, to miniaturization of the entire device,
The present invention relates to a light beam scanning device that can reduce costs. (Technical Background and Prior Art of the Invention) Conventionally, a light beam scanning W device that deflects a light beam with an optical deflector and scans a scanning sheet relatively two-dimensionally has been used in various scanning recording devices and scanning reading devices. Widely used in equipment, etc. Two-dimensional scanning of the light beam in these light beam scanning devices involves deflecting the light beam with an optical deflector to cause it to main scan on the scanning sheet, and also moving the light beam and the scanning sheet relative to the main scanning direction. This is performed by moving in a substantially orthogonal sub-scanning direction. However, in the conventional apparatus, a problem arises in that the means for performing the sub-scanning requires the apparatus to be large and expensive. Hereinafter, problems with the conventional light beam scanning device will be explained with reference to FIG. In the light beam scanning device shown in FIG.
A light beam 102 emitted from 01 is incident on a rotating polygon mirror 103, which is an optical deflector, and is reflected and deflected as the polygon mirror rotates in the direction of the arrow. Rotating polygon tJ1
Light beam reflected by 103

After passing through an fθ lens 104, which is an imaging lens, provided on the optical path, the scanning sheet 105 is main scanned in the direction of arrow B. The scanning sheet 105 is held between a rotating drum 106 rotating in the direction of arrow C and a pair of rollers 107A and 107B provided on the rotating drum 1, and is rotated in the main scanning direction as the rotating drum 106 rotates. Sub-scanning is performed by being conveyed in a substantially perpendicular direction. Therefore, the light beam 102 repeats main scanning in the direction of arrow B over the scanning sheet 105 that is conveyed (sub-scanned) in the direction of the arrow, thereby scanning the sheet 105 in two directions.
Dimensionally scanning is performed, and image information is recorded over substantially the entire surface of the scanning sheet. However, in the above-mentioned apparatus, sub-scanning is performed by moving the scanning sheet, but in order to suppress load fluctuations to the motor 108 as much as possible during DI scanning and to prevent uneven sub-scanning from occurring, the In this way, it is necessary to provide a space in which one scanning sheet can be placed, by arranging support stands 109 and 110 for supporting the scanning sheet 105 before and after the scanning position by the light beam. For this reason, the above-mentioned apparatus requires a space having a length of two or more scanning sheets in the sub-scanning direction, resulting in an increase in the size of the entire apparatus. In addition, the rotating drum 106 that conveys the scanning sheet has a width larger than the width of the scanning sheet d5 in order to stably convey the scanning sheet.
Since a motor 108 for rotating the drum 06 is further provided in the width direction of the rotating drum, the above device becomes large in the main scanning direction as well. In order to perform scanning, it is necessary to strictly control the motor so that the scanning sheet can be conveyed with high precision in the correct direction at a constant speed, and high-precision motors that can be controlled as described above are expensive. Therefore, there is also the problem that the cost of the entire device increases significantly. Also, the scanning sea (−
In order to stably convey the
01B is essential, but due to the provision of these O-ra, scanning cannot be performed at both ends of the scanning sheet in the sub-scanning direction, and if the apparatus is a light beam recording device, both ends cannot be scanned. There is also the inconvenience of not being able to respond to requests for black edge parts. (Purpose of Fe Ming) The present invention has been made in view of the above-mentioned problems, and is intended to solve the problems such as an increase in the size of the 5A machine and an increase in manufacturing costs caused by moving the scanning sheet and performing sub-scanning. The purpose of this invention is to provide a compact and inexpensive optical beam scanning device. (Structure of the Invention) The light beam scanning device of the present invention includes a main scanning optical deflector that is installed on the optical path of a light beam emitted from a beam light source and deflects the light beam, and a main scanning light beam. An imaging lens that is provided on the optical path of the light beam deflected by the deflector and capable of focusing the light beam on a predetermined straight line; an elongated sub-scanning mirror that extends in the main scanning direction, is provided at an angle with respect to the optical path of the light beam, and is movable in the optical axis direction of the imaging lens; Holding the scanning sheet on a plane formed by a straight line locus that moves with the movement in the optical axis direction and is located at a position conjugate with the straight line on which the light beam is imaged with respect to the sub-scanning mirror. The first feature of the present invention is that the light beam scanning device of the present invention has a scanning sheet holding means for holding a scanning sheet. Sub-scanning is performed by reflecting the light and making it incident on the scanning sheet and moving the sub-scanning mirror.Since the scanning sheet is fixed by the scanning sheet holding means, it is similar to when carrying the scanning sheet and performing 01 scanning. In addition, it is not necessary to make the device large in the sub-scanning direction, and the downtime of the device can be made compact.Furthermore, the motor for moving the sub-scanning mirror for sub-scanning is not used when conveying the scanning sheet. Since such load fluctuations do not occur, it is easy to control, a relatively inexpensive motor can be used, and the manufacturing cost of the device can be reduced.By the way, 1-The light distribution beam scanning device is Normally, recording or reading is performed, and in order to read or record by scanning the light beam at t'7, it is necessary to create a synchronized date synchronized with the scanning of the light beam in the main scanning direction. In other words, the modulation of the light beam during recording and the reading of the light containing image information emitted from the scanning sheet during reading are performed when the position of the light beam is shifted from a predetermined position on the scanning sheet in the main scanning direction to a predetermined position on the scanning sheet in the main scanning direction. This must be performed every time the amount changes based on *, and each time a main scan is performed, the synchronization signal is used to control the actual start position of the scan where the recording or reading is performed, and the light beam in the main scanning direction is It is necessary to uniformly align the effective scanning start positions of the apparatus of the present invention.Furthermore, as mentioned above, one of the purposes of the apparatus of the present invention is to downsize the apparatus as a whole, and the means for controlling the start point is Therefore, it is preferable that the device be large in size (and it is required to control the substantial if-scanning start position of the light beam in the main scanning direction by a compact and inexpensive means. Therefore, in the apparatus of the present invention, in order to perform the above-mentioned starting point control of the actual main scanning start, the light beam on the scanning sheet holding means is directed to the outside of the side edge of the scanning sheet held by the holding means. A reflection band is provided in the scanning area extending parallel to the side edge and reflects the light beam, and a reflection band is provided above the reflection band to detect the reflected light from the reflection band and generate a main scanning synchronization signal. The second feature is that it has a photodetector that emits light. (Actual IJ! Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an outline of a light beam recording device which is an embodiment of the light beam scanning device of the present invention. A light beam 2 emitted from a laser light source 1 is modulated by a modulator drive circuit 7 based on a signal R from an image signal output circuit 8 that outputs an image signal.
A rotating polygon that is a main scanning optical deflector that rotates in the direction of the arrow after being incident on and modulated! ! 3 and is deflected. The laser light source 1 is a 1c3-Ne laser, A
In addition to the r laser, a Rade light source, etc., which is a combination of a semiconductor laser and a beam shaping optical system, is used. Furthermore, when using a laser light source capable of direct modulation such as a semiconductor laser, the modulator 6 is not particularly provided in the optical path of the light beam 2, and the laser light source is directly controlled to modulate the light beam. You can also do that. Furthermore, in addition to the above-mentioned rotating polygon mirror, as a main scanning optical deflector, a galvanometer mirror,
Other types of optical deflectors such as acousto-optic optical deflectors (A○D) may also be used. The light beam deflected by the rotating polygon mirror 3 passes through an imaging lens 4 such as a θ lens provided on an optical grating, and then is driven by a motor 9 at a low speed in the direction of the optical axis of the imaging lens. The light beam moves linearly in the direction of arrow C and is reflected by the reflection surface 10a of the elongated sub-scanning mirror 10 extending in the main scanning direction. Further, below the 01 scanning mirror 10, on the optical path of the light beam reflected by the 01 scanning mirror, a sheet-shaped recording medium (scanning sheet) 5 such as a photographic film or photographic paper is placed. As described above, it is supported by the recording medium holding means 11 having a holding surface 11a that is inclined at a predetermined angle with respect to the incident light beam so as to have a specific relationship with the sub-scanning mirror 10. This holding means 11 is formed, for example, by processing a plate-like object or by integrally molding a synthetic resin or the like. When the recording medium 5 is held on the recording medium holding means 11 as described above, the round beam 2 is deflected by the rotating polygon mirror 3.
performs main scanning on the recording medium 5 in the direction of arrow B. The imaging lens 4 converges the light beam 2 onto a recording medium 5, and then deflects the light beam deflected at a substantially constant angular velocity by the rotating polygon 1t3 onto the flat recording medium 5 at a substantially constant velocity. This is a lens that allows scanning. In addition, in the illustrated recording apparatus, sub-scanning is performed by using an l1SIJ scanning mirror 10 with respect to the recording body 5.
This is done by moving. Next, with reference to FIG. 2, which is a conceptual side view of the apparatus shown in FIG. 1, 1) (2) the relationship between the sub-scanning mirror and the recording medium and the mechanism of sub-scanning will be explained. The light beam 2 reflected and deflected by the rotating polygon mirror 3 passes through the imaging lens 4 provided on the optical path, as described above. This imaging lens 4 is capable of focusing the nine incident beams onto a predetermined imaging position Ps on a straight line perpendicular to the plane of the drawing. As mentioned above, the long IVJ scanning mirror 10 is provided on the optical path E of the light beam that has passed through the imaging lens 4, and this 01 scanning mirror 10 has a reflection surface tOa
The sub-scanning mirror 2 is provided at an angle with respect to the optical path of the light beam so that the light beam is incident at an incident angle α, and the light beam 2 is reflected downward by this sub-scanning mirror. The light beam 2 reflected by the 01 scanning mirror forms an image at an imaging position P2 which is located at a position that is different from the imaging position P1 with respect to the DI scanning mirror. The imaging position P2 of the light beam reflected by this sub-scanning mirror changes as the sub-scanning mirror 10 moves in the direction of arrow C, but the recording body 5 changes due to the movement of this sub-scanning mirror. With respect to the sub-scanning mirror, it is held on a plane formed by the locus of an imaging position P2 that is conjugate with the imaging position P1. In other words, the recording body 5 is at the focal point ffP+ of the light beam.
, and an angle α equal to the incident angle α of the light beam on the sub-scanning mirror, a person! 8? It is arranged on a plane that is inclined with respect to the light beam reflected by the sub-scanning mirror at a position that allows the light beam reflected by the sub-scanning mirror to be incident thereon. As shown in parallel, the sub-scanning mirror 10 has enough space for the light beam to scan the entire surface of the recording medium in the direction of arrow C shown in 11 while recording image information on one recording medium. As the sub-scanning mirror moves, the main scanning line formed by the light beam 2 on the recording medium 5 is gradually moved in the direction of the arrow and is forced to move in the sub-scanning direction. Therefore, the light beam 2 is caused to two-dimensionally scan the entire surface of the recording medium by the rotating polygon mirror 3 and the sub-scanning mirror 10.The movement of the sub-scanning mirror is as shown in FIG. As shown in , a pair of pulleys 12Δ, 12B rotated by the motor 9 and a pair of driven pulleys 13A, 1
3B, and as the pulleys 12A and 12B rotate (
This is done by moving the mirror support member 15a connected to the wires 14 provided at both ends of the sub-scanning mirror on the guide rail 15b by the two moving wires 14. Note that the sub-scanning mirror can be moved by various means in accordance with the requirements of the device installation R1, etc., such as movement using a linear motor, in addition to driving the wire A7 as described above. As described above, when the sub-scanning mirror 10 moves within a predetermined range at a predetermined speed and the necessary image information is recorded over the entire surface of the recording medium, the n1-scanning mirror 10 moves in the opposite direction to the movement direction. direction and returned to the initial position in preparation for recording on the next recording medium. In this embodiment, as shown in FIG. 1, a photodetector 16 is attached to the recording medium holding means 11, and the photodetector 16 detects a light beam to start image recording scanning in the 01 scanning direction. It is designed to determine the position. However, the sub-scanning mirror 10 is moved from the initial position in the direction of arrow C, and it is detected that the light beam reaches the end of the recording medium 5 at the same speed. It operates to modulate the light beam 2 and start recording an image on the recording medium 5. Furthermore, the loading and unloading of recording bodies into and out of the recording body holding means 11 can be carried out as described below, by way of example. That is, since the holding surface 11a of the recording medium holding means 11 is obliquely inclined, the recording medium is first taken out from a supply magazine (not shown), and the recording medium is carried into the holding surface by the carrying means, and the recording medium is loaded from above the holding surface. Let it fall by its own weight along the holding surface. At the lower end of the holding surface, there is a plate 1 for stopping a pair of recording bodies.
7 is installed, the recording medium 5 comes into contact with this stop plate and is held at a predetermined position in the fVI scanning direction. J3, when the friction between the recording body 5 and the holding surface 11a is large and the recording body is difficult to fall due to its own weight, the recording body may be transported to a predetermined position using a recording body transporting means without falling due to its own weight. At that time, as indicated by the broken line in FIG.
8, and the leading edge of the recording medium is detected by these detectors, the position of the recording medium can be determined accurately and easily. After completing the positioning in the flJ scanning direction as described above,
The recording medium 5 is pushed against a guide plate 19 provided at one end of the recording medium holding means 11 by a width adjusting plate 20 provided at the other end of the recording medium holding means and rotating in the direction of the arrow. (The main scanning direction is determined.) In this way, the recording medium stop plate is positioned at a predetermined position in both the main scanning direction and the sub-scanning direction, and when the scanning by the light beam is completed at that position, 17 rotates in the direction of the arrow and retreats to a plane substantially parallel to the holding surface 11a, and the recording medium falls further downward due to its own weight and is carried out from the recording medium holding means.Note that the lower end of the recording medium holding means 11 Needless to say, the unit may be provided with a recording medium carrying out means for catching the lower end of the recording body and actively carrying out the carrying out of the recording body.As described above, in the apparatus of the present invention, Since sub-scanning is performed by fixing the recording medium and rotating the sub-scanning mirror 10 to avoid moving the light beam, the size of the apparatus in the sub-scanning direction can be reduced compared to the case where the recording medium is moved. The length of the sub-scanning mirror 10 in the main scanning direction can be reduced to about half.
[Since it is sufficient to have a length sufficient for recording 1n marks and shorter than the length of the main scanning line on the recording medium, even if the sub-scanning mirror 10 and the mirror moving means are combined, It is sufficiently possible to make the length shorter than the length of the body holding means in the main scanning direction, and the apparatus of the present invention is also compact in the main scanning direction. In addition, &511 scanning mirror 10
The motor 9 that drives the motor 9 is easy to control because load fluctuations do not occur, and a relatively inexpensive motor can be used. Furthermore, since it is possible to record on the entire recording medium 5 held by the sheet holding means 11 by avoiding irradiation of the light beam from the end of the surface in the sub-scanning direction to the rear end of the recording medium, both ends of the recording medium can be blackened. It is easy to make the edges black. By the way, in the apparatus of the above embodiment, the start of recording in the sub-scanning direction by the light beam is performed by the photodetector 16 as described above.
For $1! However, the scanning by the light beam is controlled so that recording by the light beam modulated by the modulator starts from a predetermined position in the main scanning direction such as the side edge of the recording medium even in the main scanning direction. In order to carry out such control, the above-mentioned apparatus is provided with means that make it possible to control the starting point of recording substantially for each scanning line. Hereinafter, recording start point control in the main scanning direction of the light beam will be explained with reference to FIG. 1 and the drawings from FIG. 3 onwards. As shown in FIG. 1, within the scanning area of the light beam 2 outside the side edge 5b of the record body 5 on the record body holding surface 11a, the light beam is reflected in parallel to the side edge 5b. A reflective band 21 is provided. Since the reflection bands 21 are stacked in stages, reflected light is generated every time the rotating light beam performs main scanning from the recording medium holding surface. On the other hand, above this reflective band 21, a long photodetector 22 for detecting the reflected light is provided along the reflective band 21, and this photodetector 22 detects the reflected light. A22 detects the reflected light generated each time the light beam passes through the reflection band and generates a main scanning synchronization signal. Note that this photodetector 22
It is sufficient that the reflection band f) can detect all reflected light emitted from the reflection band f)s, and does not necessarily have to be long. For example, if the size of the sheet is relatively /jX small and the reflected light can be detected sufficiently,
A relatively short photodetector may be provided above the reflection band in the center in the sub-scanning direction, or a plurality of photodetectors may be provided along the direction in which the reflection band is provided. good. Furthermore, as shown in FIG. 3, the reflective band 21 is made of a long guide plate 19' extending in the sub-scanning direction, which positions the recording medium in the ↑ scanning direction by bringing the side edges of the recording medium into contact with each other. Then, a support stand 11b may be installed perpendicularly to the guide plate 19' from the upper end of the guide plate 19' toward the outside of the recording medium holding means, and formed on this support stand 11b. As mentioned above, the reflection band 21 is provided parallel to the side edge 51) of the recording medium, and the distance between the reflection band 21 and the side edge 5b is always constant, so that the light beam passes through the reflection band 21. The light beam reaches the side edge 5b of the nO recording medium after a certain period of time has elapsed since the main scanning synchronization signal is emitted from the photodetector 22, and the oscillation of the main scanning synchronization signal occurs during each scan of the light beam. This corresponds to the timing of starting recording for each line. Therefore, by using this main scanning synchronization signal, it is possible to easily control the starting point for recording with a light beam. Hereinafter, a specific example of the above-mentioned starting point penalty will be explained in more detail with reference to FIGS. 4 and 5. Main scanning synchronization signal 81 emitted from the photodetector 22
As shown in FIG. 4, the signal is sent to the comparator 23, where it is waveform-shaped based on the voltage v1 and output as a synchronization signal S2, which is a digital signal that can be subjected to timing processing. This synchronization signal S2 is then sent to the timing clock generation circuit 24, and the timing clock generation circuit 24
In response to the synchronization signal S2, a pixel clock S3 necessary for recording an image on a recording medium is oscillated, and this pixel clock S3 is sent to the image memory 25. This image meshichiri 25
The image information to be recorded on the recording medium is stored in advance by an external device (not shown), and a digital image data signal S4 for each pixel is generated from the image memory 25 in accordance with the oscillation timing of the pixel clock. It will be done. This digital image data signal S4 is converted into an analog image signal S5 by a D/Δ converter, and then sent to the image signal output circuit 8, which converts the signal via the modulator drive circuit 7 into an analog image signal S5. The analog image signal is transmitted to the J4 device 6, and the modulator 6 modulates the light beam according to the image signal. Also, the position of the reflective band 21 and the side edge 51 of the recording body 5)
is a certain distance away from the main scanning synchronization signal 8.
1 is emitted until the pixel clock starts oscillating, a certain period of time needs to pass, that is, the time required for the light beam to reach the side edge 5b of the recording medium from the reflection band 21. . This certain period of time can be determined in advance by knowing the scanning speed of the light beam and the distance from the reflection band to the side edge. A delay circuit is provided that generates the first pixel clock with a delay of a certain amount of time. That is, as shown in the timing chart of FIG. 5, the main scanning signal SI1. The waveform is shaped based on the t$ lightning voltage 1 and becomes a synchronization signal S2 and <', and this synchronization signal is sent to the timing clock generation circuit 24, which causes the timing clock generation circuit 24 to oscillate. pixel clock S3
The first oscillation timing is T1 from the time of Domei signal transmission (
) has been delayed. Note that when the deflector that deflects the light beam is a rotating polygon mirror as shown in C in this embodiment, the blurring time T' is calculated for each n reflecting surface of the rotating polygon mirror.
+, T2, Ding 3.・・・・・・Predetermine Tn in advance, calculate the delay time for each pixel, and delay the oscillation timing of the t pixel. High-precision image recording with less jitter can be achieved. Based on the timing of the pixel clock S3 oscillated as described above, the analog image signal S5 obtained from the D/A converter 26 becomes as shown in FIG. , the range indicated by arrow R in the figure is the image area recorded during one main scan of the light beam.As shown in the figure, when the light beam passes through the reflection zone 21, the modulator has a constant In this way, in the device of the present invention, the reflection band 21 allows the reflected light of the light beam to be used for main scanning. By detecting this reflected light with the photodetector 22 and generating a main scanning synchronization signal, the timing of modulating the light beam is controlled for each scanning line, and the timing of modulating the light beam is controlled for each scanning line. In addition, since the means for performing the above-mentioned starting point control is compact and inexpensive, it is possible to control the size of the device and reduce manufacturing costs. It is possible to efficiently control the starting point of recording using a light beam.The light beam scanning device of the present invention has been described above using a light beam recording device as an example. This device is a radiation image information recording and reproducing system using a photostimulable phosphor sheet (Japanese Unexamined Patent Publication No. 55-1), which was already proposed by the applicant.
No. 2429, No. 56-11395. It can also be applied to various light beam reading devices such as the radiation image information reading device vM used in the Japanese Patent No. 56-11397, etc.), and the above-mentioned effects can be achieved in the same way in light beam reading devices. be able to. In this case, in conjunction with the rotation of the sub-scanning mirror, a reading means including a photodetector for detecting reflected light, transmitted light, 1 emitted light, etc. from the scanning sheet on the scanning sheet faces the scanning line. All you have to do is move it. In addition, the main scanning synchronization signal emitted from the photodetector that detects the reflected light from the reflection band is a signal that essentially controls the starting point of scanning in the main scanning direction for reading information recorded on the scanning sheet. This main scanning synchronization signal is sent to the reading means, and controls the reading means so that reading starts at the same time as the light beam reaches a predetermined reading start position. (Effects of the Invention) As explained above, according to the light beam scanning device of the present invention, by fixing the scanning sheet and performing sub-scanning,
The entire area M can be made to have a small firmness, especially in the sub-scanning direction. In addition, the motor that moves the sub-scanning mirror in the sub-scanning direction is easy to control because there is no load fluctuation.
A motor that is cheaper than the motor used to move the scanning sheet side can be used, and the manufacturing cost of the entire apparatus can be reduced. Furthermore, the device of the present invention provides a reflective band on the holding surface of the scanning sheet holding means to periodically generate reflected light of the light beam for each scan in the main scanning direction of the light beam. By detecting this with a photodetector to obtain a main scanning synchronization signal, it is possible to accurately control the substantial scanning start point of the light beam in the main scanning direction using an extremely compact and inexpensive means.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an overview of a light beam recording device according to an embodiment of the present invention, FIG. 2 is a conceptual side view of FIG. 1 illustrating 21 scans in the above device, and FIG. FIG. 4 is a block diagram illustrating the actual recording start point control in the main scanning direction of the light beam, and FIG.
1L signals, synchronization signals, pixel signals, timing charts 1 to 1 of analog image signals, and FIG. 6 is a perspective view showing an outline of a conventional light beam scanning device. 1...Beam light source 2...Light beam 3...
Rotating polygon &ft 4...imaging lens 5...
Recording body 10... Sub-scanning mirror 11...
- Recording body holding means 11a... Recording body holding surface 21.
...Reflection band 22...Photodetector Fig. 2

Claims (1)

[Claims] A light beam emitted from a beam source is caused to scan a scanning sheet in a main scanning direction, and the light beam and the scanning sheet are relatively moved in a sub-scanning direction substantially orthogonal to the main scanning direction. In the light beam scanning device that moves the light beam to two-dimensionally scan the light beam on the scanning sheet, the main scanning device is provided on the optical path of the light beam emitted from the beam source and deflects the light beam. a light deflector; an imaging lens that is provided on the optical path of the light beam deflected by the main scanning light deflector and is capable of focusing the light beam on a predetermined straight line; a light beam that passes through the imaging lens; an elongated sub-scan that is disposed on the optical path of the light beam, extends in the main scanning direction, is inclined with respect to the optical path of the light beam, and is movable in the optical axis direction of the imaging lens; The light beam is formed by a straight line locus that moves with the movement of the sub-scanning mirror and the sub-scanning mirror in the optical axis direction and is located at a position conjugate with the straight line on which the light beam is imaged with respect to the sub-scanning mirror. A scanning sheet holding means for holding the scanning sheet is provided on a plane, and within a scanning area of the light beam outside a side edge of the scanning sheet held by the holding means on the scanning sheet holding means. a reflective band that extends parallel to the side edge and reflects the light beam; and a light that is provided above the reflective band and detects the reflected light from the reflective band and emits a main scanning synchronization signal. A light beam scanning device comprising a detector.