Optical scanning device and image forming device

Abstract

To provide a small-sized optical scanner that can prevent a reduction in the quantity of a light beam guided to a light receiving element.SOLUTION: An optical scanner 101 according to the present invention comprises: a deflector 105 that deflects a light beam from a light source 102 to scan a surface to be scanned D in a main scanning direction; and an image forming optical system 85 that includes a first optical element 106. The first optical element 106 has a transmission surface that transmits a first light beam deflected by the deflector 105 at a first timing to guide the light beam to the surface to be scanned D, and a reflection surface that totally reflects a second light beam deflected by the deflector 105 at a second timing different from the first timing to guide the light beam to a light receiving element 108. The reflection surface is arranged on the same side as the light source 102 with respect to a sub-scanning cross section including an optical axis of the image forming optical system 85. When the incidence angle of a principal ray of the second light beam on the reflection surface is defined as α, the conditional expression of 55°≤α≤75° is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical scanning device, and is particularly suitable for image forming apparatuses such as laser beam printers and multifunction printers that use an electrophotographic process. [Background technology]

[0002] Conventionally, optical scanning devices have used a configuration including an imaging optical system that guides a first light beam deflected by a deflector onto a surface to be scanned, and a synchronous detection optical system that guides a second light beam deflected by the deflector to a synchronous detection means. It is also known that such optical scanning devices can become large depending on the relative arrangement between the light source that emits a light beam including the first light beam and the second light beam and the synchronous detection means, and the relative arrangement between the imaging optical system and the synchronous detection optical system.

[0003] Patent Document 1 discloses an optical scanning device in which a light source and a synchronization detection means are arranged close to each other, and a reflective surface that reflects the second light beam is provided outside in the main scanning direction of the area within the imaging optical element through which the first light beam passes, thereby reducing the size of the device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-203872 Summary of the Invention [Problem to be solved by the invention]

[0005] In the optical scanning device disclosed in Patent Document 1, when the second light beam deflected by the deflector is guided to a synchronization detection means arranged close to the light source, a reflecting surface is provided at the end of the imaging optical element opposite the light source in the main scanning direction. The second light beam reflected by the reflecting surface passes through the imaging optical element in the main scanning direction before being guided to the synchronous detection means, and therefore the amount of light of the second light beam received by the light receiving element included in the synchronous detection means is reduced.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a small-sized optical scanning device that can suppress a decrease in the amount of light of a light beam guided to a light receiving element. [Means for solving the problem]

[0007] The optical scanning device according to the present invention includes a deflector that deflects a light beam from a light source to scan a surface to be scanned in a main scanning direction, and an imaging optical system including a first optical element, the first optical element having a transmission surface that transmits the first light beam deflected by the deflector at a first timing to guide the first light beam to the surface to be scanned, and a reflection surface that totally reflects the second light beam deflected by the deflector at a second timing different from the first timing to guide the second light beam to a light receiving element, the reflection surface being disposed on the same side as the light source with respect to a sub-scanning cross section including an optical axis of the imaging optical system. , th Chief ray of 2 light beams The light source Towards approaching The incident angle of the chief ray of the second beam of light on the reflecting surface is α , the angle formed by the optical path between the light source and the deflector and the optical path between the first optical element and the light receiving element when projected onto the main scanning cross section is β When 55°≦α≦75° -5°≦β≦55° The present invention is characterized in that the following condition is satisfied: [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a small-sized optical scanning device that can suppress a decrease in the amount of light of a light beam guided to a light receiving element. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic main-scanning cross-sectional view of the optical scanning device according to the first embodiment. [Figure 2]FIG. 2 is a schematic partially enlarged main-scan cross-sectional view of the optical scanning device according to the first embodiment. [Figure 3] FIG. 10 is a schematic partially enlarged main-scan cross-sectional view of an optical scanning device according to a second embodiment. [Figure 4] FIG. 11 is a schematic partially enlarged main-scan cross-sectional view of an optical scanning device according to a third embodiment. [Figure 5] FIG. 10 is a schematic partially enlarged main-scan sectional view of an optical scanning device according to a fourth embodiment. [Figure 6] FIG. 13 is a schematic partially enlarged main-scan sectional view of an optical scanning device according to a fifth embodiment. [Figure 7] FIG. 2 is a sub-scanning cross-sectional view of a main part of the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The optical scanning device according to the present embodiment will be described in detail below with reference to the accompanying drawings. Note that the drawings may be drawn to a scale different from the actual scale in order to facilitate understanding of the present embodiment.

[0011] In the following description, the main scanning direction is the direction perpendicular to the rotation axis of the deflector and the optical axis of the imaging optical system (the direction in which the light beam is deflected by the deflector), the sub-scanning direction is the direction parallel to the rotation axis of the deflector, the main scanning cross section is the cross section perpendicular to the sub-scanning direction, and the sub-scanning cross section is the cross section perpendicular to the main scanning direction. In the following description, the direction parallel to the optical axis of the imaging optical system is defined as the X direction, the main scanning direction as the Y direction, and the sub-scanning direction as the Z direction.

[0012] [First embodiment] 2. Description of the Related Art Image forming devices such as laser printers are equipped with an optical scanning device for scanning a surface to be scanned with laser light. Such an optical scanning device is provided with a scanning optical element (fθ lens) for scanning the surface to be scanned at a substantially constant speed, and a synchronization detection optical system for identifying the writing start position on the surface to be scanned.

[0013] In recent years, in order to reduce the cost and size of optical scanning devices, optical systems have been proposed in which the scanning optical element and the synchronization detection optical system are integrated together. For example, an optical scanning device has been proposed in which a deflection section is provided integrally at the end of the scanning optical element in the main scanning direction, and a portion of the light beam deflected by the deflector is deflected by the deflection section, passes through the scanning optical element in the main scanning direction, and is then guided to a synchronization detection means.

[0014] However, in such an optical scanning device, the light beam passes through a scanning optical element having a large width in the main scanning direction, and therefore the amount of light received by the synchronization detection means is reduced. If the amount of light decreases, the accuracy of the writing start position on the scanned surface determined by the synchronization detection means decreases, and there is a risk that the quality of the image formed on the scanned surface will decrease.

[0015] In addition, an optical scanning device has been proposed in which a deflection section having a total reflection surface is integrally provided at the end of the scanning optical element opposite the light source in the main scanning direction, and a portion of the light beam deflected by the deflector is guided by the deflection section to a synchronization detection means located on the opposite side. However, in such an optical scanning device, a portion of the light beam deflected by the deflector is deflected by the deflection unit toward a synchronization detection means located at a position far away from the light source, i.e., on the opposite side of the light source in the main scanning direction.

[0016] Furthermore, since the deflection unit is integrally formed with the scanning optical element so as to be positioned on the opposite side of the light source across the sub-scanning cross section including the optical axis of the imaging optical system, the optical scanning device is not sufficiently miniaturized. In addition, in this optical scanning device, the light source and the synchronization detection means are arranged at a large distance from each other, and they must be provided on different substrates, which increases costs.

[0017] Therefore, an object of this embodiment is to provide an optical scanning device that is miniaturized, prevents a decrease in the accuracy of the writing start position on the surface to be scanned, and is low in cost. FIG. 1 is a schematic main scanning cross-sectional view of an optical scanning device 101 according to the first embodiment.

[0018] The optical scanning device 101 according to this embodiment includes a light source 102, a diaphragm 103, an anamorphic collimator lens 104 (second optical element), and a deflector 105. The optical scanning device 101 according to this embodiment also includes a first scanning optical element 106 (first optical element), a second scanning optical element 107, and a synchronization detection means 108 (light receiving element). The optical scanning device 101 according to this embodiment, with the above-described configuration, can scan the surface to be scanned, which is the photosensitive drum D, at a substantially constant speed in the main scanning direction.

[0019] The light source 102 is an edge-emitting laser having one light-emitting point that emits a light beam with a wavelength of, for example, 780 nm, and is attached to a substrate 109 . The diaphragm 103 has a rectangular opening that limits the diameter of the light beam emitted from the light source 102 in both the main scanning direction and the sub-scanning direction.

[0020] The anamorphic collimator lens 104 converts the light beam that has passed through the diaphragm 103 into a parallel light beam in the main scanning direction. Note that the parallel light beam here includes not only a strictly parallel light beam but also an approximately parallel light beam such as a weakly divergent light beam or a weakly convergent light beam. The anamorphic collimator lens 104 condenses the light beam that has passed through the diaphragm 103 toward a deflector 105 in the sub-scanning direction.

[0021] In the optical scanning device 101 according to this embodiment, the diaphragm 103 and the anamorphic collimator lens 104 form an incident optical system 75 . By providing the anamorphic collimator lens 104 in this manner, the number of optical elements in the incident optical system 75 can be reduced, and as will be described later, interference of the light beam traveling through the synchronous detection optical system with the incident optical system 75 can be suppressed, thereby preventing a decrease in the accuracy of synchronous detection. The light beam emitted from the light source 102 is converted into a parallel light beam in the main scanning section by the incident optical system 75, and is condensed (guided) near the deflection surface of the deflector 105 in the sub-scanning section.

[0022] The deflector 105 is a polygon mirror having four deflection surfaces and rotating at a uniform speed in the direction A in the drawing around a rotation axis 105a to deflect the light beam from the incident optical system 75 toward the surface to be scanned. The first scanning optical element 106 and the second scanning optical element 107 are optical elements that guide (focus) the light beam deflected by the deflector 105 onto the surface to be scanned, and have a shape that allows them to scan the surface to be scanned at approximately a constant speed in the main scanning direction.

[0023] In the optical scanning device 101 according to this embodiment, a light beam emitted from a light source 102 passes through a diaphragm 103 and an anamorphic collimator lens 104, and then enters (is guided into) a deflector 105. The light beam deflected by the deflector 105 is then guided onto the surface to be scanned by the first scanning optical element 106 and the second scanning optical element 107, and as the deflector 105 rotates at a constant speed, the light beam guided onto the surface to be scanned scans the effective area (printing area) on the surface to be scanned.

[0024] As will be described in detail later, the first scanning optical element 106 provided in the optical scanning device 101 according to this embodiment includes a scanning optical section S1 and a synchronization detection deflection section S2. In the optical scanning device 101 according to this embodiment, the scanning optical section S1 of the first scanning optical element 106 and the second scanning optical element 107 constitute an imaging optical system 85, and the light beam deflected by the deflector 105 is guided onto the surface to be scanned by the imaging optical system 85. Furthermore, in the optical scanning device 101 according to this embodiment, the first scanning optical element 106 is formed of a resin material, and therefore, it is possible to easily mold the exit surface 106b of the scanning optical section S1 (described later) and the total reflection surface 106d of the synchronization detection deflection section S2 so that they are connected to each other.

[0025] The synchronization detection means 108 is a photodetector such as a photodiode, and determines the scanning start position (writing position) on the surface to be scanned based on the timing at which a portion of the light beam deflected by the deflector 105 is incident and the incident light beam is received. Specifically, the light source 102 is turned off until just before the deflector 105 rotates to the angle at which synchronous detection is performed, and the light source 102 is turned on when synchronous detection is performed, i.e., when the deflector 105 reaches that angle.

[0026] Thereafter, the light source 102 is turned off again, and after a predetermined time determined by the synchronization detection means 108 has elapsed, the light source 102 is turned on again when the deflector 105 reaches the scanning start position, i.e., the angle at which scanning on the surface to be scanned begins, and the surface to be scanned is scanned with the light beam. That is, the light emission timing of the light source 102 is controlled by a control unit (not shown) based on the timing at which the synchronization detection means 108 receives the light beam deflected by the deflector 105 . This allows the scanning start position on the surface to be scanned to be the same between each scan, thereby preventing degradation in the quality of the image formed on the surface to be scanned. The synchronization detection means 108 may have a slit for improving the accuracy of determining the scan start position on the surface to be scanned, in addition to the light receiving element for receiving the incident light beam.

[0027] In the optical scanning device 101 according to this embodiment, as shown in FIG. 1, the synchronization detection means 108 is mounted on a substrate 109 which is a common substrate with the light source 102. That is, the light source 102 and the synchronization detection means 108 are arranged on the same side across the sub-scanning cross section including the optical axis of the imaging optical system 85 .

[0028] The synchronous detection deflection section S2 of the first scanning optical element 106 forms a synchronous detection optical system that guides a part of the light beam deflected by the deflector 105 to synchronous detection means 108, as will be described later. That is, the first scanning optical element 106 is shared by the imaging optical system 85 and the synchronous detection optical system.

[0029] Next, a characteristic configuration of the optical scanning device 101 according to this embodiment will be described. FIG. 2 is a schematic partially enlarged main scanning cross-sectional view of the optical scanning device 101 according to this embodiment.

[0030] As shown in FIG. 2, the first scanning optical element 106 provided in the optical scanning device 101 according to this embodiment has a scanning optical section S1 that guides the light beam (first light beam) deflected by the deflector 105 onto the surface to be scanned. The first scanning optical element 106 also has a synchronization detection deflection section S2 that deflects a part of the light beam deflected by the deflector 105 (a second light beam) toward synchronization detection means 108.

[0031] That is, the first scanning optical element 106 is an optical element in which the scanning optical section S1 and the synchronization detection deflection section S2 are integrally formed. Specifically, in the first scanning optical element 106, the synchronization detection deflection section S2 is formed on the light source 102 side of the scanning optical section S1.

[0032] The scanning optical unit S1 has an incident surface 106a (second incident surface) and an exit surface 106b (second exit surface), and the synchronization detection deflection unit S2 has an incident surface 106c (first incident surface), a total reflection surface 106d (reflecting surface), and an exit surface 106e (first exit surface). That is, the incident surface 106a (first transmitting surface) and the exit surface 106b (second transmitting surface) of the scanning optical unit S1 are transmitting surfaces (refracting surfaces) that transmit (refract) the light beam deflected by the deflector 105 at the first timing and guide it onto the surface to be scanned. In the first scanning optical element 106, the exit surface 106b and the total reflection surface 106d are connected to each other. The critical angle of total reflection surface 106d is 42.5°.

[0033] The specifications of the optical scanning device 101 according to this embodiment are shown in Tables 1 and 2 below.

[0034] [Table 1]

[0035] [Table 2] In Table 2, "Ex" is "×10 -x " is shown.

[0036] The entrance surface 106a and exit surface 106b of the scanning optical section S1 of the first scanning optical element 106 and the entrance surface and exit surface of the second scanning optical element 107 each have an aspherical shape represented by the following formula. Specifically, the generatrix shapes (shapes in the main scanning cross section) of the entrance surface 106a and the exit surface 106b of the scanning optical section S1 of the first scanning optical element 106 and the entrance surface and the exit surface of the second scanning optical element 107 are expressed by the following equations (1) and (2).

number

number

[0037] Equation (1) represents the shape of the generatrix on the light source 102 side (hereinafter referred to as the light source side) across the sub-scanning cross section including the optical axis of the imaging optical system 85. Equation (2) represents the shape of the generatrix on the side opposite to the light source 102 across the sub-scanning cross section including the optical axis of the imaging optical system 85 (hereinafter referred to as the side opposite to the light source).

[0038] In addition, in equations (1) and (2), R is the radius of curvature (generatrix radius of curvature) in the main scanning section, K, B4, B6, B8, B 10 , B 12 and B 14 indicates the aspherical coefficient. In addition, B in formula (1) 4s , B 6s , B 8s , B 10s , B 12s and B 14s indicates the aspheric coefficient on the light source side (scanning start side), and B in Equation (2) 4e , B 6e , B 8e , B 10e , B 12e and B 14e indicates the aspheric coefficient on the side opposite to the light source (the side at the end of scanning). That is, as shown in Table 2, the exit surface 106b of the scanning optical section S1 of the first scanning optical element 106 and the entrance surface and exit surface of the second scanning optical element 107 have generatrices that are asymmetric with respect to the optical axis of the imaging optical system 85.

[0039] Furthermore, the sagittal shapes (shapes in the sub-scanning cross section) of the entrance surface 106a and the exit surface 106b of the scanning optical section S1 of the first scanning optical element 106 and the entrance surface and the exit surface of the second scanning optical element 107 are expressed by the following equations (3) and (4).

number

number

[0040] Equation (3) represents the shape of the sagittal line on the light source side, and equation (4) represents the shape of the sagittal line on the opposite side from the light source. In addition, in equations (3) and (4), r' is the radius of curvature in the sub-scan section (radius of curvature of the sagittal line), r is the radius of curvature of the sagittal line on the optical axis, and E2, E4, E6, E8, and E 10indicates the aspherical coefficient. In addition, E in formula (3) 2s , E 4s , E 6s , E 8s and E 10s indicates the aspheric coefficient on the light source side (scanning start side), and E in Equation (4) 2e , E 4e , E 6e , E 8e and E 10e indicates the aspherical coefficient on the side opposite to the light source (the side where scanning ends).

[0041] In the optical scanning device 101 according to this embodiment, when synchronous detection is performed, as shown in FIG. 2, the light beam from the light source 102 is deflected by the deflector 105 at a second timing different from the first timing, and then enters the synchronous detection means 108. Specifically, as shown in FIG. 2, a part of the light beam deflected by the deflector 105 is incident on the incident surface 106c of the synchronization detection deflection section S2 of the first scanning optical element 106.

[0042] The light beam that has passed through the incident surface 106c of the deflection section S2 for synchronization detection is totally reflected by the total reflection surface 106d, and then exits from the exit surface 106e, thereby being guided to the synchronization detection means 108. As a result, the surface to be scanned is scanned while synchronous detection is performed for each deflection surface of the deflector 105.

[0043] As described above, in the first scanning optical element 106 provided in the optical scanning device 101 according to this embodiment, the synchronization detection deflection section S2 is formed on the light source 102 side of the scanning optical section S1. In other words, in the first scanning optical element 106 provided in the optical scanning device 101 according to this embodiment, a total reflection surface 106d is provided on the same side as the light source 102 with respect to the sub-scanning cross section including the optical axis of the imaging optical system 85. The angle between incident surface 106c and total reflection surface 106d is set to 65.9°, and the angle between total reflection surface 106d and exit surface 106e is set to 70.3°.

[0044] Furthermore, the angle between the direction of travel of the chief ray of the light beam deflected by deflector 105 and passing through incident surface 106c toward total reflection surface 106d and the normal to total reflection surface 106d, i.e., the angle of incidence α of the chief ray with respect to total reflection surface 106d, is 69.2°. Therefore, since the incident angle α is sufficiently larger than the critical angle 42.5° of total reflection surface 106d, the light beam that is deflected by deflector 105 and passes through incident surface 106c is totally reflected upon entering total reflection surface 106d.

[0045] That is, in the optical scanning device 101 according to this embodiment, the following conditional expression (5) is satisfied. 55°≦α≦75° (5)

[0046] In the optical scanning device 101 according to this embodiment, the conditional expression (5) is satisfied, so that it is possible to achieve a reduction in cost and a reduction in the volume of the synchronization detection deflection section S2. If the upper limit value of conditional expression (5) is exceeded, the light beam will be too wide when it is incident on the total reflection surface 106d, which is undesirable because it will increase the volume of the synchronization detection deflection unit S2 and therefore the first scanning optical element 106, thereby increasing costs.

[0047] On the other hand, if the lower limit of conditional expression (5) is not reached, the angle that the light beam reflected by total reflection surface 106d makes with total reflection surface 106d becomes large, which makes it necessary to provide incident surface 106c with a large area. As a result, the volume of the synchronization detection deflection section S2 increases, which is undesirable because it increases costs.

[0048] In the optical scanning device 101 according to this embodiment, it is preferable that the following conditional expression (5a) be satisfied instead of the conditional expression (5). 57°≦α≦70° (5a)

[0049] As described above, in the optical scanning device 101 according to this embodiment, an inexpensive and small reflective surface can be formed as the total reflection surface 106d in the synchronization detection deflection section S2 of the first scanning optical element 106, which does not require the provision of a reflective film.

[0050] Furthermore, in the first scanning optical element 106, the synchronization detection deflection section S2 is formed on the light source 102 side of the scanning optical section S1, so that the area through which the light beam traveling to the synchronization detection means 108 passes within the first scanning optical element 106 can be reduced. Therefore, it is possible to suppress a decrease in the amount of light incident on the synchronization detection means 108.

[0051] In addition, in the synchronization detection deflection section S2 of the first scanning optical element 106, the light beam is reflected by a total reflection surface 106d provided as shown in Figure 2 so that the light beam travels to a synchronization detection means 108 arranged close to the light source 102. This allows both the light source 102 and the synchronization detection means 108 to be disposed on the substrate 109, thereby reducing the component costs of the optical scanning device 101 according to this embodiment.

[0052] Also, the angle formed between the optical path of the chief ray of the light beam traveling through the incident optical system 75 and the optical path of the chief ray of the light beam traveling through the synchronous detection optical system in the main scanning cross section is defined as β. In other words, the angle β is the angle between the line segment between the light emitting point of the light source 102 and the deflection point on the deflection surface of the deflector 105 when deflecting the chief ray of the light beam guided to the synchronization detection means 108 in the main scanning cross section, and the line segment between the emission point of the chief ray on the emission surface 106e and the light receiving point of the chief ray in the synchronization detection means 108.

[0053] In this case, it is preferable that the optical scanning device 101 according to this embodiment fulfills the following conditional expression (6). -5°≦β≦55° (6)

[0054] The sign of the angle β is defined such that the smaller the angle β, the more the light receiving point of the synchronization detection means 108 shifts in the positive X direction. In the optical scanning device 101 according to this embodiment, the size of the substrate 109 in the X direction can be reduced by satisfying the conditional expression (6).

[0055] If the upper limit of conditional expression (6) is exceeded or the lower limit is not reached, the synchronization detection means 108 and the light source 102 are separated from each other by a large distance in the X direction, which undesirably increases the size of the substrate 109. Furthermore, if a folding mirror for folding the optical path in the sub-scanning direction is arranged downstream of the first scanning optical element 106, there is a risk that the holding member for holding the folding mirror and the substrate 109 may interfere with each other, which is not preferable.

[0056] Furthermore, if the upper limit value of conditional expression (6) is exceeded, the incident angle of the light beam to the photodetector constituting the synchronous detection means 108 becomes large, and the amount of light received by the synchronous detection means 108 decreases according to the incident angle characteristics of the photodetector. If the light receiving area of ​​the photodetector is increased in response to such a decrease in the amount of received light, the photodetector will become larger, which is undesirable because it will increase costs. In addition, if the incident angle of the light beam to the photodetector constituting the synchronous detection means 108 becomes large, the light beam width of the light beam becomes large relative to the light-receiving area of ​​the photodetector, which is undesirable because it reduces the amount of light received by the photodetector.

[0057] In the optical scanning device 101 according to this embodiment, it is more preferable that the following conditional expression (6a) be fulfilled instead of the conditional expression (6). -2°≦β≦45° (6a)

[0058] In the optical scanning device 101 according to this embodiment, β is set to 1°, and therefore conditional expressions (6) and (6a) are satisfied. In the optical scanning device 101 according to this embodiment, as shown in FIG. 2, the optical path of the chief ray of the light beam traveling through the incident optical system 75 and the optical path of the chief ray of the light beam traveling through the synchronous detection optical system do not intersect with each other when projected within the main scanning cross section.

[0059] In the first scanning optical element 106, a gate cut portion (gate portion) (not shown) for injecting a resin material when injection molding the resin material is preferably formed on the side opposite to the light source in the main scanning direction. This allows the optical surfaces of the first scanning optical element 106, such as the exit surface 106e, to be molded with high precision, thereby maintaining surface precision, and thus achieving good optical performance.

[0060] In the optical scanning device 101 according to this embodiment, it is preferable to provide the synchronization detection deflection unit S2 on the first scanning optical element 106, which is closer to the deflector 105 than the second scanning optical element 107. In other words, it is preferable that no scanning optical element is provided between the deflector 105 and the scanning optical element on which the synchronization detection deflection unit S2 is provided on the optical path (first optical path) of the light beam that is deflected by the deflector 105 and then guided to the surface to be scanned.

[0061] If a synchronization detection deflection section S2 is provided in the second scanning optical element 107, the light beam that passes through the synchronization detection deflection section S2 of the second scanning optical element 107 after passing through the first scanning optical element 106 will be incident on the synchronization detection means 108. That is, the amount of light of the light beam incident on the synchronization detection means 108 is further reduced by passing through the first scanning optical element 106, which is not preferable.

[0062] As described above, in the optical scanning device 101 according to this embodiment, in addition to the scanning optical section S1, the first scanning optical element 106 is formed with the synchronization detection deflection section S2 on the light source side of the scanning optical section S1. This allows the synchronous detection means 108 to be provided on the same side as the light source 102 with respect to the sub-scan section including the optical axis of the imaging optical system 85, and allows the synchronous detection optical system to be formed using only the synchronous detection deflection section S2. Therefore, in the optical scanning device 101 according to this embodiment, it is possible to suppress a decrease in the amount of light of the light beam guided to the synchronization detection means 108, and also to achieve a reduction in size and cost.

[0063] In the optical scanning device 101 according to this embodiment, the light source 102 uses, for example, an edge-emitting laser having one light-emitting point, but is not limited to this. That is, the light source 102 may be an edge-emitting laser having a plurality of light-emitting points, or a vertical-cavity surface-emitting laser (VCSEL).

[0064] In addition, in the optical scanning device 101 according to this embodiment, the light source 102 uses a light source 102 that emits a light beam with a wavelength of 780 nm, but this is not limited to this, and a light source that emits a light beam with a predetermined wavelength may be used. Furthermore, in the optical scanning device 101 according to this embodiment, the diaphragm 103 having a rectangular opening is used, but the invention is not limited to this, and the diaphragm 103 may have an elliptical or polygonal opening.

[0065] Furthermore, in the optical scanning device 101 according to this embodiment, a polygon mirror is used as the deflector 105, but the invention is not limited to this, and a reciprocating scanning mirror using a micro-electromechanical system (MEMS) may also be used. In addition, in the optical scanning device 101 according to this embodiment, the first scanning optical element 106 and the second scanning optical element 107 are formed using a glass material having a refractive index of 1.524, but they may be formed using a glass material having a predetermined refractive index.

[0066] Furthermore, in the optical scanning device 101 according to this embodiment, the synchronization detection means 108 is configured with a photodetector such as a photodiode, but is not limited to this and may be configured, for example, with a combination of a slit having a predetermined width in the main scanning direction and a photodetector. In addition, in the optical scanning device 101 according to this embodiment, it is preferable that no optical element for guiding the light beam to the synchronous detection means 108 is provided between the synchronous detection deflection section S2 of the first scanning optical element 106 and the synchronous detection means 108 in the synchronous detection optical system.

[0067] In the optical scanning device 101 according to this embodiment, the precision with which a predetermined optical element is held may be improved by attaching a rib to the predetermined optical element in the housing (not shown). In this case, it is preferable to provide a rib so as to suppress displacement of the total reflection surface 106d of the synchronization detection deflection section S2 provided on the first scanning optical element 106 in the X direction.

[0068] In addition, in order to suppress displacement in the Y direction of the exit surface 106e of the synchronization detection deflection unit S2 provided on the first scanning optical element 106, a rib may be attached at a position lower in the Z direction than the effective area from which the light beam is emitted from the exit surface 106e. This makes it possible to suppress displacement of the exit surface 106e in the Y direction so as not to unnecessarily interfere with the light beam exiting from the exit surface 106e.

[0069] In addition, in the optical scanning device 101 according to this embodiment, it is preferable to make the light beam incident approximately perpendicular to the exit surface 106e so as to prevent aberration due to decentering of each optical surface of the synchronization detection deflection unit S2 provided in the first scanning optical element 106. In addition, in the optical scanning device 101 according to this embodiment, the total reflection surface 106d of the synchronization detection deflection section S2 provided in the first scanning optical element 106 may be formed into a curved surface within a range that satisfies the total reflection condition according to the shape of the incident surface 106c.

[0070] Furthermore, the optical scanning device 101 according to this embodiment may be provided with a folding mirror for folding back the optical path in the sub-scanning direction. In this case, the folding mirror is preferably disposed downstream of the first scanning optical element 106, and a holding member for holding the folding mirror is preferably also provided.

[0071] [Second embodiment] FIG. 3 is a schematic partially enlarged main-scan cross-sectional view of an optical scanning device according to the second embodiment. The optical scanning device according to this embodiment has the same configuration as the optical scanning device 101 according to the first embodiment except for different specification values, so the same components are given the same reference numerals and their explanations are omitted.

[0072] Specifically, in the optical scanning device according to this embodiment, the exit surface 106e provided on the synchronization detection deflection unit S2 of the first scanning optical element 106 has a curvature in the main scanning cross section. More specifically, the exit surface 106e provided in the synchronization detection deflection unit S2 is a convex surface with a radius of curvature of 20 mm in the main scanning cross section, and is formed as an anamorphic surface having a different power from that in the sub-scanning cross section. As a result, in the optical scanning device according to this embodiment, the light beam emitted from the exit surface 106e can be guided to the synchronization detection means 108 while being condensed, thereby improving the synchronization detection accuracy of the synchronization detection means 108.

[0073] Furthermore, in the optical scanning device according to this embodiment, the synchronization detection deflection section S2 is formed on the light source 102 side of the scanning optical section S1 in the first scanning optical element 106, so that the area through which the light beam traveling to the synchronization detection means 108 passes within the first scanning optical element 106 can be reduced. Therefore, it is possible to suppress a decrease in the amount of light incident on the synchronization detection means 108.

[0074] The angle between incident surface 106c and total reflection surface 106d is set to 65.9°, and the angle between total reflection surface 106d and exit surface 106e is set to 70.3°.

[0075] Furthermore, the angle between the direction of travel of the chief ray of the light beam deflected by deflector 105 and passing through incident surface 106c toward total reflection surface 106d and the normal to total reflection surface 106d, i.e., the angle of incidence α of the chief ray with respect to total reflection surface 106d, is 69.2°. Therefore, since this incident angle is sufficiently larger than the critical angle of 42.5° of total reflection surface 106d, the light beam that is deflected by deflector 105 and passes through incident surface 106c is totally reflected upon entering total reflection surface 106d. In the optical scanning device according to this embodiment, the angle β is set to −1.5°, and therefore the conditional expressions (5), (5a), (6) and (6a) are satisfied.

[0076] As described above, in the optical scanning device according to this embodiment, in addition to the scanning optical section S1 in the first scanning optical element 106, the synchronization detection deflection section S2 is formed on the light source side of the scanning optical section S1. This allows the synchronous detection means 108 to be provided on the same side as the light source 102 with respect to the sub-scan section including the optical axis of the imaging optical system 85, and allows the synchronous detection optical system to be formed using only the synchronous detection deflection section S2.

[0077] In the optical scanning device according to this embodiment, the light beam is guided to the synchronization detection means 108 while being condensed. Therefore, in the optical scanning device according to this embodiment, it is possible to suppress a decrease in the amount of light of the light beam guided to the synchronization detection means 108, improve the synchronization detection accuracy of the synchronization detection means 108, and achieve miniaturization and cost reduction.

[0078] [Third embodiment] FIG. 4 is a schematic enlarged partial main-scan cross-sectional view of an optical scanning device according to the third embodiment. The optical scanning device according to this embodiment has the same configuration as the optical scanning device 101 according to the first embodiment except for different specification values, so the same components are given the same reference numerals and their explanations are omitted.

[0079] Specifically, in the optical scanning device according to this embodiment, the relative arrangement between the light source 102 and the synchronization detection means 108 is different from that of the optical scanning device 101 according to the first embodiment. More specifically, in the optical scanning device according to this embodiment, the synchronization detection means 108 is provided on the opposite side of the scanned surface across a YZ cross section that includes the position of the light source 102 and is perpendicular to the optical axis of the imaging optical system 85. Therefore, as shown in FIG. 4, the light beam emitted from the exit surface 106e of the synchronization detection deflection section S2 of the first scanning optical element 106 is guided to the synchronization detection means 108 so that it intersects with the light beam traveling through the incident optical system 75 when projected within the main scanning cross section.

[0080] That is, in the optical scanning device according to this embodiment, the optical path of the chief ray of the light beam traveling through the incident optical system 75 and the optical path of the chief ray of the light beam traveling through the synchronous detection optical system intersect with each other when projected onto the main scanning cross section. This makes it possible to reduce the angle between the incident surface 106c and the total reflection surface 106d in the synchronization detection deflection unit S2.

[0081] Furthermore, by reducing the angle between the incident surface 106c and the total reflection surface 106d, the beam width of the light beam incident on the total reflection surface 106d can be reduced. This allows the volume of the synchronization detection deflection section S2 in the first scanning optical element 106 to be reduced. Therefore, the area through which the light beam passes within the first scanning optical element 106 can be further reduced, and therefore the reduction in the amount of light beam incident on the synchronization detection means 108 can be further suppressed.

[0082] In the optical scanning device according to this embodiment, it is preferable to use the anamorphic collimator lens 104 to reduce the number of optical elements included in the incident optical system 75. This makes it possible to suppress interference of the light beam traveling through the synchronous detection optical system with the optical elements included in the incident optical system 75 and the holding members for those optical elements in a configuration in which the light beam traveling through the synchronous detection optical system and the light beam traveling through the incident optical system 75 intersect with each other.

[0083] Furthermore, in the optical scanning device according to this embodiment, the focal length of the anamorphic collimator lens 104 is set to 7.4 mm, thereby reducing the distance between the light source 102 and the anamorphic collimator lens 104. This makes it possible to suppress interference of the light beam traveling through the synchronous detection optical system with the anamorphic collimator lens 104 .

[0084] In the optical scanning device of this embodiment, the angle β in the main scanning cross section between the direction of travel of the principal ray of the light beam in the synchronous detection optical system and the direction of travel of the principal ray of the light beam in the incident optical system 75 is set to 15°. The angle between incident surface 106c and total reflection surface 106d is set to 59.1°, and the angle between total reflection surface 106d and exit surface 106e is set to 55.2°.

[0085] Furthermore, the angle between the direction of travel of the chief ray of the light beam deflected by deflector 105 and passing through incident surface 106c toward total reflection surface 106d and the normal to total reflection surface 106d, i.e., the angle of incidence α of the chief ray with respect to total reflection surface 106d, is 67.6°. Therefore, since the incident angle α is sufficiently larger than the critical angle 42.5° of total reflection surface 106d, the light beam that is deflected by deflector 105 and passes through incident surface 106c is totally reflected upon entering total reflection surface 106d. As described above, in the optical scanning device according to this embodiment, the conditional expressions (5), (5a), (6) and (6a) are satisfied.

[0086] As described above, in the optical scanning device according to this embodiment, in addition to the scanning optical section S1 in the first scanning optical element 106, the synchronization detection deflection section S2 is formed on the light source side of the scanning optical section S1. This allows the synchronous detection means 108 to be provided on the same side as the light source 102 with respect to the sub-scan section including the optical axis of the imaging optical system 85, and allows the synchronous detection optical system to be formed using only the synchronous detection deflection section S2.

[0087] Furthermore, in the optical scanning device according to this embodiment, the optical path of the chief ray of the light beam traveling through the incident optical system 75 and the optical path of the chief ray of the light beam traveling through the synchronous detection optical system intersect with each other when projected onto the main scanning cross section. As a result, in the optical scanning device according to this embodiment, it is possible to further suppress the decrease in the amount of light of the light beam guided to the synchronization detection means 108, and also to achieve miniaturization and cost reduction.

[0088] [Fourth embodiment] FIG. 5 is a schematic partially enlarged main-scan cross-sectional view of an optical scanning device according to the fourth embodiment. The optical scanning device according to this embodiment has the same configuration as the optical scanning device 101 according to the first embodiment except for different specification values, so the same components are given the same reference numerals and their explanations are omitted.

[0089] In the optical scanning device according to this embodiment, the distance between the light source 102 and the synchronization detecting means 108 is increased compared to the optical scanning device according to the third embodiment. Then, the angle between total reflection surface 106d and exit surface 106e is adjusted in accordance with the increase in the distance, thereby adjusting the exit angle of the light beam from exit surface 106e. Specifically, the angle between the total reflection surface 106d and the exit surface 106e is adjusted so that the angle β in the main scanning cross section between the traveling direction of the chief ray of the light beam in the synchronous detection optical system and the traveling direction of the chief ray of the light beam in the incident optical system 75 is 45 degrees.

[0090] In the optical scanning device according to this embodiment, the angle between incident surface 106c and total reflection surface 106d is set to 57.6°, and the angle between total reflection surface 106d and exit surface 106e is set to 96.3°.

[0091] Furthermore, the angle between the direction of travel of the chief ray of the light beam deflected by deflector 105 and passing through incident surface 106c toward total reflection surface 106d and the normal to total reflection surface 106d, i.e., the angle of incidence α of the chief ray with respect to total reflection surface 106d, is 61.5°. Therefore, since the incident angle α is sufficiently larger than the critical angle 42.5° of total reflection surface 106d, the light beam that is deflected by deflector 105 and passes through incident surface 106c is totally reflected upon entering total reflection surface 106d. As described above, in the optical scanning device according to this embodiment, the conditional expressions (5), (5a), (6) and (6a) are satisfied.

[0092] As described above, in the optical scanning device according to this embodiment, in addition to the scanning optical section S1 in the first scanning optical element 106, the synchronization detection deflection section S2 is formed on the light source side of the scanning optical section S1. This allows the synchronous detection means 108 to be provided on the same side as the light source 102 with respect to the sub-scan section including the optical axis of the imaging optical system 85, and allows the synchronous detection optical system to be formed using only the synchronous detection deflection section S2.

[0093] Furthermore, in the optical scanning device according to this embodiment, the optical path of the chief ray of the light beam traveling through the incident optical system 75 and the optical path of the chief ray of the light beam traveling through the synchronous detection optical system intersect with each other when projected onto the main scanning cross section. As a result, in the optical scanning device according to this embodiment, it is possible to further suppress the decrease in the amount of light of the light beam guided to the synchronization detection means 108, and also to achieve miniaturization and cost reduction.

[0094] [Fifth embodiment] FIG. 6 is a schematic partially enlarged main scanning cross-sectional view of an optical scanning device according to the fifth embodiment. The optical scanning device according to this embodiment has the same configuration as the optical scanning device 101 according to the first embodiment except for different specification values, so the same components are given the same reference numerals and their explanations are omitted.

[0095] In the optical scanning device according to this embodiment, the synchronization detection means 108 is provided on the opposite side of the scanned surface across a YZ cross section that includes the position of the light source 102 and is perpendicular to the optical axis of the imaging optical system 85 . Specifically, the angle β in the main scanning cross section between the direction of travel of the principal ray of the light beam in the synchronous detection optical system and the direction of travel of the principal ray of the light beam in the incident optical system 75 is set to 20°.

[0096] In the optical scanning device according to this embodiment, the exit surface 106e of the synchronization detection deflection section S2 of the first scanning optical element 106 is formed to have a curvature in the main scanning cross section. This allows the light beam emitted from the exit surface 106e to be guided to the synchronous detection means 108 while being condensed, thereby improving the accuracy of synchronous detection in the synchronous detection means 108.

[0097] The angle between incident surface 106c and total reflection surface 106d is set to 52.1°, and the angle between total reflection surface 106d and exit surface 106e is set to 65.6°.

[0098] Furthermore, the angle between the direction of travel of the chief ray of the light beam deflected by deflector 105 and passing through incident surface 106c toward total reflection surface 106d and the normal to total reflection surface 106d, i.e., the angle of incidence α of the chief ray with respect to total reflection surface 106d, is 58.2°. Therefore, since this incident angle is sufficiently larger than the critical angle of 42.5° of total reflection surface 106d, the light beam that is deflected by deflector 105 and passes through incident surface 106c is totally reflected upon entering total reflection surface 106d. As described above, in the optical scanning device according to this embodiment, the conditional expressions (5), (5a), (6) and (6a) are satisfied.

[0099] As described above, in the optical scanning device according to this embodiment, in addition to the scanning optical section S1 in the first scanning optical element 106, the synchronization detection deflection section S2 is formed on the light source side of the scanning optical section S1. This allows the synchronous detection means 108 to be provided on the same side as the light source 102 with respect to the sub-scan section including the optical axis of the imaging optical system 85, and allows the synchronous detection optical system to be formed using only the synchronous detection deflection section S2.

[0100] In the optical scanning device according to this embodiment, the light beam is guided to the synchronization detection means 108 while being condensed. Furthermore, in the optical scanning device according to this embodiment, the optical path of the chief ray of the light beam traveling through the incident optical system 75 and the optical path of the chief ray of the light beam traveling through the synchronous detection optical system intersect with each other when projected onto the main scanning cross section. As a result, in the optical scanning device according to this embodiment, the decrease in the amount of light beam guided to the synchronous detection means 108 can be further suppressed, the synchronous detection accuracy of the synchronous detection means 108 can be improved, and miniaturization and cost reduction can be achieved.

[0101] The specifications of the synchronization detection deflection unit S2 of the first scanning optical element 106 provided in each of the optical scanning devices according to the first to fifth embodiments are shown in Table 3 below.

[0102] [Table 3]

[0103] [Image forming device] FIG. 7 shows a sub-scanning cross-sectional view of a main part of a color image forming apparatus 60 including optical scanning devices 101a, 101b, 101c, and 101d according to any one of the first to fifth embodiments.

[0104] The color image forming apparatus 60 is an image forming apparatus that records image information on, for example, a photosensitive drum. The color image forming apparatus 60 includes photosensitive drums 21, 22, 23, and 24, developing units 31, 32, 33, and 34, a conveyor belt 51, a printer controller 53, a fixing unit 71, and optical scanning devices 101a, 101b, 101c, and 101d.

[0105] As shown in FIG. 7, color image forming apparatus 60 receives R (red), G (green), and B (blue) color signals output from external device 52 such as a personal computer. The input color signals are then converted by the printer controller 53 into image data (screen patterns) for each of C (cyan), M (magenta), Y (yellow), and K (black).

[0106] The converted image data is input to the optical scanning devices 101a, 101b, 101c, and 101d, respectively. Next, light beams 41, 42, 43, and 44 modulated in accordance with the image data are emitted from the optical scanning devices 101a, 101b, 101c, and 101d, respectively. The light beams 41, 42, 43, and 44 scan the photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 in the main scanning direction.

[0107] In the color image forming apparatus 60, optical scanning devices 101a to 101d correspond to the colors C (cyan), M (magenta), Y (yellow), and K (black), and each of them records image signals on the photosensitive surfaces of photosensitive drums 21 to 24 in parallel, thereby printing color images at high speed.

[0108] As described above, the color image forming apparatus 60 forms electrostatic latent images of each color on the photosensitive surfaces of the corresponding photosensitive drums 21 to 24 using light beams 41 to 44 based on the image data emitted from the four optical scanning devices 101a to 101d. Specifically, each of the photosensitive drums 21 to 24 is charged by applying a uniform voltage thereto. When the light beams 41 to 44 irradiate the photosensitive surfaces of the photosensitive drums 21 to 24 that have been uniformly charged in this manner, the voltage only at the irradiated portions drops. The voltage distribution thus formed on the photosensitive surfaces of the photosensitive drums 21 to 24 is an electrostatic latent image.

[0109] Thereafter, the electrostatic latent images of each color are developed into toner images of each color by developing devices 31, 32, 33, and 34, and the developed toner images of each color are multi-transferred onto a transfer material conveyed by a conveyor belt 51 by a transfer device (not shown). The transferred toner image is then fixed by a fixing device 71 to form a full-color image on one sheet. In this way, in the color image forming apparatus 60, by mounting the optical scanning devices 101a, 101b, 101c, and 101d according to any one of the first to fifth embodiments, it is possible to suppress degradation in the quality of the images formed.

[0110] The external device 52 may be, for example, a color image reading device equipped with a charge coupled device (CCD) sensor. In this case, the color image reading device and the color image forming device 60 form a color digital copying machine.

[0111] Furthermore, the optical scanning device according to any one of the first to fifth embodiments is not limited to being used in the color image forming apparatus 60, but can also be used in a monochrome image forming apparatus. In this case, it is only necessary to provide the monochrome image forming apparatus with an optical scanning device according to any one of the first to fifth embodiments.

[0112] Although the preferred embodiments have been described above, the present invention is not limited to these embodiments and various modifications and changes are possible within the scope of the gist thereof.

[0113] The disclosure of this embodiment includes the following configuration. (Configuration 1) An optical scanning device comprising: a deflector that deflects a light beam from a light source to scan a surface to be scanned in the main scanning direction; and an imaging optical system including a first optical element, wherein the first optical element has a transmitting surface that transmits the first light beam deflected by the deflector at a first timing and guides it to the surface to be scanned; and a reflecting surface that totally reflects the second light beam deflected by the deflector at a second timing different from the first timing and guides it to a light receiving element, wherein the reflecting surface is located on the same side as the light source with respect to a sub-scanning cross section including the optical axis of the imaging optical system, and wherein when the angle of incidence of the chief ray of the second light beam with respect to the reflecting surface is α, the optical scanning device satisfies the conditional expression 55°≦α≦75°. (Configuration 2) The optical scanning device according to configuration 1, further comprising a control unit that controls the light emission timing of the light source based on the timing at which the light receiving element receives the second light beam. (Configuration 3) The optical scanning device according to configuration 1 or 2, wherein no optical element for guiding the first light beam is provided on the optical path between the deflector and the first optical element. (Configuration 4) The optical scanning device according to any one of configurations 1 to 3, wherein the light source and the light receiving element are provided on a common substrate. (Configuration 5) An optical scanning device according to any one of configurations 1 to 4, characterized in that, when projected onto a main scanning cross section, the angle formed by the optical path between the light source and the deflector and the optical path between the first optical element and the light receiving element is β, the condition -5°≦β≦55° is satisfied. (Configuration 6) An optical scanning device according to configuration 5, characterized in that the optical path between the light source and the deflector and the optical path between the first optical element and the light receiving element intersect with each other when projected onto the main scanning cross section. (Configuration 7) An optical scanning device described in any one of configurations 1 to 6, characterized in that the first optical element has an incident surface onto which the second light beam deflected by the deflector is incident, and an exit surface from which the second light beam reflected by the reflecting surface exits. (Configuration 8) An optical scanning device described in any one of configurations 1 to 7, characterized in that the first optical element has a first transmitting surface onto which the first light beam deflected by the deflector is incident, and a second transmitting surface from which the first light beam incident from the first transmitting surface exits, and the second transmitting surface and the reflecting surface are connected to each other. (Configuration 9) An optical scanning device described in any one of configurations 1 to 8, characterized in that no optical element for guiding the second light beam is provided on the optical path between the first optical element and the light receiving element. (Configuration 10) The optical scanning device according to any one of configurations 1 to 9, wherein the first optical element is made of a resin material. (Configuration 11) The optical scanning device according to any one of configurations 1 to 10, wherein the first optical element is provided with a gate portion on the opposite side to the light source with respect to the sub-scanning cross section including the optical axis. (Configuration 12) An optical scanning device according to any one of configurations 1 to 11, characterized in that it is provided with a second optical element that converts the light beam emitted from the light source into a parallel light beam in the main scanning cross section and condenses the light in the sub-scanning cross section. (Configuration 13) An image forming apparatus comprising an optical scanning device according to any one of configurations 1 to 12, a developing unit that develops an electrostatic latent image formed on a surface to be scanned by the optical scanning device into a toner image, a transfer unit that transfers the developed toner image to a transfer material, and a fixing unit that fixes the transferred toner image to the transfer material. (Configuration 14) An image forming apparatus comprising: an optical scanning device according to any one of configurations 1 to 12; and a printer controller that converts a signal output from an external device into image data and inputs the image data to the optical scanning device. [Explanation of symbols]

[0114] 85 Imaging Optical System 101 Optical scanning device 102 Light source 105 Deflector 106 First scanning optical element (first optical element) 106a Incidence surface (transmission surface) 106b Output surface (transmission surface) 106d Total reflection surface (reflection surface) 108 Synchronous detection means (light receiving element) D Photosensitive drum (scanned surface)

Claims

1. a deflector that deflects a light beam from a light source to scan the surface to be scanned in a main scanning direction; an imaging optical system including a first optical element; the first optical element has a transmitting surface that transmits a first light beam deflected by the deflector at a first timing and guides the light to the scanned surface, and a reflecting surface that totally reflects a second light beam deflected by the deflector at a second timing different from the first timing and guides the second light beam to a light receiving element, the reflecting surface is disposed on the same side as the light source with respect to a sub-scanning cross section including an optical axis of the imaging optical system, and reflects a chief ray of the second light flux in a direction approaching the light source; When the incident angle of the chief ray of the second light flux with respect to the reflecting surface is defined as α and the angle formed by the optical path between the light source and the deflector and the optical path between the first optical element and the light receiving element when projected onto the main scanning cross section is defined as β, ５５°≦α≦７５° －５°≦β≦５５° An optical scanning device characterized by satisfying the following conditional expression.

2. 2. The optical scanning device according to claim 1, further comprising a control unit that controls the light emission timing of the light source based on the timing at which the light receiving element receives the second light beam.

3. 2. The optical scanning device according to claim 1, wherein an optical element for guiding the first light beam is not provided on the optical path between the deflector and the first optical element.

4. 2. The optical scanning device according to claim 1, wherein the light source and the light receiving element are provided on a common substrate.

5. 2. The optical scanning device according to claim 1, wherein the optical path between the light source and the deflector and the optical path between the first optical element and the light receiving element intersect with each other when projected onto a main scanning cross section.

6. 2. The optical scanning device according to claim 1, wherein the first optical element has an incident surface onto which the second light beam deflected by the deflector is incident, and an exit surface from which the second light beam reflected by the reflecting surface exits.

7. the first optical element has a first transmitting surface onto which the first light flux deflected by the deflector is incident, and a second transmitting surface from which the first light flux incident from the first transmitting surface exits, 2. The optical scanning device according to claim 1, wherein the second transmitting surface and the reflecting surface are connected to each other.

8. 2. The optical scanning device according to claim 1, wherein no optical element for guiding the second light beam is provided on the optical path between the first optical element and the light receiving element.

9. 2. The optical scanning device according to claim 1, wherein the first optical element is made of a resin material.

10. 2. The optical scanning device according to claim 1, wherein the first optical element is provided with a gate portion on the opposite side of the light source with respect to the sub-scanning cross section including the optical axis.

11. 2. The optical scanning device according to claim 1, further comprising a second optical element that converts the light beam emitted from the light source into a parallel light beam in a main scanning cross section and that condenses the light beam in a sub-scanning cross section.

12. 12. An image forming apparatus comprising: an optical scanning device according to claim 1; a developing unit that develops an electrostatic latent image formed on the scanned surface by the optical scanning device into a toner image; a transfer unit that transfers the developed toner image to a transfer material; and a fixing unit that fixes the transferred toner image to the transfer material.

13. 12. An image forming apparatus comprising: the optical scanning device according to claim 1; and a printer controller that converts a signal output from an external device into image data and inputs the image data to the optical scanning device.

Images