Optical scanning apparatus and image forming apparatus having the same

Abstract

To provide an optical scanning device that achieves sufficient miniaturization. 【Solution means】The optical scanning device according to the present invention includes a deflector and first and second optical systems that guide first and second light beams from first and second light sources deflected by the deflector to first and second scanned surfaces. The first optical system includes a first optical element and a second optical element disposed between the first optical element and the first scanned surface. The second optical system includes a third optical element and a fourth optical element disposed between the third optical element and the second scanned surface. The optical path lengths from the on-axis deflection point of the deflector to the second optical element and from the on-axis deflection point to the fourth optical element are different from each other. When the focal lengths on the optical axis in the main scanning cross-section of the first, second, third, and fourth optical elements are respectively f 11 , f 21 , f 12 and f 22 and are characterized by satisfying the condition that -0.250 < f 11 / f 21 <0.000 -0.250 < f 12 / f 22 <0.000 is satisfied.

Claims

1. A deflector that deflects the first and second luminous beams from the first and second light sources to scan the first and second surfaces to be scanned in the main scanning direction, The system comprises first and second optical systems that guide the first and second light beams deflected by the deflector to the first and second surfaces to be scanned, The first optical system includes a first imaging optical element and a second imaging optical element disposed between the first imaging optical element and the first scanned surface on the optical path of the first light beam. The second optical system includes a third imaging optical element and a fourth imaging optical element positioned between the third imaging optical element and the second scanned surface on the optical path of the second light beam. The first optical path length from the on-axis deflection point of the deflector to the second imaging optical element, and the second optical path length from the on-axis deflection point to the fourth imaging optical element are different from each other. The focal lengths of the first, second, third, and fourth imaging optical elements on the optical axis in the main scanning cross-section are f, respectively. １１ , f ２１ , f １２ and f ２２ In that case, -0.250<f １１ / f ２１ <0.000 -0.250<f １２ / f ２２ <0.000 An optical scanning device characterized by satisfying the following conditions.

2. The first optical path length is shorter than the second optical path length. 0.950<f １１ / f １２ <1.000 The optical scanning apparatus according to claim 1, characterized in that it satisfies the following conditions.

3. The optical scanning apparatus according to claim 1, characterized in that each of the first and second optical systems includes at least one reflective element.

4. The first optical path length is shorter than the second optical path length. The optical scanning apparatus according to claim 3, characterized in that the number of reflective elements included in the second optical system is greater than the number of reflective elements included in the first optical system.

5. The first distance between the image height reached by the principal ray of the first luminous beam deflected at a scanning angle θ and the on-axial image height on the first scanned surface is defined as yp1. θ The second distance between the image height reached by the principal ray of the second luminous beam deflected at a scanning angle θ and the on-axial image height is defined as yp2. θ In this case, at any angle other than 0° when the scanning angle θ 0.000100<|2×(ypq) θ --92 θ ) / (ypq θ +ypr θ )|<0.0050 The optical scanning apparatus according to claim 1, characterized in that it satisfies the following conditions.

6. The optical scanning apparatus according to claim 5, further comprising a control unit that controls the emission timing of at least one of the first and second light sources based on the difference between the first and second distances.

7. The optical scanning apparatus according to claim 1, characterized in that the optical path length from the axial deflection point to the axial image height of the first scanned surface and the optical path length from the axial deflection point to the axial image height of the second scanned surface are equal to each other.

8. The optical scanning apparatus according to claim 1, characterized in that the first and second luminous beams are deflected by a predetermined deflection surface of the deflector.

9. The optical scanning apparatus according to claim 1, characterized in that the first and third imaging optical elements are integral with each other.

10. The optical scanning apparatus according to claim 1, characterized in that the deflector is a multifaceted mirror.

11. The optical scanning apparatus according to claim 1, further comprising third and fourth optical systems that obliquely incident the first and second light beams onto the deflector in a sub-scanning cross-section.

12. A deflector that deflects the first and second luminous beams from the first and second light sources to scan the first and second surfaces to be scanned in the main scanning direction, The system comprises first and second optical systems that guide the first and second light beams deflected by the deflector to the first and second surfaces to be scanned, The first optical system includes a first imaging optical element and a second imaging optical element disposed between the first imaging optical element and the first scanned surface on the optical path of the first light beam. The second optical system includes a third imaging optical element and a fourth imaging optical element positioned between the third imaging optical element and the second scanned surface on the optical path of the second light beam. An optical scanning apparatus characterized in that the first optical path length from the on-axial deflection point of the deflector to the second imaging optical element and the second optical path length from the on-axial deflection point to the fourth imaging optical element are different from each other.

13. An image forming apparatus comprising an optical scanning apparatus according to any one of claims 1 to 12, and a developer for developing an electrostatic latent image formed on the surface to be scanned by the optical scanning apparatus.

14. An image forming apparatus comprising an optical scanning device according to any one of claims 1 to 12, and a controller that converts a signal output from an external device into image data and inputs it to the optical scanning device.

Images