| 摘要 |
An optical deflector includes a rotary body including a polygon mirror; a rotation shaft fixed to the rotary body; a bearing unit rotatably supporting the rotation shaft; and a board to which the bearing unit is fixed. Where P [rpm] is the number of revolutions of the rotary body, l [m] is a distance between a center of gravity of the rotary body and the board, m [kg] is mass of the rotary body, r [m] is a radius of the rotation shaft, E [Pa] is Young's modulus of the rotation shaft, and t [mm] is a thickness of the board, the following inequalities are satisfied: <maths id="MATH-US-00001" num="00001"> <math overflow="scroll"> <mrow> <mrow> <mfrac> <mn>1</mn> <mrow> <mn>2</mn> <mo></mo> <mi>pi</mi> </mrow> </mfrac> <mo></mo> <msqrt> <mfrac> <mrow> <mn>3</mn> <mo></mo> <mi>pi</mi> <mo></mo> <mstyle> <mspace width="0.3em" height="0.3ex"/> </mstyle> <mo></mo> <msup> <mi>Er</mi> <mn>4</mn> </msup> </mrow> <mrow> <mn>4</mn> <mo></mo> <msup> <mi>ml</mi> <mn>3</mn> </msup> </mrow> </mfrac> </msqrt> </mrow> <mo><=</mo> <mrow> <msqrt> <mn>2</mn> </msqrt> <mo>x</mo> <mfrac> <mi>P</mi> <mn>60</mn> </mfrac> </mrow> </mrow> </math> </maths> <maths id="MATH-US-00001-2" num="00001.2"> <math overflow="scroll"> <mi>and</mi> </math> </maths> <maths id="MATH-US-00001-3" num="00001.3"> <math overflow="scroll"> <mrow> <mn>0.8</mn> <mo><=</mo> <mi>t</mi> <mo><=</mo> <mrow> <mn>1.8</mn> <mo>.</mo> </mrow> </mrow> </math> </maths>
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