Optical scanner and image forming apparatus

The optical scanning device uses a diffractive optical element with defined distance and power ratios to manage temperature-induced astigmatism, ensuring stable performance across temperature changes.

JP2025166396APending Publication Date: 2025-11-06CANON KK
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Patent Information

Application Number
JP2024070396
Authority / Receiving Office
JP · JP
Patent Type
Applications
Current Assignee / Owner
Filing Date
2024-04-24
Publication Date
2025-11-06

AI Technical Summary

Technical Problem

Conventional optical scanning devices fail to sufficiently suppress the increase in astigmatism due to temperature rise, particularly in the sub-scanning cross section, despite efforts to manage temperature-induced shifts in the main-scanning cross section.

Method used

The optical scanning device employs a configuration with a single diffractive optical element, where the distance and power ratios between the light source and deflector are defined to suppress astigmatism by using a temperature compensation optical system that adjusts diffractive power in response to temperature changes.

Benefits of technology

This configuration effectively suppresses astigmatism increases across temperature variations, maintaining optical performance by canceling out focus shifts in both main and sub-scanning sections.

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Abstract

To provide an optical scanner that can sufficiently suppress an increase in astigmatism due to temperature rise.SOLUTION: An optical scanner according to the present invention comprises: a deflector that deflects a light beam from a light source and scans a scanning target surface in a main scanning direction; an incident optical system that is formed of an optical element having an incident surface and an emission surface, at least one of which is a diffraction surface, and guides the light beam from the light source to a deflection surface of the deflector; and an imaging optical system that guides the light beam deflected by the deflection surface to the scanning target surface. When the distance between a light emission surface of the light source and the incident surface of the optical element, and the distance between the emission surface of the optical element and an on-axis deflection point of the deflection surface, which are on an optical axis of the incident optical system, are defined as Df and Db, respectively, and the absolute value of a refractive power and the absolute value of a diffraction power on a main scanning cross section of the optical element are defined as |Prm| and|Pdm|, respectively, conditions of 0.20≤Df / Db≤0.40 and 1.00<|Pdm| / |Prm|≤1.50 are satisfied.SELECTED DRAWING: Figure 1
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