| 摘要 |
The invention relates to a zoom optical system that can offer an effective tradeoff between size reductions and cost reductions and electronic equipment incorporating it. The zoom optical system comprises, in order from its object side, a first lens group G 1 having negative refracting power, a second lens group G 2 having positive refracting power, a third lens group G 3 having negative refracting power and a fourth lens group G 4 having positive refracting power. The second lens group G 2 consists of one positive lens. The positive lens satisfies a condition regarding the temperature coefficient of refractive index.
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