Count number of img tags inside a div tag

My code goes like this.

<div id="some_id">
    <img src="some_image.png">
    <img src="some_image.png">
    <div class="another_div"></div>
    <div class="another_div"></div>
</div>

I want to count number of img tags inside that div element.

I found this from a similar question on stackoverflow which returns count of all the children.

var count = $("#some_id").children().length;

How do I modify this code or use some other function to count the number of img tags inside the div?