Depth of Field Diagram in Object Space

where a is the aperture, x is the subject distance and y is the circle of confusion (typically taken as 1/1500th of the field of view in the subject plane).
Then P is the furthest point and S is the nearest point that will appear acceptably sharp in the image. So the depth of field is the distance between P and S.

I believe that this diagram correctly shows the geometrical optics of the situation and that the depth of field can be computed geometrically from this diagram without using lens equations and diagrams of the optics in image space.

The object space diagrams used by Merklinger (that show the rays from a point in the plane of focus) seem to me to be unhelpful to an understanding of depth of field. I'd be interested to know of any good reasons to prefer Merklinger's diagrams to the one above.

Merklinger's Fig. 11:

It depends on your definition of "good reasons" and how it differs to other people.

For any given diagram of this type people will understand and comprehend it to varying extents based on their aptitude for these types of discussions and their ability to comprehend.

There are countless dof diagrams on the www that many beginners will find more practical and easier to understand than your diagram.

Equally there will be many that understand your diagram as well.

Yes, I've put it in my OP. Thanks for the suggestion.