Latent electrostatic image developing device having a toner concentration detector

A latent electrostatic image developing device comprising:

• a development housing for holding a developer;
• toner feed means for supplying toner into said development housing;
• developer applicator means for applying the developer in said development housing to a latent electrostatic image;
• a developer agitating/conveying mechanism disposed in said development housing and having a first agitating/conveying member for conveying the developer, while agitating it, along said developer applicator means;
• and
• a toner concentration detector disposed in the bottom wall of said development housing in opposition to said first agitating/conveying member, the upper surface and the side surface of a detector portion of said toner concentration detector being connected by an arcuate surface or a chamfered surface;
• wherein
• said toner concentration detector is fitted into an opening formed in the bottom wall of said development housing, and the upper surface of said detector portion protrudes from the inner surface of the bottom wall of said development housing by an amount nearly corresponding to the radius of the arcuate surface or the height of the chamfer of said chamfered surface.