Thank you for the well-explained answer I will also go for a fixed focus lens.
Up to now, I have done the following,
1. To reduce the field of view of the projector I 3d printed an extension tube and moved the whole lens element forward which allowed me to have a smaller field of view to scan smaller objects. But what I found was due to the large aperture the depth of field of the projector reduces significantly. Then I tried to reduce the aperture of the projector lens. But this reduced the amount of light projected. Which was not successful either.
Also with the use of the extension tube field of view gets reduced but the sharpness also reduces. So my conclusion was to buy a projector which is similar to your brand.
2. I also tried reducing the projected area from the projector itself and from the GPU settings to get a finer sinusoidal pattern. But using a finer sinusoidal pattern made the white and black contrast get reduced. So this also didnt work.
3. Due to the larger sensor size of the DSRL, I have some issues with the depth of the field. I'm thinking of using a wide-angle lens which allows me to have more depth of field.