# PRIOR ART — E4-H160

**Search performed:** 2026-11-01, two web queries on wavelength-steered OPA / dispersive beam steering
range resolution. **Not a systematic review.** Full texts were not retrieved for most sources; what is
recorded is what a search surfaced and what its title or snippet indicates.

## Claims under investigation

| # | Claim | Status after this project |
|---|---|---|
| C1 | Beam angle depends on optical frequency (dispersive steering) | **Established**, textbook grating/OPA physics |
| C2 | A chirp therefore sweeps the beam across the scene | **Established** consequence of C1 |
| C3 | Effective bandwidth saturates at `B_eff = c/(λD|dθ/dλ|)` | **Correct** for a point target; recovered independently |
| C4 | Resolution floors at `δR = λD|dθ/dλ|/2`, independent of chirp bandwidth | **Conditionally correct** — valid for a point target; not for an extended target |
| C5 | Floor grows linearly with aperture | **Correct** at fixed pitch (T1) |
| C6 | The limit is a *fundamental* bound | **Rejected.** It is an information/conditioning limit, target-dependent |
| C7 | Absent for independently phase-steered arrays | **Plausible, untested here** |

## Closest identified prior work

1. **"System trade-offs in a swept source FMCW LiDAR with dispersive OPA beam steering"**
   (Ghent/IMEC photonics publication server, `photonics.intec.ugent.be/download/pub_5126.pdf`).
   **Identified by search; full text NOT retrieved** (the fetch returned a redirect error and was not
   retried). By title, this work analyses exactly the trade-off named in C3–C5.
   **Consequence: C3–C5 should be treated as plausibly known; no novelty is claimed for them.**

2. **Pixelated optical beam scanner controlled by laser wavelength** (IEEE, cited in search results).
   Establishes wavelength-dependent beam steering and the pixel/pitch dependence of the scan range —
   directly relevant to `dθ/dλ` and to C1.

3. **Pioneer/Phased-array switching patents** (US20140023316A1, US11378689, US11782139) surfaced in the
   search. Establish that wavelength-steered array architectures and their scanning engines are
   patented prior art. Not analysed in detail.

4. **Columbia academic commons thesis chapter** on resolvable spots being set by antenna count —
   relevant to the `N` dependence and to the `Nλ` form of the dwell bandwidth.

## Where this project's contribution would sit, if it survives

The only candidate original element is **C6's refutation plus its replacement**: that the limit is the
Cramér–Rao bound on delay for the *illumination-weighted* spectrum, that it saturates only for a point
target, and that beyond `B_eff` it *worsens* slightly rather than merely flattening.

That is a **new derivation of a conditional scaling law** (not a new measurement, not a new
application). It is defensible only if the Ghent paper does not already state the target-dependence and
the super-B_eff behaviour. **I could not check.** This is the single most important unresolved
prior-art question, and it is recorded here rather than glossed.

## Honest novelty rating

| Question | Assessment |
|---|---|
| Is the trade-off new? | **Probably not.** Likely in the Ghent paper. |
| Is the `Nλ/2` constant new? | **Unlikely.** |
| Is the information-theoretic reframing new? | **Unknown** — plausible but unverified |
| Is the target-dependence new? | **Unknown** — plausible but unverified |
| Is the super-B_eff worsening new? | **Unknown** — plausible; not seen in any snippet |

**Overall: a corrected and generalized derivation whose novelty is unverified.**