Source: https://guthlabs.ai/docs/instruments/thin-lens-equation-calculator/implementation/

instrument implementation / implementation-contract

# Thin Lens Equation Calculator implementation

A source-bound implementation contract for Thin Lens Equation Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-114

**Effect**: Computation or source lookup only

## Input and validation requirements

The singular inputs do = f and do = 0 require explicit rejection or infinity handling, and the signed-distance convention is unspecified. Without validation and a documented sign convention, the calculator can produce undefined results or a different image type and magnification for the same physical setup.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "f": 50,
    "do": 300,
    "unit": "mm"
  },
  "expected_outputs": {
    "di": 60,
    "m": -0.2,
    "image_type": "real",
    "orientation": "inverted"
  },
  "working": "1/di = 1/f - 1/do = 1/50 - 1/300 = 6/300 - 1/300 = 5/300 = 1/60. Therefore di = 60 mm. m = -di/do = -60/300 = -0.2. Since di>0, the image is real. Since m<0, it is inverted."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/thin-lens-equation-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/thin-lens-equation-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/thin-lens-equation-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`