マシンビジョン用IR補正レンズ：可視光および近赤外光照射下における焦点の安定性
なぜ標準レンズは850nmまたは940nmの照明下でピントがずれるのか、色収差によるピントずれと熱やフィルターによるピントずれの違いは何か、そしてどのCommonlands M12レンズが両方の波長帯でピントを維持できるのか。
IR補正レンズは、色収差の補正範囲を近赤外帯域（通常は850nmおよび940nm）まで拡張するため、可視光と近赤外光が同一の焦点面を共有します。一方、標準レンズは可視光帯域のみに対して補正されているため、照明が近赤外光に切り替わると焦点がずれてしまいます。これは波長に依存する焦点位置のずれであり、「縦方向の色収差」と呼ばれます。
Removing an IR-cut filter does not fix this. The filter only selects which wavelengths reach the sensor. It does nothing to close the lens's visible-to-NIR focus separation. RGBIR sensors and day/night cameras that switch between visible and NIR illumination need the correction built into the lens itself.
IR補正レンズとは何ですか？
An IR corrected lens is a lens whose optical design extends chromatic focus correction beyond the visible band into the near-infrared, typically holding a common focal plane from roughly 400nm through 850nm or 940nm. A standard lens is corrected only across the visible band. Focused under visible light, that same standard lens defocuses under NIR illumination, because its designers never targeted that wavelength range for focus.
The practical test is direct: focus under visible light, switch to NIR illumination without touching focus, and capture an image. If it stays sharp, the lens is adequately IR corrected for that use. Correction ranges from an uncorrected singlet to a multi-element low-dispersion design, and reputable datasheets specify the wavelength range over which focus stability holds. For the aberration family this addresses, see lens aberrations in machine vision.
光学設計による赤外線補正の仕組み
A single lens element cannot hold visible and NIR light at the same focal plane, because every glass type has its own dispersion curve, the relationship between refractive index and wavelength. IR correction pairs element materials with complementary dispersion so the combined system brings a wider wavelength range to a common focus than any single glass could. This is the achromatic doublet principle used for visible correction, extended across a band that includes 850nm and 940nm.
Dispersion curves are nonlinear and glass catalogs are finite, so a designer usually accepts a residual visible/NIR offset rather than eliminating it. A well-corrected lens holds that offset within the system's depth of focus at the intended aperture and format. That is why datasheets specify a wavelength range, and why validating at the real wavelength, aperture, and sensor matters more than the "IR corrected" label alone.
「焦点シフト」とは何ですか？また、なぜ波長によってそれが引き起こされるのですか？
Focus shift is the movement of the plane of best focus after an optical condition changes, even though no one touched the mechanical focus setting. It is distinct from back-focus error, a static lens-to-sensor misalignment set once at assembly. Focus shift happens after a known-good focus state, driven by a condition the lens design cannot compensate for.
Three mechanisms move the focal plane, each with its own fix. A fourth condition, aperture, changes only how much shift the system tolerates, not where the plane sits. Wavelength is the chromatic case this pillar covers: glass refractive index varies with wavelength, so 850nm or 940nm NIR converges at a different axial distance than visible light. In a non-IR-corrected lens, that separation can be large relative to the sensor's depth of focus.
| Condition that changes | 何が動くのか | 典型的な症状 | 実用的な解決策 |
|---|---|---|---|
| 波長の変化（可視光域（VIS）→ 近赤外域（NIR）） | 色収差による焦点面分離 | 1つの照明モードにおけるぼやけ；昼夜での性能差 | IR補正レンズ |
| フィルターまたはスイッチャーが挿入されています | 光路長が増加する | フィルター装着時のピントがぼける；フィルターの状態によって異なる | 補償付きフィルタースイッチャー；フィルター装着状態でのバックフォーカスリセット |
| 気温の上昇または下降 | 熱による焦点面ドリフト | 極端な温度下ではフォーカス精度が低下する | 全ガラスレンズ；耐熱設計（耐環境仕様ガイドを参照） |
| 絞り値の変更（絞り込み） | 被写界深度の範囲が広がる | 絞り込むとシャープに見える（シフト現象を目立たなくするだけで、修正されるわけではない） | 実測開口での診断 |
The longitudinal chromatic aberration behind this focus shift differs from lateral chromatic aberration, which spreads color fringing across the field rather than moving the axial focal plane. IR correction targets the longitudinal component so visible and NIR bands converge closer together.
Filter-stack shift is a separate, predictable effect
Any glass added to the optical path after the lens is focused moves the focal plane away from the lens by a predictable amount. Common examples include a cover glass, a bandpass filter, or a switcher.
A 340μm shift exceeds a typical 15-25μm depth of focus by more than an order of magnitude. A day/night filter switcher must therefore hold matched optical path length between its IR-cut and bandpass states. If the two thicknesses (adjusted for refractive index) do not match, one state is always defocused relative to the other, independent of whether the lens is IR corrected.
The Commonlands CLA216-ICR-850BP compensates this: its glass thickness offset between the 650nm IR-cut and 850nm bandpass sides matches the two path lengths, so one focus setting stays valid across both.
IR補正レンズと、標準レンズおよびIRカットフィルターを取り外した状態との比較
These three things are often conflated. A standard lens with an IR-cut filter gives a sharp visible image because the filter stops out-of-focus NIR light from reaching the sensor. The lens is not corrected. The problem is only hidden. Remove that filter and NIR light gets through, but the optics still carry the same chromatic focus shift, so the NIR contribution is now visible and out of focus relative to the visible-light setting.
Commonlands labels the no-filter build NIR-pass (SKU suffix ANIR): the filter slot is empty, so visible and NIR both reach the sensor. This is not a NIR-pass longpass filter, which would block visible light.
An IR corrected lens in that NIR-pass build holds focus from visible through NIR in the optics, so no refocus is needed when illumination switches. Commonlands IR-corrected M12 lenses ship in both a 650nm IRC build (daytime visible) and this NIR-pass build (RGBIR and day/night). See the examples below.
| レンズとフィルターのセットアップ | 最適な活用例 | 主なリスク |
|---|---|---|
| 標準レンズ＋IRカットフィルター | 可視光のみによる撮像、NIR照明なし | IRカットフィルターはNIRを遮断するため、850/940nmの照明は使用できません。 |
| 標準レンズ、IRカットフィルターなし | 狭帯域近赤外（NIR）のみ、その波長に合わせて再焦点化されたもの | 可視光と近赤外光は焦点位置が異なるため、2波長を併用する場合は再焦点合わせが必要となる |
| IR補正レンズ + 650nm IRC | 昼間の可視光撮影が可能、将来的には近赤外（NIR）撮影機能も搭載可能 | デュアルバンドで使用するには、NIR透過型モデルに交換する必要があります |
| IR補正レンズ、NIR透過型（フィルターなし） | RGBIRカメラ、昼夜切替機能、純粋な850/940nmシステム | 高解像度においても、残留する可視光・近赤外領域のシフトは依然として重要である可能性がある |
RGBIRシステムやデイ/ナイトシステムにおいて、IR補正はどのような場合に重要になるのでしょうか？
IR補正は、すべての用途で必要というわけではありません。IRカットフィルターを備え、NIR照明を使用しない可視光専用システムでは、IR補正は必要ありません。IR補正が設計要件となるケースには、ある共通点があります。それは、システムが同一の焦点位置から2つ以上の波長で鮮明な画像を生成しなければならないという点です。
RGBIRセンサー
RGBIR sensors capture RGB and NIR-sensitive pixels through the same lens at one focus distance. A lens with significant chromatic focus shift leaves the NIR channel softer than the RGB channels, most visibly on high-resolution sensors with small pixel pitch. Because both share one exposure, there is no chance to refocus between them, so the lens must hold both wavelengths in focus at once, a harder requirement than sequential switching.
昼夜兼用カメラ
A day/night camera uses visible illumination in daylight and 850nm or 940nm LED illumination at night. Without an IR-corrected lens, a fixed-focus camera is sharp in one mode and soft in the other, since it has no motorized refocus on mode change. It can pass a daytime acceptance test, then image softly the moment NIR illumination activates, so validate focus under both modes before deployment rather than diagnosing it later as a camera fault.
Decide the IR-correction requirement before choosing a focal length or mount. It turns on one question: must the system stay sharp at two wavelengths from a single focus position? After that, focal length follows the usual working-distance and field-of-view process. Confirm the destination format with sensor size and lens compatibility, since residual shift bites hardest on small, high-resolution formats.
昼夜兼用マシンビジョン向け、IR補正機能を備えたM12レンズのトップモデル
Three all-glass, all-metal Commonlands IR-corrected M12 lenses that hold one focal plane from the visible band through the 850nm and 940nm NIR illumination lines. Each ships in a 650nm IRC (IR-cut installed) and a NIR-pass (filter slot empty) configuration.
Commonlands ranked these three by how broadly each covers day/night and RGBIR work: focus held across visible and NIR, image circle against common 1/2" and 1/1.7" formats, and a fast fixed F/2.0 aperture for 850/940nm LED scenes. To match a focal length to your sensor, run the lens field of view calculator.
| ランク | レンズ | EFL | F# | 像円 | こんな方に最適 |
|---|---|---|---|---|---|
| 1 | CIL046 | 4.4mm | F/2.0 | 8.9mm | 最大8MPの1/1.7インチセンサーを搭載し、RGBIRおよびデイ/ナイト機能に対応した100°の広角視野 |
| 2 | CIL122 | 12mm | F/2.0 | 9.2mm | 1/1.7インチ、8～12メガピクセルのセンサーを搭載し、昼夜対応およびロボット用途向けの43°の狭角視野 |
| 3 | CIL161 | 15.6mm (nominal 16mm) | F/2.0 | 8.0mm | 小型の1/2インチ、3～5メガピクセルセンサー搭載モデルにおける、昼夜兼用用の28.8°の狭い画角 |
Order the 650nm IRC variant for daytime visible use, or the NIR-pass variant for RGBIR or day/night sensitivity without refocusing. Where a system physically switches filters, pair an IR-corrected NIR-pass lens with the CLA216-ICR-850BP, whose glass thickness offset compensates the path-length change between filter states.
Commonlands is not the only source: Sunex and Edmund Optics also ship IR-corrected designs, and either can be the better call for a C-mount format these M12 lenses do not cover. Confirm IR correction as a distinct line item on the datasheet regardless of mount, since day/night and security marketing language is applied inconsistently across suppliers.
可視光および近赤外（NIR）領域における焦点安定性の検証チェックリスト
A datasheet claim of "IR corrected" is a starting point, not a guarantee for a specific system. Pixel pitch, aperture, working distance, and the actual NIR wavelength all affect whether the residual shift stays acceptable. Confirm a lens holds focus across visible and NIR in the real deployment configuration, not on the bench.
Commonlands provides measured MTF data per lens and can supply depth-of-focus figures on request, giving this checklist a documented baseline to test against.
- 主光源の下で焦点を合わせ、機械的な焦点位置を記録します。
- フォーカス機構を調整することなく、第2の波長に切り替えてください。
- 動作作業距離において、両方の波長で解像度テストチャートまたはファインピッチターゲットを撮影してください。
- 各波長について、画像の中心および少なくとも2か所の隅の位置で、シャープネスまたはMTFを測定する。
- 実際の動作絞り値で検証してください。量産時により開放側で動作する場合でも、シフトを隠蔽するために絞り込んで検証を行わないでください。
For reading the MTF data this produces, see how to read MTF curves. Keep the recorded focus positions and MTF results with the production documentation, so a later change of sensor, aperture, or working distance can be checked against that baseline.
よくある質問
Commonlands stocks IR-corrected M12 lens variants for NIR illumination. These answers explain when that correction is necessary.
マシンビジョンにおけるIR補正レンズとは何ですか？
An IR corrected lens extends chromatic focus correction into the near-infrared, typically 850nm and 940nm, so visible and NIR light share a common focal plane. A standard lens is corrected for visible wavelengths only and defocuses under NIR. IR correction is a property of the lens optical design, not of any filter.
IRカットフィルターを取り外すことは、IR補正レンズを使用することと同じですか？
No. An IR-cut filter only blocks which wavelengths reach the sensor. Removing it lets NIR light through but does nothing to the lens's chromatic focus shift, which still brings visible and NIR light to different focal planes. Closing that gap requires an IR corrected lens design, independent of any filter.
RGBIRカメラには、IR補正レンズが必要ですか？
Yes, for most RGBIR applications. These sensors capture RGB and NIR pixels from one frame through the same lens at one focus position, so a lens with significant chromatic focus shift leaves the NIR channel softer than RGB, most visibly on high-resolution sensors with small pixel pitch.
色による焦点シフトと熱による焦点シフトは、どのように異なるのでしょうか？
色収差による焦点位置のずれは、波長（可視光と近赤外）に応じて焦点面が移動する現象であり、IR補正された光学設計によって対処されます。これにより、可視光と近赤外間の残留オフセットをシステムの被写界深度内に収めることができます。熱による焦点位置のずれは、筒部の膨張やガラス・プラスチックのdn/dTによって引き起こされ、温度の変化に応じて焦点面が移動する現象であり、これに対しては全ガラス製または非熱膨張構造を採用することで対処されます。熱メカニズムおよびその緩和策については、耐環境性レンズガイドを参照してください。
マシンビジョンシステムにおいて、可視光および近赤外（NIR）の焦点をどのように検証すればよいでしょうか？
Set focus under the primary wavelength, then switch to the secondary wavelength without touching the focus mechanism, and capture a resolution target at both. Measure MTF at center and corners at the real working distance and aperture, not stopped down, and document any residual focus offset against the depth of focus (set by F-number and pixel pitch).
昼夜兼用カメラには、赤外線補正レンズとフィルター切替装置の両方が必要ですか？
Often, yes. The IR-corrected lens keeps the optics focused across visible and NIR. A filter switcher (or a fixed NIR-pass configuration) controls which wavelengths reach the sensor at a given time. Systems that physically swap an IR-cut filter for a bandpass filter also need those two filter states to have matched optical path length, or the swap itself introduces a separate focus shift. See the bandpass filter machine vision guide for filter-switcher selection.
IR補正レンズの選び方で困っていませんか？
Send your sensor, working distance, and illumination wavelengths to our San Diego engineering team. We will confirm whether an IRC or NIR-pass variant fits your system, and flag any filter-switcher compensation your day/night design needs. Commonlands lenses are MTF characterized, and orders placed before 12 PM PST ship the same day.