Is Your Optical Drawing Increasing Costs Without Improving Performance?
Optical Cost
10/19/20262 min read
You've found an optical supplier.
You've prepared the drawing, defined the tolerances, and requested a quotation.
But here's a question worth asking before placing the order:
Are all the specifications on your optical drawing actually necessary for your application?
In custom optics, tighter specifications can increase manufacturing difficulty, inspection requirements, and cost.
However, tighter doesn't always mean better.
The key is understanding which requirements directly affect your system's performance.
Here are four areas worth reviewing before sending your next RFQ.
1. Surface Quality: Does Your Application Really Need 20-10?
A tighter scratch-dig specification generally requires more demanding polishing and inspection.
For some laser or imaging applications, stringent surface quality may be essential.
For other applications, a less demanding specification may be perfectly adequate.
The important question isn't whether 20-10 is better than 60-40.
It's whether the improvement is necessary for your application.
2. Surface Flatness: Is λ/10 Always Better Than λ/4?
A tighter flatness requirement can increase manufacturing difficulty and cost.
But the appropriate requirement depends on the optical design, wavelength, aperture, and system performance targets.
For a precision interferometry setup, tighter flatness may be justified.
For a less demanding application, it may offer little practical benefit.
Specify the performance you need—not simply the tightest tolerance available.
3. Dimensional Tolerances: Are They Tighter Than Necessary?
Consider two drawings for a 25 mm optical component.
One specifies a diameter tolerance of ±0.05 mm. The other requires ±0.01 mm.
The second requirement may need more precise machining and inspection.
If the application doesn't benefit from that tighter tolerance, the additional cost may not be justified.
The same principle applies to thickness, centration, wedge, and other dimensional or optical requirements.
4. Coating Requirements: Are They Clearly Matched to the Application?
Coating specifications should reflect the actual operating conditions.
Wavelength range, angle of incidence, required transmission or reflection, and environmental conditions can all affect coating design.
Avoid specifying a coating based only on a general label such as “AR coated.”
At the same time, don't remove a critical coating requirement simply to lower the quotation.
The goal is to achieve the required optical performance at a reasonable cost.
Before Requesting a Quotation, Ask Three Questions
1. Which specifications are critical to system performance?
2. Which requirements are driven by the application, and which are simply carried over from an older design?
3. Can the supplier suggest a more manufacturable specification without compromising performance?
A capable optical supplier should be willing to discuss these questions rather than simply quote the drawing without clarification.
Of course, any proposed specification change should be reviewed and approved by the responsible engineer before production.
The Takeaway
A well-designed optical drawing does more than define a component.
It communicates the performance requirements that manufacturing must achieve.
Overly tight specifications can increase cost without delivering meaningful benefits. Insufficient specifications can create performance and reliability problems.
The goal is to find the right balance.
The best optical specification isn't necessarily the tightest one. It's the one that meets your application's requirements without adding unnecessary cost.
At Positive Optics, we support custom optical lenses, windows, filters, prisms, and mirrors based on customer drawings and application requirements.
If you're preparing an RFQ, sharing the intended application alongside the drawing can help clarify which specifications matter most.
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📧 info@positiveoptic.com
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